Two-dimensional hexagonal boron nitride (hBN) is gaining extensive interest as a robust host for quantum emitters (QEs). Its atomic-scale thickness offers unique advantages for integrating QEs with photonic circuits. We developed a lithography-free technique to deterministically create QEs in hBN with an atomic force microscope. This chip-compatible method helps to realize the efficient on-chip integration of hBN QEs. Furthermore, we studied the negatively charged boron vacancy (VB-) centers in hBN that are optically active spin defects. By coupling them with optimized nanoplasmonic cavities, we achieved significant brightness enhancement of VB- emitters, making them promising for advanced nanoscale sensing.

Single-photon sources are crucial components for photonic quantum technologies. Recently, robust solid-state quantum light emitters have been discovered in 2D materials. We demonstrate how single photons originating from 2D materials can be efficiently collected and routed either on a photonic chip or beamed into the far field. For on-chip coupling, we deposit GaSe crystals with embedded single-photon emitters onto silicon nitride rib waveguides. For efficient far-field collection, we 3D-print elliptical polymer microlenses on an array of hBN nanocrystals hosting single-photon emitters.

Atomically thin materials provide new capabilities for engineering quantum confinement and light-matter interaction in semiconductors that were not possible a decade ago. In this talk, I will discuss how we can leverage the optoelectronic properties of these materials for quantum information and sensing applications. I will present our recent work on engineering arrays of single-photon emitters in 2D semiconductors through defect and strain engineering, their integration with nanoantennas to enhance their brightness, and efficient room temperature, on-chip generation of single photons from emitters embedded in silicon nitride photonic resonators and waveguides. I will conclude with exciting future directions and applications.

The properties of a two-level quantum dipole emitter (DE) near an ultrathin transdimensional (TD) plasmonic film are studied theoretically [1]. TD quantum materials are atomically-thin films of precisely controlled thickness, films made of precisely controlled finite number of monolayers [2-5]. The model system studied mimics a solid-state single-photon source device. The spontaneous and stimulated emission intensity profiles are computed as functions of the excitation frequency and film thickness, followed by the analysis of the second-order photon correlations to explore the photon antibunching effect. It is shown that ultrathin TD films can greatly improve photon antibunching with thickness reduction, which allows one to control the quantum properties of light and make them more pronounced. The theory can be tested in experiments similar to those reported recently for epitaxial TiN films with thicknesses below 10 nm grown on MgO substrates and covered with an AlScN passivation layer [5], with nanodiamond NV-centers as DEs deposited on the varied-thickness passivation layer. Knowledge of these features is advantageous for solid-state single-photon source device engineering and in general for the development of the new integrated quantum photonics material platform based on the ultrathin TD plasmonic films. Acknowledgements: U.S. National Science Foundation Award No. DMR-1830874 (I.V.B.) References: [1] I.V.Bondarev, Annalen der Physik 2200331 (2022), DOI: 10.1002/andp.202200331. [2] A.Boltasseva and V.M.Shalaev, ACS Photonics 6, 1 (2019). [3] N.Rivera, I.Kaminer, B.Zhen, J.D.Joannopoulos, and M.Soljačić, Science 353, 263 (2016). [4] I.V.Bondarev, H.Mousavi, and V.M.Shalaev, Phys. Rev. Research 2, 013070 (2020). [5] D.Shah, M.Yang, Z.Kudyshev, X.Xu, V.M.Shalaev, I.V.Bondarev, and A.Boltasseva, Nano Lett. 22, 4622 (2022).

One of the attractions of resonant metamaterials is the possibility of tuning their resonant frequencies in real time by integrating them with actively-controlled materials. In this talk, I will describe how metasurfaces can be combined with liquid crystals to develop a new class of electrically-controlled varifocal metalenses operating at multiple wavelengths. Experimental demonstrations of imaging using actively controlled varifocal and bifocal metalenses will be presented, and new approaches to making widefield electrically-tunable metalenses will be described. I will also describe how electrically-biased plasmonic metasurfaces – also known as metagates – can be integrated with 2D materials to simultaneously modify the band structure of free carriers and plasmons. The resulting active material possesses emergent polaritonic properties that are absent without the metagate.

