Projects

 

Density Function Renormalization Group and Quantum Monte Carlo studies of extended Kitaev model at high temperatures

Team: Vahagn Mkhitaryan, Owen Maxwell Matthiessen

Brief Description

Kitaev model is an exactly solvable model of interacting spin on a honeycomb lattice with bond dependent anisotropic interactions proposed by Alexei Kitaev in 2006 [1]. The model is described by Hamiltonian:

A few years after Kitaev introduced honeycomb model, G. Jackeli and G. Khaliullin proposed a path to realization of such models in real materials using strong spin orbit coupling in partially filled d-shell transition metal compounds with octahedron arrangement of constituent atoms [2]. Several candidate materials have been found since then that could realize this model [3]. Although Kitaev interaction terms in most of the candidate materials are dominant, it is still an effective spin model and other type of interactions play significant role in these materials and need to be considered in real experimental data interpretation [4]. In this study we will use Density Matrix Renormalization Group (DMRG) and Quantum Monte-Carlo (QMC) approach to study extended Kitaev model and its temperature dependent properties. The focus is on derivation of inelastic light scattering intensities for the extended Kitaev model and analyzing it at different temperatures and applied external magnetic field strengths.

Figure The Kitaev honeycomb model. a) schematic representation of the honeycomb lattice of spins S=1/2 with bond-dependent interactions. b) Majorana fermion representation of the spin operators and interactions in Kitaev model

References

[1] Kitaev A 2006 Anyons in an exactly solved model and beyond Ann. Phys. 321 2–111

[2] Jackeli G and Khaliullin G 2009 Mott Insulators in the Strong Spin-Orbit Coupling L

imit: From Heisenberg to a Quantum Compass and Kitaev Models Phys. Rev. Lett. 102 017205

[3] Trebst S and Hickey C 2022 Kitaev materials Phys. Rep. 950 1–37

[4] Motome Y and Nasu J 2020 Hunting Majorana fermions in Kitaev magnets J. Phys. Soc. Jpn. 89 012002

Optical Probing and Tailoring of Optical Properties in Weyl Semimetals

Project Lead: Morris Yang

Project Team: Demid Sychev

Weyl semimetals (WSMs) is an emerging class of materials possessing unique electromagnetic properties that are not commonly achievable with conventional metals and semiconductors. The exotic phenomena emerging from the so-called Weyl nodes in WSMs where valence and conduction bands cross in single points and electrons effectively behave as Weyl fermions make WSMs very interesting for novel photonic applications in areas of non-linear optics, photovoltaics, THz electrooptics, and detection. In this work, we explore the enhancement of WSM nonlinear response by merging WSMs with the concept of plasmonics, i.e. nano-optics utilizing deeply subwavelength collective oscillations of free electrons in metallic nanostructures, and metasurfaces where arrays of plasmonic nanoantennas are used to control the phase, amplitude and polarization of the incident light. Since electrons possess non-trivial electronic states in WSMs, plasmonics could enable the observation of unique optoelectrical phenomena in WSMs with the added benefit of creating nonlinear optical elements that are smaller than the diffraction limit. Here, we realized a nanopatch plasmonic antenna array on the WSM TaAs crystal to demonstrate the enhanced non-linear optical response from TaAs. By developing a large-scale, non-destructive method of fabricating the antenna array, we address the challenge of WSM integration with photonic devices. We demonstrate a six-fold increase of the second-harmonic generation (SHG) from the Weyl semimetal TaAs surface by distributing plasmonic silver nanoantennas on TaAs.

Quantum Nanophotonics with Two Dimensional Materials

Primary Contacts: Xiaohui Xu, Dr. Demid Sychev

Additional Contacts: Zach Martin, Dr. Alexander Senichev, Dr. Alexei S. Lagoutchev

Advisors: Prof. Alexandra Boltasseva, Prof. Vladimir Shalaev

Collaborators: Prof. Yong Chen, Prof. Simeon Bogdanov, Prof. Igor Aharonovich, Andres E Llacsahuanga Allcca

Short project description:

Building large quantum communication and computation systems remain very challenging. A big step towards this goal would be the creation of deterministic sources of indistinguishable single photons which can operate at room temperature. Two dimensional (2D) materials and van der Waals crystals, such as hexagonal boron nitride (hBN) and Transition metal dichalcogenide (TMDC) possess unique optoelectronic and photonic properties. Specifically, single photon emission has been observed in various types of 2D materials, making them promising as emerging platforms for quantum sensing, quantum computing, etc. Their two-dimensional nature provides unparalleled advantages for on-chip integration and high-sensitivity applications.

While room-temperature, bright single photon emission has been observed in hBN, the origin of these quantum emitters remains unknown. In this project, we use scanning transmission electron microscopy (STEM) to investigate atomic structure of quantum emitters in hBN, with sub-angstrom resolution. We also explore the possibility to create/engineer quantum defects in hBN deterministically with the electron beam in STEM. Experiments will be combined with ab initio simulations to get a better understanding of those atomic defects in hBN.

Single photon emission in TMDCs comes from either in-layer localized excitons or interlayer excitons. The latter have attracted more interest due to the rich physics and dynamics enabled by the tunable interlayer alignments. In this project, we will investigate and enhance single photon emission from interlayer excitons with plasmonic cavities. Thanks to the out-of-plane optical dipole moment of interlayer excitons, a deterministic narrow-gap plasmonic nanocavity could be assembled, making it possible to achieve ultrabright quantum emission. A similar plasmonic cavity design will also be used to enhance emission from hBN. The ultimate goal of this project is to obtain single photon emitters that generate indistinguishable photons at room temperature with the help of plasmonics.

Papers Published:

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Machine learning assisted optimization of photonic/plasmonic meta-structures

Primary Contact: Zhaxylyk Kudyshev

Additional Contact: Omer Yesilyurt

Advisors: Profs. Alexandra Boltasseva, Vladimir Shalaev, Alexander Kildishev

Short project description:

The realization of practical optical structures and devices is an inherently complex problem due to multi-faceted requirements with manifold stringent constraints on optical performance, materials, scalability, and experimental tolerances. These multiple requirements inevitably open up an enormously large optimization space. Despite the complexity of the available parametric space, almost all nanophotonic structures to date are designed either intuitively or based on a priori selected topologies, and by adjusting a very limited number of parameters (e.g., the periodicity, the trivial geometrical shapes, and dimensions of the resonant elements). Such intuition-based models are only useful for ad hoc needs and have limited applicability and predictive power. Exhaustive parameter sweeps are often done "by hand". Since comprehensive searches in hyper-dimensional design space is extremely resource intensive, multi-objective optimization has so far been prohibitive.

