Nanostructured Metasurfaces Research Articles

Thermostable terahertz metasurface enabled by graphene assembly film for plasmon-induced transparency

With the increasing demand on high-density integration and better performance of micro-nano optoelectronic devices, the operation temperatures are expected to significantly increase under some extreme conditions, posing a risk of degradation to metal-based micro-/nano-structured metasurfaces due to their low tolerance to high temperature. Therefore, it is urgent to find new materials with high-conductivity and excellent high-temperature resistance to replace traditional micro-nano metal structures. Herein, we have proposed and fabricated a thermally stable graphene assembly film (GAF), which is calcined at ultra-high temperature (~ 3000 ℃) during the reduction of graphite oxide (GO). Compared with micro-nano metals that usually degrade at around 550 ℃, the proposed GAF maintains a high extent of stability at an extremely high temperature up to 900 ℃. In addition, to make GAF a prime candidate to replace micro-nano metals, we have modified its fabrication process for improving its conductivity to 1.3 × 106 S/m, which is quite close to metals. Thus, micro-nano optoelectronic devices could retain high efficiency even when GAF replaces the crucial micro-nano metals. To verify the thermostability of optoelectronic devices composed of GAF, we have compared the high-temperature resistance performance of two structures capable of achieving plasmon-induced transparency (PIT) at the THz region, one using micro-nano metals (Aluminum) and the other GAF. The Al metasurface displayed a near-complete loss of PIT effects after a high-temperature treatment, while GAF could remain excellent PIT properties at above 900 ℃, thus enable to fulfil its optimum performance. Overall, the proposed thermostable metasurface provides new pathway for the construction of thermostable optoelectronic devices that can operate under ultra-high temperature scenario.

Investigating spin-orbit interaction of light in micro- and nanophotonic systems using polarization Mueller matrix

Coupling between the spin and orbital angular momentum of light has led to a variety of exotic spin–orbit photonic effects, establishing a paradigm of nanophotonic meta-devices to control and manipulate light at the nanometer length scale. For the advancement of spin–orbit photonic technologies, quantitative characterization and unambiguous physical interpretation of the various spin–orbit interaction (SOI) effects exhibited in complex nanophotonic systems are of utmost importance. This Perspective addresses some of these outstanding challenges in the domain of spin–orbit photonics, focusing on the simultaneous manifestation of multiple SOI effects in hybridized nanophotonic systems and the role of polarization-based techniques in their characterization and quantification. After introducing the fundamentals and physical origins of SOI effects, we present a polarization Mueller matrix technique as a powerful tool to probe, decouple, and independently quantify these effects in a unified experimental framework, demonstrated with hybridized waveguided plasmonic crystals. We further discuss the potential of structured light and tailored polarization to enable unconventional SOI phenomena in simple nanostructured metamaterials and metasurfaces. These advancements not only enhance our fundamental understanding of SOI phenomena across micro- and nanoscale optical systems but also pave the way for the development of multifunctional and tunable spin–orbit photonic devices.

Bi-functional and tri-channel image displays based on a single-size nanostructured metasurface enabled by dual-orientation-degeneracy

Benefiting from the extraordinary ability of manipulating lightwaves at the subwavelength scale, nanostructured metasurfaces are expected to achieve multifunctional and multichannel integration to expand functionality and increase information capacity. However, multifunctional and multichannel metasurfaces always consist of various anisotropic nanostructures, inevitably bringing challenges to design and fabrication. In this study, we propose a concept of dual-orientation-degeneracy containing twofold orientation degeneracy. The first-level degeneracy is a one-to-four mapping scheme between the intensity of Channel 1 and orientation angle and the second-level degeneracy refers to a one-to-two mapping between the intensity of Channel 2 and orientation angle. Additionally, we provide a minimalist design of bi-functional and tri-channel image displays based on a single-size nanostructured metasurface. The designed metasurface integrates two functionalities of nanoprinting and holography, which can generate a continuous grayscale meta-image, a binary meta-image and a phase-only holographic image. Three channel displays can be readily switched by polarization controls. More importantly, the metasurface is achieved merely by reconfiguring the orientation angles of the nanostructures with fixed geometries, relieving the structure design and fabrication burden. The presented minimalist design strategy is universal and applicable, which can contribute to advanced research and applications in ultra-compact image displays, high-dense optical storage, multi-folded optical anti-counterfeiting, etc.

