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This work presents a study of the changes in the optical, morphological and compositional properties of SiOC thin films obtained by hot wire chemical vapor deposition (HWCVD) technique. A mixture of hydrogen (H2), oxygen (O2) and monomethyl-silane (MMS) was used as reactant gas, which was passed through a tantalum filament (Ta) in order to be decomposed and obtained the film. Changes were made in...
We optimized micro-holes in a thin slab for fast Si photodetectors at wavelength 800–950nm. Lateral modes are shown to be responsible for the effective light trapping. Small disorder and cone hole shapes helped achieve uniform quantum efficiency in a wide wavelength range.
The homogeneous broadening in Phosphorus doped Ge layers is characterized using photoluminescence spectroscopy and absorption measurements. A broadening parameter rHOM=45meV due to carrier scattering effects was extracted leading to an estimated increase in threshold current density for Ge lasers by a factor >4.
We report the results of investigations of thin films of the composite based on the semiconducting polymer polyfluorene and graphene oxide particles with different content of the graphene oxide by terahertz time-domain spectroscopy.
The sensitivity of state-of-the-art superconducting far-infrared detectors is such that astronomical observations at these wavelengths are limited by photon noise from the astronomical source unless a method of restricting the spectral bandpass is employed. One such method is to use a high resolution Fabry-Pérot interferometer (FPI) in conjunction with a lower resolution, post dispersing system, such...
We exploit the resonant enhancement of light in photonic crystal slabs to enhance selected optical properties. Enhancement of absorption and local field gradients result in applications to microscale heating and optical trapping, respectively.
We present a comprehensive photonic approach for passive cooling of solar cells by simultaneously performing radiative cooling while also selectively utilizing the sunlight. We design a photonic cooler made of multilayer dielectric stack that can strongly radiate heat through its thermal radiation while also significantly reflecting the solar spectrum in sub-band gap and ultraviolet regime. We show...
We present an experimental investigation of the nonlinear response of acceptor impurities in semiconductors to coherent excitation with intense THz fields. In Zn-doped GaAs, we observed a well-defined saturation of the transition from the impurity ground state to the excited states and valence band. In B-doped Si, however, there is a clear indication of field-induced distortion of the impurity energy...
We present the Ge Zener-Emitter injection mechanism for synthesis of an indirect semiconductor optical amplifier (ISOA), featuring gain characteristics and electro-absorption modulation with extinction ratios > 14 dB by sufficient Moss-Burstein shift, for generic Ge-on-Si Photonics platform.
The detection and amplification of molecular absorption lines from a chemical weapons simulant is demonstrated using plasmonic antennas fabricated from n-Ge epitaxially grown on Si. A free-standing Si0.25Ge0.75 microbolometer detector with n-Ge plasmonic antenna is demonstrated as an integrated mid-infrared plasmonic sensor.
We show that graphene can be provide electro-optic properties to traditionally passive optical materials and enable efficient integrated active nanophotonic devices. We show devices with GHz absorption modulation based on ring resonators. We also report the first experimental demonstration of a graphene electro-refractive modulator with VπL of 0.14 V cm, and minimal absorption modulation based on...
Photovoltaic (PV) technology development is dominated by the largest application, utility-scale energy generation. Although military PV applications share some of the same attributes as those for utility-scale PV, the Navy PV technology development is focused on filling the gaps between what exists for utility energy generation and specific military applications. In this paper, we discuss the unique...
Optical bleaching is studied on undoped and highly doped Ge layer on Si using Transient Absorption Spectroscopy. Upon optical pumping, doped Ge showed a reduction in optical bleaching as compared to undoped Ge due to the homogeneous broadening effect in doped Ge.
We propose a high-speed electro-absorption modulator based on a direct bandgap Ge0.875Sn0.125 alloy operating at mid-infrared wavelengths. Enhancement of the Franz-Keldysh-effect by confinement of the applied electric field to GeSn in a reverse-biased junction results in 3.2dB insertion losses, a 35GHz bandwidth and a 6dB extinction ratio for a 2Vpp drive signal.
A modelling platform for active carrier removal based on metal-semiconductor-metal structure is reported on analysis of carrier dynamics. The analysis reveals electric current hot spots exist in geometric singularities and curly trajectory of carriers should be considered when accurately estimating the effective carrier lifetime.
Thin film Silicon (Si) solar cells are less efficient compared to thick film solar cells, but cell absorption can be enhanced by the embodiment of metal nano particles into the cell structure. Plasmonic structures, such as metal nano particles, are promising and versatile optical engineering tools, which have the potential to enhance device efficiency and reduce the cost of harvested solar energy...
Germanium-tin alloy (Ge1−xSnx), due to its direct gap nature for x > 0.08, has higher absorption coefficient than that of pure Ge. Using COMSOL Multiphysics, we have simulated the characteristics of Ge/GeSn/Ge heterojunction phototransistor, the base of which incorporates a multiple quantum well (MQW) structure made of Ge0.87Sn0.13 barrier and Ge0.75Sn0.155 well at a wavelength of 1.55 μm. The...
A compact low-cost multicolor germanium (Ge) infrared photodetector is designed by utilizing the guided-mode resonance condition of a one-dimensional grating with adiabatically tuned (or so-called chirped) in-plane periodicity. It is shown numerically that the resonance phenomenon is accompanied by a spectral splitting, as every wavevector component is matched with different instantaneous local in-plane...
The detection and amplification of molecular absorption lines from a mustard gas simulant is demonstrated using plasmonic antennas fabricated from n-Ge epitaxially grown on Si. Approaches to integrated sensors will be presented along with a review of n-Ge compared to other mid-infrared plasmonic materials.
A TCAD based analysis is presented on the transmission efficiency η of silicon-on-insulator (SOI) and silicon nitride slab waveguides in a high-voltage standard SOI-CMOS technology, for the spectral range of 480 nm–1300 nm, and isotropic optical excitation via monolithic Si-based LEDs. The effects of geometry, wavelength and galvanic isolation on η are reported.
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