Here, we present Subsurface Controllable Refractive Index via Beam Exposure (SCRIBE), a direct-write lithographic approach that enables the fabrication of volumetric microscale gradient refractive index lenses, waveguides, and metamaterials. The basis of SCRIBE is multiphoton polymerization inside monomer-filled nanoporous silicon and silica scaffolds. Adjusting the laser exposure during printing enables 3D submicron control of the polymer infilling and thus the refractive index over a range of greater than 0.3 and chromatic dispersion tuning. A Luneburg lens operating at visible wavelengths, achromatic doublets, multicomponent optics, photonic nanojets and subsurface 3D waveguides were all formed.

This conference presentation was prepared for Photonics West, 2024.

Microring resonators are ubiquitously used in integrated photonics, including in areas such as nonlinear and quantum optics, where light-matter interactions are enhanced through their high-quality factors and small mode volumes. We have been exploring the benefits derived by utilizing photonic crystal microring resonators in such areas. These photonic crystal rings are created by inscribing a grating on the inner sidewall of the ring and offer new opportunities to impact nonlinear and quantum optics through modification of the both the spectral and spatial properties of the resonator modes in comparison to conventional microring resonators. I will discuss how we engineer these resonators to realize properties such as single-mode, few-mode, and broadband dispersion engineering in the spectral domain, and strong field localization and orbital angular momentum generation in the spatial domain. Finally, I will discuss the application of the resonators to microresonator optical parametric oscillators and frequency combs and experiments in cavity quantum electrodynamics.

Highly nonlinear polariton materials and nanostructures are essential components for resonant optoelectronic devices with enhanced bandwidth and sensitivity, such as nonlinear optical biosensors, photodetectors, and ultrafast optical switches. In this context, the ability to engineer nonlinear interactions in epsilon-near-zero (ENZ) and phonon-polariton media provides exciting opportunities. In this talk, I will discuss our recent work on the development of polariton and ENZ materials with tailored optical dispersion for resonant nanostructures with non-perturbative Kerr-type nonlinear responses on the silicon chip. In particular, I will present the design and characterization of polariton nanostructures for enhanced infrared photon detection on the Si platform.

A microresonator-based optical frequency comb pumped by a continuous-wave laser and regulated by an independent, injected tone is studied with focus on the locking range wherein the repetition rate can be controlled by the auxiliary laser. A generic phase synchronization model applicable to co- and counter-propagating injected tones and predicated on experimentally motivated assumptions is derived and investigated. The predictions of the model are compared with numerical integration of coupled mode equations describing frequency combs and with experimental data, demonstrating rich dynamics and excellent agreement despite simplicity. Applications of sideband injection in Kerr microcombs including to low phase noise radio frequency generation and the realization of dissipative discrete time crystals are discussed.

Recently, reconfigurable photonic functionalities have attracted attention in photonic information processing, especially optoelectronic computations. Here we show our recently studies of reconfigurable photonics using phase-change materials, GST. We created nano-scale patterns of GST thin films on various 2D silicon photonic crystals, and have succeeded in controlling their optical properties by the crystal phase change of GST. As a first example, we put nano-scale GST patterns on photonic crystal nanocavities, in which we tune the resonance and transmittance of the nanocavities. Secondly, we put them on photonic crystal waveguides, and demonstrated on-demand creation and annihilation of cavities by the phase change, As a last example, we put them on topological photonic crystals, and demonstrate that one can create and annihilate the photonic topological insulating phase by the material phase change of GST. Since the photonic topological phase is usually created at the fabrication process, our result enables a dynamic control of the topological insulating phase. Our achievements may pave the way for various reconfigurable functionalities in nanophotonic integrated circuits.

Complex oxides such as perovskite semiconductors possess electronic structures that are highly tunable via external stimuli. The phase switching can be volatile (threshold switches) or non-volatile (memory / synaptic). I will present an overview of correlated oxide systems where one can create sub-wavelength dielectric environments on-demand exploiting metal-insulator transitions. We will discuss use cases in analog photonic computing, meta-X devices and microwave technologies. The role of materials synthesis, defects and their influence in photonic device performance will be discussed.