Observation of Anapole Resonances in Lithium Niobate Metasurfaces with Significantly Enhanced Second Harmonic Generation

AbstractBenefiting from their large second‐order nonlinear coefficients and high integration capabilities, crystalline lithium niobate (LN) films have shown great application prospects in the field of nonlinear metasurfaces. It is necessary to endow LN metasurfaces with optical resonances to further boost nonlinear optical responses. Among these optical resonances, anapole resonances carried by LN metasurfaces have been predicted to efficiently enhance second harmonic generations (SHG) but have never been experimentally realized. Anapole resonance requires ideal nanostructures to have steep sidewalls and a high filling ratio, but the intrinsic hardness and inert chemical properties of LN materials pose great challenges for the fabrication of LN nanostructures. Here, a multi‐gas component dry‐etching technique is proposed to prepare various LN nanostructures, achieving typical LN nanopillar arrays with a sidewall angle of ≈85° at a depth of 300 nm and a filling ratio of 52%. Importantly, nanostructured LN metasurfaces are designed and fabricated to experimentally realize anapole resonances at a fundamental wavelength of ≈800 nm, demonstrating a ≈30‐fold enhancement in second harmonic generation compared with bare LN films. The work provides promising strategies for the versatile fabrication of LN nanostructures and their applications in nonlinear meta‐optics.

Laser nanostructured metasurfaces in Nb superconducting thin films

Superconducting Nb thin films have been nanostructured by means of a femtosecond UV laser. Laser induced periodic surface structures (LIPSS) with lateral modulation of ≈250nm and depth smaller than amplitude (≲20nm from crest to trough) are obtained for optimized laser scanning conditions over the film surface, i.e. power, frequency, scanning speed and polarization. This provides a fast and scalable procedure of surface control at the nanoscale. In thin films, control over the kinetics of the LIPSS formation process has been crucial. Untreated and laser-patterned samples have been characterized by electron and atomic force microscopy as well as by local and global magnetometry. The superconducting properties reveal anisotropic behavior in accordance with the observed topography. The imprinted LIPSS define channels for anisotropic current flow and flux penetration. At low temperatures, magnetic flux avalanches are promoted by the increased critical current density, though flux tends to be channeled along the LIPSS. In general, directional flux penetration is observed, being a useful feature in fluxonic devices. Scalability allows us to pattern areas of the order of cm2/min.

All-Dielectric Nanostructured Metasurfaces with Ultrahigh Color Purity and Selectivity for Refractive Index Sensing Applications

In this study, two kinds of nanostructured metasurfaces are presented and compared to exhibit ultrahigh color purity and selectivity in the visible wavelength range. The proposed nanostructured metasurfaces are composed of all-dielectric materials, which are Si3N4 fabricated on quartz substrates to form one-dimensional (1D) and two-dimensional (2D) nanogratings (NGs). These nanostructured metasurfaces exhibit over 98 % reflection intensity with ultra-narrow bandwidths less than 20 nm to perform vivid red, green, and blue colors, implying the potentials in high-saturation display. Among nanostructured metasurfaces, 2D-NGs allow a wider range of incident angle than 1D-NGs and show polarization-independent characteristic owing to the symmetric arrangement in nanoscale in the incident plane. Furthermore, the numerical simulation results prove that 1D-NGs and 2D-NGs exhibit single- and dual-resonance when exposed on the ambient environment with different refractive indexes. Such excellent optical performances verify their potentials not only in high-resolution display but also in chemical sensing applications.

