Infrared to visible image up-conversion using optically addressed spatial light modulator utilizing liquid crystal and InGaAs photodiodes

Abstract

Combination of InGaAs/InP heterojunction photodetector with nematic liquid crystal (LC) as the electro-optic modulating material for optically addressed spatial light modulator for short wavelength infra-red (SWIR) to visible light image conversion was designed, fabricated, and tested. The photodetector layer is composed of 640 × 512 photodiodes array based on heterojunction InP/InGaAs having 15 μm pitch on InP substrate and with backside illumination architecture. The photodiodes exhibit extremely low, dark current at room temperature, with optimum photo-response in the SWIR region. The photocurrent generated in the heterojunction, due to the SWIR photons absorption, is drifted to the surface of the InP, thus modulating the electric field distribution which modifies the orientation of the LC molecules. This device can be attractive for SWIR to visible image upconversion, such as for uncooled night vision goggles under low ambient light conditions.

Infrared photoconductivity and photovoltaic response from nanoscale domains of PbS alloyed with thorium and oxygen

“…Yet, most commercially available SWIR sensors and imagers are based on costly materials and fabrication techniques, such as epitaxially grown InGaAs and InGaAsP compounds [8], which limit their use. Attempts to reduce cost via developing compact IR-to-visible up-conversion imagers that do not require expensive readout electronics have also been reported recently [9]. Another research direction is based on the ability to tailor the size of colloidal semiconductor quantum dots (QDs) where the energy bandgap of the QDs can be tuned to overlap the SWIR spectral range.…”

Optical Computing: Status and Perspectives

“…The OASLMs, on the other hand, enable light to be modulated directly by light without having to go through an electronic-optical transformation [70,71]. Additionally, OASLMs are required for a variety of all-optical purposes that EASLMs cannot handle, such as coherent to incoherent image conversion, real-time optical correlation, and parallel all-optical processing [8,[72][73][74][75]. OASLMs may be built in theory using material nonlinearities, with modulation over the read light achieved by spatially precisely modifying the characteristics of the materials through nonlinear optical stimuli [76].…”

Liquid-Crystal-on-Silicon for Augmented Reality Displays

“…The state-of-the-art LC material development reaches a submillisecond response time for VA [56][57][58] and MTN [46,59] LCoS at 40 • C, and a~2 ms response time for 2π phase modulation [46,47]. More than that, these optimization strategies and the developed materials could be applied to other LC phase modulation-based devices such as tunable lenses, scanners, tunable filters, and optically addressed spatial light modulators [60][61][62][63][64], which may be incorporated in AR systems in other ways.…”