We report direct-write and rewritable photonic circuits based on a low-loss phase change material (PCM) thin film Sb2Se3, in which complete end-to-end functional photonic circuits can be created by direct laser writing in one step without additional fabrication processes. The direct-write phase-change photonic circuit affords exceptional flexibility, allowing any part of the circuit to be erased and rewritten, facilitating rapid design modification and reprogramming. We demonstrate the versatility of this technique with various photonic circuits for diverse applications, including an optical interconnect fabric for reconfigurable networking, a photonic crossbar array as a tensor core for optical computing, and a tunable optical filter for optical signal processing. Our technique unlocks new paradigms for programmable photonic networking, computing, and signal processing. Moreover, the rewritable photonic circuits enable rapid prototyping and testing in a convenient and cost-efficient manner, eliminate the need for nanofabrication facilities, thus promote the proliferation of photonics research and education to a broader research community.

We present the design and characterization of a novel metasurface absorber utilizing the phase change material, vanadium dioxide (VO2). The absorber demonstrates ultra-wideband performance, exhibiting high absorption across a broad spectrum ranging from 400 nm to 1200 nm. In addition to its spectral versatility, the absorber is designed to function effectively over a wide range of incident angles, maintaining an average absorption of approximately 80% for angles between 0 and 65 degrees. A unique feature of this absorber is its reconfigurability in the infrared regime, particularly in the 1400-1600 nm range. This capability opens up new avenues for dynamic control and optimization of absorption properties in various applications.

The applications of adaptive optics extend across multiple sectors, encompassing areas such as LiDAR, biological and chemical sensing, and free-space communications. In this study, we report on the design, fabrication, testing, and modeling of electrically reconfigurable metasurfaces using a low-loss high contrast phase change material, Ge2Sb2Se4Te integrated with an IR-transparent silicon microheater. Through this work, we introduce a reliable architecture for switching PCM-based metasurfaces within an integrated circuit configuration and the capability of controlling the transmission of electromagnetic waves through the precise stimulation of PCM-based pixels, each spanning a few hundred microns, over numerous cycles. By leveraging PCM-based pixels, we unlock the potential to create metasurfaces encompassing a diverse range of functionalities such as dielectric filters, metalens, or beam steering devices, which is governed by the design of the meta-atoms.

In this talk I will explore the hidden potential of electrochemically actuated metasurfaces. Electrochemical actuation is unique in that it provides for control over both the volume expansion of a scatterer as well as the free electron density for permittivity control. I will explore this freedom in dynamic tuning of titanium dioxide and silicon-based metasurfaces, materials already popularized in the field of photonics for their high index and low loss throughout the visible spectrum. Using these materials, we leverage electrochemical intercalation of lithium to initiate phase changes in a continuously tunable, reversible, and bi-stable manner, using bias voltages that are an order of magnitude less than similar devices.

We theoretically demonstrate electrically tunable metasurfaces, which can dynamically manipulate the wavefront of the reflected light in the near-infrared wavelength range with optical efficiencies > 80%. We achieve a dynamically tunable optical response by integrating a lithium niobate l(LNO) layer into the silicon-based resonant metasurface structure. By applying voltage, we achieve a dynamically tunable phase shift of 236 degrees when the refractive index of the LNO layer varies between 2.208 and 2.212. Finally, we analyze the beam steering performance of the designed metasurfaces. The designed metasurfaces could be useful for free space optical communications, light detection and ranging (LiDAR), and laser-based additive manufacturing.

Resonant cavity structures integrated with phase change material germanium antimony telluride (GST) function as angular insensitive mid-infrared optical filters. The one-dimensional (1D) sub-wavelength grating structures consisting of GST resonators embedded in metallic (Ag) film act as Fabry-Perot resonators with observable transmission resonances, that can be tuned by thermal excitation when GST switches from amorphous to crystalline state, while maintaining angular insensitivity up to 60 degrees. Modeling and experimental results of an interdigitated design of the 1D resonant structure for reconfigurable applications by electrical switching of the transmission spectra of the optical filter will be presented.

