Solid State Lighting Program

The project had two main tasks: One addressed the materials and device development and it was carried out at Boston University. The second addressed the theory and simulation of materials and devices and it was carried out at Science Application International Corporation (SAIC). Each task had a number of sub-tasks which are described in the following table. Progress in these tasks is described in this section

Refractive-index nonlinearities of intersubband transitions in GaN/AlN quantum-well waveguides

The refractive-index nonlinearities of intersubband transitions in GaN/AlN quantum-well waveguides are investigated. A large spectral broadening of TM-polarized near-infrared pulses is observed after propagation through these devices due to intersubband self-phase modulation. From the measured data, a nonlinear refractive index n 2 of 1.8ϫ 10 −12 cm 2 / W is estimated at the operating wavelength of 1550 nm. A detailed theoretical model of the intersubband refractive index as a function of wavelength and optical intensity is then presented. This model assumes an inhomogeneously broadened transition line and is based on experimentally determined material and device parameters. The results of this study are finally used to discuss the prospects of nitride quantum wells for all-optical switching via cross-phase modulation

The DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation

Over the next 5 yr, the Dark Energy Spectroscopic Instrument (DESI) will use 10 spectrographs with 5000 fibers on the 4 m Mayall Telescope at Kitt Peak National Observatory to conduct the first Stage IV dark energy galaxy survey. At z 10 million galaxies spanning 14,000 deg2 . In this work, we present and validate the final BGS target selection and survey design. From the Legacy Surveys, BGS will target an r 80% fiber assignment efficiency. Finally, BGS Bright and BGS Faint will achieve >95% redshift success over any observing condition. BGS meets the requirements for an extensive range of scientific applications. BGS will yield the most precise baryon acoustic oscillation and redshift-space distortion measurements at z < 0.4. It presents opportunities for new methods that require highly complete and dense samples (e.g., N-point statistics, multitracers). BGS further provides a powerful tool to study galaxy populations and the relations between galaxies and dark matter

GaN Terahertz Photodetectors for the Reststrahlen Gap of Intersubband Optoelectronics

Conference on Lasers and Electro-Optics (CLEO) -- MAY 14-19, 2017 -- San Jose, CAWOS: 000427296202271Terahertz intersubband photodetectors are developed based on GaN/AlGaN quantum wells grown on a semi-polar GaN substrate, covering the frequency range that is fundamentally inaccessible to existing III-V semiconductor devices due to Reststrahlen absorption.IEEENSFNational Science Foundation (NSF) [ECS-0824116]This work was partly supported by NSF under Grant ECS-0824116