NanoPlasMeta 2023 Abstracts

Area 1 - Photonics
Area 2 - Nanophotonics, Plasmonics and Metamaterials
Full Papers

Area 1 - Photonics

Nr: 33
Title:

Electrically Controlled Metasurfaces for Flash Tuning
Authors:

Mohsen Rahmani
Abstract: Recent advancements in nanofabrications, characterisations and computer modellings allow generating of novel metasurfaces that control the light characteristics in extraordinary ways. Such advances have led to revolutionary applications in several fields, including but not limited to metalenses, polarisation converters, nano-sensors, and holograms [1]. Meanwhile, the active and reversible tunning of metasurfaces has attracted significant attention due to the larger degree of freedom that tunable metasurfaces can offer. Tunning metasurfaces can be obtained by various external stimuli, such as mechanical, electrical, optical, etc [1]. In this talk, I will demonstrate how the encoded transmission pattern can be tuned by controlling a dielectric metasurface's temperature [2, 3]. I share our latest results on electrically tunable metasurfaces, driven by thermo-optic effect and flash-heating in silicon. A 9-folds change in transmission by <5V biasing voltage and the modulation rise-time of <625 µs are experimentally achieved. Our device consists of a silicon hole array metasurface encapsulated by transparent conducting oxide as a localised heater. It allows for video frame rate optical switching over multiple pixels that can be electrically programmed. Some of the advantages of the proposed tuning method compared with other methods are the possibility to apply it for modulation in the visible and near-infrared region, large modulation depth, working at transmission regime, exhibiting low optical loss, low input voltage requirement, and operating with higher than video-rate switching speed. The device is furthermore compatible with modern electronic display technologies and could be ideal for personal electronic devices such as flat displays, virtual reality holography and light detection and ranging, where fast, solid-state and transparent optical switches are required. References: [1] J. Yang, S Gurung, S Bej, P Ni, HW Howard Lee, Reports on Progress in Physics 85 (2022), 036101. [2] K. Zangeneh Kamali, L. Xu, N. Gagrani, H. H. Tan, C. Jagadish, A. E. Miroshnichenko, D. N. Neshev, M. Rahmani, Accepted in Light: Science and Applications [3] K. Zangeneh Kamali, L. Xu, J. Ward, K. Wang, S. Manjath, G. Li, D. Neshev, A. Miroshnichenko, M. Rahmani, Small 15 (2019), 1805142.
Nr: 29
Title:

Towards Chiral Acoustoplasmonics
Authors:

Beatriz Castillo López de Larrinzar, Antonio Garcia-Martin 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. [1] L. D. Barron, Molecular Light Scattering and Optical Activity, https://doi.org/10.1017/CBO9780511535468 [2] B. Hopkins, A. Poddubny, A. Miroshnichenko e Y. Kivshar, “Circular dichroism induced by Fano resonances in planar chiral oligomers”, Laser Phot. Rev. 10, 137 (2016) [3] B. Auguié, J. L. Alonso-Gómez, A. Guerrero-Martínez, and L. M. Liz-Marzán, Fingers Crossed: Optical Activity of a Chiral Dimer of Plasmonic Nanorods, J. Phys. Chem. Lett. 2, 846 (2011). [4] C. de Dios, A. Jiménez, F. García, A. García-Martín, A. Cebollada, and G. Armelles, Mueller Matrix Study of the Dichroism in Nano-rods Dimers: Rod Separation Effects, Opt. Express 27, 21142 (2019). [5] B. Castillo López de Larrinzar, et al., Submitted (2022). [6] N. D. Lanzillotti-Kimura, A. Fainstein, B. Perrin, B. Jusserand, L. Largeau, O. Mauguin, and A. Lemaitre, Enhanced Optical Generation and Detection of Acoustic Nanowaves in Microcavities, Phys. Rev. B 83, 201103 (2011)

Area 2 - Nanophotonics, Plasmonics and Metamaterials

Full Papers
Paper Nr: 5
Title:

Anisotropic Metasurface for Ultrafast Polarization Control via All-Optical Modulation
Authors:

Giulia Crotti, Mert Akturk, Andrea Schirato, Vincent Vinel, Remo Proietti Zaccaria, Margherita Maiuri, Anton A. Trifonov, Ivan C. Buchvarov, Dragomir N. Neshev, Giuseppe Leo, Giulio Cerullo and Giuseppe Della Valle
Abstract: The ability to manipulate light polarization at an ultrafast speed is a challenging goal in the field of Photonics: sub-picosecond control of polarization is a fundamental functionality for a variety of applications, including the developement of free-space optical links for robust information encoding. To this aim, an important paradigm consists in employing metasurfaces as platforms which can be reconfigurable by all-optical means, i.e. upon illumination by an energetic femtosecond laser pulse. Here, we present giant all-optical modulations of dichroism in an anisotropic AlGaAs metasurface. An optimized design allows to exploit a sharp extended resonance of the nanostructure in the desired spectral range, where the pump-induced band-filling effect is the dominant process presiding over the ultrafast change of permittivity.
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Nr: 7
Title:

Correlation Between Plasmonic and Thermal Properties of Metallic Nanostructures
Authors:

Marc Lamy de La Chapelle, Ines Abid, Qiqian Liu, Andreea Campu, Gwenaëlle Vaudel, Pascal Ruello, Monica Focsan and Mathieu Edely
Abstract: Thanks to their plasmonic resonances, metallic nanostructures confine light energy at the nanoscale, thus behaving as optical nanosources. This energy is relaxed in the nanoparticle in the form of heat and these resonators then become heat nanosources [1]. Thus, via the control of the optical properties of the nanoparticle, which are easily modulated, it is possible to control the temperature at the nanometric scale. In this context, we are interested in studying the relationship between the optical properties and the thermal properties of plasmonic nanostructures. Using a thermal camera and a tunable pulsed laser, we were able to measure the temperature rise inside a solution of Au nanoparticles in water as a function of the excitation wavelength. We found an increase in the temperature of the solution, directly related to the plasmonic properties for Au particles. The effect of the particle shape on this hyperthermia phenomenon was also studied. We observed a better efficiency in terms of heat release for bipyramidal particles compared to spherical particles, for equivalent concentrations. We also showed that the heating of the solution is linearly proportional to the particle concentration and the excitation optical density. These results contribute to a better understanding of the heat transfer between plasmonic nanostructures and their surrounding environment, the control of which is key for several applications such as hyperthermia cancer treatment [2], in vivo drug transfer, computer data storage [3] and thermophotovoltaics [4]. This work was supported by the European DeDNAed project (H2020-FETOPEN2018-2020, 964248). [1] Baffou, G. and Quidant, R., 7, 171-187 (2013) [2] Nardine S. Abadeer et Catherine J. Murphy, 120, 4691–4716 (2016) [3] Pan, L., Bogy, D, 3, 189–190 (2009) [4] Pillai et M.A. Green, 94, 1481–1486 (2010).
Nr: 10
Title:

Tuning of Quasi-Bound States in the Continuum with Hybrid Silicon-Phase Change Materials Metasurfaces
Authors:

Angela I. Barreda, C. Zou, A. Sinelnik, E. Menshikov, I. Sinev, T. Pertsch and I. Staude
Abstract: Emission enhancement of quantum emitters by means of photonic nanostructures has been vastly investigated in the last years due to its application for developing single-photon sources, which are key elements in quantum information and quantum communications. Optical bound states in the continuum (BIC) represent a class of states that remain localized despite residing in the continuum of radiating modes. This means that they cannot be excited by incident electromagnetic radiation, or equivalently, they cannot emit radiation, presenting an infinite Q-factor. However, BICs are not observed experimentally due to the finite size of the sample, parasitic scattering, absorption or structural disorder. In fact, in real scenarios, BICs are transformed into leaky modes, known as quasi-BICs. Symmetry protected BIC, which appear when the spatial symmetry of the mode is not compatible with the symmetry of the radiating waves can be excited in metasurfaces, gratings or waveguides arrays, among other geometries. In particular, high refractive index dielectric metasurfaces can exhibit BIC, which can be converted to quasi-BIC by breaking the symmetry. The quasi-BICs are manifested in the transmission spectra as narrow dips with a high Q-factor at certain wavelengths that are fixed by the design of the metasurface. This fact can be a constraint for applications that need tuning capabilities. With the aim to solve this problem the possibility of using phase change materials (PCMs) have been introduced. PCMs exhibit a considerable change of their optical properties upon transition from the amorphous to the crystalline phase that can be induced via thermal, electrical or optical stimuli (Galarreta, 2020). Ge2Sb2Te5 (GST) has been considered as a promising PCM due to its large refractive index contrast between the amorphous and crystalline phases. However, its significant losses in visible range have limited its utility to the near- and mid-infrared spectral region. Recently, the binary antimony compounds Sb2S3 and Sb2Se3 emerged as promising candidates to bring the phase change functionality to the visible due to the low-losses in that region. In this work, we numerically demonstrate the tuning of a quasi-BIC mode by means of a silicon metasurface consisting of two asymmetric blocks, where a thin layer of Sb2Se3 is deposited on the top. The metasurface supports a quasi-BIC at λ = 1550 nm. We expect that the results of this work find applications involving light emission (e.g. from quantum dots), as it allows simultaneous strong and narrow-band enhancement and tuning of this band across the spectral range of emission.
Nr: 14
Title:

Casimir Nanoparticle Levitation
Authors:

Vincenzo Giannini and Adrian E. Rubio Lopez
Abstract: Casimir-Polder forces are natural candidates to tackle the phenomenon of levitation but are usually attractive forces. Here, we present nanoparticle levitation only based on the design of a metamaterial showing an effective perfect magnetic behavior on a broad range of frequencies. The nanoparticle’s potential resulting from the combination of the Casimir-Polder force and its weight allows anharmonic oscillations for the nanoparticle in general and harmonic ones for energies close to the potential minimum. We show that the characteristic frequency of the latter depends linearly on Planck’s constant.
Nr: 18
Title:

Programmable Random Lasers from Reversible Colloidal Assemblies
Authors:

Giorgio Volpe
Abstract: Colloidal self-assembly has been investigated as a promising approach for the fabrication of photonic materials and devices to make, e.g., coatings, displays, and sensors for diagnostics. The final optical properties of such materials strongly depend on the interactions among the constituent colloids and on their reciprocal spatial arrangement. Photonic crystals of periodically arranged colloids for instance are optical materials that can manipulate the flow of light through controlled interference, while randomly distributed colloids can be employed to fabricate robust lasing systems where laser action is obtained thanks to the multiple scattering of light within the material. Here, I will show the self-organization of programmable random lasers from the reversible out-of-equilibrium self-assembly of colloids. Under an external light stimulus, these novel random lasers self-assemble, are responsive and show dynamic properties, such as the possibility of reconfiguring their structure and their lasing properties. These man-made lasers with their life-like features (responsiveness, reconfigurability and cooperation) are a first step towards the realization of fully animate lasers capable of independent motion and autonomous adaptation in response to external stimuli.
Nr: 19
Title:

Quantum Nanophotonics: Antibunched Light and Molecular Entanglement
Authors:

Antonio I. Fernandez Dominguez
Abstract: In this talk, I will present two different nanophotonic platforms implementing archetypal quantum-optical phenomena. First, motivated by experimental research, I will explore antibunched light emission by nanoparticle-on-mirror cavities filled with a single molecule [1]. I will analyse the quantization of the cavity fields [2] and the emergence of plasmon-exciton polaritons in these systems as well. Secondly, inspired by the large impact of inverse design techniques on recent photonics design, I will investigate the generation of entanglement between two molecules through the inverse engineering of their photonic environment. I will present a topology-optimized dielectric cloaks yielding significant steady-state Wootter's concurrence values at distances much larger than the natural wavelength of the molecules [3]. [1] R. Sáez-Blázquez et al., Nano Lett. 22, 2365 (2022). [2] I. Medina et al., Phys. Rev. Lett. 126, 093601 (2021). [3] A. Miguel-Torcal et al., Nanophotonics 11, 4387 (2022).
Nr: 20
Title:

Collective Optical Excitations in Metallic and High-Index-Dielectric Nanoparticles
Authors:

Christos Tserkezis and P. Elli Stamatopoulou
Abstract: Optical excitations either in the form of plasmons in metals or Mie-resonances in high-index dielectrics are characterized by their ability to strongly enhance incident light, thus offering a fertile ground for a wide range of photonic applications.\\ Plasmons, the collective response of free electrons in metals, are of particular interest due to their ability to confine light at the nanoscale, paving the way for a large diversity of schemes to exploit it, from sensing to optical communications [1]. At the same time, the influence of plasmonic structures on their environment sets them an ideal platform for strong light-matter interaction studies [2]. Rapid advances in nanofabrication, as well as the need to integrate ever smaller components in modern photonic applications, has driven the relevant length scales to only a few nanometers and the limits of classical theories have become apparent. Here we discuss that, rather than radically new theory, the field of plasmonics can be treated, to a large extent, with classical electrodynamics, albeit adjusted to account for finite-size and non-classical effects [3]. The appeal of the prospects of plasmonics is in fact so strong, that the nano-optics community usually finds a way to surpass the practical limitations imposed by ohmic losses. Mie resonances in high-index dielectrics that do not suffer from high losses can be employed as alternatives, even though they cannot compete with the field localization of plasmons [4]. Even though standard dark-field spectroscopy can provide information about the optical modes of plasmonic and dielectric structures, when driving structure sizes at the nanoscale, spectroscopy methods that provide better spatial resolution are required. In electron microscopy fast electron beams are employed to study the optical response of structures of various geometries and materials with fine spatial detail [5]. Here we discuss the use of electron beams for the study of optical excitations of small particles, as well as other radiative and nonradiative processes emerging from this type of excitation [6].\\\\ References\\\\ 1. Maier S. A., Plasmonics: fundamentals and applications. New York: springer, 2007.\\ 2. Fofang N. T., et al., Nano Lett. 8, 3481 (2008).\\ 3. Stamatopoulou P. E., and Tserkezis C., Opt. Mater. Express 12, 1869 (2022).\\ 4. Baranov D. G., et al., Optica 4, 814 (2017).\\ 5. García de Abajo F. J., Rev. Mod. Phys. 82, 209 (2010).\\ 6. Fiedler S., et al., Nano Lett. 22, 2320 (2022).
Nr: 22
Title:

Active Angular Tuning and Switching of Brewster Quasi Bound States in the Continuum in Magneto-Optic Metasurfaces
Authors:

Antonio Garcia-Martin, Diego Romero Abujetas, Jose M. Llorens, Nuno de Sousa and Jose A. Sanchez-Gil
Abstract: Bound states in the continuum (BICs) emerge throughout Physics as leaky/resonant modes that remain, however, highly localized[1]. They have attracted much attention in Photonics, and especially in metasurfaces[2,3]. One of their most outstanding features is their divergent Q-factors, indeed arbitrarily large upon approaching the BIC condition (quasi-BICs) [4,5]. Here we investigate how to tune quasi-BICs in magneto-optic (MO) all-dielectric metasurfaces. The impact of the applied magnetic field in the BIC parameter space is revealed for a metasurface consisting of Si spheres with MO response. Through our coupled electric/magnetic dipole formulation, the MO activity is found to manifest itself through the interference of the (MO-induced) out-of-plane electric/magnetic dipole resonances with the in-plane magnetic/electric (directly induced) dipole, leading to a rich, magnetically-tuned quasi-BIC phenomenology, resembling the behavior of Brewster quasi-BICs for tilted vertical-dipole resonant metasurfaces. Such resemblance underlies our proposed design for a fast MO switch of a Brewster quasi-BIC by simply reversing the driving magnetic field. This MO-active BIC behavior is further confirmed in the optical regime for a realistic YIG nanodisk metasurface through numerical calculations. Our results present various mechanisms to magneto-optically manipulate BICs and quasi-BICs, which could be exploited throughout the electromagnetic spectrum with applications in lasing, filtering, and sensing [6]. References [1] Chia Wei Hsu, et al., Nat. Rev. Mater. 1 16048, (2016) [2] D.C. Marinica, et al., Phys. Rev. Lett., 100, 183902 (2008) [3] Chia Wei Hsu, et al., Nature 499, 188 (2013) [4] Kirill Koshelev, et al., Phys. Rev. Lett. 121, 193903 (2018) [5] Diego R. Abujetas, et al., Sci. Rep. 9, 16048 (2019) [6] Diego.R. Abujetas, et al., Nanophotonics 10, 4223 (2021).
Nr: 23
Title:

Nanooptics in Anisotropic Flatlands
Authors:

Pablo Alonso-González
Abstract: Highly anisotropic crystals have recently attracted considerable attention due to their ability to support polaritons with unique properties, such as hyperbolic dispersion, negative phase velocity, or extreme confinement. In particular, the biaxial van der Waals semiconductor α-phase molybdenum trioxide (α-MoO3) has received much attention [1] due to its ability to support in-plane hyperbolic phonon polaritons (PhPs) —infrared (IR) light coupled to lattice vibrations in polar materials— with ultra-low losses, offering an unprecedented platform for controlling the flow of energy at the nanoscale. In this talk, we will show experimental demonstrations of the unique behavior of PhPs in these crystals, including the visualization of anomalous cases of the fundamental optical phenomena of refraction [2] and reflection, and the exotic phenomenon of canalization, in which PhPs propagate along a single direction with ultralow losses [3]. References [1] W. Ma et al., Nature, 562, 557 (2018). [2] G. Álvarez-Pérez et al., Adv. Mater. 32, 1908176 (2020). [3] J. Duan et al., Nature Communications, 12, 1, 1-8 (2021). [4] J. Duan et al., Nano Letters, 20, 7, 5323-5329 (2020).
Nr: 24
Title:

Directional Strong-Coupling Between Nanolight and the Organic Molecule Pentacene
Authors:

Ana I. Fernández-Tresguerres Mata, Pablo Alonso-González and Alexey Y. Nikitin
Abstract: Recent experiments have discovered the existence of low-loss nanolight – in the form of surface phonon polaritons (PhPs), i.e. infrared (IR) light coupled to lattice vibrations in polar crystals– with in-plane anisotropic (hyperbolic) propagation in the van der Waals (vdW) crystal α-MoO3. Our results demonstrate that this exotic nanolight enables, for the first time, the visualization of directional-dependent strong coupling phenomena with organic molecules (pentacene). To support this claim, we will show near-field images taken by scattering-type scanning near-field optical microscopy (s-SNOM) on a curved flake of α-MoO3 placed on top of a thin pentacene film, which allow us to directly corroborate the strong coupling variation as a function of the in-plane angle. This result opens the door to several new applications such as directional sensing or directional local control of chemical properties at the nanoscale.
Nr: 27
Title:

Nonlinear Photoluminescence from Metals: Theory and Comparison to Experiments
Authors:

Yonatan Sivan
Abstract: We provide a complete quantitative theory for the long-disputed effect of (nonlinear) photoluminescence from metals and use it to explain various contradicting or hard-to-explain experimental measurements.
Nr: 30
Title:

Nonlinear All-Optical Coherent Generation and Read-Out of Valleys in Atomically Thin Semiconductors
Authors:

Paul Herrmann, Sebastian Klimmer and Giancarlo Soavi
Abstract: With conventional electronics reaching its performance limits in terms of speed and size, light is the ideal candidate to realize devices operating with high speed and low consumption thanks to all-optical operations [1] and lightwave electronics. A promising approach in this direction is based on valleytronics using two-dimensional transition metal dichalcogenides (TMDs). TMD monolayers are direct gap semiconductors with two energetically degenerate but non-equivalent valleys in the K and K’ points of the Brillouin zone, owing to their honeycomb lattice structure. The valleys can be selectively excited (write) with one-photon CW excitation, nonlinear two-photon excitation and coherent excitation by optical Stark and Bloch-Siegert shift, because light of opposite helicity couples to opposite valleys. The detection (read) of VP is so far mostly based on polarization-resolved photoluminescence (PL), since the (one-photon) spontaneous emission from the valleys follows the same selection rules as the (one-photon) excitation [2]. However, this approach has two main drawbacks: (1) it detects an averaged light emission over a time-scale that is much longer compared to the valley and spin lifetimes; (2) it is intrinsically an invasive method, which measures the VP only after light emission. Nonlinear optics [3] and in particular second harmonic generation (SHG), overcomes these disadvantages and provides an ultrafast and non-destructive method for the detection of the VP in TMDs [4].In fact, the presence of a VP breaks the time-reversal symmetry of TMDs, reducing the intrinsic D3h crystal symmetry to C3h and thereby leading to new terms in the nonlinear optical susceptibility. These terms can be probed by polarization resolved SHG measurements. In this work we simultaneously pump (write) and probe (read) the VP in WSe2 with one single elliptically polarized ultra-short pulse at room temperature. We probe the VP using polarization dependent SHG measurements at different values of the fundamental wavelength (FW) corresponding to below-gap, 1s and 2p exciton resonances and find that resonant SHG at the 1s state is the best probe of the VP. In addition, we investigate the mechanism of VP generation under our experimental conditions of below gap excitation. Looking at the combined results of two-photon PL measurements and power-dependent valley SHG, we deduce that the VP observed in our experiments is generated by an ultrafast coherent optical Stark-shift, which has been recently shown to be valley selective in TMDs [5]. Our work provides a direct evidence of ultrafast and all-optical coherent generation and detection of valleys in atomically thin semiconductors. [1] S. Klimmer et al.: Nature Photonics 2021, 15(11) 837 [2] K. F. Mak et al.: Nature nanotechnology 2012, 7(8) 494 [3] O. Dogadov et al.: Laser & Photonic Reviews 2022, 16 2100726 [4] F. Hipolito et al.: 2D Materials 2017, 4(2) 021027 [5] J. Kim et al.: Science 2014, 346(6214) 1205.
Nr: 31
Title:

Near Field Excitation of Bound States in the Continuum in Metasurfaces: Unveiling Symmetry Protection and Lateral Confinement
Authors:

Jose A. Sanchez-Gil, Diego Romero Abujetas, Stan ter Huurne, Niels van Hoof and Jaime Gómez Rivas
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 [1]. On the basis of a generalized coupled electric/magnetic dipole (CEMD) theory for infinite arrays [2], we have indeed demonstrated that simple metasurface configurations may support robust, symmetry-protected BICs. In particular, a dipole-dimer array is shown here to yield a BIC at normal incidence as the dipole detuning parameter vanishes; this has been experimentally verified through Au-rod dimer metasurface in the THz domain [3]. We have also extended our CEMD formalism to include a dipole source close to the metasurface [4]. Bear in mind that BICs are not accessible through far-field excitation; rather, near field excitation is required to couple electromagnetic radiation to a BIC. From the experimental standpoint, a double near-field THz probe technique has been developed in TU/e to locally excite and detect the time evolution, thereby allowing us to measure the near field close to a metasurface. These experimental and theoretical tools have allowed us to unveil two fundamental properties of symmetry-protected BICs. First, the specific symmetry-protection mechanism is revealed in the near-field pattern through an anti-symmetric dipolar field in each unit cell, spread all over the metasurface plane with no phase difference between adjacent cells [5]. Moreover, we show that such BICs are strongly confined along the perpendicular (out-of-plane) direction, achieving an amplitude decay length from the metasurface of λ/38 at 0.39 THz [6]. Recall that this metasurface is a near lossless system, whereas electromagnetic field confinement on sub-wavelength scales usually occurs at the expense of increasing optical losses. These experimental demonstrations, supported by coupled dipole calculations, add to knowledge in the field of BICs on metasurfaces and related potential applications in planar devices where large sub-wavelength planar field enhancements might be critical, such as non-linear optics, sensing, lasing, etc. 1. C. W. Hsu, B. Zhen, A. D. Stone, D. D. Joannopoulos, and M. Solijacic, “Bound states in the continuum,” Nature Review Materials 1, 16048 (2016). 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. van Hoof, S. Huurne, J. Gómez-Rivas, and J. A. Sánchez-Gil, “Spectral and temporal evidence of robust photonic bound states in the continuum on terahertz metasurfaces,” Optica 6, 996 (2019). 4. D. R. Abujetas and J. A. Sánchez-Gil, “Near-Field Excitation of Bound States in the Continuum in All-Dielectric Metasurfaces through a Coupled Electric/Magnetic Dipole Model,” Nanomaterials 11, 998 (2021). 5. N.J.J. van Hoof et al, “Unveiling Symmetry Protection of Bound States in the Continuum with Terahertz Near field Imaging,” ACS Photon. 8, 3010 (2021). 6. S. ter Huurne et al, “Direct observation of lateral field confinement in symmetry-protected THz bound states in the continuum,” Adv. Opt. Mat. (in press).
Nr: 32
Title:

Chiral Sensing with Semiconductor Nanophotonics
Authors:

Alberto Curto
Abstract: Chirality plays a pivotal role in the functionality of biomolecules such as proteins, amino acids, and carbohydrates. Circular dichroism can distinguish enantiomers thanks to a small difference in the absorption of circularly polarized light. However, chiral sensing faces significant limitations due to inherently weak chiroptical signals. It is thus severely limited by low sensitivity and low spatial resolution. As a result, it is challenging to resolve the chirality of individual nanoscale objects using light for critical applications such as detecting protein aggregates linked to various diseases. In this presentation, I will discuss our progress in pushing the sensitivity limits of optically resolvable chirality by exploiting semiconductor nanophotonics. I will show several strategies to optimize chiral molecular sensors based on silicon metasurfaces to detect low molecular concentrations. Specifically, I will present our recent results on tailoring silicon nanostructures to enhance polarized fluorescence and Raman spectroscopies, increase optical chirality and maximize chirality transfer. Our results promise an increase in sensitivity towards the detection of single chiral molecules compatible with high-resolution imaging.
Nr: 34
Title:

Multifunctional Metasurfaces for Light Enhancement
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: 35
Title:

Classical and Quantum Effects in Ultrastrongly-Coupled Nanophotonic Systems
Authors:

Ruben Esteban
Abstract: The strong localization of light in micro and nanocavities leads to very efficient coupling with excitons and vibrations of molecules, phonons in van der Waals materials and related excitations. It then becomes possible to reach the strong [1,2] and ultrastrong [3] coupling regimes for relatively few molecules or small amounts of material. These two regimes occur for coupling strengths comparable with the losses and resonant frequencies of the system, respectively, and their interest largely relies on to the quantum phenomena involved and their potential applications, as they can modify chemical properties, introduce strong non-linearities or alter the ground state, for example [3,4]. Revealing quantum effects in nanophotonic experiments is, however, often challenging. We first consider systems where the cavity mode interacts with phonons or with many more than a single molecule. We focus on Fabry-Pérot microresonators coupled to phonon polaritons in hexagonal Boron Nitride (hBN) [5]. We show experimentally and theoretically that these systems allow to reach strong coupling for very thin hBN layers, and ultrastrong coupling with fully hBN-filled cavities. We discuss how, even for the ultrastrong coupling regime, the standard optical measurements are not affected by quantum effects, and can be treated within a classical model (based on coupled harmonic oscillators) that is equivalent to a quantum description. Further, we show that the maximum coupling strength and vacuum Rabi splitting is determined only by the properties of the bulk plasmon of hBN, not by the properties of the cavity. Next, we model the intensity correlations of the light emitted by a single exciton (in e.g. a molecule or a quantum dot) coupled to a plasmonic mode. We show [6] that the analysis of these correlations can be very advantageous to demonstrate physics beyond classical or even standard quantum models. We demonstrate that the correlations can manifest a strong bunching directly connected with non-number-conserving terms in the Hamiltonian that are behind the quantum phenomena characteristic of ultrastrong coupling. Conventionally, the ultrastrong coupling regime is considered to be reached for a coupling strength equal to 10 percent the excitonic and plasmonic frequency. In contrast, we show that the bunching induced by the non-number-conserving terms can emerge for coupling strengths much smaller than this limit, in theory arbitrarily small. Thus, the measurement of correlations seems very promising for accessing the distinctive properties of ultrastrongly coupled systems. 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. F. Kockum et al., Nat. Rev. Phys 1, 19 (2019) [4] A. Thomas et al., Science 363, 615 (2019) [5] M. Barra Murillo et al., Nat. Comm. 12, 6206 (2021) [6] A. Nodar et al., arXiv:2211.13249
Nr: 36
Title:

Hybrid Anapole Resonator for Local Heat Generation
Authors:

Javier González-Colsa, Juan D. Olarte-Plata, Fernando Bresme and Pablo Albella
Abstract: HRI dielectric materials are currently able to support strong electric and magnetic modes with eventually low absorption [1,2]. This allows them to be used in many applications [3]. However, far from the quasi-static regime, HRI nanoresonators can support a toroidal dipole, enabling the possibility of engendering anapolar excitations. An ideal anapole is characterized by an absence of radiation and optical absorption becoming an efficient electromagnetic energy reservoir [4]. Here, we present our investigation on anapoles in which we exploit these particularities to amplify the ohmic losses of a system, thus improving its thermal efficiency. We study a metallic ring [5], as heating source and an HRI dielectric disk [6], designed to support anapole modes, located in its center (electromagnetic resonator). The proposed system results in a ten-fold temperature increase when illuminated, thus behaving as powerful nanoheating source. In this work, we also discuss its tunability capabilities, that can be easily tuned by modifying the structural parameters of both, outer ring and inner disk and even the materials. On the other hand, we will present our most recent investigation on the thermal performance of a realistic janus structure under nanosecond pulsed laser illumination to determine the optimal pulse regime. Thus, we will show a simple approach to reach high temperatures in the NIR, a spectral region of particular interest in biomedical applications. This approach also helps to spatially control the thermal flow. We believe that this investigation can motivate the development of novel strategies to reach efficient nanoheating platforms that are highly demanded in applications that require temperature-controlled devices, thus being of general interest to the thermoplasmonic community. Authors would like to thank Profs C. R. Crick and Otto Muskens for the interesting and valuable discussions. We gratefully acknowledge financial support from Spanish national project INMUNOTERMO (No. PGC2018-096649-B-I), the UK Leverhulme Turst (Grant No. RPG-2018-384). J. G-C. thanks the Ministry of science of Spain for his FPI grant and P.A. acknowledges funding for a Ramon y Cajal Fellowship (Grant No. RYC-2016-20831). References 1. A. García-Etxarri, R. Gómez-Medina, L. S. Froufe-Pérez, C. López, L. Chantada, F. Scheffold, J. Aizpurua, M. Nieto-Vesperinas, and J. J. Sáenz, Optics Express 19(6), 4815 (2011). 2. A. I. Kuznetsov, A. E. Miroshnichenko, Y. H. Fu, J. Zhang, and B. Luk’yanchuk, Scientific Reports 2, 1–6 (2012). 3. A. I. Barreda, J. M. Saiz, F. González, F. Moreno, and P. Albella, AIP Advances 9(4), (2019). 4. A. E. Miroshnichenko, A. B. Evlyukhin, Y. F. Yu, R. M. Bakker, A. Chipouline, A. I. Kuznetsov, B. Luk’yanchuk, B. N. Chichkov, and Y. S. Kivshar, Nature Communications 6, (2015). 5. J. González-Colsa, G. Serrera, J. Saiz, D. Ortiz, F. Gonzalez, F. Bresme, F. Moreno, and P. Albella, Optics Express 30(1), 125–137 (2021). 6. T. Shibanuma, G. Grinblat, P. Albella, and S. A. Maier, Nano Letters 17(4), 2647–2651 (2017).
Nr: 38
Title:

Theoretical Approach to Atomic-Scale Nanoplasmonics
Authors:

Nerea Zabala, Mattin Urbieta, Eduardo Ogando, Daniel Sánchez-Portal and Javier Aizpurua
Abstract: We explore from first principles the atomistic footprints of nanometer-size plasmonic particles in optical and Electron Energy Loss (EEL) spectroscopies. Full quantum calculations using Time-Dependent Density Functional Theory (TDDFT) reveal the effect of subnanometric localization of optical fields due to the presence of atomic-scale features at the surface of metallic clusters and interparticle gaps [1]. This effect is explained within classical electrodynamics, as a non-resonant lightning rod effect at the atomic scale that produces an additional enhancement over that of the plasmonic background [2]. Atomic-scale effects in plasmonics are also revealed in EEL spectra of electron beams passing nearby or through metallic clusters. Our theoretical results demonstrate the atomic-scale sensitivity of EELS in the valence spectral range. Whereas the excitation of localized surface plasmons (LSPs) is very sensitive to the surface atomic structure probed by the electron beam, confined bulk plasmons (CBPs) excited for penetrating trajectories reveal the quantum size effects in the volume of the nanoparticles. Moreover, we prove that classical local dielectric theories that go beyond the spherical approximation and mimic the atomistic icosahedral shape of the nanoparticles, reproduce the trends of the LSPs, but fail to describe properly the behaviour of the CBPs. We interprete these volume plasmonic excitations considering a non-local hydrodynamical model of spherical nanoparticles [2,3]. [1] M. Barbry, et al., Nano Lett., 15, 3410 (2015). [2] M. Urbieta, et al., ACS Nano, 12, 585 (2018); M. Urbieta, PhD thesis, UPV/EHU 2021. [3] T. Christensen, et al., ACS Nano, 8, 1745 (2014).
Nr: 39
Title:

Strain Tuning of Quantum Emitters in 2D Materials by Strain Fields
Authors:

Javier Martín-Sánchez
Abstract: The development of novel ultra-compact two-dimensional (2D) photonic technologies for application in quantum information processing, relies on our ability to fabricate single photon sources (SPS) in 2D van der Waals materials where we are able to control their position as well as their optical emission properties [1]. However, the challenge still remains to fully understand their physical origin in order to be able to efficiently utilize them and to actively tune their optical properties. One solution is to implement elastic strain engineering through the introduction of a novel class of piezoelectric actuators [2,3,4]. In this work, we demonstrate the possibility to reversibly reconfigure the potential landscape leading to formation of site-controlled SPSs upon introduction of in-plane elastic strain fields with controlled magnitude and sign. To do that, we fabricated hybrid piezoelectric devices by transferring a WSe2 monolayer on top of piezoelectric nanopillars. Moreover, a reversible and robust tuning of the SPSs emission energy (as well as exciton redistribution between individual SPSs) is further shown without affecting the single photon emission purity with relatively large energy shifts. The experimental results are further corroborated by numerical simulations along with analytical calculations showing that all SPSs can be energy blue shifted. Interpretations on the origin of the SPSs will be discussed based on an exciton diffusion model accounting for the variations on the micro-photoluminescence spectra corresponding to individual quantum emitters. Our findings shed light on the understanding of the physical origin of SPSs in 2D monolayers and are of strong relevance for the practical implementation of single photon devices based on 2D materials for future applications in quantum information processing. References [1] A. Srivastava et al. Nat. Nanotechnol. 10 491 (2015). [2] J. Martín-Sánchez et al. Semicond. Sci. Technol. 33 013001 (2018). [3] R. Trotta, J. Martín-Sánchez et al. Nat. Commun. 7 10375 (2016). [4] O. Iff, D. Tedeschi, J. Martín-Sánchez et al. et al. Nano Lett. 19 6931 (2019).
Nr: 42
Title:

DNA-Origami-Based Plasmonic Assemblies with Tailored Stimuli and Optical Responses
Authors:

Anton Kuzyk, Minh-Kha Nguyen, Joonas Ryssy, Jacky Loo, Rafal Klajn, Pablo Albella and Yike Huang
Abstract: The DNA origami technique has emerged as one of the most versatile bottom-up nanofabrication methods. In this talk we will discuss our recent results related to application of DNA origami for fabrication of plasmonic systems with novel stimuli and optical responses. Specifically, we will present fabrication of i) light-responsive dynamic plasmonic assemblies with easily regulated steady out-of-equilibrium states1; ii) chiral plasmonic systems with visually detectable reconfigurable optical activity; iii) metal shells with tailored complex morphologies and optical responses within near-infrared transparency window(s). References [1] J. Ryssy et al. 2021. Light-Responsive Dynamic DNA-Origami-Based Plasmonic Assemblies . Angew. Chem. Int. Ed. 60: 5859-5863.
Nr: 43
Title:

Understanding Properties, Opportunities and Challenges of Nanoalloys with Plasmonic and Transition Metals
Authors:

Vincenzo Amendola
Abstract: Despite the traditional plasmonic materials are counted on one hand, there are a lot of possible combinations leading to alloys with other elements of the periodic table, in particular transition metals renowned for magnetic or catalytic properties. It is not a surprise, therefore, that nanoalloys are considered for their ability to open new perspectives in the panorama of plasmonics, with multiple applications envisaged in photonics, photocatalysis, sensing and magneto-optics.[1] Here we show that, in some remarkable cases, the amplification of the conventional properties is possible[2] but also that this field is still in its infancy and several challenges must be overcome, starting with the frequently observed decrease in plasmonic performances.[3,4] Thus, it is thus crucial to understand and predict the properties of these alloys, as well as to synthesize them for further studies. Considering the several plasmonic nanoalloys under development as well as the large number of those still awaiting synthesis, modelling, properties assessment and technological exploitation, we expect a great impact on the forthcoming solutions for sustainability, ultrasensitive and accurate detection, information processing and many other fields. [1] Coviello, Vito; Forrer, Daniel; Amendola, Vincenzo; Recent developments in plasmonic alloy nanoparticles: synthesis, modelling, properties and applications, ChemPhysChem 2022, 23, e202200136 [2] Amendola, Vincenzo; Saija, Rosalba; Maragò, Onofrio M; Iatì, Maria Antonia; Superior plasmon absorption in iron-doped gold nanoparticles, Nanoscale, 2015, 7, 8782-8792 [3] Amendola, Vincenzo; Scaramuzza, Stefano; Agnoli, Stefano; Strong dependence of surface plasmon resonance and surface enhanced Raman scattering on the composition of Au–Fe nanoalloys, Nanoscale, 2014, 6, 1423-1433 [4] Alexander, Duncan T. L.; Forrer, Daniel; Rossi, Enrico; Lidorikis, Elefterios; Agnoli, Stefano; Bernasconi, Gabriel D.; Butet, Jérémy; Martin, Olivier J.F.; Amendola, Vincenzo; Electronic Structure-Dependent Surface Plasmon Resonance in Single Au−Fe Nanoalloys, Nano Letters, 2019, 19, 5754−5761
Nr: 45
Title:

A Novel Pathway for the Design of Efficient Directional Plasmonic Nanoheaters
Authors:

Pablo Albella
Abstract: Metallic nanoparticles can act as nanoheaters when optically excited due to the presence of localized plasmonic resonances. These resonances are generally accompanied by large resistive losses that come from the transitions that the Fermi surface electrons experience when absorbing photons. This effect, often referred to as thermoplasmonic, can lead to the heating of the nanostructure and its surroundings. This fact is undesirable in applications like sensing or spectroscopy, and dielectric alternatives have been successfully proposed to overcome this problem, however it is necessary in optoelectronic applications, drug delivery or photothermal cancer therapies. In this talk, I will present our most recent results in this active topic paying especial attention to those showing exceptional properties on directional heat delivery.
Nr: 47
Title:

DNA Origami Assembled Nanoantennas for Manipulating Single-Molecule Spectral Emission
Authors:

Guillermo P. Acuna
Abstract: Optical nanoantennas can affect the decay rates of nearby molecules by changing the local density of states around them [1,2]. The emission spectrum of a fluorophore is given by the energy of the possible transitions weighted by the probability of each of them to occur. By engineering the resonance of a nanoantenna, one can selectively enhance specific radiative vibronic transitions of an emitter, thus re-shaping its emission spectrum. Since interactions between molecules and nanoantennas are known to be position dependent, we make here use of the DNA origami [3] technique to precisely place an individual emitter at different positions around a gold nanorod (see Figure 1, left panel). In this nanometer-controlled configuration, we observe the appearance of a second fluorescence peak whose position and intensity are correlated with the resonance wavelength of the nanorod, that we obtain from its photoluminescence spectrum (Figure 1, center and right panels). This second peak comes from the selective enhancement of transitions to different vibrational levels of the ground state whose energy is in resonance with the nanorod´s longitudinal plasmon mode. We observe that the relative intensity of these two transitions can be up to 60 times higher than in the case of an isolated molecule.
Nr: 48
Title:

Wafer-Scale Fabrication of Metasurfaces for Infrared and Energy Applications
Authors:

Otto Muskens
Abstract: Functional metasurfaces combine expertise in advanced materials, state-of-the-art nanofabrication, and sophisticated design. In recent years, our team has worked on different aspects in a variety of projects and here I will provide examples toward scalable metasurface technology using wafer-scale production level tools. In the domain of advanced materials capabilities our work has focused on a number of tunable and switchable oxides that can be deposited reproducibly and with high accuracy using Atomic Layer Deposition. This includes transparent conducting oxides for infrared plasmonics and metasurfaces using Al-doped ZnO, where doping levels can be tuned not only by Al-doping, but importantly through oxygen plasma treatment [1]. We have demonstrated ability of precise lateral patterning of doping profiles with resolution better than 100nm, which can be used to define infrared metasurfaces through local doping in an otherwise completely planar structure. Wafer-scale fabrication of infrared metal oxide metasurface was demonstrated to achieve a dual band control over the spectral response in the mid and long-wave infrared [2]. We have also reported the first demonstration of 200mm wafer-scale fabrication of tungsten-doped vanadium dioxide (W:VO2) using atomic layer deposition, showing room-temperature insulator-to-metal phase transition [3]. This capability opens up a wide range of new applications in integration of non-volatile switching in metasurfaces and integrated photonics, with potential applications in communications, optical data processing and, thermal control coatings for energy applications [4]. [1] K. Sun, W. Xiao, S. Ye, N. Kalfagiannis, K. S. Kiang, C. H. de Groot, O. L. Muskens, Embedded metal oxide plasmonics using local plasma oxidation of AZO for planar metasurfaces, Adv. Mater. 2001534 (2020) [2] K. Sun, E. Vassos, X. Yan, C. Wheeler, J. Churm, P. R. Wiecha, S. A. Gregory, A. Feresidis, C. H. de Groot, O. L. Muskens, Wafer-Scale 200 mm Metal Oxide Infrared Metasurface with Tailored Differential Emissivity Response in the Atmospheric Windows, Adv. Optical Mater. 2200452 (2022) [3] K. Sun, C. Wheeler, J. A. Hillier, S. Ye, I. Zeimpekis, A. Urbani, N. Kalfagiannis, O. L. Muskens, C. H. de Groot, Room Temperature Phase Transition of W-Doped VO2 by Atomic Layer Deposition on 200 mm Si Wafers and Flexible Substrates, Adv. Optical Mater. 2201326 (2022) [4] K. Sun, W. Xiao, C. Wheeler, M. Simeoni, A. Urbani, M. Gaspari, S. Mengali, C.H. de Groot, O. L. Muskens, VO2 metasurface smart thermal emitter with high visual transparency for passive radiative cooling regulation in space and terrestrial applications, Nanophotonics 11, 4101-4114 (2022)
Nr: 51
Title:

Optical Printing of Metal Nanoparticles as a Tool for Ultrasensitive SERS Detection: From Biomolecules to Nanoplastics
Authors:

Pietro G. Gucciardi, Antonino Foti, S. Bernatova, M. Kizovsky, Maria Grazia Donato, Jan Jezek, O. Samek, Onofrio M. Maragò and P. Zemanek
Abstract: Aggregation by optical and thermophoretic forces [1, 2] of gold nanoparticles in liquid solutions containing molecules at very low concentrations or sparse nanoparticulate matter is of particular interest in view of the possibility to trigger surface-enhanced Raman scattering (SERS) and enable ultrasensitive detection of the species dispersed in the liquid [3]. In this article I will give an overview of how optical printing [4] of plasmonic gold nanorods can be used to detect molecules, toxins and proteins down to pM concentration [5] in short times (tens of seconds). Printing experiments are shown on surfaces made of glass [3, 5], plastics [6] and graphene [7], as well as in microfluidic chips [8]. The crucial role of the optical scattering force in the process will be highlighted by comparing aggregation times and detection speed when varying the laser energy across the localized plasmon resonance profile of the gold nanorods, and as a function of the irradiation power [8]. Finally, I will show how mixing gold nanorods with nanoplastics leads to thermophoretic fluxes that locally concentrate the nanoparticles under the laser spot, enabling and favouring their detection [9]. Acknowledgment The authors acknowledge support from the Czech Academy of Sciences, project MSM100652101 supporting international cooperation of beginning researchers and from the projects MERLIN-MICROPLASTIQUE (agreement 17/1212947B), ASI-INAF n.2018-16-HH.0 “SPACE Tweezers,” MSCA ITN (ETN) project “Active Matter,” COST Action CA20101 - Plastics monitoRIng detectiOn RemedIaTion recoverY (PRIORITY), and Ecosistema dell’Innovazione “Sicilian Micronano- Tech Research And Innovation Center - SAMOTHRACE” (ECS00000022). References [1] P. H. Jones, et al., Optical Tweezers: Principles and Applications; Cambridge University Press: Cambridge, 2015 [2] L. Lin, et al., “Optothermal Manipulations of Colloidal Particles and Living Cells,” Acc. Chem. Res., vol. 51, pp. 1465-1474, 2018 [3] B. Fazio et al. “SERS detection of Biomolecules at Physiological pH via aggregation of Gold Nanorods mediated by Optical Forces and Plasmonic Heating.” Sci Rep UK, vol. 6, pp. 26952, 2016 [4] J. Gargiulo, et al., “Accuracy and ́Mechanistic Details of Optical Printing of Single Au and Ag Nanoparticles,” ACS Nano, vol. 11, pp. 9678−9688, 2017 [5] A. Foti et al. “Optical aggregation of gold nanoparticles for SERS detection of proteins and toxins in liquid environment: Towards ultrasensitive and selective detection” Materials, vol. 11, p. 440, 2018 [6] M. G. Donato, et al., “Optical Force Decoration of 3D Microstructures with Plasmonic Particles,” Opt. Lett., vol. 43, pp. 5170−5173, 2018 [7] A. Foti et al. “Optically induced aggregation by radiation pressure of gold nanorods on graphene for SERS detection of biomolecules” The European Physical Journal Plus vol. 136, p. 30, 2021 [8] S. Bernatova, et al. “Wavelength-Dependent Optical Force Aggregation of Gold Nanorods for SERS in a Microfluidic Chip, ” J. Phys. Chem. C., vol. 123, pp. 5608-5615, 2019 [9] S. Bernatova et al. “Detection of Plastic Nanoparticles in Aqueous Enviroment Based on Optical Manipulation in Combination with Raman Spectroscopy” 2022 IEEE International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea), 2022, pp. 349-352, doi: 10.1109/MetroSea55331.2022.9950839.
Nr: 15
Title:

Observation of DNA Stand Interaction with SERS
Authors:

Aicha Azziz, Qiqian Liu, Marjan Majdinasab, Yang Xiang, Mathieu Edely and Marc Lamy de La Chapelle
Abstract: Surface-enhanced Raman spectroscopy has demonstrated its ability as powerful tool that can provide us information about the structure and the conformation of molecules such as DNA. In this work, we used an Hamamatsu commercial SERS substrate [1], to study the interaction between a DNA sequence consisting of 20 Bases of poly-Thymin (PolyT) with its complementary poly-Adenin (PolyA). The PolyA strand is grafted at the surface of the gold nanostructured surface using a thiol group at the 5' extremity of the DNA strand. the SERS substrate is incubated in 450 µl of PolyA (10-4 M) in TE buffer for 15 hours. The surface is then washed to remove the PolyA excess. 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. 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). References [1] A. Azziz, W. Safar, Y. Xiang, M. Edely, M. Lamy de la Chapelle, Sensing performances of commercial SERS substrates. J. Mol. Struct. 2022, 12, 1248. [2] Safar, W.; Tatar, A. S.; Leray, A.; Potara, M.; Liu, Q. Q.; Edely, M.; Djaker, N.; Spadavecchia, J.; Fu, W. L.; Derouich, S. G. et al. New insight into the aptamer conformation and aptamer/protein interaction by surface-enhanced Raman scattering and multivariate statistical analysis. Nanoscale 2021, 13, 12443–12453.
Nr: 16
Title:

Sensing Performances of Commercial SERS Substrates
Authors:

Aicha Azziz, Wafa Safar, Yang Xiang, Mathieu Edely and Marc Lamy de La Chapelle
Abstract: Since the discovery of Surface Enhanced Raman Spectroscopy (SERS) and the proven ability for this tech- nique to detect molecules at trace level, numerous techniques have been reported for fabricating sub- strates that ensure reliable and reproducible SERS signal on its whole surface. In this paper we studied the capabilities and sensing performances of three commercial SERS substrates (RAM-SERS-SP from Ocean Optics, QSERS from Nanova Inc. and Hamamatsu from Hamamatsu Photonics) by using diluted solution of 4-mercaptobenzoic acid (MBA) at two different excitation wavelengths (633 and 785 nm). Large datasets were obtained through Raman mappings collected randomly on different areas on the substrate surface. The averaged SERS signals for one specific vibrational band of the MBA were used to compare limit of detection (LOD), limit of quantification (LOQ) and sensitivity of the three substrates. LOD and LOQ be- tween 1 μM and 10 μM were calculated with a range of use of only one or two orders of magnitude. The best sensing performances were reached by the Hamamatsu substrate for an excitation wavelength of 633 nm.
Nr: 17
Title:

Correlation Between DNA Bases and the Intensity of the Raman Bands with SERS
Authors:

Aicha Azziz, Qiqian Liu, Marjan Majdinasab, Gunnar Klös, Aitziber López Cortajarena, Mathieu Edely and Marc Lamy de La Chapelle
Abstract: Raman spectroscopy has become a popular tool for analyzing biological samples such as DNA. It allows us to access to the vibrational levels of molecules and thus to identify the chemical composition and to observe the structure of molecular systems.[1] In this work, we recorded the SERS spectra of DNA strands with different sequences and grafted at the surface of gold nanoparticles. Our objective is to study the correlation between the DNA sequences and its base composition and the intensity of Raman bands observed in SERS. To reach a high density of DNA on the surface of the gold nanoparticles, the DNA strands include a thiol group (SH) at their 5' end and are conjugated to gold nanoparticles using the freeze-thaw cycle method. SERS measurements are performed on dried drops deposited on a glass slide. We recorded 5 spectra for each sample using a 785nm excitation wavelength. We observed several bands that can be assigned to the different bases and to the phosphate backbone. For instance, the bands of ring breathing mode of adenine and the carbonic skeleton of the DNA are observable at 733cm-1 and 1029cm-1 respectively.[2] We then compare the relative intensity of the different bands such as the 733cm-1 or 1029cm-1 ones. We found that the relative intensity of the 733cm-1 band is correlated with the amount of adenine in the DNA sequence. This study provides a new approach for reliable quantification and analysis of genetic information associated with DNA molecule sequencing. This work was supported by the European project DeDNAed (H2020-FETOPEN2018-2020, n° 964248). References [1] E. Garcia-Rico, R. A. Alvarez-Puebla, and L. Guerrini, Chem. Soc. Rev., 2018, 47, 4909–4923. [2] E. Papadopoulou and S.E.J. Bell, Chem. Commun. 2011, 47, 10966-10968.