Plasmonic apertures can concentrate optical fields into subwavelength areas, thereby enhancing the optical gradient force. This facilitates the precise trapping of nanoscale entities. Traditionally, design involved intuition followed by electromagnetic simulations with parameter variations. Here we instead use a computational algorithm is employed to create plasmonic apertures for nanoparticle trapping. These algorithmically generated apertures possess highly irregular shapes and, in conjunction with ring couplers also optimized by the algorithm, are expected to produce trapping forces over ten times stronger than those achieved with the initial double nanohole design used as the starting point for optimization. This research was published in Advanced Optical Materials in 2021 (2100758). We will also discuss recent, yet-to-be-published work that employs an inverse design approach, specifically the gradient descent method with adjoint sensitivity analysis, to develop plasmonic nanotweezers.

In the realm of nanophotonics, establishing the intricate relationship between design parameters and the ultimate response of a given nanophotonic devices stands as a formidable challenge. The prevalent utilization of numerical solutions to Maxwell's equations, whether through in-house codes or commercial software, often conceals the underlying physics. In this talk, we present machine-learning (ML) algorithms for elucidating the connection between design parameters and device response. We discuss two distinct ML methods to discern the roles and significance of individual design parameters, namely SHAP (SHapley Additive exPlanations) values and Pruning. By scrutinizing two diverse nano-devices using these complementary techniques, this talk sheds light on the compelling insights derived from this innovative approach.

In this work, we present an efficient approach based on Bayesian optimization for the design of reconfigurable metaphotonic devices with a considerable reduction in computation for achieving optimal design while reducing the chance of converging to local optimal. The unique features of this approach will be discussed and compared with existing design techniques. To show its practical utility, we will use our approach for designing metasurfaces with reconfigurable absorptance and scattering in a wide wavelength range in the non-volatile, Poly(3,4-ethylenedioxythiophene)/poly (styrenesulfonate) (PEDOT:PSS) as a promising candidate for realization reconfigurable meta-device. Theoretical and experimental results will be presented to further support our claims.

The recent advent of tailorable photonic materials is currently driving the development of durable, compact, chip-compatible devices for information- and quantum technologies, sustainable energy, harsh-environment sensing, aerospace, chemical and oil & gas industries. In this talk, we will discuss advanced machine-learning-assisted photonic designs, materials optimization, and fabrication approaches for the development of efficient thermophotovoltaic (TPV) systems, lightsail spacecrafts, high-T sensors utilizing TMN metasurfaces and beyond. We also explore the potential of TMNs (titanium nitride, zirconium nitride) and TCOs for switchable photonics, high-harmonic-based XUV generation, refractory metasurfaces for energy conversion, high-power applications, photodynamic therapy and photocatalysis. The emphasis will be put on novel machine-learning-driven design frameworks that leverage the emerging quantum solvers for meta-device optimization and bridge the areas of materials engineering, photonic design, and quantum technologies.

Abstract: Our study presents an innovative approach to metasurface design, marrying Fourier techniques from image processing with artificial intelligence (AI). Metasurfaces, vital in compact optical system creation, have been a focus. Conventional topological optimization methods show promise but face challenges in computational efficiency, especially with large-scale devices. AI-driven techniques, though effective, are often limited to devices with few design parameters. Our proposed methodology addresses these issues, offering a robust design framework for expansive metasurfaces. We interpret unit cell dimensions as Fourier series coefficients, simplifying design complexities and addressing periodicity concerns. By utilizing AI on the captured Fourier series coefficients, we drastically reduce design parameters, facilitating specialized AI metasurface applications. This fusion of Fourier and AI methodologies promises breakthroughs in metasurface design, enriching optical engineering possibilities.