Challenges in temperature measurements in gas-phase photothermal catalysis

Luca Mascaretti completed his PhD in 2018 at Politecnico di Milano, Italy. Afterwards, he has worked as a postdoc researcher at the Regional Centre of Advanced Technologies and Materials, Palacký University in Olomouc (Czech Republic). His research activity is related to titanium oxide/nitride-based nanostructured materials for solar energy conversion processes. Andrea Schirato is currently a physics PhD candidate across Politecnico di Milano and the Italian Institute of Technology (Genoa) under the supervision of Profs. G. Della Valle and R. Proietti Zaccaria. His research activities focus on the theoretical study and numerical modeling of ultrafast nonlinear phenomena driven by hot carriers, including non-equilibrium electronic and phononic energy transfer in nanostructured materials and metasurfaces. Tiziano Montini is associate professor at the University of Trieste in Italy. He received his PhD in chemistry from the University of Trieste in 2006, followed by a postdoc fellowship. His research activity concerns on nanomaterials as catalysts for renewable energy production and environmental protection. Alessandro Alabastri is currently an assistant professor in the Electrical and Computer Engineering Department at Rice University. He received his PhD in nanosciences in 2014 from the Italian Institute of Technology and the University of Genoa. In 2015, he was visiting researcher in the Molecular Foundry at the Lawrence Berkeley National Laboratory. He worked on several aspects of light-to-heat conversion, photothermal effects in nanostructures, and heat recovery in light-powered thermofluidic devices. Alberto Naldoni is currently an associate professor at University of Turin, Italy. Since 2017, he is the co-leader of the photoelectrochemistry group at the Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc (Czech Republic). He obtained his PhD in chemical sciences from University of Milan (2010). From 2014 to 2017, he was visiting research faculty at the Birck Nanotechnology Center of Purdue University. His group focuses on nanomaterials for plasmonics, photocatalysis, and photoelectrochemistry. Paolo Fornasiero is a professor at the University of Trieste in Italy. He received his PhD in chemistry from the University of Trieste in 1997, followed by a postdoc fellowship at Reading University (UK). His group currently focuses on research into nanomaterials for environmental and energy-related applications.

Characterization of gap-plasmon-based metasurfaces with scanning white-light interferometry

Subject of study. The possibility of using the well-established method of scanning white-light interferometry (SWLI), implemented as a commercially available device, is studied for characterizing promising metasurfaces based on third-order plasmon resonance. The characteristics of the samples were determined for two types of experimental metasurfaces, namely, for a binary grating with a period of 12.6 µm and a phase gradient grating with a period of 6.75 µm. Objective. The main goals of this study were to test the fundamental possibility of using a commercially available white-light interferometer to determine the phase characteristics of plasmonic metasurfaces and to estimate experimentally the lateral optical resolution in the phase image of metasurfaces. Main results. Although the method of SWLI was originally intended for measuring a geometric microrelief, it was found that it can be used to determine the phase increment of the optical radiation reflected from the studied metasurfaces in the range of 10°–100° with a relative accuracy of approximately 50% without any modification of the signal processing algorithm. The possibility of obtaining a phase mapping of the surface with such accuracy in this configuration is not obvious because the metasurface is a matrix of nanoelements with the same height of 50 nm, and the phase shift in the reflected optical radiation is created due to third-order gap plasmon resonance. On the obtained optical phase images of metasurfaces, unit (single) cells of the metasurface are reliably resolved owing to a sufficiently high lateral resolution (approximately 450 nm). The results of the characterization of metasurfaces obtained using SWLI are compared with those obtained in a laboratory setup using scanning differential heterodyne microscopy (SDHM). Although the SWLI method demonstrates better lateral resolution compared with the SDHM method, it is less accurate in restoring the phase characteristics of metasurfaces with a phase gradient. Practical significance. The results obtained allow us to conclude that the evaluation of the phase optical characteristics of nanostructured plasmonic metasurfaces by the method of SWLI is possible and requires further experimental and theoretical studies.

Plasmonic metasurface assisted by thermally imprinted polymer nano‐well array for surface enhanced Raman scattering

AbstractPlasmonic nanometasurfaces/nanostructures possess strong electromagnetic field enhancement caused by resonant oscillations of free electrons, and has been extensively applied in biosensing, nanophotonic and photocatalysis. However, fabrication of uniform nanostructured metasurfaces by conventional methods is complicated and costly, which mitigates a wide‐spread use of this technique in ubiquitous applications. Here, we present a facile and scalable method to fabricate an active nanotrench plasmonic gold substrate. The surface comprises sub‐10 nm plasmonic nanogaps and their formation is assisted by a pre‐fabrication of nano‐imprinted polymer nano‐well arrays. The plasmonic metasurface is optimized to maximize the density of the nano‐trenches by tuning the substrate material, imprinting procedure and film deposition. We show that the surface Raman enhancement due to plasmonic resonances correlates well with trench density and reach a meritorious enhancement factor of EF > 105 over large surfaces.We further show that the electric field strength at the nanotrench features are well explained by finite element method simulations using COMSOL Multiphysics. The plasmonic substrate is transparent in the visible spectrum and conductive. In combination with a scalable bottom‐up fabrication the plasmonic metasurface opens up for a wider use of the sensitive and reliable SERS substrate in applications such as portable sensing devices and for future internet of things.