I will focus on the subject of strong light-matter coupling in excitonic 2D and 1D semiconductors. I will then discuss opportunities for light conversion and modulation using superlattices and metastructures made using excitonic materials and also magnetic semiconductors if time permits.

Quantum technologies usually require cryogenic environments to maintain quantum states and/or limit noise. The talk will discuss how nearfield nanoplasmonics can be an enabler of ambient strong coupling and quantum dynamics. We will highlight recently demonstrated ambient temperature near-field strong coupling of single quantum dots as well as and single quantum emitter Dicke enhancement paving the road towards single-photon quantum nonlinearities. The presentation will also explain near-field enhanced single-photon emission in near-zero index materials and multipartite dynamic quantum entanglement.

Optical metasurfaces are sub-wavelength patterned surfaces that interact strongly with light. They offer several critical advantages, including the miniaturization of optical elements, empowering novel functionalities that process hidden modalities of light, and the opportunity to tune their properties on demand. For many exciting new applications, such as 3D imaging, holographic displays, and light detection and ranging (LIDAR), dynamically reconfigurable and programable functionalities of metasurfaces is of utmost importance. This talk will overview the recent advances and challenges in tunable metasurfaces. I will discuss metasurface tunability through several control mechanisms, including optically and electrically driven metasurfaces. In particular, we demonstrate the highest ultrafast modulation of over 80% and multi-pixel operation with over 70% transmission modulation. The presented developments hold promise for real-world applications of active meta-optics.

Van der Waals materials offer a unique platform for controlling light materials interaction. In this talk I will discuss emergent all van der Walls systems for integrated nanophotonics and for infrared radiation taming. Specifically, I will demonstrate that exciton-photon interaction in bulk transition metal dichalcogenides can lead to highly confined optical modes. I will then discuss our theoretical and experimental studies of deeply subwavelength MoS2 integrated optical devices. I will show that 1-micron light can be efficiently controlled in devices that are just 60 nm thick. While exciton photon interaction is manifested at optical frequencies, at mid infrared we utilize strong light-phonon coupling to control emissivity. In particular, I will demonstrate that bulk hBN allows selectively controlling optical emission across 6 - 12 micron range.

We propose utilizing coherently coupled laser networks for neural computing. The proposed scheme is built on harnessing the collective behavior of laser networks for storing phase patterns as stable fixed points of the governing dynamical equations and retrieving such patterns through proper excitation conditions, thus exhibiting an associative memory property. We further show that limitations on the number of images can be overcome by using nonreciprocal coupling between lasers, thus allowing for utilizing the large storage capacity inherent to the laser network. This work opens new possibilities for neural computation with coherent laser networks as a novel physical analog processor.

Analog quantum simulators rely on programmable quantum devices to emulate Hamiltonians describing various physical phenomenon. Photonic coupled cavity arrays are a promising platform for realizing such devices. Using a silicon photonic coupled cavity array made up of 8 high quality-factor resonators and equipped with specially designed thermo-optic island heaters for independent control of cavities, we demonstrate a programmable device implementing tight-binding Hamiltonians with access to the full eigen-energy spectrum. We report a ~50% reduction in the thermal crosstalk between neighboring sites of the cavity array compared to traditional heaters, and then present a control scheme to program the cavity array to a given tight-binding Hamiltonian.

We explore the possibility of communicating encrypted information using infrared metamaterials. We first describe our algorithm for encrypting a plain image in multiple cipher images, each corresponding to a different wavelength channel. Our scheme is designed so that an interloper will not be able to recover the image from the summed intensity or the individual channels. However, the intended recipient can easily reconstruct the image by performing a mathematical operation over the channels. We implement this scheme in a 4-channel infrared metamaterial and demonstrate image encryption and decryption.

Photonic computing is literally becoming big business with the rise of several private companies trying to commercialize this technology. One of the advantages of using photonics is of course the ability to multiplex in wavelength - in principle providing highly parallel information processing through a given set of "weights" or system variables. Effectively, this can greatly enhance throughput. However, the use of multiple wavelengths, while very feasible still requires use of several filters and multiplexers. Here we report a technique to parallelize data processing through photonic hardware accelerators, particularly in-memory computing systems both with or without photonic hardware.

