This PDF file contains the front matter associated with SPIE Proceedings Volume 12010, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Periodic optical lattices consisting of isolated-particle arrays in vacuum are treated with rigorous electromagnetics. These structures possess a wealth of interesting properties including perfect reflection across small or large spectral bandwidths depending on the choice of materials and design parameters. Pertinent spectral expressions have been observed theoretically and experimentally via one-dimensional (1D) and two-dimensional (2D) structures commonly known as resonant gratings, metamaterials, and metasurfaces. The physical cause of perfect reflection and related properties is guided-mode resonance mediated by lateral Bloch modes excited by evanescent diffraction orders in the subwavelength regime. Here, we review recent results on differentiation of local Mie resonance and guided-mode lattice resonance in causing resonant reflection by periodic particle assemblies. We treat a classic 2D periodic array consisting of dielectric spheres. To disable Mie resonance, we apply antireflection (AR) coatings to the spheres. Reflectance maps for coated and uncoated spheres demonstrate that perfect reflection persists in both cases. We find that the Mie scattering efficiency of an AR-coated sphere is greatly diminished. Additionally, in a 1D cylindrical rod-type lattice, we investigate and compare local field profiles in periodic assemblies and in the constituent isolated particles. In general, the lattice and particle resonance wavelengths differ. When the lateral leaky-mode field profiles approach the isolated-particle Mie field profiles, the resonance locus tends towards the Mie resonance wavelength. This correspondence is referred to as Mie modal memory. These fundamentals may help distinguish Mie effects and leaky-mode effects in generating the observed spectra in this class of optical devices while elucidating the basic resonance properties across the entire spectral domain.

Plasmonic nanoparticles are key to the realization of selective light absorbers, and especially metallic nanoparticles that exhibit tunable optical properties with implications in multiple fields such as photovoltaic, photodetectors and optical filters [1]. Among those nanoparticles, metallic split-ring resonators are metamaterials with optically induced magnetic responses allowing unique possibilities for controlling light and enhance absorption in the visible and near IR domains depending on their geometric parameters. The objective of this research is to show the enhancement of absorption at optical frequencies by not only designing a metasurface made of silver split-rings with realistic geometric parameters but also providing a first proof of concept of those tunable circular nanorings entirely made by scalable bottom-up approaches. First, Finite Difference Time Domain (FDTD) simulations were performed to optimize the silver nanoring geometric properties thanks to a parametric study (inner, outer diameters, thickness, split-ring gap, array periodicity). This showed full control on resonance peaks and absorbance enhancement in the visible and near IR. Next, we showed the realization of circular silver split-ring arrays on a large area via bottom-up techniques. Silver single-crystalline nanocubes (synthesized in solution via the polyol process) were self-assembled in Polydimethylsiloxane (PDMS) templates previously nanostructured with a pre-defined split-ring motif. Epitaxial nanowelding techniques at low temperature [2] were then employed to connect the individual nanocubes together to obtain a continuous quasi-monocrystalline material.

We report a computational study of how light propagates within a self-collimating, hexagonal photonic crystal. The photonic crystal can be described as a two-dimensional hexagonal lattice of air holes extruded into the third dimension. While traveling inside the device, light is forced by self-collimation to propagate along the extrusion direction. Finite-difference time-domain calculations show that the lattice must have at least four rings of unit cells surrounding the innermost unit cells where light is centered for it to propagate under strong self-collimation, with low scattering loss.

State-of-the-art nanofabrication permits the realization of highly aligned multi-layered metasurfaces with high lateral resolution and wide areas. The exploitation of the vast degrees of freedom and material choice is hampered by the difficulty in the inverse design of metasurfaces. The prevalent design approach of unit-cell library creation and element juxtaposition is known to result in reduced efficiency owing to the inaccurate accounting of inter-element coupling. We report on our recent efforts in accelerated evolutionary optimization for designing metasurfaces with extended unit-cells using learned surrogate models. The difficulty in creating learned models with acceptable predictive capacity in higher dimensional parameter spaces arises from the need for extensive ground-truth generation. By a systematic study of network architectures and dataset sampling strategies, we uncover efficient ground-truth generation strategies. Specifically, we consider 2 and 3-nanoellipse titania metaatoms allowing full control over the elliptical parameters and with an optical response consisting of the spectral behavior of various transmission and reflection-mode diffracted orders for proof-of-concept demonstration. The systematic investigation reveals that densely connected neural architecture and judicious sampling strategies can allow learned model creation even with smaller ground-truth datasets.

We propose a two-dimensional triangular lattice solid/fluid phononic crystals (PnC) for the determination of the acoustic properties and in particular dynamic viscosity of a fluid. We show that this device is very sensitive to the acoustic parameters of the liquid, such as density or sound velocity, and could consequently be used as a temperature sensor. This temperature sensitivity is investigated through the existence of sharp waveguide acoustic modes localized in the band gap of the PnC at well-defined frequencies. We show that this device can also be used for dynamic viscosity measurements of liquid, based on the attenuation of the guided modes.