Local ultra-densification of single-walled carbon nanotube films: Experiment and mesoscopic modeling

Fabrication of nanostructured metasurfaces poses a significant technological and fundamental challenge. Despite developing novel material systems that support reversible elongation and distortion, their nanoscale patterning and control of optical properties remain an open problem. Herein we report the atomic force microscope lithography application for nanoscale patterning of single-walled carbon nanotube films and the associated optical reflection coefficient tuning. Large scale mesoscopic distinct element method atomic force nanoindentation simulations of single-walled carbon nanotube samples comprising entangled dendritic nanotube bundles with branches extending down to individual tubes explain the mesoscale mechanism of local irreversible densification and further predict its impact on mechanical properties. All observed and calculated phenomena support each other and present a platform for developing patterned optical devices using nanofibrous matter.

Tailoring Accidental Double Bound States in the Continuum in All‐Dielectric Metasurfaces

AbstractBound states in the continuum (BICs) have been thoroughly investigated due to their formally divergent Q‐factor, especially those emerging in all‐dielectric, nanostructured metasurfaces from symmetry protection at the Γ point (in‐plane wavevector k|| = 0). Less attention has been paid to accidental BICs that may appear at any other in the band structure of supported modes, being in turn difficult to predict. Here, a coupled electric/magnetic dipole model is used to determine analytical conditions for the emergence of accidental BICs, valid for any planar array of meta‐atoms that can be described by dipolar resonances, which is the case of many nanostructures in the optical domain. This is explored for all‐dielectric nanospheres through explicit analytical conditions that allow in turn to predict accidental BIC positions in the parameter space (ω, k||). Finally, such conditions are exploited to determine not only single, but also double (for both linear polarizations) accidental BICs occurring at the same position in the dispersion relation ω − k|| for realistic semiconductor nanodisk meta‐atoms. This might pave the way to a variety of BIC‐enhanced light–matter interaction phenomena at the nanoscale such as lasing or nonlinear conversion, that benefit from emerging at wavevectors away from the Γ point (off‐normal incidence) overlapping for both linear polarizations.

Broadband continuous achromatic and super-dispersive metalens in near-infrared band

For a long time, dispersion is always an important issue in optics. In recent decades, metasurfaces with the excellent optical field manipulating performance have provided a new solution to realize dispersion management. However, existing strategies usually rely on numerous simulations to select appropriate nanostructures, which are not intuitive and time-consuming. Here, we theoretically analyzed the dispersion controlling mechanism of nanostructured metasurfaces based on the effective refractive index theory. By simultaneously controlling the basic phase and the phase–frequency slope, phase profiles of the dispersion-tailored metalens can be reproduced. Adopting this strategy, continuous achromatic and super-dispersive cylindrical metalenses were designed using a transmissive dielectric metasurface with simple nanostrips. Simulated result shows that, in the near-infrared band from 1200 to 1600 nm, the chromatic dispersion can be reduced to less than a quarter of the regular one for the achromatic metalens, while it has about two times increase for the super-dispersive metalens. In addition, the two different types of metalenses have high efficiency of above 60% and narrow full width at half maximum near the diffraction limit over the 400 nm near-infrared band. These extraordinary properties offer a broad application prospect for the metalens in the field of highly integrated imaging, multispectral detection, tomography, etc.

Metasurface-based nanoprinting: principle, design and advances

Metasurface-based nanoprinting (meta-nanoprinting) has fully demonstrated its advantages in ultrahigh-density grayscale/color image recording and display. A typical meta-nanoprinting device usually has image resolutions reaching 80 k dots per inch (dpi), far exceeding conventional technology such as gravure printing (typ. 5 k dpi). Besides, by fully exploiting the design degrees of freedom of nanostructured metasurfaces, meta-nanoprinting has been developed from previous single-channel to multiple-channels, to current multifunctional integration or even dynamic display. In this review, we overview the development of meta-nanoprinting, including the physics of nanoprinting to manipulate optical amplitude and spectrum, single-functional meta-nanoprinting, multichannel meta-nanoprinting, dynamic meta-nanoprinting and multifunctional metasurface integrating nanoprinting with holography or metalens, etc. Applications of meta-nanoprinting such as image display, vortex beam generation, information decoding and hiding, information encryption, high-density optical storage and optical anti-counterfeiting have also been discussed. Finally, we conclude the opportunities and challenges/perspectives in this rapidly developing research field of meta-nanoprinting.