An integrated photonic circuit architecture to perform a modified-convolution operation based on the discrete fractional Fourier transform (DFrFT) is introduced. This is accomplished by utilizing two nonuniformly-coupled waveguide lattices of different lengths that perform DFrDT operations of complementary orders. Numerical simulations show that smoothing and edge detection tasks are indeed performed even for noisy input signals. A design recipe based on the standard silicon-on-insulator fabrication technology is provided. The scaling properties of the proposed architecture are discussed. Finally, the use of the proposed photonic convolutional accelerator for chip-scale photonic AI systems is discussed.

Transparent Conducting Oxides (TCOs) and Transition Metal Nitrides (TMNs) are emerging platforms for applications in nonlinear optics such as all-optical switching, harmonic generation and photonic time crystals and more. We report on various methods to both dynamically tune their optical properties in ultrafast time scales, and also statitcally tailor their properties. We demonstrate great control in varying the epsilon-near-zero response of TCOs such as aluminum-doped zinc oxide (AZO) and yttrium doped cadmium oxide. We also investigate the strong thickness dependence of the TCOs and TMNs optical properties. Employing the Berreman modes of TiN and AZO films on the same platform, we demonstrate variable switching speeds of an optically-pumped metasurface. We also demonstrate the nonlinear capabilities of undoped ZnO for all optical switching6 and third harmonic generation. To explore the realization of photonic time crystals, we investigate the fastest material response to an optical pump in AZO, showing sub-10 femtosecond rise time. Our approach paves the way to novel phenomena and device design with ultrafast tunable and tailorable materials.

Electromagnetic momentum inside a material is notion quite subtle to define, related to the Abraham-Minkowski debate. With new class of metamaterials emerging, allowing for extreme electromagnetic parameters such as near-zero refractive index materials or time-varying materials, those subtilties should treated with great care. Here, we revise fundamental radiative processes, momentum transfer experiments, diffraction, Doppler shift, Heisenberg inequality and microscopy applications inside near-zero refractive index. Furthermore, we demonstrate that the Minkowski momentum -related to spatial translation - is a conserved quantity inside time-varying media by three independent approaches. However, we stress how the Abraham momentum – related to energy transport – is not a conserved quantity in time-varying media.

Controlling thermal emission is crucial for many applications, such as passive radiative cooling and solar thermophotovoltaic energy conversion. A key characteristics of thermal radiation is its coherence property. However, all existing studies on coherence properties of thermal radiation consider only passive systems. Here, we show that the spatial coherence of thermal radiation can be manipulated in time-modulated photonic systems supporting surface polaritons. We develop a fluctuational electrodynamics formalism for such systems to calculate the cross-spectral density tensor of the emitted thermal electromagnetic fields in the near-field regime. Our calculations indicate that, due to time-modulation, spatial coherence can be transferred between different frequencies, and correlations between different frequency components become possible. All these effects are unique to time-modulated systems. We also show that the decay rate of optical emitters can be controlled in the proximity of such time-modulated structure. Our findings open a promising avenue toward coherence control in thermal radiation, dynamical thermal imaging, manipulating energy transfer among thermal or optical emitters, efficient near-field radiative cooling, and engineering spontaneous emission rates of molecules.

We employ Phase-Change Materials (PCMs) for local addressing of individual meta-atoms in both metallic and low-loss dielectric metasurfaces, with special emphasis on tuning electric dipole (ED) and magnetic dipole (MD) resonances simultaneously or individually. Individual control of the electric and magnetic dipole resonances of split-ring resonators (SRRs) is demonstrated by locally changing the refractive index of aluminum SRRs in the corresponding hotspots of the antenna resonances and by direct writing and reconfiguration of SRRs in the new plasmonic PCM In3SbTe2.