Transition metal dichalcogenides (TMDs) are recognized as low toxicity materials with excellent physical, electrical, and optical properties. Molybdenum disulphide (MoS₂) is a prototype material in the family of 2D TMDs. Extensive exploration of the material has been done for the past decade. Owing to its peculiar optical and electronic properties such as high current carrying capacity, large carrier mobility, quantum confinement, and edge effects, it is a suitable candidate for optoelectronic and photonic applications. Although extensive exploration of 2D MoS₂ has taken place, not much work has been done on its 0D counterparts i.e., MoS₂-Quantum Dots (QDs). It is expected that MoS₂ QDs will be highly luminescent as compared to its 2D structures due to higher levels of confinement in QDs.

We report, excellent emitting MoS₂ quantum dots (QDs) fabricated by a colloidal route. Optimization of the fabrication process was done to obtain the optimal temperature, precursor concentration, and ligand concentrations for high-quality QD precipitation. By careful control of the synthesis conditions, colloidally synthesized MoS₂ quantum dots emitted blue color under UV illumination. To further investigate the quality of the QDs, their absorption and emission spectra were studied. The absorption edge is highly blue shifted to around 303 nm as compared to 600 nm in bulk, showing strong quantum confinement effects. The QDs show emission spectra centered around 401 nm at incident excitation wavelength of 360 nm. It is observed that the MoS₂ QDs were highly stable which could lead to application in optoelectronics.

Inspite of the varying compositions for two-dimensional (2D) layered materials, their unifying feature arises from the weak van der Waals (vdW) interaction that serves as the glue between adjacent layers. Here, in the first part of this work, we will discuss our efforts in studying the light-matter interactions in ensembles of graphene, a quintessential 2D layered material in its laterally confined quantum dot (GQD) form, as it is integrated with 2D membranes of MoS₂. The interactions of zero dimensional (0D) GQDs with underlying semiconducting 2D MoS₂ have been investigated, which exhibits outstanding properties for optoelectronic devices surpassing the limitations of MoS₂ photodetectors alone, where the GQDs extend the optical absorption into the near-UV regime. In addition, a more complex crystalline structure of 2D materials is discussed, that based on 2D halide perovskites. Just like graphene, MoS₂, and other inorganic 2D layered materials, the 2D halide perovskites have also recently drawn significant interest due to their tunable optoelectronic properties. These tunable optoelectronic properties in the 2D halide perovskites have led to their use in photodetectors as well as in solar cells. In the second part of this study, we discuss the use of 2D halide perovskites for their integration in photovoltaic applications, where we start with a discussion on the synthesis of the solution processed 2D layered organo-halide (CH₃(CH₂)₃NH₃)₂(CH₃NH₃)_n-1Pb_nI_3n+1 (n = 4) perovskites. This is then followed with our initial efforts toward the integration of the 2D perovskites into solar cells on ITO substrates.

Researches on polarization using metamaterials are applied in various fields. In particular, asymmetrically aligned nanostructured arrays have unique applications because they support interesting optical properties that differ from symmetrical structures. However, conventional nanostructures like 2D hole arrays rely on E-beam lithography or focused ion beam methods requiring complex processes, and they are not suitable for fabricating 3D nanostructures. In this work, we demonstrated the inclined-gold nanopillar arrays through one-step stencil lithography on 0.5mm x 0.5mm area. The angle between the substrate and the vapor flux was precisely controlled by tilting the substrate to form an inclined nanorod. The polarization direction dependences of inclined pillar arrays are experimentally measured in the visible regime. Unlike symmetric structures, breaking of symmetry between nanostructures and electromagnetic fields leads to polarization direction dependence plasmonic effect in asymmetric structure. We experimentally analyzed that reflectance is adjustable by controlling the plasmon coupling distribution of the localized surface plasmon resonance occurring on the surface of the nanostructure using polarization on the asymmetric nanostructure. Based on this concept, we expect that this concept is applicable in the field of three-dimensional metasurface, polarization-controlled color printing, and polarization detecting system.

In this work, an optimized all-optical 2x1 line selector is designed and simulated using a nonlinear optical effect inside metal-insulator-metal plasmonic waveguides based Mach–Zehnder interferometers. The proposed design is simulated using an optical source of 1550 nm and obtained the results by finite-difference time-domain (FDTD) method and results are verified with MATLAB simulation.

A tunable Fabry-Perot interferometer (FPI) can be used for high-resolution spectral measurements with precise control of the distance between the two FPI mirrors, which can be accomplished via feedback. We mechanically connect the FPI cavity mirrors to those of a shearing interferometer (SI) that is actively stabilized by a simple and inexpensive optical feedback method comprising a single HeNe laser, photodiode array, and Arduino microprocessor. The FPI transmission frequency can be held constant to within a standard deviation of 0.35 GHz for wavelengths in the near infra-red range. Scans of the transmission frequency are repeatable with a standard deviation of 0.11 GHz.