Spatially resolved birefringence measurements with a digital micro-mirror device.

We demonstrate a novel technique to measure spatially resolved birefringence structures in an all-digital fashion with a digital micro-mirror device (DMD). The technique exploits the polarization independence of DMDs to apply holographic phase control to orthogonal polarization components and requires only a static linear polarizer as an analyzer for the resulting phase shift polarization measurements. We show the efficacy of this approach by spatially resolving complex polarization structures, including nano-structured metasurfaces, customized liquid crystal devices, as well as chiral L-Alanine and N-Acetyl-L-cystein crystals. Concentration dependent measurements of optical rotation in glucose and fructose solutions are also presented, demonstrating the technique's versatility. Unlike conventional approaches, our technique is calibration free and has no moving parts, offers high frame rates and wavelength independence, and is low cost, making it highly suitable to a range of applications, including pharmaceutical manufacturing, saccharimetry and stress imaging.

Optical vector field rotation and switching with near-unity transmission by fully developed chiral photonic crystals

State-of-the-art nanostructured chiral photonic crystals (CPCs), metamaterials, and metasurfaces have shown giant optical rotatory power but are generally passive and beset with large optical losses and with inadequate performance due to limited size/interaction length and narrow operation bandwidth. In this work, we demonstrate by detailed theoretical modeling and experiments that a fully developed CPC, one for which the number of unit cells N is high enough that it acquires the full potentials of an ideal (N → ∞) crystal, will overcome the aforementioned limitations, leading to a new generation of versatile high-performance polarization manipulation optics. Such high-N CPCs are realized by field-assisted self-assembly of cholesteric liquid crystals to unprecedented thicknesses not possible with any other means. Characterization studies show that high-N CPCs exhibit broad transmission maxima accompanied by giant rotatory power, thereby enabling large (>π) polarization rotation with near-unity transmission over a large operation bandwidth. Polarization rotation is demonstrated to be independent of input polarization orientation and applies equally well on continuous-wave or ultrafast (picosecond to femtosecond) pulsed lasers of simple or complex (radial, azimuthal) vector fields. Liquid crystal-based CPCs also allow very wide tuning of the operation spectral range and dynamic polarization switching and control possibilities by virtue of several stimuli-induced index or birefringence changing mechanisms.

Plasmonic and Dielectric Metasurfaces for Solid State Lighting

The coupling of layers of light emitting materials to nanostructured surfaces and metasurfaces provides an unique opportunity to tailor the emission, and opens new venues for the design of phosphors in solid-state-lighting. A significant enhancement of the photoluminescence, both spectrally and spatially, have been demonstrated in recent year using metallic metasurfaces.[1] In contrast, the effect of optical absorption by metals on the conversion efficiency is less studied. Here, we investigate the conversion efficiencies for emitter layers deposited on metasurfaces consisting of the periodic arrays of plasmonic and dielectric nanoparticles using an integrating sphere. [2]Total photoluminescence intensity measured in the integrating sphere (see Figure (a)) is larger for the emitting layer on the silver (Ag) nanoparticle array than the same layer on the titanium dioxide (TiO2) array and on unpatterned flat substrate, manifesting a larger pump or absorption enhancement for the Ag nanoparticle array. The conversion efficiencies are 0.95 and 0.38 for the TiO2 and Ag arrays, respectively (Figure (b)). The excitation wavelength of λ = 532 nm is well below the bandgap of TiO2 and the nanoparticles are virtually transparent, which leads to a conversion efficiency of almost one. For the Ag array, the conversion efficiency is lower due to the intrinsic losses of Ag. The results show that absorption at the excitation wavelengths by the emitter has a critical impact on the conversion efficiency.The evaluation technique used in this work to quantify the optical absorption by the array, leads to a working recipe to design resonant systems that can be exploited in solid-state-lighting applications.[1] G. Lozano et al., Light: Sci. Appl. 2 (2013) e66[2] S. Murai et al., ECS J. Solid State Sci. Technol. 9 (2020) 011614 Figure 1