The innovatory field of the inverse design has recently been transforming conventional nanophotonics by allowing for the discovery of unorthodox optical structures via computer algorithms. The realization of these computer generated designs requires truly new approaches combined with already established diverse optimization and sensitivity methods such as genetic algorithms and different variations of the adjoint method. Within this project, we seek to develop 'physics-driven' machine learning optimization frameworks for rapid optimization of meta-structures with extreme properties. Specifically, we propose to combine conventional optimization algorithms with generative networks (GANs and autoencoders) for addressing different interdisciplinary problems.

[1] Zh. A. Kudyshev, A. V. Kildishev, V. M. Shalaev, A. Boltasseva, Machine-learning-assisted global optimization of photonic devices, Nanophotonics, accepted (arXiv:2007.02205)

[2] W. Ma, Z. Liu, Zh. A. Kudyshev, A. Boltasseva, W. Cai, Y. Liu, Deep learning for the design of photonic structures, Nature Photonics, 2020, https://www.nature.com/articles/s41566-020-0685-y

[3] Zh. A. Kudyshev, A. V. Kildishev, V. M. Shalaev, A. Boltasseva, Machine-learning-assisted metasurface design for high efficiency thermal emitter optimization, Applied Physics Reviews,Vol.7,2, 021407 (2020), Featured Article, AIP Scilights

[4] Zhaxylyk A. Kudyshev, Alexander V. Kildishev, Vladimir M. Shalaev, and Alexandra Boltasseva "Deep learning assisted photonics", Proc. SPIE 11461, Active Photonic Platforms XII, 114610C (20 August 2020); https://doi.org/10.1117/12.2567198

[5] Zhaxylyk A. Kudyshev, Simeon Bogdanov, Alexander V. Kildishev, Alexandra Boltasseva, and Vladimir M. Shalaev "Machine learning assisted plasmonics and quantum optics", Proc. SPIE 11460, Metamaterials, Metadevices, and Metasystems 2020, 1146018 (20 August 2020); https://doi.org/10.1117/12.2567310

[6] Zhaxylyk A. Kudyshev, Alexander V. Kildishev, Vladimir M. Shalaev, and Alexandra Boltasseva, Machine-learning-assisted topology optimization for highly efficient thermal emitter design, in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper FTh3C.2.

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Machine learning assisted quantum photonics

Primary Contact: Zhaxylyk Kudyshev

Advisors: Profs. Alexandra Boltasseva, Vladimir Shalaev, Alexander Kildishev

Collaborators: Prof. Simeon Bogdanov

Short project description:

Integrated quantum photonics has recently emerged as one of the key enablers of quantum information science and technology. Typically, quantum photonic circuits are realized using nonlinear sources of single photons that operate probabilistically. These do not allow for the generation of large multi-photon states. Alternatively, solid-state quantum emitters have recently offered near-ideal single-photon emission characteristics. Successful implementation of quantum photonic circuits depends crucially on the selection of quantum emitters from a large inhomogeneous set. In particular, efficient and rapid identification of bright, stable single-photon emitters with fast emission rates, high quantum yield, and narrow optical linewidth is critical. This project aims to develop ML-assisted quantum material characterization and metrology measurement techniques.

Recently, we have developed a method of applying advanced ML and deep learning algorithms to autocorrelation measurements of quantum emission, the back-bone of the quantum optical characterization, and demonstrated rapid identification of the "purity" of a quantum emitter (in our case, nitrogen-vacancy centers in nanodiamonds) with unparalleled speed. The new ML-based approach enables a hundredfold speedup and can be applied to the next generation of single-photon sources and future quantum materials metrology.

Within this project, we are combining quantum optics with a machine/deep leaning algorithm to achieve dramatic speed-up and high precision in a broad range of quantum characterization and quantum metrology applications. One of the directions of the project is ML assisted characterization techniques of single-photon sources based on 2D material platforms and solid state. Yet another direction is the development of ML assisted frameworks for sensing and imaging applications.

[1] Zh. A. Kudyshev, S. Bogdanov, T. Isacsson, A. V. Kildishev, A. Boltasseva, V. M. Shalaev, Rapid classification of quantum sources enabled by machine learning, Advanced Quantum Technologies, DOI: 10.1002/qute.202000067, (arXiv:1908.08577), Highlighted by AAAS EurekAlert, Phys.org

[2] Zhaxylyk A. Kudyshev, Simeon Bogdanov, Alexander V. Kildishev, Alexandra Boltasseva, and Vladimir M. Shalaev "Machine learning assisted plasmonics and quantum optics", Proc. SPIE 11460, Metamaterials, Metadevices, and Metasystems 2020, 1146018 (20 August 2020); https://doi.org/10.1117/12.2567310

[3] Zhaxylyk A. Kudyshev, Simeon Bogdanov, Theodor Isacsson, Alexander V. Kildishev, Alexandra Boltasseva, and Vladimir M. Shalaev "Machine learning-assisted classification of quantum emitters (Conference Presentation)", Proc. SPIE 11295, Advanced Optical Techniques for Quantum Information, Sensing, and Metrology, 112950N (10 March 2020); https://doi.org/10.1117/12.2545404

[4] Z. Kudyshev, S. Bogdanov, T. Isacsson, A. V. Kildishev, A. Boltasseva and V. M. Shalaev, "Merging Machine Learning with Quantum Photonics: Rapid Classification of Quantum Sources," 2020 Conference on Lasers and Electro-Optics (CLEO), San Jose, CA, USA, 2020, pp. 1-2.

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On-Chip Photonics and High Speed Optical Modulators

Primary Contact: Soham Saha

Collaborator: The Leuthold Group, ETH

Advisors: Prof. Vladimir Shalaev, Prof. Alexandra Boltasseva

Optoelectronics – the ultrafast processing of signals on a chip - by combining the compactness of electronics with the bandwidth of photonics, is the key to driving computational speeds beyond the limits of Moore’s Law. Plasmonics or metal optics is key to achieving this. Surface plasmons are collective oscillations of electrons that emanate when light strikes the surface of a metal under the right conditions. These oscillations have large wavevectors and can confine light beyond the diffraction limit, making it possible to build optical devices that confine light into nanometer-scale dimensions, well beyond the diffraction limit. This project serves to design ultrafast optical modulators with cheap, industry-compatible materials, namely transition metal nitrides and transparent conducting oxides [1]. Titanium nitride, a low-loss, CMOS-compatible material, has been demonstrated to outperform gold in long-range plasmonic waveguide configurations [2]. Electroabsorption modulators with transparent conducting oxides can be used to make ultra-compact modulators on silicon chips [3]. Emerging technologies such has organic electrooptic polymers can also be used to attain ultra-low loss, hybrid plasmonic modulators that transfer data at high-speeds [4]. The findings of this project will benefit the design of low-loss, high-speed on-chip modulators made with fabrication friendly, industry compatible materials.