Recent advances in photonic phase change materials (PCMs) brought about a new alloy, GSS4T1,-a fully dielectric PCM for free-space wavelengths above 5 microns in both its amorphous and crystalline phases. The refractive index of GSST4T1 changes by about Dn=~1.4, when transitioning from the amorphous to the crystalline phase. Hence, GSS4T1 has opened new powerful capabilities for reconfigurable beam manipulation with all-dielectric platforms [2]. In particular, a binary metagrating comprising amorphous GSS4T1 and GaAs behaves as a homogenous film within wide spectral regions because of the similar refractive index of amorphous GSS4T1 and GaAs. On the other hand, the same binary metagrating with GSS4T1 switched to its crystalline phase, exhibits a rich spectral response, favoring many Fano resonances in its transmission spectrum. These emanate from the underlying leaky Floquet-Bloch modes supported by the metagrating. Depending on the structural parameters the emerging Fano spectral features can be very different, ranging from highly asymmetric to quasi-symmetric. Here, we discuss how the characteristics of these Fano features relate to the performance of the beam steering and splitting capability in the crystalline GSS4T1 metagrating. Specifically, our results support that an efficient re-configuration of the light beam from a straight to a back-bent path can occur only when the crystalline GSS4T1 metagrating supports quasi-symmetric Fano resonances [2, 3]. [1] Y. Zhang et al., Broadband transparent optical phase change materials for high-performance nonvolatile photonics, Nature Comm. 10, 4279 (2019). [2] N. L. Tsitsas and S. Foteinopoulou, Non-volatile MWIR/LWIR beam reconfigurability with all-dielectric metagratings comprising phase-change materials with a high-refractive-index shift, Opt. Mat. Express 12, pp. 3187-3212 (2022). [3] N. L. Tsitsas and S. Foteinopoulou, Semi-Analytical approach for the design of reconfigurable all-dielectric metagratings with phase-change material constituents, paper accepted in EuCAP 2023, to appear in IEEExplore.

The demand for reconfigurable components in neuromorphic computing, quantum computing and nanophotonics has led to a growing interest in active integrated photonic components. Phase change materials change their physical properties through reversible phase transitions, making them ideal for light manipulation. By altering the material's phase near a localized electromagnetic element, it is possible to achieve non-volatile, reconfigurable, and programmable functionality. However, this results in time-dependent inhomogeneous changes of physical properties, requiring a self-consistent description of electromagnetic, carrier transport, thermal, and phase transition processes. This presentation covers recent developments and applications of multiphysics simulations for phase change material-based nanophotonics.

Photonics information processing strategies offer the unique ability to perform analog computation with ultra-low latency and high efficiency. However, designing compact and reconfigurable photonic architectures which scale well is a challenge. The combination of nonvolatile optical materials (such as Ge2Sb2Te5) and integrated photonics is a promising approach which enables non-volatile optical memory on-chip with low drift, compact footprint, and high-speed readout. The first part of the talk will focus on using this photonic memory—together with wavelength division multiplexing and “in-memory” computing techniques—to enable high-speed matrix-vector operations for machine learning applications. The second half of this talk will cover methods for configuring these optical phase-change materials using electrical programming schemes, such as mixed-mode plasmonic memory and electro-thermal switching with on-chip microheaters.

We demonstrated nonvolatile, electrically programmable, phase-only modulation of free-space infrared radiation in transmission based on low-loss phase change materials (PCMs) Sb2Se3. By coupling ultra-thin PCM to a high quality-factor (Q~406) diatomic metasurface, we demonstrated a phase-only modulation of ~0.25π (~0.2π) in simulation (experiment), ten times larger than without using the metasurface. The metasurface is robust against reversible switching over 1,000 times. Finally, we showed independent control of 17 meta-molecules, achieving ten deterministic resonance levels in a tunable notch filter with a maximum spectral shift of ~8nm. The independent control also allowed us to achieve varifocal lensing. This work paves way to a nonvolatile phase-only SLM.

Nonlocal metasurfaces, which have uniform geometric arrangements but respond to incident angles differently, are uniquely capable of processing images. Phase change materials are promising functional building blocks to make metasurfaces reconfigurable owing to the significant refractive index contrast between amorphous and crystalline states. This presentation shows a novel tunable nonlocal metasurface based on the lossless phase change material Sb2Se3. It demonstrates the integration of two on-demand switchable functions, bright field imaging and second-order spatial differential imaging, on a single device.