Advances in exploiting the degrees of freedom in nanostructured metasurface design: from 1 to 3 to more

Abstract The unusual electromagnetic responses of nanostructured metasurfaces endow them with an ability to manipulate the four fundamental properties (amplitude, phase, polarization, and frequency) of lightwave at the subwavelength scale. Based on this, in the past several years, a lot of innovative optical elements and devices, such as metagratings, metalens, metaholograms, printings, vortex beam generators, or even their combinations, have been proposed, which have greatly empowered the advanced research and applications of metasurfaces in many fields. Behind these achievements are scientists’ continuous exploration of new physics and degrees of freedom in nanostructured metasurface design. This review will focus on the progress on the design of different nanostructured metasurfaces for lightwave manipulation, including by varying/fixing the dimensions and/or orientations of isotropic/anisotropic nanostructures, which can therefore provide various functionalities for different applications. Exploiting the design degrees of freedom of optical metasurfaces provides great flexibility in the design of multifunctional and multiplexing devices, which can be applied in anticounterfeiting, information encoding and hiding, high-density optical storage, multichannel imaging and displays, sensing, optical communications, and many other related fields.

Analysis of the focal spot by variation of immersion medium for nanostructured metasurfaces

The refractive index of the immersion medium has a significant influence on the shape of the focal spot in the field of diffraction optics. For a refractive index of the immersion medium that varies from the designed one, the change in the focal properties of the diffractive optical elements needs to be verified. By combining the vectorial angular spectrum (VAS) theory with a genetic algorithm, multiannular nanostructured metasurfaces with super-resolution focusing abilities were designed with a linearly polarized beam in an oil immersion medium. The intensity distribution of the focusing field was calculated via the finite-difference time-domain, and the results agreed well with calculations using the VAS theory. The results of the theoretical calculations demonstrated an obvious shift of the focal spot and change in the spot size as the refractive index varied. The calculations showed that the refractive index had an impact on the focal properties of multiannular metasurfaces. This work provides theoretical guidance for super-resolution focusing and imaging.

Structured Semiconductor Interfaces: Active Functionality on Light Manipulation

Structured interfaces with subwavelength features enable modulations of phase, amplitude, and polarization on demand, leading to a plethora of flat-profile devices and metasurfaces. Plasmonic and dielectric metasurfaces have been intensively explored, building up the frameworks of flat optics for ultrathin and integrated nanophotonics. The in situ controllability and tunability of aforementioned family of metasurfaces, however, has been a grand challenge, due to the intrinsic limitations of the materials. Semiconductors with diversified catalogs of material candidates thus demonstrate promising potentials, owing to the mature and versatile technologies developed nowadays. The fuse of semiconductors and nanostructured metasurfaces has been witnessed more recently, paving a distinct avenue toward active, tunable, reconfigurable light manipulation for next-generation optical nanodevices. Judicious selection of the active materials for metasurfaces empowers the active functionality of the designer applications. This paper presents a review of this merging semiconductor paradigm for active metasurfaces across a wide range of spectrum and shows unprecedented potentials in the future interface-based optoelectronics, quantum optics, nano-optics, and surface engineering with full compatibility of semiconductor foundry.

Ultrathin and multicolour optical cavities with embedded metasurfaces

Over the past years, photonic metasurfaces have demonstrated their remarkable and diverse capabilities in advanced control over light propagation. Here, we demonstrate that these artificial films of deeply subwavelength thickness also offer new unparalleled capabilities in decreasing the overall dimensions of integrated optical systems. We propose an original approach of embedding a metasurface inside an optical cavity—one of the most fundamental optical elements—to drastically scale-down its thickness. By modifying the Fabry–Pérot interferometric principle, this methodology is shown to reduce the metasurface-based nanocavity thickness below the conventional λ/(2n) minimum. In addition, the nanocavities with embedded metasurfaces can support independently tunable resonances at multiple bands. As a proof-of-concept, using nanostructured metasurfaces within 100-nm nanocavities, we experimentally demonstrate high spatial resolution colour filtering and spectral imaging. The proposed approach can be extrapolated to compact integrated optical systems on-a-chip such as VCSEL’s, high-resolution spatial light modulators, imaging spectroscopy systems, and bio-sensors.