References:

[1] N. Kinsey, M. Ferrera, V. M. Shalaev, and A. Boltasseva, Examining nanophotonics for integrated hybrid systems: a review of plasmonic interconnects and modulators using traditional and alternative materials [Invited], JOSA B, 32, 121-142 (2015); https://doi.org/10.1364/JOSAB.32.000121

[2] S. Saha, A. Dutta, N. Kinsey, A. V. Kildishev, V. M. Shalaev, and A. Boltasseva, On-Chip Hybrid Photonic-Plasmonic Waveguides with Ultrathin Titanium Nitride Films, ACS Photonics 5 (11), 4423–4431 (2018,); https://doi.org/10.1021/acsphotonics.8b00885

[3] Babicheva, V. E.; Kinsey, N.; Naik, G. V.; Ferrera, M.; Lavrinenko, A. V.; Shalaev, V. M.; Boltasseva, A. Towards CMOS-Compatible Nanophotonics: Ultra-Compact Modulators Using Alternative Plasmonic Materials. Opt. Express 2013, 21 (22), 27326. https://doi.org/10.1364/OE.21.027326.

[4] Haffner, C.; Chelladurai, D.; Fedoryshyn, Y.; Josten, A.; Baeuerle, B.; Heni, W.; Watanabe, T.; Cui, T.; Cheng, B.; Saha, S.; Elder, D. L.; Dalton, L. R.; Boltasseva, A.; Shalaev, V. M.; Kinsey, N.; Leuthold, J. Low-Loss Plasmon-Assisted Electro-Optic Modulator. Nature 2018, 556 (7702), 483–486. https://doi.org/10.1038/s41586-018-0031-4.

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Plasmon-induced magnetic-field-assisted nanomagnet switching with femtosecond laser pulses

Primary Contact: Aveek Dutta

Collaborators: Prof. Ernesto Marinero (Purdue), Prof. Vladimir Belotelov (Russian Quantum Center), Prof. Arata Tsukamoto (Nihon University) and Prof. Aleksei V. Kimel (Radboud University)

Advisors: Prof. Vladimir Shalaev, Prof. Alexandra Boltasseva

Background: The first demonstration of ultrafast demagnetization with femtosecond (fs) laser pulses was done by Beaurepaire et in in 1996 using a Ni film [1]. Since then the field of ultrafast dynamics in magnetic materials induced by fs laser pulses has been extensively studied both theoretically and experimentally [2]. In this regard, the phenomenon of All Optical Magnetization Switching, or AOMS, deserves a special mention. Figures (a) and (b) highlighting this phenomenon are taken from the work by Stanciu et al [3]. Figure (a)-before exposure shows a ferrimagnetic GdFeCo layer with out-of-plane magnetization in two opposite orientations as depicted by the dark and white areas. Figure (a)-after exposure shows that, depending on its helicity, a circularly polarized 800 nm 100 fs laser pulse can switch the magnetization of one domain while leaving the other un-affected (σ+ and σ- are right and left circularly polarized light respectively). The linearly polarized light L however leads to a random magnetization of the GdFeCo layer. Figure (b) shows that even a single pulse of circularly polarized laser light can reverse the magnetization of the illuminated area. It was later shown that heating of the magnetic material due to the fs laser pulse illumination plays a crucial role in the magnetization reversal of GdFeCo [4,5]. So one could achieve magnetization reversal in GdFeCo even with linearly polarized light. Therefore, enhancing light absorption in GdFeCo should make this magnetization reversal process more energy efficient. This can be achieved by plasmonics.

Research: Figure (c) shows the schematic of the fabricated nanostructure which consists of GdFeCo nanomagnet and Au plasmonic resonator. The entire stack configuration is: MgO substrate / 20 nm Si3N4 / 5 nm Gd31Fe60.4Co8.6 / 3 nm Si3N4 / 5 nm Al2O3 / 30 nm Au / 20 nm SiO2. Figure (d) shows the reflection measurements performed on a nanodisk array of this stack with 250 nm diameter and 400 nm period. The black and red curves are for p and s polarized light respectively. All measurements were done at 20° angle of incidence. The peak in the reflection data corresponds to a plasmon resonance. It was verified with simulations (using COMSOL Multiphysics) that the plasmon resonance corresponds to an increased absorption in the GdFeCo nanomagnet. The fabricated array was illuminated with 100 fs 800 nm linearly polarized light at a fluence of 5.47mJ/cm2. Figure (e) shows the results of our experiment. Following the first laser pulse, the dark area shows the portion of the nanodisk array where GdFeCo magnetization reversed. The second pulse, re-aligns the magnetization in the original direction. The third pulse has a similar effect as the first one. This shows reversible magnetization switching for the nanodisk array. No such switching was observed at the given fluence in an array without the Au plasmonic resonator. This shows that the Au plasmonic resonator increases light absorption and therefore can switch the GdFeCo magnetization at fluences where the GdFeCo nanomagnet by itself won’t switch. It should be noted that a 3mT magnetic field needed to be applied in order to assist the reversible switching of the GdFeCo nanomagnet coupled to Au plasmonic resonator.

References:

[1] E. Beaurepaire, J.-C. Merle, A. Daunois, and J.-Y. Bigot, Phys. Rev. Lett. 76, 4250 (1996)

[2] A. Kirilyuk, A. V Kimel, and T. Rasing, Philos. Trans. A. Math. Phys. Eng. Sci. 369, 3631 (2011)

[3] C. D. Stanciu, F. Hansteen, A. V. Kimel, A. Kirilyuk, A. Tsukamoto, A. Itoh, and T. Rasing, Phys. Rev. Lett. 99, 1 (2007)

[4] I. Radu, K. Vahaplar, C. Stamm, T. Kachel, N. Pontius, H. A. Dürr, T. A. Ostler, J. Barker, R. F. L. Evans, R. W. Chantrell, A. Tsukamoto, A. Itoh, A. Kirilyuk, T. Rasing, and A. V Kimel, Nature 472, 205 (2011)

[5] J. H. Mentink, J. Hellsvik, D. V. Afanasiev, B. A. Ivanov, A. Kirilyuk, A. V. Kimel, O. Eriksson, M. I. Katsnelson, and T. Rasing, Phys. Rev. Lett. 108, 057202 (2012)