Programmability is demanding in integrated photonics, while a suitable photonic platform is still lacking. It should have no static power, easy tuning knobs, high endurance, and many operation levels. We report a wide-bandgap PCM antimony sulfide (Sb2S3)-clad silicon photonic platform, based on which essential building blocks for programmable photonics are demonstrated, including micro-ring resonators, Mach-Zehnder Interferometers, and directional couplers. The fabricated devices simultaneously achieved low loss (<1.0 dB), high extinction ratio (>10 dB), high cyclability (>1,600 switching events), and 5-bit (32 operation levels) operation.

Optical Phase change material (O-PCM) components are rapidly becoming a mainstream implementation for non-volatile active control of photonic integrated circuits, metasurfaces and free-space photonics. In this work we explore the practical limitations of the reversible optical switching of the low-loss antimony-based O-PCM Sb₂Se₃ using a range of static tester and time-resolved techniques and demonstrates cyclability in Sb₂Se₃beyond 10^6 reversible transitions. We demonstrate that optical pumping at 488nm results in a well-defined depth limit in the crystal to glass transition, which arises from the confinement of the nanosecond thermal excitation in the top region of the Sb₂Se₃ film.

It is known that manipulating the polarization of light on the microscale or nanoscale is essential for integrated photonics and quantum optics. In this talk, we present our recent studies on polarization manipulation and multiplexing in optical metasurfaces. One is to realize multichannel distribution and transformation of entangled photons with dielectric metasurface, and the other is to break the limitation of polarization multiplexing in optical metasurfaces with engineered noise. The approaches achieve potential applications in optical display, data storage, information encryption, and quantum information networks.

Supersymmetric (SUSY) transformations that originated in quantum physics and were recently adapted to photonics, offer a robust, physics-based approach to designing photonic structures such as optical filters, gratings, and lasers. On the other hand, second-order supersymmetry (2-SUSY) facilitates the engineering of quantum wells in order to optimize second-order nonlinear interactions. In this talk, we discuss a number of linear and nonlinear photonic structures designed using the 2-SUSY. In particular, we demonstrate the design of strongly enhanced second-order nonlinear optical susceptibilities in quantum wells that are being fabricated using digitally graded alloys.

I will present some novel AI techniques for photonics and physics in general. In particular, techniques which enable AI training with orders of magnitude less data (so-called few-shot learning techniques) will be discussed, including transfer learning and contrastive learning. Next, certain interpretable AI techniques will be discussed, including symbolic regression. Finally, our new concept of machine-learned chemical property (which we call “topogivity”) will be presented: roughly, topogivity of a given atom presents that material’s propensity to form topological materials.

The spin Hall effect of light is a spin-dependent transverse splitting at the optical interface. In this presentation, I will explain the concept and working principle of the spin Hall effect of light metasurface with theoretical descriptions. Then I will introduce examples of the spin Hall effect of light metasurfaces which achieve high efficiency and polarization-independent shift enhancement. I also suggest the experimentally proven nanophotonic-assisted system which enhances the precision and it can broaden the practicability in state-of-art sensing and detecting systems such as medical science, material engineering, and other interdisciplinary areas.

Optical nonreciprocity is required in many optical systems for signal stabilization, laser protection, non-destructive probing. Here, we experimentally demonstrate a nonreciprocal fiber-optic amplifier enabled by encircling-an-exceptional-point emulation and gain-saturation nonlinearity. We realize the proposed system by combining optical attenuators, Erbium-doped fiber amplifiers (EDFA), and 2x2 couplers. We obtain remarkably high nonreciprocal transmission ratio > 20 dB persisting over the entire gain band from 1,530 to 1,560 nm at moderate input power conditions from 0.1 to 1 mW.