The emission wavelength of self-assembled quantum dashes can be controlled by their height. Uncapped InAs/InGaAsP/InP quantum dashes are found to have two distinct heights, which we have measured with atomic force microscopy and denoted the plateau and the peak heights. These heights range from 0.50 nm to 2.35 nm. Under the same growth conditions, for increasing uncapped quantum dash heights we observe an increase in the photoluminescence peak emission wavelength from approximately 1535 to 1543 nm for the capped layers. A growth temperature of 520°C is determined to achieve uniform height distribution for 1550 nm emission using chemical beam epitaxy.

In–Ga intermixing occurrence in InAs/In(Ga)As sub–monolayer (SML) quantum dots (QDs) is very consequential for the understanding of some optoelectronic properties. In this current study, we have performed a rapid thermal annealing (RTA) process at various annealing temperatures (T_a: 650 – 800°C) on multiple SML QD layers (4,6,8,10) grown at 490°C by Molecular – beam Epitaxy (MBE) technique and it has led to some positive conclusions on the analysis of 19 K photoluminescence (PL) data. A blueshift in the ground-state PL peak indicates the formation of smaller – sized dots and at the same time we see the full – width at half – maximum (FWHM) gets narrowed down through annealing suggesting for uniform dot size distribution. It is noteworthy to mention that samples with 4 and 6 QD layers showed a same degree of In–Ga intermixing when compared to asgrown (ASG) samples (62 meV), while 8 and 10 QD layers was changeable due to multimodal dot characteristics and perhaps the intermixing induced defects. This derives to conclude that the latter possess more QD size inhomogeneity issues and it can affect the charge carrier confinement energy. The FWHM broadening seen in 8 and 10 QD layers will lead to the formation of broader electronic minibands as dots of various size distributions merge altogether from these vertically – aligned layers with increase in T_a, while the redistribution of thermal mass transport species led to a narrower FWHM in 4 and 6 QD layers (and discrete energy states). Also, In–Ga intermixing effects are more pronounced in 8 and 10 stacks encouraging the defect creation. Hence, for the fabrication of room-temperature high gain infrared photodetectors (IRPDs), samples containing 4 and 6 QD layers with higher thermal stability against annealing (at 700°C) are the best candidates.

In this study, the author proposed a new technique for strain minimization, called linear alloy technique (LAT), for the symmetric dot-in-a-well (DWELL) heterostructure. Here, three different DWELL InAs QDs heterostructures with 6 nm thick In_xGa_1-xAs as well material have been simulated using 8 band k.p. model-based Nextnano software. Here, the first sample is analog alloyed DWELL heterostructure having In_0.15Ga_0.85As well (Sample A), the second sample is digital alloyed DWELL heterostructure where the well layer is divided into three sub-layers of 2nm thickness with indium composition varied from 45% to 15% in the step of 15%(Sample D), and the third sample is linear alloyed DWELL heterostructure where indium composition is varied from 45% to 15% (Sample L) in linear fashion have been studied. The Lower the magnitude of hydrostatic strain better will be carrier confinement. The more the biaxial strain, the more the heavy-hole and light-hole band splitting, which reduces the transition energy gap. The computed biaxial strain is increased by 1.52% and 2.21%, and the magnitude of hydrostatic strain is reduced by 3.66% and 1.13% in sample Lcompared with samples A and D, respectively. Strain inside the well layer of sample L reduces more smoothly than samples A and D, respectively. The computed PL emission wavelength for all three samples are 1329, 1418, and 1419 nm for the samples A, D, and L, respectively. Hence, this proposed technique can be the best choice for fabricating future optoelectronicbased devices.

In this study, the effect of high energy proton implantation in strain coupled Sub-monolayer (SML) and Stranski Krastanov (SK) quantum dot (QD) heterostructures have been investigated. The incident proton energy has been varied from 2 MeV to 5 MeV at a fixed proton dose of 1E-12 ions/cm². Ion beam irradiation has used to demonstrate the ex-situ tailoring of structural morphology, vertical strain coupling and optoelectronic interaction between the seed and top layer QDs of the coupled SK-SML QD heterostructure by utilizing the precise control over depth-wise defect alteration and the size modulation. The optical and structural properties have been studied through photoluminescence (PL) spectroscopy and high-resolution X-ray diffraction (HR-XRD) measurements. The penetration depth can be controlled by proton energy which influences the intensity and shifting in luminescence spectra. Red shift in PL emission wavelength has been observed for ion implanted samples as compared to as-grown samples. Subsequent power dependent photoluminescence (PDPL) study has been carried out to investigate the preferential photogenerated carrier transitions between ground and excited states of the aforementioned coupled QDs. Further, the quantum carrier confinement has been investigated through temperature dependent PL (TDPL) spectra. Strain profile analysis and crystalline quality investigation have been carried out through rocking curve analysis in (004) plane. The improved strain profile and morphology have been observed in ion implanted samples as compared to as-grown sample. The proton energy can directly control the intermixing within the dots and materials around the QDs.