25 research outputs found
Interpretable inverse-designed cavity for on-chip nonlinear and quantum optics
Inverse design is a powerful tool in wave-physics and in particular in
photonics for compact, high-performance devices. To date, applications have
mostly been limited to linear systems and it has rarely been investigated or
demonstrated in the nonlinear regime. In addition, the "black box" nature of
inverse design techniques has hindered the understanding of optimized
inverse-designed structures. We propose an inverse design method with
interpretable results to enhance the efficiency of on-chip photon generation
rate through nonlinear processes by controlling the effective phase-matching
conditions. We fabricate and characterize a compact, inverse-designed device
using a silicon-on-insulator platform that allows a spontaneous four-wave
mixing process to generate photon pairs at 1.1MHz with a coincidence to
accidental ratio of 162. Our design method accounts for fabrication constraints
and can be used for scalable quantum light sources in large-scale communication
and computing applications
On the Potential of Optical Nanoantennas for Visibly Transparent Solar Cells
This study aims to determine the maximum possible energy conversion efficiency of visibly transparent solar cells using the detailed balance limit (also known as the Shockley–Queisser limit) and compare it to the efficiency of traditional single-junction solar cells. To achieve this, a new optical nanoantenna has been designed to absorb incoming light selectively, enhancing the average visible transmission while maintaining high absorption in the infrared and UV regions. The color appearance of the antennas has also been evaluated through colorimetrical characterization. Our findings indicate that it is possible to achieve high average visible transparency and energy conversion efficiency of over 80 and 18%, respectively, by carefully selecting semiconductor materials. Such solar cells are versatile enough to be integrated seamlessly into smart windows, agrivoltaic concepts in open and protected cultivation, mobile devices, and appliances without compromising their appearance or functionality. The dimensions and optics of the proposed antennas and visibly transparent solar cells have been thoroughly discussed
Achieving higher photoabsorption than group III-V semiconductors in silicon using photon-trapping surface structures
The photosensitivity of silicon is inherently very low in the visible
electromagnetic spectrum, and it drops rapidly beyond 800 nm in near-infrared
wavelengths. Herein, we have experimentally demonstrated a technique utilizing
photon-trapping surface structures to show a prodigious improvement of
photoabsorption in one-micrometer-thin silicon, surpassing the inherent
absorption efficiency of gallium arsenide for a broad spectrum. The
photon-trapping structures allow the bending of normally incident light by
almost ninety degrees to transform into laterally propagating modes along the
silicon plane. Consequently, the propagation length of light increases,
contributing to more than an order of magnitude improvement in absorption
efficiency in photodetectors. This high absorption phenomenon is explained by
FDTD analysis, where we show an enhanced photon density of states while
substantially reducing the optical group velocity of light compared to silicon
without photon-trapping structures, leading to significantly enhanced
light-matter interactions. Our simulations also predict an enhanced absorption
efficiency of photodetectors designed using 30 and 100-nanometer silicon thin
films that are compatible with CMOS electronics. Despite a very thin absorption
layer, such photon-trapping structures can enable high-efficiency and
high-speed photodetectors needed in ultra-fast computer networks, data
communication, and imaging systems with the potential to revolutionize on-chip
logic and optoelectronic integration.Comment: 24 pages, 4 figure
All-silicon quantum light source by embedding an atomic emissive center in a nanophotonic cavity
Silicon is the most scalable optoelectronic material, and it has
revolutionized our lives in many ways. The prospect of quantum optics in
silicon is an exciting avenue because it has the potential to address the
scaling and integration challenges, the most pressing questions facing quantum
science and technology. We report the first all-silicon quantum light source
based on a single atomic emissive center embedded in a silicon-based
nanophotonic cavity. We observe a more than 30-fold enhancement of
luminescence, a near unity atom-cavity coupling efficiency, and an 8-fold
acceleration of the emission from the quantum center. Our work opens avenues
for large-scale integrated all-silicon cavity quantum electrodynamics and
quantum photon interfaces with applications in quantum communication, sensing,
imaging, and computing
rGO coated cotton fabric and thermoelectric module arrays for efficient solar desalination and electricity generation
One promising solution to the freshwater crisis is solar-driven interfacial evaporation-based desalination. However, an alternate strategy is needed to address both water and energy shortages in parallel. Additionally, the disposal of desalination brine necessitates specific consideration while designing a sustainable solar interfacial desalination system. Herein, we demonstrate a single system that utilizes incident solar irradiance to produce interfacial steam using reduced graphene oxide (rGO) coated cotton fabric (CF) to desalinate seawater with an evaporation efficiency of 86.98%. The high thermal conductivity and excellent optical absorption of rGO contribute to the absorption of a broad solar spectrum. The system also produces 339.26 mW of electricity simultaneously by deploying commercially available thermoelectric generator (TEG) modules that use the squandered heat, increasing the overall system efficiency by 7.3%. The use of a custom-made power electronics module ensures operating at the maximum power point which has also been verified by computer simulation. Finally, hydrogen gas with zero carbon emission is produced by electrolyzing the seawater utilizing the electricity generated by the TEG module using solar-induced heat at a rate of 0.52 mmol h −1. Converting brine into hydrogen and oxygen gas by electrolysis demonstrates a potential in situ approach for desalination waste remediation
Nanophotonic design of perovskite/silicon tandem solar cells
The perovskite material system allows for the realization of perovskite/silicon tandem solar cells with high energy conversion efficiencies at low cost. To realize such solar cells, the device geometry, the device processing, and the contact materials have to be modified in comparison to single junction perovskite solar cells. In this study, perovskite/silicon tandem solar cells are designed allowing for the generation of short-circuit current densities and energy conversion efficiencies exceeding 20 mA cm−2 and 30%, while using realistic device structures. High short-circuit current densities can be achieved by minimizing reflection losses and optical losses of the contact layers. A hybrid approach is used to investigate the optics by combining finite-difference time-domain simulations with experimental measurements. Details on the nanophotonic design will be provided and discussed
Investigation and Performance Analysis of Some Implemented Features of the ZigBee Protocol and IEEE 802.15.4 Mac Specification
The manuscript represents wireless sensor networks using numerous topologies of ZigBee. Along with coordinator load, the uses of coordination with such networks were inspected. The investigation has been accomplished via the use of various plots in the OPNET Modeler simulator. The results of the simulation explore the use of coordination with mesh and tree routing to verify the suitability of the topology. It also demonstrates some of the implemented features of the ZigBee protocol and IEEE 802.15.4 MAC specification, using OPNET's ZigBee model suite, like: Mesh routing vs. tree routing, Roaming between Personal Area Network (PANs) & Failure and Recovery procedures. The simulation has been carried out for 20 minutes to investigate the response of routing topologies on the delay, coordinator load and the MAC Load and the data have been collected. The results indicate that the End to End delay, number of hops and MAC load for mesh routing is lower than the tree routing. The results also show that in case of failure and recovery procedures, the simulated networks perform according to the ZigBee Standard