[6] A. Dutta, A. V. Kildishev, V. M. Shalaev, A. Boltasseva, and E. E. Marinero, Surface-plasmon opto-magnetic field enhancement for all-optical magnetization switching, Opt. Mater. Express 7(12), 4316-4327 (2017)

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Epsilon-near-zero (ENZ) and Nonlinear Optics

Primary Contact: Soham Saha

Secondary Contacts: Zhaxylyk Kudyshev, Mustafa Ozlu

Collaborators: Prof. Daniele Faccio (Glasgow University), Marcello Ferrera, Heriot-Watt University

Advisors: Prof. Vladimir Shalaev, Prof. Alexandra Boltasseva

Many extraordinary optical phenomena are enhanced in the epsilon-near-zero (ENZ) regime - the wavelength regime where the complex permittivity of a material is near zero. The slow-light interactions in this regime increase light-matter interactions, bolstering phenomena such as enhanced nonlinearities [1], ultrafast reflection modulation [2], and emitter radiation engineering [3]. Transparent conducting oxides are natural homogeneous ENZ media and they exhibit extremely low-index behavior needed to realize the full potential of extraordinary nonlinear optics for photonics [4]. In this project, we investigate largely unexplored nonlinear optical phenomena in near-zero-index materials, enhanced by the extreme light-matter interaction resulting from the slow-light effect, without a need for complex nanostructure fabrication. Furthermore, the optical properties of these materials can be tuned by doping, thus enabling a great level of control over both the ENZ wavelength and the switching times [5]. We utilize low-loss transparent conducting oxides (TCOs) as homogeneous low index materials with the low-index region in the technologically relevant telecommunication spectrum [6]. We experimentally demonstrate nonlinear effects such as negative refraction [7] and broadband wavelength shifts [8] near the epsilon near zero region in aluminum-doped zinc oxide and tin-doped indium oxide. We also establish theories to better understand and predict the observed nonlinear enhancements. The findings of our research will enable the design of fast, low-loss, and efficient devices for optical modulation, beam steering, and optical isolator design.

References:

[1] Caspani, L.; Kaipurath, R. P. M.; Clerici, M.; Ferrera, M.; Roger, T.; Kim, J.; Kinsey, N.; Pietrzyk, M.; Di Falco, A.; Shalaev, V. M.; Boltasseva, A.; Faccio, D. Enhanced Nonlinear Refractive Index in ϵ -Near-Zero Materials. Phys. Rev. Lett. 2016, 116 (23), 233901. https://doi.org/10.1103/PhysRevLett.116.233901.

[2] Kinsey, N.; DeVault, C.; Kim, J.; Ferrera, M.; Shalaev, V. M.; Boltasseva, A. A. Epsilon-near-Zero Al-Doped ZnO for Ultrafast Switching at Telecom Wavelengths. Optica 2015, 2 (7), 616–622. https://doi.org/10.1364/OPTICA.2.000616.

[3] Kinsey, N.; DeVault, C.; Boltasseva, A.; Shalaev, V. M.; DeVault, C.; Boltasseva, A.; Shalaev, V. M. Near-Zero-Index Materials for Photonics. Nat. Rev. Mater. 2019, 4 (12), 1–19. https://doi.org/10.1038/s41578-019-0133-0.

[4] Kim, J.; Dutta, A.; Naik, G. V.; Giles, A. J.; Bezares, F. J.; Ellis, C. T.; Tischler, J. G.; Mahmoud, A. M.; Caglayan, H.; Glembocki, O. J.; Kildishev, A. V.; Caldwell, J. D.; Boltasseva, A.; Engheta, N. Role of Epsilon-near-Zero Substrates in the Optical Response of Plasmonic Antennas. Optica 2016, 3 (3), 339. https://doi.org/10.1364/OPTICA.3.000339.

[5] Saha, S.; Diroll, B. T.; Shank, J.; Kudyshev, Z.; Dutta, A.; Chowdhury, S. N.; Luk, T. S.; Campione, S.; Schaller, R. D.; Shalaev, V. M.; Boltasseva, A.; Wood, M. G. Broadband, High‐Speed, and Large‐Amplitude Dynamic Optical Switching with Yttrium‐Doped Cadmium Oxide. Adv. Funct. Mater. 2019, 1908377. https://doi.org/10.1002/adfm.201908377.

[6] Naik, G. V; Kim, J.; Boltasseva, A. Oxides and Nitrides as Alternative Plasmonic Materials in the Optical Range [Invited]. Opt. Mater. Express 2011, 1 (6), 1090. https://doi.org/10.1364/OME.1.001090.

[7] Vezzoli, S.; Bruno, V.; Devault, C.; Roger, T.; Shalaev, V. M.; Boltasseva, A.; Ferrera, M.; Clerici, M.; Dubietis, A.; Faccio, D. Optical Time Reversal from Time-Dependent Epsilon-Near-Zero Media. Phys. Rev. Lett. 2018, 120 (4), 043902. https://doi.org/10.1103/PhysRevLett.120.043902.

[8] Khurgin, J. B.; Clerici, M.; Bruno, V.; Caspani, L.; DeVault, C.; Kim, J.; Shaltout, A.; Boltasseva, A.; Shalaev, V. M.; Ferrera, M.; Faccio, D.; Kinsey, N. Adiabatic Frequency Shifting in Epsilon-near-Zero Materials: The Role of Group Velocity. Optica 2020, 7 (3), 226. https://doi.org/10.1364/OPTICA.374788.

[9] V. Bruno, C. DeVault, S. Vezzoli, Z. Kudyshev, T. Huq, S. Mignuzzi, A. Jacassi, S. Saha, Y. D. Shah, S. A. Maier, D. R. S. Cumming, A. Boltasseva, M. Ferrera, M. Clerici, D. Faccio, R. Sapienza, and V. M. Shalaev, Negative Refraction in Time-Varying Strongly Coupled Plasmonic-Antenna–Epsilon-Near-Zero Systems, Phys. Rev. Lett. v. 124, p. 043902 (2020)

[10] V. Bruno, S. Vezzoli, C. DeVault, T. Roger, M. Ferrera, A. Boltasseva, V.M. Shalaev, D. Faccio, Dynamical Control of Broadband Coherent Absorption in ENZ Films, Micromachines, v. 11, p. 110 (2020)

[11] V. Bruno, S. Vezzoli, C. DeVault, E. Carnemolla, M. Ferrera, A. Boltasseva, V. M. Shalaev, D. Faccio, M. Clerici, Broad Frequency Shift of Parametric Processes in Epsilon-Near-Zero Time-Varying Media, Applied Sciences, v. 10, p. 1318 (2020)