We study the use of deep neural networks towards the prediction of the optical properties of two-dimensional photonic crystals, as well as their inverse design. We incorporate a rigorous tight-binding model as a known operator in the machine learning algorithm. This physics-informed approach allows the prediction of meaningful model parameters rather than the high-dimensional full response, allowing for an efficient method as well as potential insight in the physical workings of specific designs. We demonstrate a four-order-of-magnitude speedup of prediction of bandstructures and field symmetries over full-field calculations, and proof-of-concept inverse design of photonic crystals with large gaps, flat bands, and Dirac-point degeneracies.

This work presents a comprehensive investigation aimed at identifying the most streamlined neural network architecture for the inverse design of nanophotonic structures. In pursuit of this objective, we delve into the statistical and computational complexities inherent in neural network design, contextualized within the realm of nanophotonic structures, as defined by their design complexity, e.g., the number of constituent parameters. The study encompasses two critical dimensions: statistical complexity, where we explore the optimal quantity of training data, and computational complexity, where our aim is the study of the required computation and model complexity for accurately modeling the input-output relation in a class of nanophotonic structures. Through the integration of these two facets, we will determine the simplest neural network configuration for the given class of nanophotonic structures, facilitating efficient and accurate inverse design, and understanding the effect of design parameters on the output response complexity. In addition to reporting the details of this novel technique, we will show its implementation for two important classes of nanophotonic devices.

We show that anomalous static elastic behavior of periodic metamaterials is fundamentally connected to minima in their (real-valued) phonon band structure via the Cauchy-Riemann equations for analytical functions. This connection allows us to systematically engineer anomalously large characteristic decay lengths in static elasticity. We discuss different theoretical examples and an experimental validation based on 3D laser microprinted metamaterials with roton-like acoustic phonon band structure. Herein, statically pulling on one end of a metamaterial beam, while fixing the other end, leads to pronounced spatial oscillations of the displacement field along the beam axis. Such behavior also violates Saint Venant’s principle.

Integrated photonics on lithium niobate has been rejuvenated in the last decade, thanks to the development of submicron optical waveguides on thin-film wafers of the material. For example, record-high performance electrooptic modulators and nonlinear wavelength converters on the platform have been maturing and quantum-optic applications are emerging. Progress in thin-film lithium niobate integrated photonics, its future directions, opportunities, and challenges will be presented.

Nanophotonics based on III-nitride materials enable devices in the visible and ultraviolet frequencies that are important for many applications like solid-state lighting, lasers, flat optics and quantum information science.We will discuss InGaN quantum well based nanowire array photonic crystals demonstrating optically pumped low threshold lasing. We will also discuss electrochemical and laser assisted photelectrochemical etching of III-nitride nanostructures for creating new functionalities and phenomena such as quantum dots in wire for single photon generation and nanowire array based metasurfaces. Sandia National Laboratories is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

We report the scalable fabrication and characterization of photonic crystals (PhC) with feature sizes below 100 nm. In particular, we demonstrate antislot PhC nanobeam waveguides featuring hourglass-shaped unit cells that support enhanced light-matter interaction in silicon, and slotted PhC nanobeam waveguides that support enhanced light-matter interaction in air or other low refractive index media. These PhCs were fabricated using a monolithic silicon photonics technology at GlobalFoundries. Applications of deep subwavelength featured photonic crystals in optical modulators and biosensors will be discussed.

We designed a metasurface-integrated topological photonic crystal that controls the polarization and beam shape of emission. The topological photonic crystal (TPC) bulk cavity works based on band-inversion-induced reflection at the interfaces of different topological structures. Therefore, it can be manufactured with a small-sized cavity, and it is a device capable of sufficiently lasing even at a relatively low threshold. Here, by integrating with dielectric metasurface that can control the phase, amplitude, and polarization of light, we designed and fabricated a TPC cavity that generates circularly polarization and simultaneously beam shape of emission.

Recently, metasurfaces are integrated with existing devices such as LEDs and lasers, further extending their applications more. Here, we have attempted to miniaturize existing bulky optical components by combining metasurfaces with a surface-emitting photonic bandedge laser. We designed a photonic bandedge laser that generates linearly polarized light by changing circles as ellipses in photonic crystals. By combining metasurface-based quarter-wave plates, axicon lenses, and vortex lenses on the photonic crystals, we confirmed the effective generation of circularly polarized light that simultaneously forms Bessel beams and vortex beams. Our proposed structure is expected to be used in various fields where circularly polarized light is used, such as 3D displays, optical communications, and light detection and ranging (LiDAR)s etc.

