We present a design optimization of highly transparent glasses with broadband antireflective subwavelength structures (SWS) based on the theoretical calculation using a rigorous coupled wave analysis method. It is found that optical transmission characteristics of SWS integrated glasses are governed mainly by the zero-order condition considering multiple internal reflections but not external reflection. By utilizing parabola-shaped SWS on both sides of the glasses with a period of 200 nm and a height of 200 nm, an average transmittance of 99.58% is achieved over a whole range of visible wavelength. Transmission band shrinkage effects of the SWS integrated glass are also observed with increasing the incident angle of light.

Abstract. A 20-MHz switching high-speed light-modulating device for three-dimensional (3-D) image capturing and its system prototype are presented. For 3-D image capturing, the system utilizes a time-of-flight (TOF) principle by means of a 20-MHz high-speed micromachined electroabsorptive modulator, the so-called optical shutter. The high-speed modulation is obtained by utilizing the electro-absorption mechanism of the multilayer structure, which has an optical resonance cavity and lightabsorption epilayers grown by metal organic chemical vapor deposition process. The optical shutter device is specially designed to have small resistor-capacitor-time constant to get the high-speed modulation. The optical shutter is positioned in front of a standard high-resolution complementary metal oxide semiconductor image sensor. The optical shutter modulates the incoming infrared image to acquire the depth image. The suggested novel optical shutter device enables capturing of a full high resolution-depth image, which has been limited to video graphics array (VGA) by previous depth-capturing technologies. The suggested 3-D image sensing device can have a crucial impact on 3-D-related business such as 3-D cameras, gesture recognition, user interfaces, and 3-D displays. This paper presents micro-opto-electro-mechanical systemsbased optical shutter design, fabrication, characterization, 3-D camera system prototype, and image evaluation. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

We present a single-material titanium oxide (TiO 2 ) bi-layer antireflection coating (ARC) produced using oblique angle deposition for improving the power conversion efficiency (PCE) of III-V compound semiconductor triple-junction (TJ) solar cells. Experimental demonstration of the porous TiO 2 layers and optical modelling by rigorous coupled-wave analysis indicate that bi-layer TiO 2 could be used as universal ARC for all known TJ stacks with various material combinations. The optimum TiO 2 bi-layer ARC produced on a Ga 0.5 In 0.5 P/GaAs/Ge TJ solar cell exhibits considerably enhanced PCE of 31.6%, which is higher than that of the cells without ARC (23.8%) and with TiO 2 single-layer ARC (29.1%).Incident angle-dependent device characteristics of the fabricated TJ solar cells are also discussed.

For reliable three dimensional (3D) imaging system, it is necessary for the optical shutter to have a wide spectral bandwidth operation and enhanced modulation depth. We propose an electro-absorption modulator (EAM) based on coupled Fabry-Perot cavities with micro-cavity (CCMC) which uses asymmetric tandem quantum wells (ATQWs) to obtain improved spectral bandwidth and enhanced modulation depth. Several modulator designs are investigated to obtain improved modulation performance such as wider spectral bandwidth and enhanced modulation depth. It was found that among all the studied modulator geometries, CCMC structure with ATQWs provides the widest spectral bandwidth of 9.6nm and high modulation depth in excess of 50% at -24V, which is good agreement with theoretical calculations. These results suggest that EAM has excellent potential as optical shutter for 3D imaging application.