NanoPlasMeta 2025 Abstracts

Area 1 - Nanophotonics, Plasmonics and Metamaterials

Area 1 - Nanophotonics, Plasmonics and Metamaterials

Nr: 46
Title:

A Colloidal Approach for the Fabrication of Plasmonic Metasurfaces (Invited)
Authors:

Leonardo Scarabelli
Abstract: Metamaterials development is entering a new phase, where chemistry and chemical concepts are explored for the design of metamaterials with functions that cannot be achieved by traditional nanofabrication. The use of colloidal building blocks for the bottom-up fabrication of optical metasurfaces represents a tremendous step in this direction, taking advantage of the unmatched level of control over nanoparticle morphology, crystallography, composition, and surface chemistry. As such, fabrication techniques based on colloidal synthesis and self-assembly are emerging as valid alternatives for nanofabrication due to their versatility in terms of materials and geometries. In this work, we explored fabrication techniques of high-quality colloidal-based NP 2D arrays by using two different bottom-up approaches. First, we applied colloidal templated self-assembly technique to fabricate a colloidal lasing architecture where a thin film of photoresist doped with Rhodamine B acts as emitting layer. The high efficiency of the device was proved by a low threshold lasing action (0.3 mJ/mm2). In the second part of the talk, I will introduce the concept of Chemical Contrast in Situ Growth, a site-directed growth approach based on a reductant chemical ink and a sacrificial stencil capable of producing nanscaled ordered plasmonic arrays over hundreds of microns squared in a single step and within minutes. Taking advantage of the capability of soft-lithography to fabricate almost unlimited complex growth patterns with advanced plasmonic properties, we demonstrated the preparation of plasmonic square arrays of different lattice parameters capable of sustaining collective lattice plasmon resonances. Moving forward, this new approach opens the door to the rational design of addressable nanostructures in a time-efficient and scalable manner, avoiding colloidal pre-synthesis, self-assembly, top-down lithography, and clean-room processing, fostering the creation of new architectures and functionalities for photoelectrocatalysis, non-linear optics, energy production and storage.
Nr: 47
Title:

Plasmonic Gas Nanosensors to Probe Adsorption and Reactivity
Authors:

Benjamin Demirdjian, Igor Ozerov, Frederic Bedu, Alain Ranguis and Claude R. Henry
Abstract: Gold nanodisks are highly effective plasmonic sensors. This is especially true when gas molecules adsorb onto them or interact with them. This interaction changes the local dielectric properties and induces a wavelength shift in the gold localized surface plasmon resonance (LSPR). We have used nanoplasmonic sensing (NPS) to investigate the interactions of different gas molecules with both bare and coated gold disks (Demirdjian, 2018), as well as with nanoparticles (Demirdjian, 2015; Demirdjian, 2021) or small atomic clusters supported on them (Demirdjian, 2024b). NPS is highly sensitive, quantitative and non-destructive, making it suitable for studying a wide range of gas pressures and temperatures. FDTD calculations have also been performed to interpret LSPR results (Demirdjian, 2024a). REFERENCES Demirdjian, B., Bedu, F., Ranguis, A., Ozerov, I., Karapetyan, A., Henry, C.R. (2015). JPCL 6, 4148-4152. Demirdjian, B., Bedu, F., Ranguis, A., Ozerov, I., Henry, C.R. (2018). Langmuir 34, 5381-5385. Demirdjian, B., Ozerov, I., Bedu, F., Ranguis, A., Henry, C.R. (2021). ACS Omega 6, 13398-13405. Demirdjian, B., Ozerov, I., Bedu, F., Ranguis, A., Henry, C.R. (2024a). CPL 837, 141063. Demirdjian, B., Vaidulych, M., Ozerov, I., Bedu, F., Vajda, S., Henry, C.R. (2024b). Nanoscale, Advance Article.
Nr: 53
Title:

Influence of Surface-Response Functions on the near-Field Performance of Plasmonic Nanostructures (Invited)
Authors:

Christos Tserkezis
Abstract: One of the biggest appeals of plasmonic nanostructures is their ability to enhance and confine electromagnetic (EM) fields, in volumes of a few decades of nm^3 or smaller, thus beating the diffraction limit [1]. The resulting high local density of optical states (LDOS) [2] finds numerous applications in antennas, energy transfer, fluorescence enhancement, catalysis, and strong light--matter interactions [3]. To harness this potential, efforts are often focused on making as small plasmonic nanostructures as possible or, to further exploit plasmon hybridisation [4], bringing individual nanoparticles (NPs) as close to each other as possible. This approach, however, is accompanied by a transition from classical electromagnetism to mesoscopic physics, once the characteristic length scales become comparable to the Fermi wavelength in the metal [5]. In such situations, phenomena related to the solid-state/quantum response of the material, such as electron spill-in or -out, nonlocality, dynamical screening, and Landau damping become relevant, altering the performance of the nanostructures as compared to the predictions of the local response approximation, and a variety of theoretical approaches has been proposed, in an attempt to implement some of the missing microscopic mechanisms into large-scale classical calculations [6]. One such method that has been gaining in popularity in recent years is the surface-response formalism (SRF) based on the Feibelman d parameters [7], where all relevant effects are implemented into the selvedge region between the bulk metal and its environment, through appropriate modification of the traditional boundary conditions [8]. This technique has proven successful in capturing resonance red- or blue-shifts (depending on the metal) and the increased broadening of far-field spectra [6]. Here I will discuss some recent work focusing on near-field properties instead. Initially, I will discuss how introduction of the appropriate Feibelman parameters can largely modify both the Purcell factor and the Lamb shift for quantum emitters placed nearby metallic films or spherical NPs [9]. Subsequently, I will focus on the performance of the so-called self-similar plasmonic nanolens [10], and study how the near-field enhancement that this asymmetric nanosphere trimer provides is affected by both quantum corrections and fabrication imperfections [11]. Once such imperfections are considered, the structure has the potential of exhibiting strong optical activity, and here I will focus on its role on enhancing the local optical chirality density [12] within either LRA or SRF, showing that mesoscopic physics cannot be ignored when such quantities are the main focus. [1] J. A. Schuller et al. - Nature Mater. 9, 193 (2010). [2] R. Carminati et al. - Surf. Sci. Rep. 70, 1 (2015). [3] L. Novotny & B. Hecht - Principles of Nano-Optics (2nd Ed, Cambridge University Press, 2012). [4] E. Prodan et al. - Science 302, 419 (2003). [5] N. A. Mortensen - Nanophotonics 10, 2563 (2021). [6] P. E. Stamatopoulou & C. Tserkezis - Opt. Mater. Express 12, 1869 (2022). [7] T. Christensen et al. - Phys. Rev. Lett. 118, 157402 (2017). [8] P.A.D. Gonçalves et al. - Nature Commun. 11, 366 (2020). [9] M. H. Eriksen et al. - Nanophotonics 13, 2741 (2024). [10] K. Li et al. - Phys. Rev. Lett. 91, 227402 (2003). [11] N. Kyvelos et al. - arXiv: 2410.21871v1 (2024). [12] Y. Tang & A. E. Cohen - Phys. Rev. Lett. 104, 163901 (2010).
Nr: 57
Title:

Hybrid Cavities for Enhancing the Purcell Factor (Invited)
Authors:

Angela I Barreda, Laura Mercadé and Alejandro Martínez
Abstract: Enhancing the efficiency of quantum emitters is essential for achieving single-photon sources, a key component in advancing quantum computation and communication. To this end, optical cavities have been proposed due to their high Q-factors. However, their mode volumes (V) are diffraction-limited to V≈1, which constrains the attainable Purcell factors (FP) [1]. Metallic nanoparticles have been explored as an alternative to optical cavities. Their primary advantages include a broadband electromagnetic response and strong electromagnetic energy confinement in the vicinity of the nanoparticles (NPs) [2]. While metallic NPs achieve small mode volumes, their Q-factors are low due to Joule losses, which again restricts the Purcell factors. Hybrid nanostructures combining plasmonic NPs with dielectric photonic crystals offer a promising solution, merging the benefits of both: small V from the metallic NPs and high Q-factors from the photonic crystals [3]. In particular, the local density of optical states in such hybrid cavities can be engineered by controlling the coupling between the plasmonic and photonic modes, allowing for simultaneous tuning of both the Q-factor and V. Previous studies have shown that a hybrid system consisting of a metallic bow-tie antenna and a dielectric photonic crystal can achieve Purcell factors of FP ≈ 105 [3]. However, reaching such high FP values requires extremely small gaps between nanoparticles (2-5 nm), which are challenging to fabricate with current technology. In this work, we present a novel hybrid system that combines a nanoparticle-on-a-mirror configuration with a dielectric photonic crystal. This system consists of a metallic NP coupled to a high-index GaP photonic nanobeam. The proposed configuration supports a highly confined transverse-magnetic (TM) mode at visible wavelengths (λ = 700 nm) [4]. This design enables the experimental realization of sub-nanometer gaps (smaller than 1 nm), resulting in normalized mode volumes of 10−3 and Q-factors of 103. Compared to Purcell factors obtained in hybrid plasmonic-photonic (TE) configurations with feasible gaps (d ≈ 10 nm), our structure demonstrates an order of magnitude improvement. Acknowledgements A.B. gratefully acknowledges financial support from Spanish national project No. PID2022-137857NA-I00 and MICINN for the Ramón y Cajal Fellowship (grant No. RYC2021-030880-I). References [1] E. M. Purcell, “Spontaneous emission probabilities at radio frequencies,” Phys. Rev. 69, 681 (1946). [2] A. F. Koenderink, “On the use of Purcell factors for plasmon antennas,” Opt. Lett. 35, 4208–4210 (2010). [3] I. M. Palstra, H. M. Doeleman, and A. F. Koenderink, “Hybrid cavity-antenna systems for quantumoptics outside the cryostat?” Nanophotonics 8, 1513–1531 (2019). [4] Angela I. Barreda, Mario Zapata-Herrera, Isabelle M. Palstra, Laura Mercadé, Javier Aizpurua, A. Femius Koenderink, and Alejandro Martínez, "Hybrid photonic-plasmonic cavities based on the nanoparticle-on-a-mirror configuration," Photon. Res. 9, 2398-2419 (2021).
Nr: 64
Title:

Optical Resonances of Hybrid Metasurfaces Driving by Bound States in the Continuum (Invited)
Authors:

Andrey Evlyukhin
Abstract: The features of optical properties of hybrid silicon-gold nanoparticles are studied, demonstrating that internal material inhomogeneity can lead to a strong bianisotropic response of the particles associated with the distortion of their inversion symmetry. A method for obtaining information on the structure of the dipole polarizability tensor of hybrid particles based on the analysis of symmetry properties and the multipole composition of their eigenmodes is discussed. The spectral response of metasurfaces composed of such particles, in turn, can have narrow resonance features associated with resonant multipole coupling and excitation of quasi-bound states in the continuum (quasi-trapped modes). It is shown that these resonance features strongly depend on the polarization of incident waves and are accompanied by an increase in absorption and field enhancement in the plane of the metasurface. It is also shown that, using a special procedure for determining (tuning) the period of the metasurface, it is possible to implement switching control of the excitation of quasi-trapped modes of magnetic and electric types by changing the polarization of the incident wave.
Nr: 65
Title:

Harnessing Droplets Driven out of Equilibrium with and Without Light (Invited)
Authors:

Giorgio Volpe
Abstract: The manipulation and control of droplets are important for phenomena as diverse as printing, thin-film deposition, and self-assembly [1]. Here, I will discuss our recent advances in the manipulation of droplets driven out of equilibrium by different energy sources including light. I will focus on two main examples: (i) the remote manipulation of evaporating droplets on solid substrates due to Marangoni flows [2-3], and (ii) the capillary-assisted self-assembly of droplets at solid-like liquid-liquid interfaces [4]. Beyond discussing the origin and fundamental aspects of these two approaches, I will also discuss their application to the deposition, printing, and patterning of materials. [1] R. Malinowski, I.P. Parkin and G. Volpe, Chem. Soc. Rev. 49 (2020), 7879. [2] R. Malinowski, I.P. Parkin and G. Volpe, J. Phys. Chem. Lett. 9 (2018), 659. [3] R. Malinowski, I.P. Parkin and G. Volpe, Sci. Adv. 6 (2020), eaba3636. [4] A. Thapa, R. Malinowski, M. O. Blunt, G. Volpe and J. Forth, arXiv:2405.00609 (2024).
Nr: 66
Title:

Superchiral Light Emerging from Bound States in the Continuum in Metasurfaces of Si Nanorod Dimers
Authors:

Beatriz Castillo López de Larrinzar, Jose L. Pura, Minpeng Liang, Antonio Garcia-Martin, Jaime Gomez Rivas and Jose Antonio Sanchez-Gil
Abstract: Bound states in the continuum (BICs) in all-dielectric metasurfaces are known for their ability to enhance light-matter interaction at the nanoscale due to their infinite Q factors and strong field confinement. Superchiral light is defined as an electromagnetic field whose chirality (helicity density) is higher than that of free-standing monochromatic circularly polarized light. Here, we analyze both the circular dichroism (CD) of the far-field (FF) interaction and the helicity density of the near-field (NF) distribution. Our findings reveal that extrinsic chirality in the FF is optimally achieved through quasi-BICs (q-BICs) in slanted nanorod dimers. On the other hand, shifted dimers exhibit intrinsic chirality, leading to a significant enhancement of the near-field helicity density. Interestingly, these high values of the chirality can be obtained without breaking the BIC conditions that result in a diverging value of the Q-factor. These superchiral fields, confined at the nanoscale, offer exciting potential for applications in strong-coupling, photoluminescence emission, chiral sensing, and other localized light–matter interaction phenomena.
Nr: 68
Title:

Mock Magnetic Monopoles in Isotropic Spinning Fields (Invited)
Authors:

Manuel Marques, Shulamit Edelstein, Pedro A. Serena, Beatriz Castillo López de Larrinzar and Antonio Garcia-Martin
Abstract: Constant magnetic fields are known to interact with electrically charged particles inducing Lorentz forces that point in a direction perpendicular to the field. However, if the particle is electrically discharged, it is impossible to induce a force using a constant magnetic field. An exotic option is to mimic a magnetic charge on a neutral particle. This false magnetic monopole will interact with the magnetic field just as an electric charge would do with an electric field through the Coulomb interaction. Attempts to generate this magnetic charge have mainly relied on quasiparticles generated using condensed matter spin ice networks [1-3]. In this work we present another option based on neutral magneto-optical particles illuminated by a spinning monochromatic light field [4]. We will analyze the behavior of these particles under different isotropic optical configurations [5,6], and we will calculate the value of the induced magnetic charge [7]. [1] S. T. Bramwell, S. R. Giblin, S. Calder, R. Aldus, D. Prabhakaran, and T. Fennell, Measurement of the charge and current of magnetic monopoles in spin ice, Nature 461, 956 (2009). [2] S. J. Blundell, Monopoles, magnetricity, and the stray field from spin ice, Phys. Rev. Lett. 108, 147601 (2012). [3] C. Castelnovo, R. Moessner, and S. L. Sondhi, Magnetic monopoles in spin ice, Nature 451, 42 (2008). [4] S. Edelstein, R. M. Abraham-Ekeroth, P. A. Serena, J. J.Saenz, A. Garcia-Martin, and M. I. Marques, Magnetooptical stern-gerlach forces and nonreciprocal torques on small particles, Phys. Rev. Res. 1, 013005 (2019). [5] J. Luis-Hita, M. I. Marques, R. Delgado-Buscalioni, N. de Sousa, L. S. Froufe-Perez, F. Scheold, and J. J.Saenz, Light induced inverse-square law interactions between nanoparticles: “mock gravity" at the nanoscale, Phys. Rev. Lett. 123, 143201 (2019). [6] J. Luis-Hita, J. J. Saenz, and M. I. Marques, Active motion induced by random electromagnetic fields, ACS Photonics 9, 1008 (2022). [7] M. I. Marqués, S. Edelstein, P. A. Serena, B. Castillo López de Larrinzar, and A. Garcia-Martín, Magneto-optical Particles in Isotropic Spinning Fields Mimic Magnetic Monopoles, Phys. Rev. Lett. 133, 046901 (2024).
Nr: 69
Title:

Torsional Mechanical Modes in Acousto-Plasmonic Antennas (Invited)
Authors:

Antonio Garcia-Martin, Beatriz Castillo López de Larrinzar, Jorge García Martín, Chushuang Xiang and Daniel Lanzillotti Kimura
Abstract: Metallic nanoantennas have been studied as efficient coherent phonon generators and detectors, harnessing their characteristic optical absorption and polarization dependence of the optical modes [1-2]. The ability to control the excitation of phononic modes depends on the properties of the multiple optical resonances of the system. Lately, it has been made possible to optimally excite and detect phonon modes via plasmon resonances at the same optical frequency using chiral nanostructures and circularly polarized light [3]. However, torsional modes remain elusive in nanophononic studies. In this work we present two different approaches, one consisting in a twisted single nanostructure [4] the second being composed of two coupled bars [5]. In both cases torsional mechanical modes are excited using light with null angular momentum. The twisting of the phononic mode is provided by the peculiar geometry of the nano-nanoantenna, either intrinsic or provided by the interaction of the bars though the substrate. We will present a complete theoretical analysis of the phononic and plasmonic modes, as well as their surface deformation field profiles. References [1] K. O’Brien, et al. Nature communications, 5, 4042 (2014). [2] N.D. Lanzillotti-Kimura, et al. Pysical Review B, 97, 235403 (2018). [3] B. Castillo López de Larrinzar, C. Xiang, E.R. Cardozo de Oliveira, N.D. Lanzillotti-Kimura, and A. García-Martín. Nanophotonics 12, 1957-1964 (2023). [4] B. Castillo López de Larrinzar, J.M. Garcia, N.D. Lanzillotti-Kimura, and A. García-Martín, Nanomaterials, 14, 1276 (2024) [5] B. Castillo López de Larrinzar, J.M. Garcia, C. Xiang, N.D. Lanzillotti-Kimura, and A. García-Martín, Nanophotonics (in press 2025).
Nr: 70
Title:

Topological Nonlinear Optics and All-Optical Detection of Broken Time-Reversal Symmetry (Invited)
Authors:

Giancarlo Soavi and Jan Wilhelm
Abstract: Since decades, nonlinear optics has been one of the most powerful spectroscopy tools to probe space symmetries of bulk materials and surfaces. In this talk, I will show new approaches of modern nonlinear optics to study time reversal symmetry and the Berry curvature in non-magnetic materials. I will show our recent results of all-optical bandgap modulation and read-out of broken time-reversal symmetry in mono- and bilayer transition metal dichalcogenides, thus demonstrating a new powerful approach to probe broken time reversal symmetry in both centrosymmetric and non-centrosymmetric crystals. I will conclude my talk with an overview of how nonlinear optics, and in particular second harmonic generation, can be used to probe the Berry curvature close to optical resonances.
Nr: 71
Title:

Rhodium Nanospheres for Ultraviolet and Visible Plasmonics (Invited)
Authors:

Vincenzo Amendola
Abstract: Compared to gold and silver nanostructures, the promising plasmonic attributes of rhodium nanoparticles remain poorly investigated. In particular, due to the high cohesive energy, it is difficult to synthesize and investigate Rh nanospheres larger than just a few nm. Here, we show that the laser synthesis of spherical Rh nanoparticles with sizes in the 20–40 nm range was possible. The localized surface plasmon (LSP) of Rh NPs falls in the ultraviolet spectral range (195–255 nm), but the absorption tail in the visible region increases significantly upon clustering of the nanospheres. The surface binding ability of Rh NPs towards thiolated molecules is equivalent to that of Au and Ag NPs, while their chemical and physical stability at high temperatures and in the presence of strong acids such as aqua regia is superior to those of Au and Ag NPs. The plasmonic features are well described by classical electrodynamics, and the results are comparable to Au and Ag NPs in terms of extinction cross-section and local field enhancement, although blue shifted. This allowed, for instance, their use as an optical nanosensor for the detection of ions of toxic metals in aqueous solution and for the surface enhanced Raman scattering of various compounds under blue light excitation. This study explores the prospects of Rh NPs in the realms of UV and visible plasmonics, while also envisaging a multitude of opportunities for other underexplored applications related to plasmon-enhanced catalysis and chiroplasmonics.
Nr: 73
Title:

Polarization-Resolved Sensing with Photonic Crystal Multilayers (Invited)
Authors:

Paolo Biagioni, Erika Mogni, Giovanni Pellegrini, Jonathan Barolak, Jorge Gil-Rostra, Francisco Yubero, Michele Celebrano, Marco Finazzi, Katharina Schmidt, Stefan Fossati and Jakub Dostalek
Abstract: One-dimensional photonic crystal multilayers are well-established and fully consolidated tools in the palette of nanophotonic design, yet they still offer exciting and unexplored possibilities with novel ways to control the local density of optical states in the energy-momentum space. In this framework, an appealing perspective is provided by the exploitation of Bloch surface waves for surface-enhanced, polarization-resolved experiments, in which e.g. two orthogonal polarization states are used to assess the orientation of molecules within a thin molecular layer or electromagnetic fields carrying an enhanced optical chirality are exploited for the sensing of chiral molecules. In this presentation we will review recent experimental results and perspective opportunities opened by numerical predictions employing photonic crystal multilayers that support degenerate TE and TM Bloch surface wave modes [1-4]. We employ them to experimentally monitor the growth by rolling circle amplification of single-stranded DNA chains on the surface of the photonic crystal and assess the anisotropy (birefringence) that is a signature of the molecular orientation. Moreover, we discuss analytical and numerical results where we highlight the superior performance that the coherent combination of the TE and TM surface modes guarantees in superchiral sensing and in the optical sorting of chiral molecules. Such a combination allows for the creation of superchiral fields that are uniformly distributed and evenly enhanced over the sample surface. In perspective, they can be tuned to cover the whole spectral range from the UV to the mid IR, granting an enhancement of two orders of magnitude in the optical discrimination of chiral enantiomers. This work was partially funded by the European Union – Next Generation EU - PNRR - M4C2, investimento 1.1 - “Fondo PRIN 2022” – “SPIRAL – Lossless surface waves for chiral spectroscopy” – id 2022WFM5MZ – CUP D53D23002400006 [1] G. Pellegrini, M. Finazzi, M. Celebrano, L. Duò, and P. Biagioni. “Chiral surface waves for enhanced circular dichroism”. Phys. Rev. B 95:241402(R), 2017. [2] G. Pellegrini, M. Finazzi, M. Celebrano, L. Duò, and P. Biagioni. “Surface-enhanced chiroptical spectroscopy with superchiral surface waves”. Chirality 30:883, 2018. [3] G. Pellegrini, M. Finazzi, M. Celebrano, L. Duò, M. A. Iatì, O. M. Maragò, and P. Biagioni. “Superchiral surface waves for all-optical enantiomer separation”. J. Phys. Chem. C 123:28336, 2019. [4] E. Mogni, G. Pellegrini, J. Gil-Rostra, F. Yubero, G. Simone, S. Fossati, J. Dostálek, R. Martínez Vázquez, R. Osellame, M. Celebrano, M. Finazzi, and P. Biagioni. “One-dimensional photonic crystal for surface mode polarization control”. Adv. Opt. Mater. 10:2200759, 2022.
Nr: 74
Title:

Microcavity Polaritons: Their Democratization and Use for Improving Organic Optoelectronics (Invited)
Authors:

Konstantinos Daskalakis
Abstract: Planar microcavities are a versatile photonic architecture for tailoring the electromagnetic environment in materials and are central to advancing modern organic optoelectronics. In recent years, microcavities have been extensively utilized in the study of polaritons—hybrid light-matter states that emerge when the energy exchange rate between a material and its environment surpasses intrinsic losses. Polaritons have primarily been explored in exotic phenomena such as Bose-Einstein condensation and superfluidity at room temperature[1]. More recently, these systems have demonstrated groundbreaking performance improvements in organic optoelectronic devices, including organic light-emitting diodes (OLEDs), transistors, and photovoltaics [2]. In fundamental polariton studies, microcavity mirrors are almost exclusively fabricated using vacuum deposition processes, which require infrastructure unavailable to many researchers. While metal-clad microcavities are simpler to produce, their broadband reflectivity and the lossy nature of metals significantly reduce the quality factor (Q), hindering radiative enhancement (Purcell effect), a key advantage of microcavities. On the other hand, dielectric distributed Bragg reflectors (DBRs) solve these issues by providing high reflectivity and low losses, but their fabrication is complex and time-intensive. In the first part of my talk, I will introduce a method we developed to fabricate dielectric DBR microcavities entirely using solution-processing techniques[3]. Our microcavities are not only suitable for polariton studies but also demonstrate remarkable performance. Using Rhodamine 6G, we achieved one of the highest coupling strengths reported, matching those of metallic-clad microcavities. Additionally, our samples exhibited strong photoluminescence for the lower polariton mode and a tenfold suppression of the bimolecular annihilation density threshold compared to bare films. For applied polariton studies, a persistent challenge has been achieving holistic performance gains—optical and electrical—across polariton-based devices. Despite their potential, polariton devices have struggled to compete with state-of-the-art organic optoelectronic technologies, limiting their broader adoption in practical applications. In the second part of my talk, I will present our investigation into polariton gains in OLEDs by tuning the lower polariton mode to the triplet energy levels of fluorescent emitters [4]. Furthermore, I will introduce what I believe is an ideal platform for polariton-enhanced optoelectronics: narrowband organic photodiodes (OPDs). Our work reports record responsivity values of up to 0.24 A/W at 965 nm under -2 V bias, coupled with a practically angle-insensitive response [5]. [1] Daskalakis et.al., Nat. Mater., vol. 13, no. 3, pp. 271–278, (2014); [2] Zhao et.al, Nature, vol. 626, no. 7998, pp. 300–305, (2024); and reference therein [3] Qureshi et al. https://arxiv.org/abs/2410.19392 (2024); Palo et- al, J. Phys. Chem. C, vol. 127, pp. 14255–14262, (2023) [4] Abdelmagid et. al., Nanophotonics, vol. 13, pp. 2565–2573, (2024); Siltanen et.al., http://arxiv.org/abs/2404.04257 (2024) [5] Abdelmagid et. al., https://arxiv.org/abs/2412.06741 (2024).
Nr: 75
Title:

Brewster Quasi-BICs in Out-of-Plane Symmetry Broken Si Nanodisk Metasurfaces (Invited)
Authors:

Jose Antonio Sanchez-Gil, Lucía Hidalgo-Arteaga, Diego R. Abujetas, Beatriz Castillo López de Larrinzar and Antonio Garcia-Martin
Abstract: Brewster quasi-bound states in the continuum (qBICs) have been observed in all-dielectric metasurfaces operating in the microwave regime [1]. These states arise from a symmetry-protected BIC linked to a strong, spectrally isolated vertical magnetic dipole resonance. They emerge when the out-of-plane symmetry is disrupted by tilting the meta-atoms, which are centimeter-sized disks with an exceptionally high refractive index. These qBICs exhibit distinctive features: they remain dark at specific Brewster-like angles, θ = ±φ (where φ is the tilt angle), are highly asymmetric, and exhibit a large but finite Q-factor. In this work, we show that similar Brewster qBICs can also be realized in the optical domain using Si nanodisk metasurfaces, in spite of the spectral overlap between in-plane and out-of-plane dipolar resonances within these meta-atoms. By employing a coupled electric/magnetic dipole model [2], we reveal that optical Brewster qBICs occur in tilted nanodisks at modified Brewster angles, which can significantly deviate from the nanodisk tilt angles (θ ≠ φ). This deviation arises due to the hybridization of in-plane and out-of-plane dipolar resonances and is observed for both magnetic and electric dipole resonances. Numerical simulations confirm the asymmetric nature of these qBICs in their near-field and absorption (extinction) profiles. Furthermore, we propose a practical metasurface design to support Brewster qBICs, achievable through oblique epitaxial growth to fabricate inclined cylinder arrays rather than merely tilted ones. Other configurations based on dimer meta-atoms that may support Brewster qBICs will be discussed too. The diverse phenomena associated with Brewster qBICs make them ideal for tuning or switching nano-optical devices between on/off qBIC states [3], presenting exciting opportunities for enhanced light-matter interactions at the nanoscale. Financial support is acknowledged from Spanish MCIN/AEI/10.13039/501100011033/ and “ERDF A way of making Europe” (LIGHTCOMPAS, PID2022-137569NB-C41). 1. D. R. Abujetas, Á. I. Barreda, F. Moreno, et al., “Brewster quasi bound states in the continuum in all-dielectric metasurfaces from single magnetic-dipole resonance meta-atoms,” Sci. Rep. 9, 16048 (2019). 2. D. R. Abujetas, J. Olmos-Trigo, J. J. Sáenz, J. A. Sánchez-Gil, “Coupled electric and magnetic dipole formulation for planar arrays of particles: Resonances and bound states in the continuum for all-dielectric metasurfaces,” Phys. Rev. B 102, 125411 (2020). 3. D. R. Abujetas, N. de Sousa, A. García-Martín, et al., “Active angular tuning and switching of Brewster quasi bound states in the continuum in magneto-optic metasurfaces,” Nanophotonics 10, 4223–4232 (2021). 4. L. Hidalgo-Arteaga, B. Castillo López de Larrinzar, D. R. Abujetas, A. García-Martín, J. A. Sánchez-Gil, “Dark asymmetric quasi bound states in the1 continuum in semiconductor metasurfaces with2 out-of-plane symmetry breaking,” preprint.
Nr: 77
Title:

Control of 3-Dimensional Motion in Plasmonic Nanomotors with Optical Pulling Forces
Authors:

Guillermo Serrera, Yoshito Y. Tanaka and Pablo Albella
Abstract: The transfer of momentum during light-matter interactions generates significant optical forces, which play a crucial role in various micro- and nanotechnology applications, particularly in the development of lab-on-a-chip systems [1]. In these systems, components such as pumps, valves, mixers, etc. have traditionally relied on gradient optical forces from optical tweezers, which significantly restricts the materials, sizes and geometries of the actuated objects. To address this challenge, several nanomotors based on scattering forces from asymmetric plasmonic nanoantennas or nanophotonic metasurfaces have been recently proposed [2,3]. These approaches have been relatively successful in controlling movement within the transversal plane, even to the three degrees of freedom in two-dimensional movement. However, controlling movement in the longitudinal direction remains an unsolved challenge [4]. In particular, while optical pushing forces are relatively straightforward as a result of photons recoiling on the material; the counterintuitive concept of optical pulling forces was only discovered and explored in the last decade [5]. To achieve such forces, the recoil of photons must generate a negative force, i.e., the object must collimate or squeeze the incident light. This imposes strict limitations on both the object’s properties and the characteristics of the incident light. To address these challenges, large cone angle Bessel beams or pairs of light sources have been utilized, with significant efforts dedicated to enhancing their practicality and applicability [6]. Here we theoretically propose a realistic nanomotor design whose motion can be controlled both transversely and longitudinally. A suitable platform for optical pulling was first developed, based on waveguide coupling between an azimuthally polarized Bessel beam and a glass cylinder. Then, using this cylinder as the main body for the nanomotor, asymmetric plasmonic dimers were strategically placed within the dielectric cylinder to avoid strong interaction with the pulling beam. Therefore, a plane wave incidence produces lateral motion, driven by the lateral force from the plasmonic dimers, while incidence with a Bessel beam provides movement on the longitudinal axis via the optical pulling force on the cylinder. Our design enables the selection of motion modes: pulling, pushing, and lateral movements (left-right, forward-backward) by adjusting the polarization or switching between plane wave and Bessel beam illuminations. Furthermore, we demonstrate that the optical pulling force achieved in our system is highly robust against rotations, translations and Brownian motion, furthering the versatility and practical applicability of our device. REFERENCES [1] J. Glückstad, Nat Mater 3(2004), 9–10. [2] Y. Y. Tanaka et al. Sci Adv 6(2020), eabc3726. [3] D. Ardrén et al. Nat Nanotechol 16(2021), 970-974. [4] X. Wu et al. Nat Nanotechol 17(2022), 477–484. [5] J. Chen et al. Nat Photonics. 5(2011), 531-534. [6] X. Li et al. Sci Adv 5(2019), eaau7814.
Nr: 81
Title:

Light-Controlled Nanomagnetic Logic (Invited)
Authors:

Paolo Vavassori, Yoav Urbina Elgueta, Matteo Menniti and Mikel Anzola
Abstract: Single-domain nanoscale magnets interacting via magnetostatic interactions are potentially key metamaterials to develop novel paradigms for versatile, low-power computation [1]. Examples include in-memory computing to circumvent the so-called van Neumann gap between data storage and data processing units on conventional chips and neuromorphic inspired probabilistic computation paradigms. Their properties and functionality are determined by the capability to reverse the moment of each nanomagnet to minimize the mutual dipolar interactions, which happens more quickly at elevated temperatures. As of today, thermal excitation of nanomagnetic logic networks is achieved by thermal contact to a hot reservoir (global heating). This approach is energetically inefficient, spatially non-discriminative, and intrinsically slow, with time scales of seconds. Furthermore, for implementation in devices of magnetic metamaterials, e.g., magnonic crystals and nanomagnetic logic circuits, global heating lacks the control, spatial discrimination, and speed required for integrated operation with CMOS technology. We propose and demonstrate an approach in which the nanomagnetic arrays are made of hybrid nanostructures that combine a plasmonic nano-heater with a magnetic element. We achieve the reliable and contactless plasmon-assisted optical heating of nanomagnets with a flexible control of length (down to the micrometer) and time (down to sub-ns) scales of the thermal excitation [2]. Furthermore, the polarization-dependent absorption cross section of elongated plasmonic elements enables selective heating of a desired subset of nanomagnets within the illuminated area depending on their in-plane, which is not possible with conventional heating schemes [3]. This provides the spatial discrimination and speed required for their integration with CMOS technology. Furthermore, the here presented concept of plasmon-assisted optical heating offers powerful prospects for novel functionalities and applications in the fields of magneto-calorics, spintronics, magnonics. [1] H. Arava, N. Leo, D. Schildknecht, J. Cui, J. Vijayakumar, P. M. Derlet, A. Kleibert, and L. J. Heyderman, “Engineering Relaxation Pathways in Building Blocks of Artificial Spin Ice for Computation”, Phys. Rev. Applied 11, 054086 ( 2019). [2] M. Pancaldi, N. Leo, and P. Vavassori, “Selective and fast plasmon-assisted photo-heating of nanomagnets”, Nanoscale 11, 7656–7666, (2019). [3] P. Gypens, N. Leo, M. Menniti, P. Vavassori and J. Leliaert, “Thermoplasmonic nanomagnetic logic gates”, Phys. Rev. Applied 18, 024014 (2022); selected as Editors' suggestion.
Nr: 82
Title:

Photothermal Response of DNA-Au Core/Shell Toroidal Nanostructures: Insights into Design and Performance in the Context of Advanced Therapies (Invited)
Authors:

Javier González-Colsa, Anton Kuzyk and Pablo Albella
Abstract: Toroid-like nanostructures have emerged as promising candidates for photothermal applications due to their thermal performance, spectral tunability and versatility [1,2]. In recent numerical investigations we revealed that toroidal gold nanoparticles achieve temperatures higher than alternative geometries, such as nanodisks or rods, while maintaining rotational tolerance and large heating areas ideal for biomedical applications [3]. The challenges associated with fabricating such structures motivated us to explore alternative approaches inspired by the DNA-origami philosophy, which offers the tools needed for their potential production [4]. Recently, we computationally explored DNA/Au core-shell toroids, demonstrating their significant advantages over solid counterparts [5]. These structures exhibit superior temperature increases and optimal resonance within the NIR-II therapeutic window, enabling deeper tissue penetration and enhanced efficacy in photothermal therapy. Our findings emphasized the importance of the experimental parameters, such as asymmetric gold growth and surface roughness, on the photothermal response. While ensuring at least 80% surface coverage is critical for achieving the thermal performance of a continuous shell, the results reveal that a perfectly connected surface is not strictly necessary to generate a toroidal resonance. Additionally, the high stability and minimal thermal variation due to nanoparticle rotations further validate their potential for diverse applications beyond the NIR regions. This work establishes core-shell toroidal nanostructures as innovative platforms for targeted heating, with promising implications for cancer therapy and other biomedical fields. References [1] Javier González-Colsa; Guillermo Serrera; Jose Maria Saiz; Dolores Ortiz;Francisco González; Fernando Bresme; Fernando Moreno; Pablo Albella. Gold Nanodoughnut as an Outstanding Nanoheater for Photothermal Applications. OptExpress 2022, 30(1), 125. [2] Javier González-Colsa; Juan D. Olarte-Plata; Fernando Bresme; Pablo Albella. Enhanced Thermo-Optical Response by Means of Anapole Excitation. J.Phys.Chem.Lett. 2022, 13(26), 6230−6235. [3] Javier González-Colsa; Alfredo Franco; Fernando Bresme; Fernando Moreno; Pablo Albella. Janus-Nanojet as an Efficient Asymmetric Photothermal Source. Sci.Rep 2022, 12(1), 14222. [4] Anton Kuzyk; Roman Schreiber; Zhiwei Fan; et al. DNA-based self-assembly of chiral plasmonic nanostructures with tailored optical response. Nature 2012, 483, 311–314. [5] Javier González-Colsa; Anton Kuzyk; Pablo Albella. On the photothermal response of DNA–Au core/shell nanotoroids as potential agents for photothermal therapies. Small Structures 2024, 2300523.
Nr: 83
Title:

Nonlinear Generation of Orbital Angular Momentum in Metasurfaces (Invited)
Authors:

Giuseppe Leo
Abstract: We report on the generation of high-purity second harmonic (SH) optical vortices via dielectric meta-holograms. Through full-wave simulations and a fabrication based on AlGaAs pillars on an AlOx substrate,3 we achieve efficient SHG from an unstructured pump beam into SH vortices with topological charges from 1 to 10 (see Fig. 1). Interferometric and modal-purity measurements confirm the SHG of high-quality vortices with minimal deviations from the intended design thanks to a quasi-local control over the SH phase. Through systematic comparisons between experimental data and semi-analytical calculations, we also provide a clear insight into the occurrence of ghost vortices in the metasurface-generated harmonic beams, highlighting the importance of simple designs that can be readily transposed into fabricated devices with high fidelity. Our findings underscore the potential of nonlinear dielectric metasurfaces for versatile structured-light generation and manipulation, paving the way for future developments in integrated photonic systems.
Nr: 84
Title:

Direct Computation of Fundamental Photonic Resonance Modes in Dense Spectra (Invited)
Authors:

Sven Burger, Felix Binkowski, Fridtjof Betz, Martin Hammerschmidt and Lin Zschiedrich
Abstract: Resonances are essential for understanding interactions between light and matter in photonic systems. We discuss a framework based on AAA rational approximation for determining resonance frequencies and modes, as well as complete modal expansions. Hollow core photonic crystal fibers are investigated as an example where fundamental modes are embedded in a dense spectrum of further modes, such as cladding modes. The framework is adapted such that the fundamental modes of interest are directly computed, i.e., such that mode filtering is not required. The framework further allows for automatic differentiation as well as for straight-forward treatment of material systems with complex material dispersions. [F. Betz, et al., Laser Photonics Rev. 18, 2400584 (2024)] [F. Binkowski, et al., in preparation (2024)] [F. Binkowski, et al., Phys. Rev. Research 6, 023148 (2024)] [F. Binkowski, et al., Commun. Phys. 5, 202 (2022)].
Nr: 85
Title:

Design and Realization of Dielectric Highly Reflective Metasurfaces
Authors:

Mariia Matiushechkina, Andrey Evlyukhin, Boris Chichkov and Michèle Heurs
Abstract: The research focuses on the realization process of highly reflective silicon metasurfaces on a sapphire substrate at a selected wavelength. The principles of Mie scattering allow the selection of appropriate nanoparticle dimensions to create destructive interference in the direction of propagation, resulting in effective high reflectivity. Our investigation aims at developing mirror coatings with nanometer-scale thickness, specifically for 1064 nm or 1550 nm wavelengths, which have potential applications in the field of gravitational wave physics. Beginning with a theoretical approach supported by numerical simulations, we demonstrate how to determine the optimal parameters for the metasurface configuration. We discuss the key aspects of fabrication and conclude with the characterization results of the metasurface reflectivity. Our findings show that the experimental outcomes agree well with the theoretical predictions. The research is supported by our recent publications: 1. M. Matiushechkina, A. B. Evlyukhin, V. A. Zenin, B. N. Chichkov and M. Heurs. ‘Perfect mirror effects in metasurfaces of silicon nanodisks at telecom wavelength’. Advanced Optical Materials 12.18 (April 2024), p. 2400191. DOI:10.1002/adom.202400191. 2. M. Matiushechkina, A. B. Evlyukhin, R. Malureanu, V. A. Zenin, T. Yezekyan, A. Lavrinenko, S. I. Bozhevolnyi, B. N. Chichkov and M. Heurs. ‘Design and experimental demonstration of wavelength-selective metamirrors on sapphire substrates’. Advanced Photonics Research 2400116 (November 2024). DOI: 10.1002/adpr.202400116.
Nr: 86
Title:

Reconfigurable Plasmonics Enabled by Phase Change Materials (Invited)
Authors:

Yael Gutierrez, Gonzalo Santos, Capucine Laprais, Lofti Berguiga, Saul Vázquez-Miranda, Shirly Espinoza, Fernando Moreno and Maria Losurdo
Abstract: The dynamic modulation of the optical response in plasmonic systems through optical, mechanical, and electrical stimuli is pivotal for advancing nanophotonic applications, including optical switches, modulators, reconfigurable antennas, LIDAR systems, and photonic integrated circuits. In this work, we present an innovative approach to achieve tunable plasmonic properties by integrating phase-change materials (PCMs) with plasmonic structures. We investigate the dynamic plasmonic response of low-loss PCMs coupled with gold (Au) and gallium (Ga) plasmonic gratings and nanoparticles (NPs). Our study encompasses active systems ranging from periodic gratings to hybrid core-shell PCM-plasmonic nanoparticles, exhibiting tunability across a broad spectral range from UV-VIS to IR. These active heterostructures enable spectral tuning of the optical response—traditionally fixed during fabrication—through the reversible phase transitions of the PCM layer. We demonstrate the reversible and tunable plasmonic response of these heterostructures via controlled, low-energy thermal and laser-induced amorphous-to-crystalline (and reverse) phase transitions in the PCM. Finally, we showcase potential applications of these dynamic plasmonic structures in optical switches, light modulators, broadband plasmonically enhanced photodetectors, and switchable scattering nanoantennas, highlighting their versatility and technological potential.
Nr: 88
Title:

Nanoparticle-on-Mirror Active Plasmonic Surfaces (Invited)
Authors:

Anton Kuzyk, Mohammed Al Hussain, Abraham Kipnis, Kosti Tuomas Olavi Tapio, Sesha Manuguri, Xuan Pham and Arri Priimägi
Abstract: Nanoparticle-on-mirror (NPoM) plasmonic surfaces (PS) exhibit rich ensemble of interesting optical properties, e.g., strong field enhancement and vivid structural colors [1]. NPoM plasmonic systems can be easily fabricated via the drop-casting method and their optical responses can be tailored by the size and material composition of NPs and/or thickness of a spacer between the NP and the metal film. Despite the ease of fabrication, implementing active tunability of optical responses in NPoM PS has remained challenging. We have recently developed two novel approaches for controlling and modulating optical responses of NPoM PS using light and electric field as external stimuli. For the light-based control of optical responses in NPoM PS we utilize unique photoplasticity properties of azobenzene containing materials. In this approach the distance and, hence, coupling between the metal NPs and metal film can be precisely tuned with light exposure, which enables creation of PS with complex multicolour patterns. For the electric field modulation of optical responses in NPoM PS we utilize NP attached to metal film with flexible DNA linkers. In this approach the metal NPs-film distance and coupling are controlled by the electric potential of the metal film and the optical responses of NPoM PS, e.g., reflectivity, can be reversibly modulated at frequencies up to 100 Hz. Both approaches enable fabrication of novel active nanoparticle-on-mirror plasmonic surfaces with tailored functionalities. The ability to create complex patterns of plasmonic colors with simple light illumination has potential for development of new methodologies for NPoM PS-based anti-counterfeit applications. Electrically driven plasmonic surface, on the other hand, is an example of novel, lithography free approach to fabrication of active plasmonic surface with strong and reversible modulation of optical responses. [1] Moreau, A.; Ciracì, C.; Mock, J. J.; Hill, R. T.; Wang, Q.; Wiley, B. J.; Chilkoti, A.; Smith, D. R. Controlled-Reflectance Surfaces with Film-Coupled Colloidal Nanoantennas. Nature 2012, 492 (7427), 86–89.
Nr: 89
Title:

Impact of Hybrid Nanoparticle Aggregation on Optical Response, Heat Generation, and MRI Contrast
Authors:

Cédric Adelson Bernard Georges Rousseau, Gilles Rosolen, Bjorn Maes, Yves Gossuin and Quoc Lam Vuong
Abstract: Superparamagnetic iron oxide nanoparticles are utilized in magnetic resonance imaging (MRI) to improve image contrast, by modifying a key MRI parameter, the transverse relaxation rate (R2). Coating these nanoparticles with a gold shell enables their transformation into nanoparticles capable of plasmonic excitation. This excitation induces a collective oscillation of electrons within the nanoparticle, generating heat via the Joule effect. When the temperature rises by approximately 5 degrees Celsius, cancer cells can be destroyed, a technique known as phototherapy. Hybrid nanoparticles, consisting of an iron oxide core and a gold shell, can thus be employed in a theranostic approach that integrates diagnostic and therapeutic functions. In a recent paper, we conducted the numerical optimization of an ideal system composed of these hybrid nanoparticles. We observed a modification of R2 relaxation rate under laser illumination, and we showed that such nanoparticles could theoretically allow real-time monitoring, by MRI, of the heat generated by the laser illumination [1]. However, once injected into the patient, these particles are internalized into cells and can undergo significant aggregation. Therefore, in our new work, we are investigating the effect of this aggregation on the optical response of these nanoparticles, their heat generation, and their R2 response. We demonstrate that two optical effects occur for these nanoparticles when a high level of aggregation is considered: optical shielding and a shift in the resonance wavelength. From a heat generation perspective, there is an optimal level of nanoparticle aggregation. Our study also reveals that aggregation significantly modifies the transverse relaxation induced by the particles after laser illumination. [1] C. Rousseau, Q. L. Vuong, Y. Gossuin, B. Maes, et G. Rosolen, « Concurrent photothermal therapy and nuclear magnetic resonance imaging with plasmonic–magnetic nanoparticles: A numerical study », Computer Methods and Programs in Biomedicine, vol. 257, p. 108453, 2024.
Nr: 90
Title:

Lattice Resonances in Complex Periodic Arrays (Invited)
Authors:

Alejandro Manjavacas
Abstract: Two-dimensional periodic arrays of metallic nanostructures can support collective optical modes known as lattice resonances. These excitations occur at wavelengths commensurate with the periodicity of the array and give rise to very strong and spectrally narrow optical responses. Thanks to these exceptional properties, periodic arrays are being exploited in a wide variety of applications, including ultrasensitive biosensing, nanoscale light emission, and color printing, to cite a few. In this talk, we will discuss some recent theoretical advances on the topic of lattice resonances. In particular, we will explain how the interplay between the response of the individual constituents of the array and their collective interaction determines the ultimate limits of the near-field enhancement provided by lattice resonances as well as their quality factor. We will also discuss the response of arrays with multi-particle unit cells using an analytical approach based on hybridization theory, which provides a simple and efficient way to design periodic arrays with engineered properties. Furthermore, we will explore how the response of a periodic array is affected by the characteristics of the source used to excite it. Finally, we will analyze different array geometries that support lattice resonances with extraordinary properties such as perfect circular dichroism and perfect absorption.
Nr: 91
Title:

Surface-Enhanced Raman Spectroscopy for Characterization of Intramolecular Vibrational Redistribution at the Single-Molecule Level (Invited)
Authors:

Aurelian Loirette-Pelous, Roberto A. Boto, Javier Aizpurua and Ruben Esteban
Abstract: Intramolecular Vibrational energy Redistribution (IVR) refers to the exchange processes between vibrational modes by which an excited molecule relaxes back to equilibrium. IVR plays a pivotal role in chemistry, as the energy flow inside molecules determines the outcome of chemical reactions [1]. Hence, accurate identification and quantification of IVR channels could be an important step toward precise control over chemical reactivity, a long-sought goal in chemistry. Several pump-probe techniques have been developed to characterize IVR [2]. However, most of them are only suited to study large molecular ensembles. On the other hand, a well-established method for the detection of a few or even a single molecule is Surface-Enhanced Raman Spectroscopy (SERS), and this technique has been used recently to improve the sensitivity of IVR measurements [3-5]. However, measuring IVR with SERS is more difficult than detecting Raman lines, as it also involves probing vibrational populations. Hence, accurate characterization of IVR with SERS at the few-molecules level remains difficult and likely requires further developments to become a widely used technique. Here, we present a cavity quantum electrodynamical model based on molecular optomechanics [6], which accounts both for SERS and IVR, and we use this model to analyze strategies to improve IVR characterization. In particular, we consider pump-probe schemes that pump the vibrational modes of a single molecule by either infrared illumination or by Stokes SERS, and probe the vibrational populations by incoherent anti-Stokes SERS. As a prototypical intramolecular redistribution process, we focus on a Fermi resonance that couples the overtone of a vibrational mode and the fundamental of a second mode. For the two pumping configurations, we study the spectral signatures of population transfer between the pumped vibrational mode and the other mode. We observe that pumping with continuous-wave infrared light enables accurate identification of the IVR pathways, while pumping with pulsed Stokes SERS enables to track the redistribution dynamics efficiently. Finally, given the realistic molecular and SERS parameters used, our results show that these signatures of IVR are likely to be accessible at the single-molecule level with current experimental platforms. REFERENCES [1] M. Gruebele and P. G. Wolynes, Accounts of Chemical Research 37, 261 (2004). [2] M. D. Fayer, Ultrafast infrared vibrational spectroscopy (CRC Press, 2013). [3] R. R. Frontiera et al., The Journal of Physical Chemistry Letters 2, 1199 (2011). [4] S. Yampolsky et al., Nature Photonics 8, 650 (2014). [5] L. A. Jakob et al., Physical Review B 109, 195404 (2024) [6] R. Esteban, J. J. Baumberg, and J. Aizpurua, Accounts of Chemical Research 55, 1889 (2022).
Nr: 92
Title:

Fluorescence-Based Chiral Sensing with Silicon Metasurfaces (Invited)
Authors:

Alberto Curto
Abstract: Chirality is omnipresent in biochemistry, where molecules with opposite handedness can have markedly different biological functionalities. Detecting molecular chirality is, however, plagued by low sensitivity, limiting the possible use cases to high concentrations and large volumes. Here, we use silicon nanophotonic structures to create optical resonances of electric and magnetic dipole origin to strongly enhance the sensitivity of chiral molecular detection in small volumes. We also demonstrate a new polarization-modulation microscope built to push the limits of chiral sensing using fluorescence.
Nr: 95
Title:

Single-Molecule Fluorescence Microscopy Reveals that Hot Charge Carriers Mediate Tip-Selective Thiol Cleavage of Gold Nanorods
Authors:

Martina Russo, Lorenzo Albertazzi, Peter Zijlstra and Kees Flipse
Abstract: Plasmonic nanoparticles have become an innovative tool for driving chemical reactions at their surface, selectively affecting molecular adsorbates and thus offering control at the nanometer scale. The key processes that trigger chemical reactions at the particle's interface are two nonradiative decay pathways of photoexcited charge carriers, namely their decay into hot charge carriers or photothermal heat. The capability to drive interfacial chemistry has revolutionized the field of catalysis and plasmon-assisted surface chemistry, with applications ranging from photovoltaics to nanomedicine, while also providing deeper insights into the relaxation pathways of the excited gold electrons and a limited understanding of photothermal and hot-carrier chemical processes. Here, we study the cleavage of the Au-S bond using DNA-functionalized nanoparticles [1]. We quantify the DNA desorption at the single-particle level using DNA points accumulation for imaging nanoscale topography (DNA-PAINT) microscopy. Such single-molecule microscopy directly reveals changes in the number of DNA strands on each particle through the frequency of binding events with a complementary fluorescent probe. Surprisingly, we find efficient Au-S cleavage using continuous wave laser excitation at 532 nm, thereby eliminating the need for femtosecond pulsed lasers. Varying the excitation wavelength suggests a d-band-holes driven cleavage process mediated by interband transitions [2]. To rule out any contribution from photothermal heating we monitor the nanoparticle temperature in real time using optical phase imaging [3]. Our studies reveal that the cleavage of the Au-S bond is enhanced at the tips of the particles, irrespective of the illumination polarization. This indicates a directional and anisotropic nature in the generation and transfer efficiency of hot-charge carriers and confirming that the reactive hot spots for d-band holes are primarily located at the nanorod tips [4]. We apply this novel concept to achieve site-selective functionalization of single particles. We illustrate the potential of this process for biosensing by specifically functionalizing the tips of particles with DNA and protein through a cycle of sequential cleavage and refunctionalization. Our work enables regioselective functionalization for any thiol-conjugated capture probe and paves the way to a novel platform for single-molecule biosensing applications, with simultaneous and real-time temperature monitoring at the nanoscale level. REFERENCES 1. Martina Russo, Lorenzo Albertazzi, Kees Flipse and Peter Zijlstra. Single-molecule fluorescence microscopy reveals that hot charge carriers mediate tip-selective thiol cleavage of gold nanorods (Manuscript in preparation) (2024). 2. Rifat Kamarudheen et al., ACS Energy Letters 5, 2605-2613 (2020). 3. Guillame Baffou et al., ACS Nano 6, 2452-2458 (2012). 4. Alexander Al-Zubeidi et al., The J. ournal of Physical. Chemistry. Letters. 14, 5297-5304 (2023).
Nr: 96
Title:

DNA Origami Self-Assembled Optical Antennas for Single-Photon Chiral Emission (Invited)
Authors:

Guillermo Pedro Acuna
Abstract: In the realm of chirality, the helicity of photons, akin to the spins of electrons, holds promise for encoding information swiftly through the polarization of light in both classical and quantum computing. However, the development of a chiral single photon source remains a significant challenge due to the degeneracy of magnetic sublevels in achiral emitters. Here, we demonstrate the achievement of chiral single-photon sources made by a DNA templated trimer antenna (Figure 1) with C2v symmetry group, excited by an asymmetrically positioned achiral emitter without vector beam excitation. In this 2D configuration without inherent structural chirality, the antenna still exhibits chiral emission with a high degree of circular polarization (DCP), attributed to the presence of excited rotating orthogonal electric dipoles inside the structure.
Nr: 100
Title:

Optical Forces in Front of Epsilon-Near-Zero (ENZ) Metasurfaces (Invited)
Authors:

Maria Grazia Donato, Michael Hinczewski, Theodor Letsou, Mohammed El Kabbash, Francesco Patti, Rosalba Saija, Pietro G. Gucciardi, Nader Engheta, Onofrio M. Maragò and Giuseppe Strangi
Abstract: Optical tweezers [1] can be used to measure very tiny forces, in the order of few tens of fN, with a sensitivity one order of magnitude lower [2]. A micro- or nano-sized trapped particle can be used as a probe of the interaction forces in front of surfaces, obtaining an all-optical scanning-force microscope [3]. Recently, it has been demonstrated [4] that in front of Epsilon-Near-Zero (ENZ) metasurfaces a repulsive force is expected on a point dipole, reminding the Meissner effect in superconductors. Thus, both a theoretical and experimental study of the interaction forces between larger particles and ENZ metasurfaces is interesting. In this talk, we review the results [5] obtained by means of different theoretical approaches (dipole approximation, finite elements calculations, transition (T-)matrix), looking at the general features of the repulsive-attractive optomechanics of a range of complex particles (dielectric, core-shell, plasmonic ellipsoids), with size ranging from the nano to the microscale. In addition, we show the experimental results obtained by using photonic force microscopy to measure forces in front of dielectric, plasmonic and metamaterial surfaces. As a probe we use a dielectric bead in liquid environment, trapped by a tightly focused near IR laser beam. The axial position of the trapped particle is perturbed by a second pulsed laser in the visible. We observe that the optomechanics of the particle depends on the type of surface in front of which it is trapped. Moreover, in front of ENZ surface a dependence on the wavelength of the probing beam is observed. The possible origin of these behavior is also discussed. Acknowledgement. Funding by European Union (NextGeneration EU), through the project PRIN2022 "EnantioSelex – Mapping and controlling nanoscale optomechanical forces for separation of chiral analytes" (grant number 2022P9F79R) is gratefully acknowledged. [1] A. Ashkin, “Acceleration and trapping of particles by radiation pressure,” Phys. Rev. Lett., vol. 24, pp. 156, 1970. [2] O. M. Maragò, P. H. Jones, P. G. Gucciardi, G. Volpe, and A. C. Ferrari, “Optical trapping and manipulation of nanostructures,” Nature Nanotechnol., vol. 8, pp. 807, 2013. [3] L. P. Ghislain and W. W. Webb, “Scanning–force microscope based on an optical trap,” Opt. Lett., vol. 18, pp. 1678–1680, 1993 [4] F. J. Rodríguez-Fortuño, A. Vakil, and N. Engheta, “Electric levitation using epsilon-near-zero metamaterials,” Physical Review Letters, vol. 112, no. 3, p. 033902, 2014 [5] Y. Kiasat, M. G. Donato, M. Hinczewski, M. ElKabbash, T. Letsou, R. Saija, O. M. Maragò, G. Strangi, and N. Engheta, “Epsilon-near-zero (ENZ)-based optomechanics,” Communications Physics, vol. 6, no. 1, p. 69, 2023.
Nr: 102
Title:

Quantum State Preparation with Nanophotonics Tools (Invited)
Authors:

Antonio I. Fernandez Dominguez
Abstract: In this talk, I will present two different nanophotonics-based strategies to generate pure states of quantum emitters. First, I will investigate the creation of highly entangled multiqubit states through the inverse engineering of their photonic environment under incoherent [1] and coherent pumping conditions [2]. Second, I will show the capabilities of modulated electron beams for the preparation and readout of the quantum state of single emitters [3] and polaritonic systems [4]. [1] A. Miguel-Torcal et al. Nanophotonics 11, 4387 (2022). [2] A. Miguel-Torcal et al. Optica Quantum 5, 371-378 (2024). [3] J. Abad-Arredondo and A. I. Fernández-Domínguez, Nanophotonics 13, 2015-2027 (2024). [4] J. Abad-Arredondo and A. I. Fernández-Domínguez, arXiv:2407.17885 (2024).
Nr: 104
Title:

Directional Chiral Emission from Quasi-BICs and Surface Modes in Silicon Metasurfaces (Invited)
Authors:

Jaime Gomez Rivas, Minpeng Liang, Lucio Andreani, Jose L. Pura, Jose Antonio Sanchez-Gil, Beatriz Castillo López de Larrinzar and Antonio Garcia-Martin
Abstract: We present an approach to achieving directional chiral emission by coupling achiral dye molecules with metasurfaces that exhibit extrinsic chiral quasi-bound states in the continuum (Q-BICs). These metasurfaces, composed of silicon nanodisks and nanorod dimers, utilize tailored detuning of geometric parameters, such as size and relative positioning, to break symmetry and induce optical chirality. The resulting Q-BICs maintain high-quality factors (Q-factors) and provide a platform for significantly enhancing chiral light–matter interactions. Through finite-element simulations and guided-mode expansion analysis, we identify and characterize the dispersion and near-field properties of these Q-BICs. Experimentally, the metasurfaces enable circularly polarized, highly directional photoluminescence (PL) from the achiral dye molecules. Remarkably, the degree of circular polarization (DCP) reaches values as high as 0.8, with a divergence angle of approximately 2°. These results are achieved without relying on intrinsically chiral emitters, making the design highly versatile and applicable to a broad range of optoelectronic systems. Furthermore, tuning the lattice constants of the metasurfaces alters the dispersion of Q-BICs, allowing for precise control of emission directionality and wavelength. This tunability, combined with the metasurfaces’ ability to enhance photoluminescence by up to 13 times, highlights their potential in advanced photonic applications, such as optical communication, displays, and sensing. The integration of symmetry-broken metasurfaces with achiral molecular emitters offers a transformative approach to creating highly directional and polarized light sources, addressing critical needs in photonics.
Nr: 105
Title:

Analog Image Processing with Nonlinear Flat Optics (Invited)
Authors:

Costantino De Angelis
Abstract: Digital signal processing has revolutionized many fields of science and engineering, but it still shows critical limits; a long-sought solution is optical analog computing. We demonstrate here that nonlinear phenomena combined with engineered nonlocality in flat optics can be leveraged to synthesize Volterra kernels able to outperform linear devices.
Nr: 107
Title:

Optical Trapping Using Laguerre Gaussian Modes with Well Defined Helicity (Invited)
Authors:

Gabriel Molina-Terriza and Iker Gomez-Viloria
Abstract: Optical trapping has become a technique ubiquitous in many areas of Science and Technology. It has applications in the fields of biophysics, micromotors and optical engineering. It also serves as a tool to study statistical physics out of the equilibrium, non-conservative forces and more recently it has become a toolbox for the study of quantum phenomena in mesoscopic systems. However, the optical trapping and manipulation of large particles, i.e. those whith an optical size of the order of the wavelength or larger, is rather limited. On the one hand, these particles scatter light very efficiently, therefore small differences in wavelength or optical size can result in very different forces. On the other hand, the typical approximations used for small particles (dipolar or Rayleigh regime), or the ones used for very large particles (ray optics or geometrical regime) cannot be applied and one has to resort to the full solution given by Maxwell equations to theoretically understand this regime. This is the so-called Mie regime, because it can be analytically solved used the Lorentz-Mie theory for the scattering of light with spherical particles. In a recent publication we have make a significant advance in this regime. First, we have been able to experimentally trap particles using structured light. We have used several optical modes with well defined angular momentum and helicity. These modes are first prepared in the paraxial regime using Spatial Light Modulators and polarization waveplates. Afterward, we highly focus those modes with a high Numerical Aperture microscope objective onto our samples. We have observed that these modes can achieve higher forces than the usual Gaussian modes. Then, we have complemented our experimental results with a full theoretical model of the scattering of these light modes by the large particles. This theoretical model allowed us to better understand the physics of optical trapping in this regime and also to effciently numerically simulate the behaviour of these particles. We acknowledge support from CSIC Research Platform on Quantum Technologies PTI-001, from IKUR Strategy under the collaboration agreement between Ikerbasque Foundation and DIPC/MPC on behalf of the Department of Education of the Basque Government and from the project PID2022-143268NB-100 of Ministerio de Ciencia.
Nr: 108
Title:

Strain-Induced Exciton Transfer Among Quantum Emitters in WSe2 Monolayers (Invited)
Authors:

Javier Martín-Sánchez
Abstract: The discovery of quantum emitters (QEs) in two-dimensional materials (2D) has triggered a surge of research to assess their suitability for quantum photonics [1]. The microscopic origin of such emitters is still the subject of intense studies, which constraints the possibility of a deliberate fabrication of identical quantum emitters. Nevertheless, it is widely assumed that their formation is intimately linked to the presence of local strain fields and defects in the 2D crystals. Moreover, position-controlled QEs are routinely fabricated using static strain gradients, which are used to drive excitons towards localized regions of the crystal where quantum light emission takes place [2]. In this work, we introduce a novel hybrid semiconductor piezoelectric device in which WSe2 monolayers are integrated onto piezoelectric pillars that provide both static and dynamic strains. The static strains are first used to induce the formation of QEs, whose emission shows photon anti-bunching. Their energy and brightness are then controlled via the application of voltages to the piezoelectric pillars. Numerical simulations combined with drift-diffusion equations show that these effects are due to a strain-induced modification of the confining-potential landscape, which in turn leads to a net redistribution of excitons among the different QEs. Our work provides a method to dynamically control the brightness of single photon sources based on 2D materials [3]. [1] Y.-M. He et al. Nat. Nanotechnol., 10, 497 (2015) ; P. Tonndorf et al., Optica, 2, 347 (2015). A. Srivastava et al., Nat. Nanotechnol., 10, 491 (2015). [2] A. Branny et al., Nat. Commun., 8, 15053 (2017) ; C. Palacios-Berraquero et al., Nat. Commun., 8, 15093 (2017). [3] G. Ronco et al., arXiv:2301.10273
Nr: 113
Title:

The Role of Interfacial Thermal Conductance in the Photothermal Response of Asymmetric Nanoheating Systems Under Pulsed Illumination (Invited)
Authors:

Pablo Albella, Javier González-Colsa and Fernando Bresme
Abstract: Metallic nanoparticles exhibit the capability to convert optical energy into heat through resistive losses [1-2]. While this characteristic is generally considered undesirable in applications such as biosensing and spectroscopy, it can be strategically harnessed in applications like cancer therapy, where the generation of efficient localized heat at the nanoscale, referred to as nanoheaters, is essential. Single-material plasmonic nanoheaters have been extensively utilized in tumor ablation; however, they often function as highly homogeneous heat sources, leading to isotropic heating of the surrounding biological medium [3-4]. This non-selective heating can have detrimental effects on both cancerous and healthy cells. In the first section of this presentation, I will show how plasmonic Janus nanoheaters (JNs) exhibit exceptional directional heat generation and release under continuous wave excitation [4-5]. Despite this, photothermal therapies typically employ pulsed light sources. In the second section, I will focus on the influence of interfacial thermal conductance (ITC) on the transient thermal dynamics, including heating and cooling processes, under nanosecond-pulsed illumination. References [1] A. O. Govorov, H. H. Richardson. Generating heat with metal nanoparticles. Nano Today 2007, 2 (1), 30–38. [2] G. Baffou, R. Quidant and F. J. García De Abajo. Nanoscale Control of Optical Heating in Complex Plasmonic Systems. ACS Nano 2010, 4 (2), 709–716. [3] J. González-Colsa, Guillermo Serrera, Jose M. Saiz; D. Ortiz, F. González, F. Bresme, F. Moreno and P. Albella. Gold Nanodoughnut as an Outstanding Nanoheater for Photothermal Applications. Optics Express 2022, 30(1), 125. [4] J. González-Colsa, A. Franco, F. Bresme, F. Moreno and P. Albella. Janus-Nanojet as an Efficient Asymmetric Photothermal Source. Sci.Rep 2022, 12(1), 14222. [5] J. González-Colsa, F. Bresme and P. Albella. Impact of the interfacial thermal conductance on the thermoplasmonic response of metal/polymer hybrid nanoparticles under nanosecond pulsed illumination. J. Phys. Chem. C 2023, 127, 38, 19152.
Nr: 114
Title:

Positioning Single Photon Emitters on Nanodevices (Invited)
Authors:

Josep Canet-Ferrer
Abstract: The positioning of single photon emitters has become a key issue for the development of Further and Emerging technologies. Either embedded into a photonic crystal cavity or touching a plasmonic nanoantenna single photon emitters are expected to exhibit a bright emission of quantum light. This explains the huge effort in the development of techniques for the positioning of quantum emitters, with tenths of successful approaches in literature. However, positioning the single photon emitter into an optical mode only solves half of the problems and spectral and polarization tuning much be also achieved. In this presentation I will introduce a new nanopositioning method able to locate a quantum emitter the surroundings of different kind of devices. Then, I will show few examples showing the advantages of our method for applications in nanophotonics, magnetism and sensing. I will conclude with a discussion of the pros and cons of this new method with previous results in literature.
Nr: 116
Title:

Photoluminescence from Metals: Theory and Experiments (Invited)
Authors:

Yonatan Sivan
Abstract: We provide a simple quantitative analytical expression describing photoluminescence from metals, show that it yields essentially the same predictions as a full scale discrete quantum mechanical calculation, and use it to explain seemingly contradicting experimental measurements. We provide a complete quantitative theory for the important, 50-year old, yet unresolved problem of photoluminescence from metals [1]. Indeed, the countless previous experimental works revealed disagreements on a long series of fundamental aspects associated with this emission. These were not accompanied by a complete theory because the poor understanding of the hard-to-calculate electron non-equilibrium distribution under illumination, as well as the absence of a description of the uncorrelated emissions from a macroscopic object. Based on our recently derived steady-state non-equilibrium quantum electron distribution in metals [2], we first computed numerically and analytically in [3] the local emission spectra from an excited metal illuminated by CW illumination. This solution reveals the (polynomial) dependence of the metal emission on the electric field and the exponential dependence of the latter on the electron temperature. Further, we resolve the arguments associated with the emission statistics, showing that it is primarily a non-thermal (“hot”) electron effect giving rise to a series of bosonic-like emission terms, and show that the emission manifests the electron rather than lattice temperature. Then, we show how Pelous-Loirette and Greffet [4] extended the famous Fluctuation-Dissipation Theorem to non-equilibrium electron systems and use their expression to describe the overall (rather than local) emission from metal spheres and layers of various sizes; this expression requires knowledge only of the local electric field and the temperature. We then show that our predictions match nicely a series of experimental results for structures even more complicated than those we studied. Remarkably, our simple one-line theory shows an excellent match to the lengthy fully rigorous discrete k-space quantum mechanical calculation of the emission described in [5] by using the well known quantum-size correction to the imaginary part of the permittivity [6]. Our approach thus provides a simple way to determine the PL from complex nanostructures, and establishes a trivial link to the huge body of thermal emission engineering. Finally, I will review the remaining open questions, e.g., the role of interband transitions, PL from systems under strong non-uniform illumination and the reconciliation with inelastic light emission approaches.
Nr: 117
Title:

Unidirectional Ray Polaritons in Twisted Asymmetric Stacks
Authors:

José Álvarez-Cuervo
Abstract: The emergence of a vast repository of van der Waals (vdW) materials supporting polaritons – light coupled to matter excitations – offers a plethora of different possibilities to tailor electromagnetic waves at the subwavelength-scale [1]. In particular, the development of twistoptics – the study of the optical properties of twisted stacks of vdW materials – allows the directional propagation of phonon polaritons (PhPs) along a single spatial direction, which has been coined as canalization [2,3]. Here we demonstrate a complementary type of nanoscale unidirectional propagation that naturally emerges thanks to twistoptics: unidirectional ray polaritons (URPs). [4] This natural phenomenon arises in two types of twisted hyperbolic stacks: homostructures of α-MoO3 and heterostructures of α-MoO3 and β-Ga2O3, each with very different thicknesses of its constituents. URPs are characterized by the absence of diffraction and the presence of a single phase of the propagating field. Importantly, we demonstrate that this ray behavior can be tuned by means of both relative twist angle and illumination frequency variations. Additionally, an unprecedented “pinwheel-like” propagation emerges at specific twist angles of the homostructure. We show that URPs emerge due to the twist between asymmetrically stacked biaxial slabs, while the shear effect in monoclinic β-Ga2O3 is of minor importance. Our findings demonstrate a natural way to excite unidirectional ray PhPs and offer a unique platform for controlling the propagation of PhPs at the nanoscale with many potential applications like nanoimaging, (bio)-sensing or polaritonic thermal management. References [1]Ma, W.; Alonso-González, P.; Li, S.; et al. Nature, 562, 557−562. (2018) [2]Duan, J.; et al. Nano Letters, 20, 5323–5329. (2020) [3]Chen, M.; et al. Nature Materials, 19, 1307−1311. (2020) [4]Álvarez-Cuervo, J.; et. al. Nature Communications, 15, 9042. (2024).
Nr: 118
Title:

Real-Space Visualization of Canalized Ray Polaritons in a Single van der Waals Thin Slab
Authors:

Enrique Terán-García
Abstract: Polaritons -- hybrid light-matter excitations [1] -- are central to the development of nanophotonics, as they provide mechanisms for manipulating light at the nanoscale. A key advancement has been the demonstration of polariton canalization [2-4] in which the energy flow is directed along a single direction. An intriguing case is the canalization of ray polaritons [5], characterized by an enhanced density of optical states. Experimental demonstrations of ray polaritons are scarce and their observation in single crystal slabs remains elusive. Here [6], we propose a novel polaritonic platform based on single thin slabs allowing for the excitation of canalized ray polaritons. By performing near-field nanoimaging, we demonstrate that the necessary conditions for their observation (a synergistic combination of large material permittivity modulus and dielectric environment) are fulfilled for phonon-polaritons at mid-IR frequencies in thin $\alpha$-MoO3 slabs on SiO2 substrates. Our real-space images reveal the propagation of unidirectional phonon-polaritons exhibiting a constant propagating phase. These results might impact the development of compact, low-loss optical nanodevices for applications requiring strong light directionality. References [1] Ma, W.; Alonso-González, P.; et al., Nature 562, 557–562 (2018). [2] Duan, J.; et al., Nano Lett. 20, 7, 5323-5329 (2020). [3] Duan, J.; et al., Nat. Mater. 22, 867–872 (2023). [4] F. Tresguerres-Mata, A.I.; et al., Nat Commun. 15, 2696 (2024). [5] Álvarez-Cuervo, J.; et al., Nat Commun 15, 9042 (2024). [6] Terán-García, E.; et al. Real-space visualization of Canalized Ray Polaritons in a single van der Waals Thin Slab, Nano Lett. (2025) DOI: https://doi.org/10.1021/acs.nanolett.4c05277. References [1] Ma, W.; Alonso-González, P.; et al., Nature 562, 557–562 (2018). [2] Duan, J.; et al., Nano Lett. 20, 7, 5323-5329 (2020). [3] Duan, J.; et al., Nat. Mater. 22, 867–872 (2023). [4] F. Tresguerres-Mata, A.I.; et al., Nat Commun. 15, 2696 (2024). [5] Álvarez-Cuervo, J.; et al., Nat Commun 15, 9042 (2024). [6] Terán-García, E.; et al. Real-space visualization of Canalized Ray Polaritons in a single van der Waals Thin Slab, Nano Lett. (2025) DOI: https://doi.org/10.1021/acs.nanolett.4c05277.