Nanoimprinting can fabricate nanostructures with low manufacturing costs and high throughput, overcoming the limit of conventional fabrication. In this research, we fabricate a photonic crystal resonator composed of QDs and TiO2 nanoparticles using the nanoimprinting technique. The PL of the QDs is enhanced by coupling to high quality factor optical mode, which is supported by the photonic crystal consisting of no loss dielectric composite. We demonstrate the imprinted nanophotonic device can operate as an optical resonator to enhance the light-matter interaction. Additionally, this research can give a promising way for high-resolution QLEDs with luminescence enhancement.

Optical metasurfaces consist of planar subwavelength nanoantenna arrays that offer singular ability to sculpt wavefront in almost arbitrary manners. They are thereby poised to become a powerful tool enabling compact and high-performance optics. Multifunctional metasurfaces, whose optical responses vary according to the operation conditions, further allow a plurality of new functionalities unattainable with traditional optical systems. In this talk, we discuss the development of multifunctional meta-optics and demonstrations in imaging and sensing applications.

Image compression is a crucial operation in any optical system. This talk will present an optical implementation of the mathematical operation involved in image compression, specifically the discrete wavelet transform, that can lead to a reduction of the information entropy of an input signal without loss of information, with zero power consumption and a speed limited only by the frequency of the electromagnetic waves used in the system.

Theoretical and experimental results demonstrating reversible and irreversible regimes of laser-metasurface interactions will be presented. We will show how different types of semiconductor metasurfaces enable the generation of high harmonics, including even ones. We will also demonstrate laser-assisted nanostructuring of pre-fabricated metasurfaces that produce high-aspect features with strongly sub-wavelength (less than wavelength/50) feature sizes.

Photonic integration offers great potentialities for the realization of compact, light-weight, and low-cost systems for free-space applications, noteworthy in the field of 3D imaging and optical communications. However, several shortcomings still limit the widespread applicability of integrated solution, e.g., low efficiencies, narrow operational bandwidth, and polarization sensitivity. The use of metamaterial and metasurfaces, combined with innovative design approaches, represents a powerful tool to overcome these limitations. In this talk, we will present our recent advances in the realization of highly-performing devices for free-space applications and optical beam control, with a particular focus on integrated grating antennas based on metamaterials and metasurfaces.

Among optical devices aimed at accelerated and energy efficient computing, metasurfaces look promising because of the large number of degrees of freedom they can access but they suffer weak nonlinearity. Here, we introduce passive and low-threshold nonlinear image filters based on local dipolar guided-mode resonant (DGMR) metasurfaces. With no incident angle dispersion over a 40° field of view, resonantly enhanced photo-thermal redshifts can switch local metasurface regions from opaque to transparent at incident intensities of just 44 μW/μm^2, with micrometer scale resolution. Such devices can serve as accelerators for digital computing and even all-optical neural networks.

This conference presentation was prepared for Photonics West, 2024.

Optical vortices promise enhanced optical and quantum information processing via the orbital angular momentum multiplexing. Nanophotonics opens the possibility of realizing subwavelength optical vortices through coupling optical beams into subwavelength surface polaritons in the near-field, although the topological charge is always fixed. We report dispersion-driven topological charge multiplication by leveraging the strong sublinear dispersion of low-loss surface phonon polaritons on silicon carbide membranes, capable of switching the topological charges within a small ∼3% frequency range in the mid-infrared frequency range. This offers the possibility of all-optical ultrafast switching of optical vortices at mid-infrared frequencies.