Conventional optical devices use geometry and refractive index of materials as design tools. The real part of the refractive index is often the only significant part used in designs. But, the imaginary index is also an equally important design parameter. Here, we demonstrate a novel thermal light source using the imaginary refractive index as a design parameter. Employing non-Hermitian physics, we demonstrate a directional thermal emitter that suppresses thermal emission on one side of the metasurface in a desired spectral window for enhancing thermal imaging through it. In another case, we build an extremely spectrally selective thermal emitter for thermophotovoltaic conversion of heat to electricity. We demonstrate that the non-Hermitian thermal emitter greatly enhances conversion efficiency.

Chiral quantum elements play an increasingly important role in quantum optical technologies and quantum networks. One potential route toward scalable, on-chip chiral elements is by using photonic crystal waveguides (PWCs) integrated with semiconductor quantum dots. Topological PCWs show significant promise in this area and are reputed to reduce backscatter from fabrication disorder. This talk will compare the key optical metrics of topological PWCs to traditional PCWs for such applications. We will also present fast inverse design techniques to significantly improve figures-of-merits for chiral coupling to quantum dots and discuss why topological PWCs are not topologically protected against disorder-induced backscattering.

Here we demonstrate that a unitary transformation due to nonuniform artificial gauge field enables a new class of topological boundary states carrying both spin and valley polarization. We show that such transformations also allow to tune radiative lifetimes of the hybrid spin-valley boundary modes. Then we demonstrate that gauge transformations, when applied adiabatically to the boundary modes, offer a mechanism for flipping the pseudo-spin without back reflection thus implementing an X-gate acting in synthetic Bloch subspaces spanned by pseudo-spins. Finally, we show that such adiabatic evolutions give rise to the geometrical phases, which offers a generic Phase-gate operation. Our results unveil a new versatile approach to control modes in topological photonics and also envisions topological materials as one of promising candidates for integrated quantum photonics applications.

I will present our recent results in understanding the role of classical optical nonlinearity in topological phases. Specifically, I will focus on our recent theoretical and experimental results on Floquet topological phases achievable in dynamically modulated nonlinear optical systems.

Topological photonics aims to utilize topological photonic bands and corresponding edge modes to implement robust light manipulation, which can be readily achieved in the linear regime of light-matter interaction. In this talk, I will review some recent results regarding nonlinear interactions of one-way edge-modes in frequency mixing processes in topological photonic crystals (PhCs) and graphene metasurfaces. In particular, I will demonstrate SHG via nonlinear interaction of double topological valley-Hall kink modes in PhCs with hexagonal lattice. I will first show that two topological frequency band gaps can be created around a pair of frequencies, ω0 and 2ω0, by gapping out the corresponding Dirac points. Importantly, I demonstrate that tunable, bidirectional phase-matched SHG via nonlinear interaction of the valley-Hall kink modes inside the two band gaps can be achieved. More specifically, by using Stokes parameters associated with the magnetic part of the valley-Hall kink modes, we introduce the concept of SHG directional dichroism, which is employed to characterize optical probes for sensing chiral molecules. I also show that these ideas can be extended to graphene metasurfaces, where the Kerr-type nonlinearity of graphene can be used to control the light transmission in topological domain-interface waveguides. In the second part of my talk I will illustrate how bound states in the continuum (BICs) of certain silicon nitride PhC slabs, engineered to possess sharp resonances with high quality factors at both the fundamental-frequency and second-harmonic, can be used to achieve an orders-of-magnitude enhancement of the SHG. Certain connections between the topological charge of the BICs and the properties of the nonlinear optical interaction (SHG) are also revealed.

The intrinsically strong and actively tunable light-matter interactions available in atomically-thin materials offer unique opportunities to trigger nonlinear and quantum optical phenomena on the nanoscale. Here we discuss the excellent nonlinear optical response associated with plasmon polaritons in ultrathin crystalline noble metal films, exhibiting thickness-dependent properties and potentially lower loss than their amorphous counterparts, and in graphene heterostructures, characterized by extreme optical confinement and electrical tunability. We shall then explore strategies to harness strong light-matter interactions in atomically-thin materials to mediate single-photon-level nonlinear optical interactions on the nanoscale and to optically drive atomic systems into actively-tunable bistable states.