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MURI: Near-Field Radiative Heat Transfer between Nanostructured Materials

Primary Contacts: Zelong "Bruce" Ding, Harsha Reddy, Zhaxylyk Kudyshev

Advisors: Profs. Vladimir Shalaev and Alexandra Boltasseva

Collaborators: Profs. Pramod Reddy (UMich), Edgar Meyhofer (UMich), and Shanhui Fan (Stanford)

Short project description:

Illustration of NFRHT between two nanostructured metasurfaces separated by a nano gap

The principles of near-field (NF) radiative heat transfer (RHT), i.e. the transfer of heat or energy across nanoscale gaps via electromagnetic fields, are of great interest as several remarkable phenomena arise exclusively in the NF. Far-field (FF) RHT, explored at the beginning of the 20th century, culminated in Max Planck’s theory of RHT and played a central role in the development of quantum mechanics. However, Planck explicitly noted that his FFRHT theory was only applicable to scenarios where the separation between the hot and cold objects is significantly larger than the Wien’s wavelength (~10 μm at room temperature). With the advent of micro- and nanotechnology that features nanoscale dimensions, an urgent need to understand thermal radiation in nanoscale gaps has emerged.

Recent experiments have measured RHT rates in the NF [1-3], which have revealed several orders of magnitude enhancements in RHT rates, compared to FFRHT, when the separation between the hot and cold objects is reduced to length scales below Wein’s wavelength. Specifically, close to 1,000 fold enhancements in RHT were observed from experiments for gap sizes below 100 nm [3, 4]. These exciting discoveries have spurred researchers to explore ways to further engineer and enhance NFRHT. In this regard, recent theoretical studies [5-7] have predicted the possibility of further enhancing NFRHT via spectral engineering with metasurfaces that feature judiciously patterned nanostructures. Our group is currently working towards testing the validity of these interesting theoretical predictions. We are closely working with our collaborators (Prof. Shanhui Fan, Prof. Pramod Reddy and Prof. Edgar Meyhofer) towards fabricating these metasurfaces on suspended picowatt resolution calorimeters (designed and fabricated in Prof. Pramod Reddy and Prof. Edgar Meyhofer’s group). The performance of the fabricated metasurfaces will be characterized by our collaborators at University of Michigan, Ann Arbor, using their state-of-the-art nanopositioning platform. Along with their fundamental importance, these studies are expected to play a crucial role in the development of innovative thermal technologies, ranging from thermophotovoltaics to near-field photonic refrigeration.

References:

[1] Rousseau, E. et al. Radiative heat transfer at the nanoscale. Nat. Photonics. 3, 514-517 (2009).

[2] Shen, S. et al. Surface phonon polaritons mediated energy transfer between nanoscale gaps. Nano Lett. 9, 2909-2913 (2009).

[3] Kim, K. et al. Radiative heat transfer in the extreme near-field. Nature 528, 387-391 (2015).

[4] Song, B. et al. Radiative heat conductances between dielectric and metallic parallel plates with nanoscale gaps. Nat. Nanotechnol. 11, 509-514 (2016).

[5] Fernandez-Hurtado, V. et al. Enhancing Near-Field Radiative Heat Transfer with Si-Based Metasurfaces. Phys. Rev. Lett. 118, 203901 (2017).

[6] Miller, O.D. et al. Limits to the Optical Response of Graphene and Two-Dimensional Materials. Nano Letters 17, 5408-5415 (2017).

[7] Miller, O.D. et al. Shape-Independent Limits to Near-Field Radiative Heat Transfer. Phys. Rev. Lett. 115, 204302 (2015).

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Mapping the nanoscale energy distributions of plasmonic hot-carriers

Contacts: Harsha Reddy, Zhaxylyk Kudyshev

Collaborators: Profs. Pramod Reddy and Edgar Meyhofer (University of Michigan, Ann Arbor)

Advisors: Profs. Vladimir Shalaev, Alexandra Boltasseva, and Alexander Kildishev

The generation of hot-carriers in plasmonic nanostructures, via plasmon decay, is of great current interest as hot-carriers play key roles in applications like photocatalysis, energy harvesting and in novel photodetection schemes that circumvent band-gap limitations. However, experimental quantification of steady-state energy distributions of hot-carriers in plasmonic nanostructures, which is critical for systematic progress, has not been possible. To address this outstanding challenge, we recently developed an experimental approach that enabled the direct measurement of hot-carrier energy distributions under steady-state conditions [1]. Specifically, we combined scanning probe-based quantum transport measurement techniques that record charge transport through single molecular junctions with nanoplasmonic experimental methods to directly quantify hot-carrier energy distributions in a key model system—a thin gold film that supports propagating surface plasmon polaritons. Furthermore, from our measurements, we obtained key physical insights on the role of Landau damping in producing hot-carriers and the contributions of different plasmonic modes towards hot-carrier generation. These studies were done in collaboration with Prof. Pramod Reddy and Prof. Edgar Meyhofer’s group at the University of Michigan, Ann Arbor.

On the left, graphic representation of the experimental approach to determine the energy distributions of plasmonic hot-carriers in a thin gold film. Surface plasmon polaritons are excited by illuminating the grating coupler with a laser, which leads to the generation of hot-carriers. The energy distributions of the generated hot-carriers are measured from the current flowing through a (voltage controlled) tunable molecular filter that selectively allows transport of carriers in a narrow energy window.

References:

[1] H. Reddy, K. Wang, Z. Kudyshev, L. Zhu, S. Yan, A. Vezzoli, S. J. Higgins, V. Gavini, A. Boltasseva, P. Reddy, V. M. Shalaev, and E. Meyhofer, "Determining plasmonic hot-carrier energy distributions via single molecule transport measurements,” Science, 10.1126/science.abb3457, 2020.