Stimulated Brillouin scattering (SBS) is a highly efficient nonlinear optical interaction between acoustic waves and light. It enables the mediation of spectrally fine radio-frequency signals, with potential applications in quantum signal processing. Here, we investigate the storage of the state of polarization of light in a silica optical nanofiber (ONF) that guides both optic and acoustic waves. It adds an extra degree of information to Brillouin optoacoustic memories. The ONF possesses multiple acoustic modes. We show promising results with read/write operation for a longitudinal acoustic mode and investigate the TR21 acoustic mode polarization sensitivity.

Recent progress is subwavelength optics is driven by the physics of optical resonances. This provides a novel platform for localization of light in subwavelength photonic structures and opens new horizons for metamaterial-enabled photonics, or metaphotonics. Recently emerged field of Mie-resonant metaphotonics (also called "Mie-tronics") employs resonances in high-index dielectric nanoparticles and dielectric metasurfaces and aiming for novel applications of the subwavelength optics and photonics. High-index subwavelength resonant dielectric structures emerged recently as a new platform for nanophotonics. They benefit from low material losses and provide a simple way to realize magnetic response which enables efficient flat-optics devices reaching and even outperforming the capabilities of bulk component. In this talk, I will review the recent advances in Mie-tronics and its applications in metaphotonics and metasurfaces.

Inspired from electronic systems, topological photonics and polaritonics aims to engineer optical devices with robust properties in metamaterials. A popular model was proposed by Wu and Hu for realizing a bosonic Z2 topological crystalline insulator with “robust” edge states, which led to intense studies including extensions to polaritons. Utilizing topology in photonic designs can lead to robust optical propagation with promising implications for integrated photonics. However, detailed analyses using topological quantum chemistry tools reveal that the Wu-Hu model is topologically trivial but is a higher order topological photonic insulator (Phys Rev. Lett, 131, 053802 (2023). Therefore, the waveguided edge mode in the Wu-Hu model cannot host robust helical states, as previously believed. We are exploring new ways of incorporating nontrivial topology in photonic systems where the excitations are bosonic in nature. We will discuss our efforts in incorporating quantum geometry in photonic systems by utilizing fragile topology. Our efforts and challenges to realize fragile topological photonic and polaritonic lattices will be discussed.

Lasers play a fundamental role in science and technology from quantum computing, to communications, sensing, and imaging. The scaling of lasers and in-particular of surface emitting lasers is a multi-decade long question that has been investigated since the invention of lasers in 1958. In the first part of the talk, I will argue that a surface emitting laser that remains single mode irrespective of its size, should of necessity also waste light at the edge. This is a fundamental departure from the Schawlow-Townes two-mirror strategy that preserves gain and minimizes loss by keeping light away from mirrors. The strategy was implemented in our recent discovery of the Berkeley Surface Emitting Laser (BerkSEL). In the second part of this talk, I will discuss our invention of functional topological lasers: integrable non-reciprocal coherent light sources as well as compact bound state in continuum sources.

Programmable photonic integrated circuits represent an emerging technology that amalgamates photonics and electronics, paving the way for light-based information processing at high speeds and low power consumption. Here, we present a novel architecture for efficient integrated photonic implementation of arbitrary matrix operations. The proposed architecture is built on interlacing discrete fractional Fourier transform layers with programmable phase shifter arrays. This circuit is resilient to defects in the phase shifters and perturbations in the intervening Fourier operators. We delve into the core attributes of this architectural design and explore its practical applications in the realm of analog information processing.

We present surface plasmon resonance-based sensing devices with Aluminum (Al) as the plasmonic metal in the near-infrared region and analyze the output performances in terms of higher sensitivity and the Figure of Merit (FOM). The optical characteristics of Al-based plasmonic sensors are explored using different interrogation modes (angle and wavelength). Biorecognition elements help to enhance the sensor’s performance, for which 2D nanomaterials are explored for the biofunctionalization of the top surface. In the end, we also present an Al-based plasmonic device that utilizes both prism and nanostructure-based configurations, and the same designed parameters for the device offer high sensitivity and FOM in both angle and wavelength interrogation.