Nonlinear optical effects like Optical Rectification are needed to achieve signals and provide feedback and active control of photonic platforms. Simpler materials having tunable nonlinear optical effects that respond across much of the spectrum, instead of semiconductors. Building on our earlier results, we report a new experimental observation with theoretical analysis of a transverse, or ‘Hall Effect’ optical rectification current from surface plasmons in a simple 1-D gold metasurface, without photon drag effects. Due to the strong nanoscale resonant enhancement of the electromagnetic field, higher order polarization terms cross-couple the orthogonal planes of incidence and transverse rectified current.

Confinement and enhancement of light in structures only few atomic diameters across may enable a new class of devices with functionalities in the macroscopic continuum. Pushing toward the ultraviolet range calls for renewed studies of metals, semiconductors, and conductive oxides. For example, aluminum is inexpensive, stable, abundant, has a unique spectral response, and is compatible with metal-oxide-semiconductor technology. We use a hydrodynamic-Maxwell approach to study harmonic generation in nanolayers and gratings in the femtosecond regime and compare with predictions of harmonic generation from gold and silicon gratings, and a cadmium oxide nanofilm arranged in a Kretschmann configuration.

Iridescent structural color is abundant in nature, arising in the saturated blues of the Morpho butterfly wing or the greens of jewelled beetle shells. At the micrometer scale and smaller, these naturally occurring, three-dimensionally (3D)-architected photonic crystals are composed of ordered, geometrically anisotropic features which exhibit distinct interactions with polarized light. Here, we design artificial 3D-architected colorimetric metasurfaces. We use two-photon lithography to fabricate multilayer grating structures which surpass the polarization-sensitive colorimetric response attainable in nature. Bringing additive manufacturing to the regime of visible light-matter interactions, our metasurfaces hold promise for versatile imaging, display and sensing technologies.

Gallium and gallium-rich alloys are metals in the liquid phase near room temperature and possess unique and appealing properties for a wide range of applications including photonics. However, microscopic liquid metal structures cannot be fabricated using the conventional techniques developed for solid metal structures. Although several techniques have been developed to pattern liquid metal structures with resolutions down to few micrometers, realizing liquid metal nanostructures with precisely controlled shapes, sizes and locations remains a challenging task. In this talk, we will discuss our recently developed selective-wetting-based technique for realizing liquid metal nanophotonic structures which can be reconfigured via different mechanisms.

We present the optimization of dielectric multilayers (DM) for improved total internal reflection fluorescence sensitivity. The desired resonances require a design that achieves a field enhancement and an angular tolerance of the resonance in the order of the illumination divergence. We studied the effect of the imaginary part of the refractive index k of the DM top layer on the fluorescence enhancement. We established a protocol to fabricate a single layer with a controlled k and fabricated three structures of various k. We tested the concept on fluorescent beads and observed a good agreement with the predicted fluorescence enhancement.

Polymer waveguides around the 800nm are still relatively unexplored. Our aim is to advance the state-of-the-art for polymer photonics in this key quantum technology application domain. Moreover, these platforms demand cryogenic temperatures and between the polymers, SU-8 is one that can work at these temperatures due to low losses and low volumetric shrinkage. We report the design and fabrication of resonators (Racetracks and MicroRing Resonators, MRR) that allow us to intuit the changes in the refractive index of the Su-8 at room and at cryogenic temperatures.

We have designed and experimentally realized a polaritonic topological insulator based on bulk transition metal dichalcogenide crystals (TMDC, ~40nm-thick WS2 film). We have demonstrated that due to their high refractive index and the presence of exciton modes in the optical range, they represent an excellent platform for topological polaritonics, offering both excellent confinement and strong light-matter interactions in a single material. The successful patterning of TMDC into the topological crystal was demonstrated and emergence of the topological polaritonic boundary modes was directly confirmed by the back focal plane imaging and real space imaging techniques.

Microbolometers with ultrathin and efficient absorber can improve specific detectivity and response time. Resonance enhanced absorber increases thermal mass and hence reduces response time. However, for an ultrathin film to absorb light efficiently, the dielectric function of the film and its thickness must satisfy strict requirements. We experimentally demonstrate an average absorptance of 48% +/-2.5% in the 8–13 microns (769–1250 cm-1) spectral range for 10nm thick titanium nitride (TiN) supported by 100nm thick SiN suspended membrane, a value bordering on the fundamental absorptance limit of 50%.