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Quantum Nano-optics

Primary Contacts: Dr. Demid Sychev, Dr. Alexander Senichev

Secondary Contacts: Dr. Zhaxylyk Kudyshev, Xiaohui Xu, Zach Martin, Dr. Alexei Lagoutchev (Purdue)

Collaborators: Prof. Simeon Bogdanov, Prof. Alexey V. Akimov, Prof. Igor Aharonovitch, Prof. Jacob Khurgin, Prof. Sergey I. Bozhevolnyi, Prof. Ilya A. Rodionov

Advisors: Profs. Vladimir Shalaev, Alexandra Boltasseva, and Alexander Kildishev

Short project description:

Color centers in diamond are crystalline defects that share many quantum properties with single atoms. At the same time, they are easier to manipulate than the latter and can be integrated into various solid-state devices. They are also promising platforms for realizing quantum devices such as nanoscale sensors, single-photon sources or quantum memories. Our research aims at discovering whether it is possible to draw on the potential of the dynamic field of nanophotonics in order to enhance or better harness the quantum properties of such systems. In particular, novel nanophotonic structures such as hyperbolic metamaterials, plasmonic waveguides, and plasmonic nanocavities are good candidates for increasing color centers’ spontaneous emission rate and controlling the directionality of their emission over a broad frequency range. The use of CMOS-compatible epitaxially grown plasmonic materials in the design of plasmonic structures promises a new level of functionality for a variety of integrated room-temperature quantum devices based on diamond color centers.

In the scope of this project, we have examined different types of nanodiamonds and identified the characteristics that lead to optimal optical and chemical properties. We have demonstrated broadband enhancement of emission from nitrogen-vacancy (NV) centers in nanodiamonds for both single NV centers and ensembles of NV centers using hyperbolic metamaterials (HMM), nanopatch antennas (NPA), and integrated plasmonic launchers (PL). As part of this work, we have studied the correlations between Purcell factor and optical measurements of NV’s spin state and the possibility to perform nanoscale sensing of photonic density of states using NV’s spin properties. By reducing the fluorescence lifetime from single NV centers, we also hope to enhance their single-photon emission rate such that we can perform a single-shot measurement of an NV center’s spin state. At the same time, we are also interested in developing nanoscale quantum devices from silicon-vacancy (SiV), germanium-vacancy (GeV), and lead-vacancy (PbV) centers in nanodiamonds. By enhancing the rate of emission from these defects, it may be possible to produce indistinguishable photons at room temperature. Similarly, we are also interested in developing quantum emitters in new materials such as 2D perovskite nanocrystals, transition metal dichalcogenide (TMDC) bilayers, and hexagonal boron nitride (hBN) flakes. Finally, we collaborate with other research groups to use defect centers in nanodiamonds and other materials for quantum sensing applications.

Papers Published:

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Robust Vivid Plasmonic Color Printing

Primary Contact: Sarah Nahar Chowdhury

SAdditional Contacts: Dr. Alexei S. Lagoutchev, Zhaxylyk Kudyshev

Collaborators: Dr. Piotr Nyga, Dr. Esteban Garcia

Advisors: Profs. Vladimir Shalaev, Alexandra Boltasseva, Alexander Kildishev

Short project description:

We demonstrate a method of generation of bright colors through laser post processing on a multilayer structure comprising of a very thin layer of Ag semicontinuous metal film (SMF) on a dielectric spacer with mirror. Such a structure is not only inexpensive, environment-friendly, and non-bleaching but also has the potential of microscopic printing to 1.44µm (approx.). The process employs a SMF comprising of random nanostructures with different particle sizes and shapes which are responsible for absorption at different wavelengths. SMF on spacer with mirror (SMFM) upon interaction with light can localize electromagnetic energy in nanoscale regions. With laser illumination, reshaping and fragmentation of metallic nanostructures occur in the vicinity of these regions and change in optical response occurs. Through varying the scan speed, number of pulses, energy density, power, and exposure time of 800 nm, 80 fs, 1 kHz laser illuminated on the structure, highly contrasting and vivid colors can be obtained. This structure can be fabricated easily and can be applied to the macroscopic, mesoscopic and nanoscopic printing of innovatory fade-free artistic images as one example of application.

Papers Published:

[1] Laser-induced color printing on semicontinuous silver films: red, green and blue, Piotr Nyga, Sarah N Chowdhury, Zhaxylyk Kudyshev, Mark D Thoreson, Alexander V Kildishev, Vladimir M Shalaev, Alexandra Boltasseva, Optical Materials Express 9 (3), 1528-1538

[2] Laser Color Printing on Semicontinuous Silver Films, Sarah N Chowdhury, Piotr Nyga, Zhaxylyk Kudyshev, Alexander V Kildishev, Vladimir M Shalaev, Alexandra Boltasseva, CLEO: Science and Innovations, JW2A. 55

[3] Laser Color Printing on Semicontinuous Ag Films, Sarah N. Chowdhury, Piotr Nyga, Zhaxylyk Kudyshev, Alexander V. Kildishev, Vladimir M. Shalaev, Alexandra Boltasseva, Women in Engineering Program 50th Anniversary Celebration

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Transdimensional Plasmonic Materials

Primary Contact: Deesha Shah

Collaborators: Prof. Igor Bondarev (North Carolina Central University), Dr. Arrigo Calzolari (CNR-Nano, Italy)

Advisors: Profs. Vladimir Shalaev and Alexandra Boltasseva

Short project description:

As plasmonic materials transition from the three dimensional (3D) form to two dimensional (2D), unique optical and electronic phenomena arise that are unattainable in bulk materials and conventional thin films. Similar to 2D materials, ultra-thin films in the transdimensional regime spanning a few atomic layers, known as transdimensional materials (TDMs), are expected to exhibit strong dependences on structural and compositional properties, as well as extreme sensitivities to external optical and electrical perturbations. Additionally, the small thicknesses may lead to strongly confined surface plasmons and unique quantum phenomena such as forbidden atomic transitions and enhanced nonlinearities. The strong tunability and light confinement offered by TDMs has resulted in a search for atomically thin material platforms that facilitate active metasurfaces with novel functionalities in the visible and NIR range.

Epitaxial thin films are particularly ideal in investigating the size dependent response as there are no contributions to losses from grain boundaries. Epitaxial TiN can be routinely grown on substrates such as c-sapphire and MgO with standard sputtering processes, enabling the formation of continuous ultrathin films down to 1 nm (5 monolayers) while maintaining high quality. Due to its high-quality growth, chemical stability, and tailorable optical properties, TiN is an ideal material choice to study plasmonic properties at the atomic level. We are investigating the thickness dependent properties of ultra-thin TiN experimentally and theoretically, which hold great promise for realizing a new generation of tunable metasurfaces with quantum and nonlocal effects.

Papers:

[1] Shah, D., Kudyshev, Z. A., Saha, S., Shalaev, V. M. & Boltasseva, A. Transdimensional material platforms for tunable metasurface design. MRS Bull. 45, 188–195 (2020).

[2] Boltasseva, A. & Shalaev, V. M. Transdimensional Photonics. ACS Photonics 6, 1–3 (2019).

[3] Shah, D. et al. Controlling the Plasmonic Properties of Ultrathin TiN Films at the Atomic Level. ACS Photonics 5, 2816–2824 (2018).

