NanoPlasMeta 2024 Abstracts

Area 1 - Nanophotonics, Plasmonics and Metamaterials

Area 1 - Nanophotonics, Plasmonics and Metamaterials

Nr: 16
Title:

Observation of DNA Strand Interaction with SERS (Invited)
Authors:

Marc Lamy de La Chapelle, Aicha Azziz, Marjan Majdinasab, Célia Arib, Qiqian Liu and Mathieu Edely
Abstract: Surface-enhanced Raman spectroscopy (SERS) has demonstrated its ability as powerful tool that can provide us information about the structure and the conformation of biomolecules such as DNA. One can probe the interaction between two biomolecules and extract some evidences of the conformation changes induce by the interaction. It is of primary importance to understand such interaction to improve the performances of sensors that are based on the capture of analyte by a bioreceptor. In addition, molecular interactions are the basis of many biological mechanisms. It is therefore important to have a better understanding of these phenomena and to be able to answer to specific questions as: how does the interaction take place? is it dynamic or static? is there any specific conformation for the interaction? In this work, we focus on the interaction between two DNA complementary strands as well as strands containing mismatch in their sequences. To do this, we study the interaction between a DNA sequence of poly-Adenin (PolyA) consisting of 20 Bases with its complementary poly-Thymin (PolyT). The PolyA strand is grafted at the surface of the gold nanostructured surface (Hamamatsu commercial SERS substrate [1]) using a thiol group at the 5' extremity of the DNA strand. We assume that we form a monolayer of PolyA. Some solutions of PolyT with different concentrations (10-7, 10-6, 10-5 and 10-4 M) are successively deposited on the SERS substrate. We performed Raman mapping on the surface and we recorded 400 spectra using a 633 nm excitation wavelength. One can observe the 735 cm-1 band assigned to the ring breathing mode of the PolyA and some variations of its intensity depending on the position on the map. By changing the concentration, we observe a decrease of the average SERS intensity of this band as well as a decrease of the standard deviation of the intensity of this band. We interpret this intensity change by some modification of the orientation and flexibility of the PolyA DNA strands interacting with the PolyT [2]. The increase of the concentration of Poly-T induced a loss of flexibility of the PolyT/PolyA molecular complex. We performed similar experiments by introducing a mismatch inside the PolyA sequence. A C base is inserted at different positions in the sequence of polyA and we can observe some modifications of the interaction between the PolyA and the PolyT strands. Using Principal Component Analysis, we were able to determine some spectral markers of the hybridisation and of its disruption due to the single base mismatch. This study provides a new approach for the reliable quantification and structural analysis of biological molecules. This work was supported by the European project DeDNAed (H2020-FETOPEN2018-2020, n° 964248) and by the project “Plasmon mediated biology: Exploitation of plasmonics to investigate and enhance biological processes and application to biomedical issues (acronym: BioPlasmonics)” funded by European Union – NextgenerationEU and Romanian Government, under National Recovery and Resilience Plan for Romania, contract no760037/23.05.2023, cod PNRR-C9-I8-CF-199/28.11.2023, through the Romanian Ministry of Research, Innovation and Digitalization, within Component 9, Investment I8. References [1] A. Azziz et al., J. Mol. Struct. 12, 1248 (2021). [2] W. Safar et al. Nanoscale 13, 12443–12453 (2021).
Nr: 33
Title:

Actuating Soft Matter with Light: Towards Applications of Active Colloids and Droplets (Invited)
Authors:

Giorgio Volpe
Abstract: Light carries energy and momentum. It can thus influence the motion of objects from atomic to astronomical scales. Being widely available, readily controllable and broadly biocompatible, light is also an ideal tool to actuate small particles, from colloids to droplets. In this talk, I will discuss our recent efforts to control the actuation of these soft materials towards their use for applications ranging from photonic and thermoplasmonic devices to printing patterns and molecules.
Nr: 34
Title:

Optimising Modulation Depth of Ultra-Low Loss Phase Change Chalcogenide Sb2Se3 for Silicon Photonics Platforms
Authors:

Sophie Blundell, Otto Muskens and Ioannis Zeimpekis
Abstract: Phase change materials (PCMs) exist in multiple solid states with different refractive indices which can be switched between thermally, electrically or optically. Interest in the antimonides, namely Sb2Se3 and Sb2S3, has increased over the last decade, due to the ultralow loss of such materials [1]. In this work, we propose and investigate a method for increasing modulation depth of Sb2Se3 used within integrated photonic devices as a phase shifter. By increasing the thickness of Sb2Se3 while embedding it deeper into the Si waveguide we see an increased modulation. Varying the capping layer used on PCMs integrated into nanophotonic chips affects crystallisation dynamics, whilst also providing protection from ions being lost during the switching process [2]. It has been shown that rapid thermal annealling applied to dopants in Si increases diffusion of the dopant ions [3]. As such, whilst also using a capping layer of SiO2 in this work, we investigate the benefits of putting a barrier oxide layer between the PCM and Si chip, to prevent diffusion of ions into the Si chip. We present results to support use of a barrier layer between PCM and chip when depositing thinner layers, as this is where the diffusive effect appears to affect modulation efficiency most potently. We will demonstrate this improved modulation contrast when the PCM is embedded into multimode interferometers (MMIs) as a method of changing the splitting ratio between the output couplers, simply by switching specific areas of the PCM. Over a total length of 50µm, Sb2Se3 is incrementally crystallised by 1µm and the MZI spectra taken after each switching event. This gives a wavelength shift in the spectrum, a direct analogy for the phase shift induced by each of these incremental switching events. Wavelength shift is presented against length of PCM crystallised, showing that increasing amount of Sb2Se3 crystallised increases wavelength shift. We investigate this process for five depositions of increasing thickness and etch depth, the gradients of which are then extracted. This gives the difference in wavelength shift imposed by incorporating a barrier oxide layer between PCM and Si waveguide, most noticeable in the thinner depositions. This can be attributed to the greater impact that ion diffusion into the Si waveguide has at smaller thicknesses of Sb2Se3; little difference is seen at greater thicknesses due to the smaller surface area to volume ratio of the Sb2Se3 in this case. [1] Matthew Delaney et al., Advanced Functional Materials 30.36 (Sept. 2020), p. 2002447. [2] Ting Yu Teo et al., ACS Photonics 10 (2023), pp. 3203–3214. [3] R. Angelucci, P. Negrini, and S. Solmi., Applied Physics Letters 49.21 (Nov. 1986), pp. 1468–1470.
Nr: 36
Title:

Contour Integration Methods for Computing Poles and Zeros of Nanophotonic Devices (Invited)
Authors:

Sven Burger, Felix Binkowski, Fridtjof Betz and Lin Zschiedrich
Abstract: Resonances are essential for understanding interactions between light and matter in photonic systems. The real frequency response of the systems depends on the complex-valued resonance frequencies, which are the poles of the electromagnetic field. We discuss approaches to compute poles and quantities derived from the electromagnetic field, like reflection or transmission zeros, based on contour integration. This also allows to extract sensitivities with respect to geometrical or other parameters, as well as to perform complete modal expansions of physical observables. [F. Binkowski, et al., Commun. Phys. 5, 202 (2022)] [F. Binkowski, et al., arXiv:2307.04654].
Nr: 37
Title:

Multipole Mechanisms of Electromagnetic Resonances of Composed Particle Structures (Invited)
Authors:

Andrey Evlyukhin
Abstract: The presentation is devoted to a discussion of the multipole approach, based on symmetry analysis and secondary multipole decomposition, for describing the electromagnetic response and the effect of resonant directional scattering by particle structures that support electric and magnetic multipole resonances. Several related tasks are presented. In particular, it is discussed how the symmetry properties and multipole composition of particle eigenmodes can be used to explain and tune the scattering directivity of electromagnetic waves. Then, the secondary multipole approach is applied for investigation of toroidal and anapole responses of composed particle structures. In particular, both single trimers of disk-shaped particles and metasurfaces composed on such trimers supporting the anapole state are considered. Application of the secondary multipole analysis allowed to associate the anapole state in such structures with the resonant multipole moments of trimer’s constitutive particles. Finally, a mechanism, operating on lattice-induced multipole interaction, of the effect of resonant mode trapping in metasurfaces is also discussed. Its implementation does not require any special conditions for irradiation of incident light or geometric distortion of the symmetry of periodic structures and based only on the symmetrical properties of individual particles. In the case of metallic or hybrid particles, this makes it possible to design metasurfaces with an absorption band in the required spectral range.
Nr: 38
Title:

Polaritons Twist and Shout (Invited)
Authors:

Christos Tserkezis
Abstract: With the tremendous growth that the field of polaritons in nanophotonics has experienced in recent years [1,2], its basic understanding and theoretical analysis has gradually reached maturity [3,4], and we are now entering the stage where novel strong-coupling templates with additional alternative functionalities are being explored [5]. To this end, and following the terminology of quantum optics, both the cavity and the emitter part can be selected or engineered accordingly. Here, I will discuss some of our recent theoretical activities focused on ways to manipulate both aspects. One of the most rapidly growing directions for polariton-related research is what can be termed chiral polaritonics [6]. This term can refer to either chiral emitters (systems that emit circularly polarised light) [7], or chiral cavities, typically in the form on nanoparticle (NP) aggregates [8]. Following the latter approach, we show [9] that chiral NPs, or collections thereof, can be used in combination with achiral emitter layers, to induce a reconfigurable chiroptical response, where the new hybrid modes inherit the chirality properties of the original NP cavity. At the same time, since circular dichroism (CD), one of the most typical measurables in experiments), can be used as a more conclusive indication of having achieved the strong-coupling regime, because by default it removes all resonant features not related to the coupling. Despite the aforementioned flexibility provided by CD, the most conclusive evidence of strong coupling is still the observation of Rabi-like oscillations in the occupation of the emitter or in the amplitudes of the coupled modes. But in nanophotonics, these oscillations have typically periods of the order of fs, and their real-time observation is notoriously challenging [10]. To tackle this problem, we propose introducing an externally controlled amount of gain in the cavity, to compensate the internal losses (Ohmic or radiation) [11]. This has the effect of decelerating the Rabi oscillations, to the extend that they can be rendered observable, while one can then extrapolate to the gain-less case to draw conclusions about the coupling strength in the original emitter-cavity system. Finally, moving towards the opposite direction, that of controlling the emitter, we discuss the case of hexagonal boron nitride (hBN) and, in particular, the excitons they sustain in the ultraviolet (UV) regime. We show that these exciitonic transitions can be externally controlled by an external superlattice potential [12], which can actively tune the excitonic binding energies and conductivities, in a wide range of frequencies spanning from the deep-UV to the near-infrared, turning thus a relatively uninteresting material into a strong candidate for polaritonics. [1] P. Törmä & W. L. Barnes - Rep. Prog. Phys. 78, 013901 (2015) [2] D. N. Basov et al. - Nanophotonics 10, 549 (2021) [3] C. Tserkezis et al. - Rep. Prog. Phys. 83, 082401 (2020) [4] Sánchez-Barquilla M et al. - ACS Photonics 9, 1830 (2022) [5] D. G. Baranov et al. - ACS Photonics 5, 24 (2018) [6] D. G. Baranov et al. - ACS Photonics 10, 2440 (2023) [7] F. Wu et al - ACS Nano 15, 2292 (2021) [8] J. T. Collins et al. - Adv. Opt. Mater. 5, 1700182 (2017) [9] P. E. Stamatopoulou et al. - Nanoscale 14, 17581 (2022) [10] P. Vasa et al. - Nat. Phot. 7, 128 (2013) [11] C. Tserkezis et al. - Phys. Rev. A 107, 043707 (2023) [12] P. Ninhos et al. - arXiv 2312.01913 (2023)
Nr: 40
Title:

Towards Active Plasmonic Substrates by DNA Nanotechnology
Authors:

Kosti Tapio, Mohammed Al Hussain, Abraham Kipnis, Jacky Loo and Anton Kuzyk
Abstract: Exploiting light-matter interaction is crucial for innovation in chemistry, sensing, and compact optics[1,2]. Active plasmonic substrates show promise due to strong interactions between metallic nanostructures and light[3,4]. Several approaches can realize tuning of optical properties of plasmonic substrates[5-7], where one of the simplest ways to achieve active plasmonics in the visible spectrum is by reconfiguring the 3D spatial arrangement of optical components. Here, we utilize DNA, which allows creation of programmable nanoscale molecular architectures with a plethora of functionalization schemes and provides a versatile toolbox for realizing nanoscale actuation[8]. We present a fast and high modulation plasmonic substrate assembled from DNA and nanoparticles: gold surface bound and DNA-tethered silver nanocubes are actuated on top of the surface using an electric field, where the plasmonic coupling between the cubes and gold surface alters the reflection of the substrate. This can be seen as spectral or colour shifts of the gold substrate. Our system shows excellent reversibility up to kHz frequencies and hundreds of switching cycles. [1] A.M. Shaltout, V.M. Shalaev, M.L. Brongersma, Science 2019, 364, 648. [2] J.J. Giner-Casares, L. M. Liz-Marzán, Nano Today 2014, 9, 265-377. [3] N. Jiang, X. Zhuo, J. Wang, Chem. Rev. 2018, 118, 3054-3099. [4] J.K. Bhattarai, M.H.U. Maruf, K.J. Stine, Processess 2020, 8, 115. [5] J. Peng, H.-H. Jeong, Q. Lin, H.-L. Liang, M.F.L. de Volder, S. Vignolini, J.J. Baumberg, Sci. Adv. 2019, 5, eaaw2205. [6] A. Abass et. al., Nano Lett. 2014, 14, 10, 5555-5560. [7] X. Yin, M. Schäferling, A.-K.U. Michel, A. Tittl., M. Wuttig, T. Tuabner, H. Giessen, Nano Lett. 2015, 15, 7, 4255-4260. [8] K. Tapio, I. Bald, Multi. Funct. Mater. 2020, 3, 3, 032001.
Nr: 42
Title:

Unidirectional Meta-Emitters Based on the Kerker Condition Assembled by DNA Origami
Authors:

Maria Sanz-Paz, Ayşe Tuğça Mina Yeşilyurt, Fangjia Zhu, Jer-Shing Huang and Guillermo P. Acuna
Abstract: Optical quantum emitters near nanostructures have access to additional relaxation channels and thus exhibit structure-dependent emission properties, including emission enhancement and directionality. A well-engineered quantum emitter-plasmonic nanostructure hybrid can be considered as an optical meta-emitter consisting of a transmitting nanoantenna driven by an optical-frequency generator. In this work, the DNA origami fabrication method is used to construct ultracompact unidirectional meta-emitters composed of a plasmonic trimer nanoantenna driven by a single dye molecule. The origami is designed to bring the dye to the nanoantenna gap to simultaneously excite the electric and magnetic dipole modes of the trimer nanoantenna. The interference of these modes fulfills the Kerker condition at the fluorophore’s emission band, enabling unidirectional fluorescent emission. We report unidirectional emission from a single molecule with a front-to-back ratio of up to 10.7 dB, accompanied by a maximum emission enhancement of 23-fold.
Nr: 43
Title:

Chiral Structures and Acoustoplasmonic Transducers (Invited)
Authors:

Antonio Garcia-Martin, Beatriz Castillo López de Larrinzar, Chushuang Xiang, Edson Cardozo de Oliveira and Daniel Lanzillotti Kimura
Abstract: The possibility of creating and manipulating nanostructured materials encouraged the exploration of new strategies to control electromagnetic properties. Among the most intriguing nanostructures are those that respond differently to helical polarization, i.e., exhibit chirality.[1] Circularly polarized light can be used to probe and determine the chiral nature of a plasmonic structure, which is usually reflected as quantitative differences in the values of the absorption or scattering cross-sections. However, reaching maximum absorption and minimum scattering for one helicity, and the opposite for the other is not usually found to occur at the same wavelength.[2] In the present work, we propose a simple chiral plasmonic structure based on crossed elongated bars where light-handedness defines the dominating cross-section absorption or scattering, as it identifies the two different enantiomers in a chiral structure which determine how the system interacts with its environment. The system is yet maintained simple enough to understand the actual nature of the response observed, be open to future developments, and warrant fabrication for future experimental verification [3,4]. Based on this structure, our work demonstrate that, not only through the interactions between different elements it is possible to make the absorption and scattering cross-sections radically and qualitatively different for the two circular polarizations, but also that the dominating cross-section can be switched from absorption to scattering by simply changing the polarization of the impinging beam. Also, we theoretically propose a simple pump-probe experiment using circularly polarized light. [5] In the reported structures, the generation of acoustic phonons is optimized by maximizing the absorption, while the detection is enhanced at the same wavelength -and different helicity- by engineering the scattering properties [6]. Thus, the presented results constitute one of the first steps towards harvesting chirality effects in the design and optimization of efficient and versatile acoustoplasmonic transducers. References [1] S L. D. Barron, Molecular Light Scattering and Optical Activity, Cambridge, Cambridge Univeristy Press, (2004) [2] B. Hopkins, et al., Laser Phot. Rev. 10, 137 (2016). [3] B. Auguié, et al., J. Phys. Chem. Lett. 2, 846 (2011) [4] C. de Dios, et al., Opt. Express 27, 21142 (2019) [5] B. Castillo López de Larrinzar, et al., Nanophotonics 12, 1957 (2023) [6] N. D. Lanzillotti-Kimura, et al., Phys. Rev. B 83, 201103 (2011).
Nr: 45
Title:

Exploring Imaging Applications Through Learning-Enhanced Metasurface Optics (Invited)
Authors:

Humeyra Caglayan
Abstract: I will present the applications of metaoptics for extended depth of field, light field microscopy, and hyperspectral imaging. A series of conventional optical components, such as lenses and mirrors, are employed in traditional optics solutions. In pursuit of a more compact form factor, we demonstrate that the metasurface optics provide key advantages in imaging, such as extreme extended depth of field (EDOF), where the extended DOF range is well beyond what is demonstrated in state-of-the-art. This can be further implemented in a light field microscope to obtain a compact light field microscopy with high-speed volumetric imaging and high spatio-temporal resolution. Finally, I will demonstrate how metaoptic components can be utilized for a compact and efficient snapshot hyperspectral camera model. In all of these examples, we take advantage of end-to-end design. We have developed a fully-differentiable wave optics-based deep learning framework, combining novel hardware (metaoptics) and software (artificial neural computing). This will enable efficient sampling and reconstruction of the high-dimensional plenoptic function. In this concept, metasurface delivers new optics functionality, while neural computing delivers complex and fast inverse imaging for a high amount of data.
Nr: 46
Title:

All-Optical Computing with Nonlinear Photonic Metasurfaces (Invited)
Authors:

Costantino De Angelis
Abstract: Flat optics has been recently unveiled as a powerful platform to perform data processing in real-time, and with small footprint [1, 2, 3, 4]. So far, these explorations have been mostly limited to linear optics, while arguably the most impactful operations stem from nonlinear processing of the incoming signals. In this context, here we demonstrate that nonlinear phenomena combined with engineered nonlocality in flat-optics devices can be leveraged to synthesize Volterra kernels able to perform complex operations on incoming images in real-time [5]. In particular, here we show that using nonlinear nonlocality in flat optics we can realize analog image processing with previously not accessible functionalities. By exploring the simple scenario of a uniform χ(2) thin sheet, we demonstrate edge detection operation with exciting potentials. In our proposed nonlinear flat-optics solution, the non-resonant nature of the nonlinear interaction involved in image processing allows edge detection over a broadband spectrum with ultra–high contrast and superior resilience to noise. Our results indicate that Volterra kernels of nonlinear nonlocal flat optics can open new opportunities in applications such as image processing, item recognition for computer vision, and high-contrast, high-resolution microscopy. References 1. Silva, A., Monticone, F., Castaldi, G., Galdi, V., Alù, A., Engheta, N., Science 343(6167), 160–163 (2014). 2. Overvig, A., Alù, A., Laser & Photonics Reviews 16(8), 2100633 (2022). 3. Vabishchevich, P., Kivshar, Y., Photon. Res. 11, B50-B64 (2023) 4. Schlickriede, C., Waterman, N., Reineke, B., Georgi, P., Li, G., Zhang, S., Zentgraf, T., Advanced Materials 30(8), 1703843 (2018). 5. D. de Ceglia, A. Alù, D. Neshev, C. De Angelis, Opt. Mater. Express 14, 92-100 (2024).
Nr: 48
Title:

Harmonic-Oscillator Descriptions of Strong and Ultrastrong Coupling in Nanophotonic Systems (Invited)
Authors:

Ruben Esteban, Unai Muniain, Rainer Hillenbrand, Luis Martín-Moreno and Javier Aizpurua
Abstract: Optical resonances in nanophotonic systems can interact efficiently with optical matter excitations in molecules and other materials. When the coupling strength g is sufficiently large, the regime of strong coupling is reached, characterized by new polaritonic modes with novel properties [1-3]. Further, even larger g leads to the ultrastrong coupling regime, where new effects emerge such as the modification of the ground state or strongly bunched emission[4-7]. Strong and ultrastrong coupling is often analyzed by fitting simulated or measured spectra with classical coupled harmonic oscillator models. This simple approach is typically appropriate to extract the value of the coupling strength g. On the other hand, it is often not clear how to obtain other relevant physical magnitudes, such as the value of the near fields. Further, two different types of coupling terms have been considered, often without a clear justification about how to choose between them. The results obtained using these two types of coupling can differ very significantly in the ultrastrong coupling regime. We show that, by starting from the Lagrangian of the system, it is possible to clarify these questions, as well as to establish a direct connection between classical and cavity Quantum Electrodynamics (cavity QED) descriptions of ultrastrong coupling based on the interaction of harmonic oscillators. We show that the type of coupling term that needs to be introduced on the classical harmonic oscillator equations i) is different if the interaction between the matter excitations and nanophotonic resonances is mediated by transverse electromagnetic modes or by Coulomb coupling and ii) it is directly connected to the presence or absence of the so-called diamagnetic term in the cavity QED Hamiltonian that would model the same system. Additionally, we describe the connection between the amplitude of the classical harmonic oscillators and physical magnitudes of the system. This work thus leads to a more solid foundation of the classical description of ultrastrong coupling and its relationship to cavity-QED descriptions. REFERENCES [1] P Törmä and W. L. Barnes, Rep. Prog. Phys. 78 013901 (2015) [2] M. Autore et al., Light: Sci. Appl. 7, 17172 (2018) [3] A. Thomas et al., Science 363, 615 (2019) [4] A. F. Kockum et al., Nat. Rev. Phys 1, 19 (2019) [5] M. Barra Murillo et al., Nat. Comm. 12, 6206 (2021) [6] Yoo, D. et al. Nat. Photonics 15, 125-130 (2021) [7] A. Nodar et al., Phys. Rev. Research 5, 043213 (2023).
Nr: 49
Title:

Multifunctional Hybrid Nano-Devices: Prospects for Reconfigurability (Invited)
Authors:

Josep Canet-Ferrer
Abstract: Further and Emerging technologies are continuously demanding for the development of multifunctional devices capable of integrating components of different nature into a single platform. After being assembled in compact architectures for an easy portability and interconnection those devices are expected to manage information by responding to external stimuli e.g. optical, electrical or magnetic pulses. However, most of the proposed multifunctional systems are limited to the additive combination of materials which do not show a clear interplay among their properties. In this talk I will review the different strategies developing multifunctional metasurfaces based of both physical and chemical approaches. Then, I will show some examples of the capabilities we have in house for the synergic coupling among the optical emission, the magnetization and thermal transport in our nanodevices. With these examples I will discuss the potential of combining the increase on the optical density of states into a metasurface for applications in microelectronics, magnetism and sensing.
Nr: 50
Title:

Exploiting Hybrid Metasurfaces for enhanced Linear and Nonlinear Chiral Sensing Applications
Authors:

Guillermo Serrera, Javier González-Colsa and Pablo Albella
Abstract: The concept of chirality, denoting the absence of specular symmetry in any plane of an object and the consequent existence of two mirror images (enantiomers) of the same object, holds paramount significance in the biological functionality of numerous molecules. This recognition has spurred increasing industrial interest in discriminating molecular chirality. A key challenge in this pursuit is augmenting the inherently weak circular dichroism (CD) chiroptical effect to facilitate efficient chiral sensing and separation. Over the past decade, the development of nanophotonic platforms designed for this purpose has garnered considerable attention [1]. Various strategies have been employed to address this challenge. One of them originates originating from the realms of plasmonics, exploiting the substantial field enhancement arising from the Surface Plasmon Resonance (SPR) phenomenon [2]. Another is the use of High Refractive Index Dielectric (HRID) materials due to their low-loss characteristics and magnetic resonances [3]. Hybrid structures, combining enhanced electric and magnetic resonances, have also been proposed, offering more advantageous chiroptical conditions for sensing applications [4]. In this context, we present our ongoing research on this subject. In particular, leveraging numerical simulations aided by multipole decomposition analysis, we illustrate how a straightforward hybrid gold-silicon metasurface can capitalize on the superposition of multiple resonances with non-radiating anapole states. This, results in remarkable conditions for enhancing the CD effect in the near-infrared spectrum. Furthermore, we demonstrate the direct relation of these anapole states with enhanced Third Harmonic Generation (THG), thereby opening avenues for background-free CD signals [5,6]. REFERENCES [1] E. Zor, H. Bingol and M. Ersoz, Trends Analyt Chem 121(2019), 115662. [2] M. Hentschel, et al. Sci. Adv. 3(2017), 160273. [3] K. Tanaka et al. ACS Nano 14(2020), 15926. [4] E. Mohammadi et al. ACS Photonics 8 (2021), 1754-62. [5] T. Shibanuma et al. Nano Lett. 17(2017), 2647-51. [6] J. Gonzalez-Colsa et al. J Phys Chem Lett., 13,6230-34.
Nr: 51
Title:

Long-Lived Hot Electron Dynamics and Ultrafast All-Optical Switching in Hyperbolic Meta-Structures
Authors:

Rakesh Dhama, Alessandro Pianelli and Humeyra Caglayan
Abstract: Ordinary plasmonic nanoantennas exhibit scattering and absorption bands at the same wavelength region, which makes their utilization to full potential impossible for both features simultaneously [1]. Here, we take advantage of spectrally separated scattering and absorption resonance bands in hyperbolic meta-antennas (HMA) to enhance the hot electron generation and prolong the relaxation dynamics of hot carriers. In this regard, we first demonstrate the extended plasmon-modulated photoluminescence spectrum in HMA towards longer wavelengths due to its scattering spectrum in comparison to the corresponding NDA [2]. Then, we show that the tunable absorption band of HMA controls and modifies the lifetime of the plasmon-induced hot electrons with enhanced excitation efficiency in the near-infrared region and broadens the utilization of the visible/NIR spectrum in comparison to NDA meta-antennas and can lead to the design of efficient hot carrier devices. Furthermore, all-optical switches enable the ON/OFF conversion function by following the concept of light-controlled-by-light. In this context, we also propose and demonstrate a multilayered ENZ metamaterial utilizing Si-compatible titanium nitride and indium-tin-oxide materials with two effective working wavelengths in the visible and near-infrared spectrum. This realized device enables switching time down to a few hundred femtoseconds utilizing minimal energy at the corresponding ENZ regions induced by intraband pumping [3]. Our novel approach can enhance the adaptability in designing ENZ metamaterials towards new hybrid integrated photonic circuit components for low-power ultrafast all-optical terahertz modulation. References [1] N. Maccaferri, et al. Nano letters 19, 1851–1859 (2019). [2] R. Dhama, et al. Nano Letters 23, 3122-3127 (2023). [3] A. Pianelli, R. Dhama..and H. Caglayan arXiv:2305.06731
Nr: 53
Title:

DNA Origami Self-Assembled High-Index Dielectric Optical Antennas for Single-Molecule Fluorescence Manipulation (Invited)
Authors:

Guillermo P. Acuna
Abstract: Over the last decade, the DNA origami method [1] has established itself as one of the most versatile techniques for the bottom-up synthesis of hybrid species with tailored functionality [2]. This approach, which is based on the self-assembly of DNA strands into arbitrarily designed 3D structures, can be exploited to organize different entities, such as fluorophores, proteins, or NPs with nanometer precision and stoichiometric control. Consequently, it has been widely used to produce a variety of optical antennas for sensing and light manipulation at the single molecule level in controlled geometries. However, to date this approach has been constrained to Au, Ag and QD NPs with no works reported so far on combining DNA origami with high-index dielectric NPs. In this work, we develop a technique to functionalize high-index dielectric colloidal Si NPs [3] with DNA sequences using click-chemistry. To further demonstrate these findings, we self-assemble Si NP dimers using the DNA origami technique (Figure 1). Finally, we also exploit the DNA origami technique to position both Si NPs and organic fluorophores at controlled gaps to study the distance dependance energy transfer, the modification on the fluorescence rates and the emission directivity. Our results show that in the vicinity of the Si NPs the radiate rate increases more than the non-radiative rate and that the Kerker condition can be exploited to obtain emission unidirectionality. References: [1] P. W. K. Rothemund, Nature, 440, 297–302 (2006) [2] A. Kuzyk, R. Jungmann, G. P. Acuna, N. Liu, ACS Photonics 5, 1151 (2018) [3] H. Negoro, H. Sugimoto, M. Fujii, Nano Lett. 23, 5101 (2023)
Nr: 56
Title:

Interfacial Thermal Conductance as a Driver for Asymmetric Heat Generation in Plasmonic Janus Particles
Authors:

Javier González-Colsa, Fernando Bresme and Pablo Albella
Abstract: Plasmonic Janus nanoparticles have attracted considerable attention in thermoplasmonics for their potential application in fields like biomedicine and thermoelectronics, among others [1-3]. Their photothermal response and consequently the maximum temperature of the particle and the spatial thermal distribution can be regulated by using pulsed lasers and by modifying the particle-fluid interfaces, since the dynamics of nanoparticle-fluid heat transfer is mainly conducted by the pulse features and the interfacial thermal conductance [4]. Here, we present one of our most recent works [5] where the impact of the interfacial thermal conductance on the thermal relaxation of plasmonic Janus nanoparticles is investigated. Among the main results, we will show that these particles present directional heat dissipation under nanosecond pulsed light. Additionally, we will explore how overlooking the temperature dependence of thermophysical properties can result in an overestimation of the temperature of the nanoparticle. We also demonstrate that such nanoheaters can serve as promising candidates for photothermal therapies by employing a gold/polymer semishell nanostructure. We believe that these findings can inspire the formulation of innovative strategies to develop efficient nanoheating platforms, addressing the high demand in applications requiring temperature-controlled devices and thus holding broad significance for the thermoplasmonic community. 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] Juan D. Olarte-Plata; J. Gabriel; Pablo Albella; Fernando Bresme. Spatial Control of Heat Flow at the Nanoscale Using Janus Particles. ACS Nano 2022, 16(1), 694−709. [5] Javier González-Colsa, Fernando Bresme, and Pablo 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, 19152–19158.
Nr: 57
Title:

Electron-Assisted Probing of Polaritonic Light-Matter States (Invited)
Authors:

Antonio I. Fernandez Dominguez
Abstract: Thanks to their exceptional spatial, spectral and temporal resolution, highly-coherent free-electron beams have emerged as powerful probes for material excitations, enabling their characterization even in the quantum regime. Here, we investigate strong light-matter coupling through monochromatic and modulated electron wavepackets. In particular, we consider an archetypal target, comprising a nanophotonic cavity next to a single two-level emitter. We propose a model Hamiltonian describing the coherent interaction between the passing electron beam and the hybrid photonic-excitonic target, which is constructed using macroscopic quantum electrodynamics and fully parameterized in terms of the electromagnetic Dyadic Green’s function. Using this framework, we first describe electron-energy-loss and cathodoluminescence spectroscopies, and photon-induced near-field electron emission microscopy. Finally, we show the power of modulated electrons beams as quantum tools for the manipulation of polaritonic targets presenting a complex energy landscape of excitations.
Nr: 58
Title:

Spectral Tuning of Laser Emission by quasi-BIC All-Dielectric Metasurfaces
Authors:

Ayesheh Bashiri, Aleksandr Vaskin, Katsuya Tanaka, Michael Steinert, Marijn Rikers, Bayarjargal Narantsatsralt, T. Pertsch and I. Staude
Abstract: All-dielectric metasurfaces are of great interest for nanoscale lasing due to the low absorption loss and coupling compatibility with a wide range of gain media [1]. Efficient spectral tunability of the laser emission requires both an efficient gain medium with broad emission spectra and an optical cavity supporting high quality factor (Q-factor) modes. All-dielectric metasurfaces supporting quasi bound states in the continuum (qBICs) with high Q-factor resonances have significant potential for achieving low threshold lasing [2]. Here, we experimentally demonstrate lasing action from a gain medium containing rhodamine 6G (Rh6G) laser dyes coupled to all-dielectric qBIC metasurfaces. To this end, we designed and fabricated broken symmetry titanium dioxide (TiO2) metasurfaces supporting high Q-factor resonances in the visible spectral range. We spin-coated the fabricated metasurfaces with SU8 photoresist doped with Rh6G laser dyes and performed power-dependent fluorescence spectroscopy measurements. The sample was excited with a 532 nm pulsed laser with a pulse duration of 0.5 ns. By varying the metasurface geometry parameters, we were able to tune the lasing wavelength over the broad Rh6G gain spectrum, from 555 nm to 595 nm. tour results may find applications in integrated sensors and highly efficient on-chip light sources. [1] I. Staude, and J. Schilling, “Metamaterial-inspired silicon nanophotonics,” Nat. Photonics 11, 274-284 (2017). [2] J. H. Yang, et al., “Low-threshold bound state in the continuum lasers in hybrid lattice resonance metasurfaces.” Laser & Photonics Reviews, 15, 2100118 (2021).
Nr: 59
Title:

Active Tuning of Bound States in the Continuum in Graphene Metasurfaces (Invited)
Authors:

Jose A. Sanchez-Gil, Jose L. Pura, Juan R. Deop-Ruano, Diego R. Abujetas, Alejandro Manjavacas and Vincenzo Giannini
Abstract: Bound states in the continuum (BICs) have attracted much interest lately in photonics for their (theoretically) infinite Q factor. These states lie in the radiation continuum, but counterintuitively cannot couple to any radiation channel. A common approach is to exploit metasurfaces, planar arrays in the non-diffractive regime, which limit the outgoing channels to only the specular ones, which can in turn be suppressed by tuning the parameters of the system in various manners, leading to symmetry-protected or accidental BICs. Nonetheless, whereas tunable metasurfaces based on a variety of mechanisms have been proposed, the active tunability of symmetry-protected BICs remains largely unexplored (for instance, magneto-optic BIC control), mostly due to the strong dependence on geometrical constraints. In this regard, graphene metasurfaces, artificially engineered sheets of graphene disposed in periodic arrays of subwavelength-scale5, could be exploited. These structures can manipulate electromagnetic waves with high efficiency and flexibility, enabling a wide range of potential applications in areas such as sensing, imaging, and communications. In this work we present a metasurface comprised of a square array of graphene microdisk dimers that supports bound states in the continuum (BICs) for both TE and TM polarizations. The BICs in this system arise at normal incidence as a result of the C2 symmetry of the pairs of graphene disks. Since BICs are dark states with theoretically infinite Q factor, the symmetry protecting the BIC should be carefully broken to obtain more practical states with finite but large values of the Q factor. These quasi-BICs are typically obtained by geometrically breaking the underlying symmetry, e.g., by having different diameters for each graphene microdisk. We propose here another approach to control the frequency and Q factor of the quasi-BIC by using identical graphene microdisks but inducing different Fermi levels with an external voltage. The Fermi level directly affects graphene conductivity, and hence its polarizability. By applying a different potential to each disk, the BIC symmetry can be broken in a controlled manner allowing to select an optimum value of the Q factor for the desired application. Furthermore, the configuration could be modified during the metasurface operation on demand. We acknowledge the financial support from the grants BICPLAN6G (TED2021-131417B-I00), LIGHTCOMPAS (PID2022-137569NB-C41 and PID2022-137569NB-C42), and TEM-FLU PID2019-109502GA-I00 funded by MCIN/AEI/10.13039/501100011033, “ERDF A way of making Europe”, and European Union NextGenerationEU/PRTR. We also acknowledge the financial support from a Margarita Salas contract CONVREC-2021-23 (University of Valladolid and European Union NextGenerationEU), a predoctoral fellowship from the MCIU/AEI assigned to Grant No. PID2019-109502GA-I00 and a 2022 Leonardo Grant for Researchers in Physics, BBVA Foundation. J. L. Pura, J. R. Deop-Ruano, D. R. Abujetas, A. Manjavacas, V. Giannini, J. A. Sánchez-Gil, “Tunable bound states in the continuum in active metasurfaces of graphene disk dimers,” Nanophotonics 12, 4453, 2023.
Nr: 60
Title:

How Thin Film Photonics Unlocks the Power of Fano Resonance and Extreme Optomechanics (Invited)
Authors:

Giuseppe Strangi
Abstract: In recent years, significant interest has emerged in the inverse design1 of artificial layered heterostructures for photonic applications2. Specifically, the unique optical properties of near-zero permittivity (ENZ) metamaterials have enabled the exploration of novel physical effects and mechanisms. In this presentation, I will delve into how thin film photonics harnesses the potential of Fano resonances3-4 and extreme optomechanics5. By layering metal-dielectric thin films, we can create a distinct type of optical coating that exhibits photonic Fano resonance, referred to as a Fanoresonant optical coating (FROC). We extend the concept of coupled mechanical oscillators to thinfilm nanocavities, shedding light on semi-transparent FROCs that can both transmit and reflect the same color, akin to a beam splitter filter. This remarkable property is beyond the capabilities of conventional optical coatings. In the latter part of my presentation, I will discuss recent theoretical.
Nr: 61
Title:

Amplification of Magneto-Optical Activity Through Plasmonic Modes Hybridization (Invited)
Authors:

Paolo Vavassori
Abstract: Magneto-optical (MO) effects are widely used in studying technologically relevant magnetic materials as well as to realize optical devices exploiting non-reciprocal propagation of light. The continuously developing field of magnetoplasmonics merges the concepts from plasmonics and magneto-optics to realize novel phenomena and functionalities for the manipulation of light at the nanoscale. Owing to the intertwined optical and magneto-optical properties, magnetoplasmonics offers a versatile toolbox for actively tunable optical ultrathin surfaces and metasurfaces. Enhancing magneto-optical effects is crucial for size reduction of key photonic devices based on non-reciprocal propagation of light and to enable active nanophotonics. Most studies focused on the amplification of the MO response produced by the excitation of localized dipolar plasmonic resonances (LPRs) in metallic magneto-plasmonic nanostructures. Here, we explore magnetoplasmonic-disk/plasmonic-ring nanocavities to achieve free-space light excitation and hybridization of multipolar modes. We show that the enhanced tunability and linewidth sharpening of Fano resonances in metasurfaces made of periodic arrangements of such hybridized magnetoplasmonic nanocavities produce a large amplification of the magneto-optical response together with the control of reflectance (Kerr configuration) and transmittance (Faraday configuration), well beyond that achievable using conventional magneto-plasmonic nanostructures.
Nr: 63
Title:

Novel Pathways in Thermoplasmonics for Improved Localized Heat Control (Invited)
Authors:

Pablo Albella, Javier González-Colsa, Guillermo Serrera, Alfredo Franco, Fernando Moreno, Dolores Ortiz, José M Saiz, Fernando Bresme and Francisco González
Abstract: Plasmonic nanostructures, commonly known as nanoheaters in the field of thermoplasmonics, have garnered significant attention in nanomedicine owing to their ability to show extraordinary photothermal capabilities [2,3] at the nanoscale. Despite the existence of numerous nanostructures capable of producing robust photothermal responses and heat delivery, there remains a considerable journey ahead. For instance, many of these structures exhibit symmetric heat delivery or necessitate specific orientations concerning the excitation source for optimal performance [2]. In this talk, we will initially provide an overview of innovative designs, both entirely plasmonic or hybrids of dielectric/plasmonic materials. These designs exhibit an enhanced photothermal response coupled with directional heat delivery. In the case of hybrid nanoheaters, the thermal enhancement mechanism relies on exciting either dipolar or anapolar modes [5], both proven to be efficient mechanisms for efficiently generating heat at the nanoscale. The rest of the talk will delve into our recent findings concerning the thermal performance of nanostructures based on DNA origami. This exploration will offer theoretical insights into their potential for applications in photothermal therapy. [1] J. González-Colsa, G. Serrera, J. M. Saiz, D. Ortiz, F. González, F. Bresme, F. Moreno and P. Albella. Gold Nanodoughnut as an Outstanding Nanoheater for Photothermal Applications. OptExpress 2022, 30(1), 125. [2] 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. [3] J. González-Colsa, F. Bresme and Pablo 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, 19152–19158. [4] G. Baffou, F. Cichos and R. Quidant. Applications and challenges of thermoplasmonics. Nat. Mater. 2020, 9, 19, 946-958. [5] J. González-Colsa, J. D. Olarte-Plata, F. Bresme and P. Albella. Enhanced Thermo-Optical Response by Means of Anapole Excitation. J. Phys. Chem. Lett. 2022, 13(26), 6230−6235.
Nr: 64
Title:

Spin-Valley Nanophotonics with Atomically Thin Semiconductors (Invited)
Authors:

Alberto Curto
Abstract: Circularly polarized light, which carries optical spin, is the basis for applications like electron spin excitation and read-out in semiconductors, all-optical control of magnetization, or manipulation using optical torque. Atomically thin semiconductors such as WS2 can display spin-valley polarization and emit circularly polarized light. In this presentation, we first demonstrate high spin-valley polarization in a few-layer WS2 at room temperature and investigate the physical origin of its high polarization compared to a similar system, WSe2, which shows low polarization. Then, we focus on understanding the electrodynamic nature of valley-polarized emission. Using back focal plane imaging, we demonstrate the properties of evanescent optical spin radiated by the atomically thin semiconductor. Finally, we will discuss a Drexhage experiment to enhance valley-polarized emission. We demonstrate that an atomically thin semiconductor can radiate different degrees of circular polarization when placed at different distances from a mirror. By understanding, controlling, and enhancing the circular polarization of light emitted by WS2, our results open up new possibilities for spin-based nanophotonic and optoelectronic devices.
Nr: 65
Title:

Nonlinear Generation of Optical Beams with Orbital Angular Momentum with Either a Crystalline Film or Metasurface (Invited)
Authors:

Giuseppe Leo
Abstract: The generation of vortex beams is a research field with a potential impact on both fundamental and applied physics. Here, we report on our recent results on the generation of second-harmonic vortices with either a uniform dielectric film or an optical metasurface. In the former case we demonstrate spin-to-orbital angular momentum mediated by the nonzero electric-field longitudinal component of the pump beam, while in the latter we generate orbital angular momentum with an arbitrary topological charge via a nonlinear meta-hologram. Both results are achieved in a hybrid AlGaAs-on-sapphire platform.
Nr: 44
Title:

Photonic and Phononic Characterization of Twisted Acoustoplasmonic Nanostructures
Authors:

Beatriz Castillo López de Larrinzar, Jorge García Martínez, Antonio Garcia-Martin, Chushuang Xiang and Daniel Lanzillotti Kimura
Abstract: Simple acoustoplasmonic resonators, such as nanobars and crosses, are efficient light-hypersound transducers [1-2]. The excitation of hypersonic modes in these structures strongly depends on the spatial profile of the acoustic and plasmonic eigenmodes and the optical properties of the system's resonances. Lately, it has been made possible to selectively excite and detect phonon modes via plasmon resonances at the same frequency using chiral nanostructures and circularly polarized light [3]. In this work we present a system that is composed of a metallic propeller-like structure, based in a three lobed perforated clover whose top face is twisted with respect to its bottom one. The presence of the twisting angle gives rise to the excitation of non-conventional phononic modes. We will present a complete theoretical analysis of the phononic and plasmonic modes, their surface deformation field and electromagnetic field profiles.[4] [1] Ultrafast acousto-plasmonic control and sensing in complex nanostructures, K O’Brien, ND Lanzillotti-Kimura, J Rho, H Suchowski, X Yin, X Zhang Nature communications 5 (1), 4042, 2014 [2] Polarization-controlled coherent phonon generation in acoustoplasmonic metasurfaces, ND Lanzillotti-Kimura, KP O’Brien, J Rho, H Suchowski, X Yin, X Zhang Physical Review B 97 (23), 235403, 2018 [3] B. Castillo López de Larrinzar, C. Xiang, E.R. Cardozo de Oliveira, N.D. Lanzillotti-Kimura, and A. García-Martín. "Towards chiral acoustoplasmonics", Nanophotonics, 12, 1957-1964 (2023). https://doi.org/10.1515/nanoph-2022-0780.