We have designed an infrared absorber with an electrically switchable narrowband resonance. The absorbers are two identical, coupled, metal-semiconductor-metal resonators that support a dark supermode. The semiconductor layer of the resonators is gallium arsenide, which has a refractive index shift under applied voltage. Electrically tuning one of the coupled resonators breaks the symmetry of the system and allows the dark supermode to couple to an incoming plane wave, producing a narrowband absorption resonance. Our designed absorber is predicted to achieve an absorption modulation of 97% when switching from 0V to 1.65V.

Aligned carbon nanotubes (CNTs) make a promising platform for thermal radiation applications due to their broadband IR hyberbolic dispersion and their ability to withstand high temperatures. However, their temperature dependent optical properties remain to be explored. Previously, the thermal stability of CNTs have been studied in helium and hydrogen atmospheres and vacuum, yet ambient air is yet to be explored. Here, we study optical properties of aligned CNTs at high temperatures in ambient air. We show that these films can withstand high temperatures when coated with a thin layer of dielectric and exhibit broadband IR hyperbolic dispersion at elevated temperatures.

Here, we report on realizing colorful holographic mimicry by metasurfaces. Firstly we propose a general mathematical method, called phase matrix transformation, to accomplish the holographic mimicry process. Based on this method, a dynamic metasurface hologram is designed, which shows an image of a “bird” in the air, and a distinct image of a “fish” when the environment is changed to oil. Furthermore, to make the mimicry behavior more generic, holographic mimicry operating at dual wavelengths is also designed and experimentally demonstrated.

Hybrid organic-inorganic perovskite (HOIP) is a promising semiconductor for optoelectronic devices. Here, we first introduce a HOIP metasurface to enhance light absorption and boost photocurrent by more than ten times in the frequency ranging from ultraviolet to visible. Based on the HOIP metasurface, a broadband photodetector is realized. Then with a chiral perovskite metasurface, we achieve a multi-polarization-sensitive photodetector, which is sensitive to both linear and circular polarized light simultaneously. Further we develop a flexible and ultra-thin HOIP photodetector. For the application demo, the photodetector has been applied as a signal receiver for transmitting messages in broadband optical communication.

Photonic honeycomb lattices have edge states that are protected against weak perturbations in the couplings as long as it respects certain symmetries. This topological property is the result of the existence of Dirac points in the band structure of honeycomb lattices. Here, we show by adding a certain degree of non-Hermiticity we can move an edge state and relocate it at the position of the non-Hermitian defect. To be specific the non-Hermitian defect is a local one-dimensional Parity-Time symmetric gain and loss mechanism added along the lattice in parallel to the edge. Our proposal enriches the engineering of topological states.

Phase-change materials (PCMs), capable of non-volatile electrically or optically induced transitions, are being actively explored as a promising option for use in silicon photonic neuromorphic integrated circuits and compact modulators in telecom networks to overcome the limitations in footprint and power consumption imposed by the utilization of weak and volatile thermo-optic effects in current architectures. We present the first-ever broadband measurement of the thermo-optic effect in a number of widely explored chalcogenide PCMs across visible to telecom frequencies. Our measurements show that beyond their non-volatile phase change properties, PCMs also possess giant switchable broadband thermo-optic coefficients.

Here, we demonstrated electrochemically driven polarization sensitive structural color metasurface using conductive polymer. The basic structure of metasurface is designed as Fabry-Pérot structure which is composed of a bottom silver mirror, electrochemically responsive polyaniline (PANI) spacer, and top silver nanogratings. The bottom silver mirror acts as electrode, and top silver nanogratings act as polarization sensitive transmissive filter. The PANI spacer is electrochemically changed between oxidized form and reduced form, resulting in large refractive index change in visible wavelength. Based on this concept, we achieved tunable structural color filter with polarization sensitive transmission by electrochemically response.