[4] Bondarev, I. V., Mousavi, H. & Shalaev, V. M. Optical response of finite-thickness ultrathin plasmonic films. MRS Commun. 8, 1092–1097 (2018).

[5] Bondarev, I. V. & Shalaev, V. M. Universal features of the optical properties of ultrathin plasmonic films. Opt. Mater. Express 7, 3731–3740 (2017).

[6] Shah, D., Reddy, H., Kinsey, N., Shalaev, V. M. & Boltasseva, A. Optical Properties of Plasmonic Ultrathin TiN Films. Adv. Opt. Mater. 5, 1700065 (2017).

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Refractory Plasmonics

Primary Contact: Bruce Ding

Additional Contact: Harshavardhanareddy Eragamreddy

Advisors: Prof. Vladimir M. Shalaev, Prof. Alexandra Boltasseva, Prof. Alexander Kildishev

Collaborators: Prof. Ernesto Marinero, Prof. Peter Bermel, Prof. Tim Sands, Prof. Ali Shakouri, Prof. Ted Norris, Prof. Oana Malis, Prof. Sergey Bozhevolnyi

Short project description:

Some of the proposed plasmonic applications require extreme operating conditions such as high temperatures and chemically aggressive environment. Conventional plasmonic materials such as noble metals bring limitations due to their lower melting point, softness etc. Refractory materials, exhibiting high melting points and chemical stability above 2000 oC, with plasmonic properties in the visible and near infrared regions can be the solutions to major problems hindering the improvement of potentially high-impact applications such as heat assisted magnetic recording (HAMR), solar/thermophotovoltaics (S/TPV) and solar thermoelectric generators (STEG).

Transition metal nitrides, in particular titanium nitride (TiN) and zirconium nitride (ZrN), are known as refractory materials and exhibit plasmonic resonances in the visible and near infrared regions. Nanoantennas made of refractory plasmonic materials can be employed as durable near field transducers for HAMR heads where antenna temperatures are estimated to be above 400°C. Furthermore, ultrathin broadband absorbers and selective emitters made of refractory plasmonic materials offer durability at higher temperatures and higher overall device efficiencies for S/TPVs and STEGs.

Papers:

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Quantum Nanophotonics with Color Centers in Diamond

Primary Contact: Dr. Demid Sychev

Advisors: Prof. Alexander Kildishev, Prof. Vladimir Shalaev

Additional Contact: Dr. Alexei S. Lagoutchev

Collaborators: Dr. Alexey V. Akimov (RQC), Dr. Mikhail Y. Shalaginov, Prof. Simeon Bogdanov

Short project description:

Color centers in diamond are crystalline defects that share many quantum properties with single atoms. At the same time they are easier to manipulate than the latter and can be integrated into a solid state infrastructure. They are promising for realizing quantum devices such as nanoscale sensors, single-photon sources or quantum memories. Our research aims at discovering whether it is possible to draw on the promising potential of the fast developing field of nanophotonics in order to enhance or better harness the quantum properties of such systems. In particular, novel nanophotonic structures such as hyperbolic metamaterials and plasmonic waveguides are good candidates for increasing the color center's spontaneous emission rate and controlling the directionality of their emission in a broad frequency range. The broadband optical Purcell factor in plasmonic systems can be also used to control the spin readout. Conversely, the color centers' spin degree of freedom can simplify the measurement of the photonic density of states on the nanoscale. The use of CMOS-compatible epitaxially grown plasmonic materials in the design of plasmonic structures promises a new level of functionality for a variety of integrated room-temperature quantum devices based on diamond color centers.

In the scope of this project, we have examined different types of nanodiamonds and identified the characteristics that lead to optimal optical and chemical properties. We have demonstrated broadband enhancement of emission from nitrogen-vacancy (NV) center ensembles in nanodiamonds using conventional gold/alumina hyperbolic metamaterials (HMM). We have theoretically shown that planar multilayer HMM make single photon emission more directional. We have showed both the fluorescence lifetime reduction and the enhancement of single-photon emission from single NV centers in nanodiamonds coupled to an epitaxially grown CMOS-compatible HMM made of novel plasmonic materials TiN/AlScN. In our most recent work, we have studied the correlations between Purcell factor and optical measurements of NV’s spin state and the possibility to perform nanoscale sensing of photonic density of states using NV’s spin properties. Our results may enable CMOS-compatible integrated quantum devices operating at room temperature.

Quantum Nanophotonics with Color Centers in Diamond Project

Papers Published:

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Cloud Computing Nanophotonics Tools @ nanoHUB.org

Primary Contact: Dr. Zhaxylyk Kudyshev

Additional Contact: Dr. Ludmila Prokopeva

Advisors: Prof. Alexander Kildishev, Prof. Vladimir Shalaev

Collaborators: Dr. Xingjie Ni, Dr. Satoshi Ishii, Dr. Zhengtong Liu, Dr. Uday. K. Chettiar, Jan Trieschmann

Short project description:

We developed simulation tools for nanophotonics, staged at www.nanoHUB.org to deliver a scientific application as a cloud computing service. Our on-line tools provide electromagnetic and multiphysics simulations of planar, circular and spherical multilayered nanophotonic devices, the full list is:

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Nanophotonics Tools @ nanoHUB.org
Nanophotonics Tools @ nanoHUB.org

Publications and other contributions:

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Novel Optics with Metasurfaces

Primary Contact: Soham Saha

Additional Contact: Deesha Shah, Sarah Nahar Chowdhury

Advisors: Prof. Vladimir Shalaev, Prof. Alexandra Boltasseva, Prof. Alexander Kildishev

Collaborator: Dr. Amr Shaltout

Short project description:

Nanophotonics Tools @ nanoHUB.org

Subwavelength cavities are obtained by replacing conventional mirrors with reflecting metasurfaces that introduce arbitrary phase-shifts compensating for reduced accumulated phase through the ultra-small cavity. Same concept works for waveguides, where propagating modes require round trip phase-shift in the transverse direction to be integer multiple of 2p. This causes the minimum cross-section size to be the diffraction limit of ?/2, and introducing reflecting metasurfaces change the phase condition allowing the cross-section to go below the diffraction limit.

Nanophotonics Tools @ nanoHUB.org

We design, fabricate, and experimentally demonstrate optically active metasurfaces of ?/50 thickness. Our approach is built on supercell metasurface design methodology: by judiciously designing the location and orientation of individual antennas in the structural supercells, we achieve effective chiral metasurfaces through a collective operation of non-chiral antennas.