We have demonstrated an electrically driven photonic crystal (PhC) surface-emitting laser using deep-hole dry etching. The laser is based on the gamma-point PhC band-edge mode, which has a single-mode nature and a surface-emitting characteristic. The square lattice PhC pattern was provided using e-beam lithography and inductively-coupled-plasma reactive-ion etching, wherein the deeply etched holes induce sufficient lateral optical feedback. Under pulsed injection mode, we observed lasing action at a single wavelength of 1532 nm, and the threshold current density was measured to be ~1.05 kA/cm2.

Dielectric and metallic metasurfaces are proposed to demonstrate the sensing applications in the near-infrared region under normal incidence light. The geometrical parameters of the proposed metasurfaces are designed using Rigorous coupled analysis under wavelength interrogation, and the results are verified using Comsol Multiphysics software. A layer of 2D nanomaterial (MoS2) is considered to increase the adsorption on the sensing surface. Aluminum-based metallic metasurfaces offer a sensitivity of 1100nm/RIU with a figure of merit of 250 RIU-1. The proposed metasurfaces are further used for the detection of cancer cells in human blood, and a red shift in the wavelength spectra is observed due to the increase in the refractive index.

We designed a vertical split ring resonator metamaterial to achieve a highly directive perfect absorber and emitter in the mid-infrared region based on the Generalized Kerker Condition. The results show zero backscattering and high directivity via the electric dipole-electric quadrupole interference. The metal stress-driven self-folding method was applied to fabricate the vertical metamaterial efficiently. We both experimentally and analytically demonstrated the absorption and the angular dispersion. The angle-resolved emission radiation pattern is visualized which agrees with the simulation results. This metamaterial can not only be an Infrared receiver but also an emitter. We provide a novel strategy to conceive a polarization-sensitive/-insensitive, single-/multiband, and highly directive vertical metamaterial perfect absorber and emitter in the Mid-Infrared region.

BIC is a promising resonant mode with attractive mode properties such as an infinite quality factor and a vortex far field pattern. UCNPs emit visible photons when they are excited by NIR photons. In this research, we design a BIC metasurface that wavelengths of the BICs are targeted to the NIR excitation wavelength and visible emission band of the UCNPs. As a result of the coupling between the photons and BICs, the vortex emission can be observed in the far-field and PL was significantly enhanced.

The nonlocal metasurface modulates optical properties with a high wavelength selectivity. In this research, we demonstrate a polarization-wavelength selective nonlocal metasurface using nanoparticle-embedded resin printing. QDs are also embedded in the nanoparticle composites so that the nonlocal metasurface operates as both an emitter and a resonator simultaneously. The nonlocal metasurface contributes to enhancing the photoluminescence of the QDs, as well as the QDs’ emission is controlled by the polarization. This work provides a way that the nonlocal metasurface can be utilized for a polarization-selective light source, sensing, and display.

Grating couplers are inevitable building blocks of integrated photonic circuits, so their design and performance are always crucial. We present a straightforward strategy for designing optimal grating couplers by incorporating a photonic bandgap analysis for each element of a grating to achieve better performances. We show that our approach removes unwanted back-scatterings within the grating region. To demonstrate the advantage of our approach, we demonstrated a few important designs for practical applications, especially the design and demonstration of efficient focusing grating couplers with diminished sidelobes at their focal plane.

In this study, we introduce a novel metaphotonic structure using phase-change materials for efficient beam steering through linearly variable refractive index manipulation. Leveraging the unique properties of Sb₂Se₃, a versatile phase change material, we create a metasurface capable of precisely controlling light propagation. By inducing a linear phase variation in the incident light, our metasurface effectively deflects light in the desired direction, following the principles of the generalized Snell's law. Simulation results demonstrate the development of a highly efficient beam steerer, achieving an impressive redirection range of approximately 10 degrees with an exceptional efficiency exceeding 80% in one material phase. In the other phase, where material loss impacts efficiency, we still achieve rates exceeding 40%. These remarkable levels of efficiency highlight the potential of phase change materials in photonic applications and position our metastructure as a promising candidate for advanced photonic devices and systems, offering precise and efficient beam steering capabilities.