 
Nanophotonics Tools @ nanoHUB.org

Ultrathin metamaterial layers are modeled by a homogeneous bi-anisotropic film to model various kinds of broken symmetries in photonic nanostructures. It successfully modeled rotational asymmetry, mirror asymmetry and directional asymmetry. It has been also used to replace an array of nanostructured plasmonic elements (e.g. V-shape antennas) with a thin metasurface of equivalent bianisotropic tiles, which enabled significant reduction of computational load for simulation purposes.

Papers Published:

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Nanolasers

Primary Contact: Dr. Xiangeng Meng

Additional Contact: Dr. Alexei S. Lagoutchev

Advisors: Prof. Vladimir Shalaev, Prof. Alexandra Boltasseva, Prof. Alexander Kildishev

Short project description:

The nanolaser project aims to develop compact light sources using plasmonic nanostructures as resonant cavities. The nanolaser is based on amplification of surface plasmons ? surface waves propagating along a metallic-dielectric interface, thus also entitled spaser (short for surface plasmon amplification by stimulated emission of radiation). The fact that plasmon modes have no cutoff allows for creation of compact light sources at real nanometer scale in terms of either the device size or optical mode volume. There are currently several challenges that are being addressed in this area, including the control of spasing propagation direction and the achievement of spasing in the visible. Numerical simulations are being conducted to help understanding of spasing dynamics.

Namolasers

Papers Published:

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Completed Projects

Plasmonic Titanium Nitride Powder

Primary Contact: Dr. Urcan Guler

Advisors: Prof. Vladimir M. Shalaev, Prof. Alexandra Boltasseva, Prof. Alexander Kildishev

Collaborators: Dr. Dmitry Zemlyanov, Dr. Alberto Naldoni, Dr. Swati Pol, Prof. Nicholas Kotov, Prof. Ted Norris, Dr. Vladimir Liberman, Prof. Boris N. Chichkov

Short project description:

Transition metal nitrides, particularly titanium nitride and zirconium nitride, exhibit plasmonic resonances in the visible and near infrared region of the electromagnetic spectrum. Combined with their optical properties similar to Au, additional superior material properties such as high melting point, corrosion resistance and hardness offer high potential for several plasmonic applications. In addition, TiN offers CMOS and bio-compatibility where application and process specific requirements are determinative.

Plasmonic properties and material superiority of TiN can be demonstrated with top-down fabrication methods for proof-of-concept studies. However, plasmonic powder of TiN is crucial for many practical applications. We investigate production techniques of TiN powders and their plasmonic properties for several applications such as plasmonic photothermal therapy, drug delivery, photocatalysis, and solar thermophotovoltaics.

Papers Published:

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Unlocking New Physics and Novel Applications using Nanowire-based Hyperbolic Metamaterials

Contact: Rohith Chandrasekar

Advisors: Dr. Xiangeng Meng, Prof. Alexander Kildishev, Prof. Vladimir Shalaev

Collaborators: Prof. Alexandra Boltasseva, Prof. Alexander Wei, Dr. Yantao Pang (Shandong Jianzhu University)

Short project description:

Hyperbolic metamaterials are a new class of metamaterials that exhibit hyperbolic dispersion, a characteristic that can be applied to achieve exciting phenomena such as subdiffraction imaging, radiative decay engineering, hyperlensing and single-photon sources, to name a few. Hyperbolic metamaterials can be fabricated using two geometries: (1) alternating metal and dielectric layers, or (2) growing metal nanowires in a dielectric host matrix.

In this project, we focus on fabricating highly-ordered, high-quality gold and silver nanowire arrays in an alumina matrix. The samples are grown directly on a glass substrate for ease in characterization and device implementation. Using these new materials, we are currently pushing forward on multiple efforts: (1) measuring lifetime enhancement of dyes and nanodiamonds placed on or embedded in nanowire arrays, (2) studying lasing characteristics of nanowire arrays embedded in laser dyes, and (3) fabricating curved nanowire structures for future studies in hyperlensing and subdiffraction imaging.

Nanowire_HMM

Papers Published:

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Second-Harmonic Generation with Plasmonic Metasurfaces

Primary Contact: Rohith Chandrasekar

Additional Contact: Naresh K. Emani

Advisors:Prof. Alexander Kildishev, Prof. Vladimir Shalaev

Collaborators: Prof. Alexandra Boltasseva; Dr. Alexei S. Lagoutchev, Prof. David R. Smith (Duke University), Dr. Cristian Ciraci (Duke University)

Short project description:

In this project, we would like to directly compare the enhancement provided by electric and magnetic resonances for second harmonic generation (SHG). We study SHG by a metasurface consisting of coupled silver nanostrips that exhibits both electric and magnetic resonance for TM-polarized light. We set the electric resonance at the second harmonic and the magnetic resonance at the fundamental. By tuning the magnetic resonance on and off the fundamental, we can study each resonance individually and study their combined effects. We find that the electric resonance provides twice the enhancement provided by magnetic resonance. We use simulations and fittings to show that SHG by magnetic resonance is inhomogeneously broadened due to its broad tunability.

Namolasers

Papers Published:

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Near field characterization of plasmonic nanostructures

Contact: Clayton DeVault

Additional Contacts: Paul West, Alexei Lagoutchev

Advisors: Prof. Vladimir Shalaev, Prof. Alexandra Boltasseva

Short project description:

The ability to "see" at the nano-scale is enormously important to the fields of plasmonics and metamaterials. Although the ultimate spatial resolution of a far-field imaging system is limited by diffraction to roughly half the wavelength of the light source, there are several methods to circumnavigate this diffraction limit. Near-Field Scanning Optical Microscopy (NSOM) is a technique that allows resolution well below the natural restriction imposed by diffraction. This is accomplished by maintaining an optical fiber in extremely close proximity (a fraction of the wavelength) to a sample’s surface. At these distances, the optical probe interacts with non-propagating evanescent fields. The spatial resolution is then limited only by the size of the optical fiber’s aperture, which may be as small as 50nm. We utilize this technique to study structures such as nano-antennas, plasmonic waveguides, and metasurfaces. Our NSOM system is capable of operating in reflection, collection, and illumination modes at wavelengths of 532, 633, 785, and 1550 nm.

Near-Field_Characterization

Papers Published:

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Chemical synthesis of nanomaterials

Contact: Dr. Swati Pol

Advisors: Prof. Vladimir Shalaev, Prof. Alexandra Boltasseva

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Computer modeling of random plasmonic nanostructures

Contact: Jieran Fang

Advisors: Prof. Alexander Kildishev, Prof. Vladimir Shalaev

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