Publications

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We report on the application of MEMS and other microsystem technologies to photovoltaic (PV) cells, modules, and systems, taking advantage of several, significant benefits that are realized as the size of solar cells decrease to sub-mm length scales. To demonstrate these effects, we have developed both crystalline silicon and III-V PV cells. These cells are from 2 to 20 microns thick and from 250 microns to one millimeter across. We have demonstrated conversion efficiencies of up to 14.9% for a 14 micron thick crystalline silicon PV cell. This work contributes to two broad PV applications: 1) highly flexible PV modules with conversion efficiencies greater than 20%, and 2) commercial/utility scale PV systems using moderate concentration flat plate modules with simple single-axis or coarse dual-axis tracking. Cost models indicate that systems based on these technologies can achieve unsubsidized energy costs of less than $0.10/kWh. © The Electrochemical Society.

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Thermal detection has made extensive progress in the last 40 years, however, the speed and detectivity can still be improved. The advancement of silicon photonic microring resonators has made them intriguing for detection devices due to their small size and high quality factors. Implementing silicon photonic microring or microdisk resonators as a means of a thermal detector gives rise to higher speed and detectivity, as well as lower noise compared to conventional devices with electrical readouts. This LDRD effort explored the design and measurements of silicon photonic microdisk resonators used for thermal detection. The characteristic values, consisting of the thermal time constant ({tau} {approx} 2 ms) and noise equivalent power were measured and found to surpass the performance of the best microbolometers. Furthermore the detectivity was found to be D{sub {lambda}} = 2.47 x 10{sup 8} cm {center_dot} {radical}Hz/W at 10.6 {mu}m which is comparable to commercial detectors. Subsequent design modifications should increase the detectivity by another order of magnitude. Thermal detection in the terahertz (THz) remains underdeveloped, opening a door for new innovative technologies such as metamaterial enhanced detectors. This project also explored the use of metamaterials in conjunction with a cantilever design for detection in the THz region and demonstrated the use of metamaterials as custom thin film absorbers for thermal detection. While much work remains to integrate these technologies into a unified platform, the early stages of research show promising futures for use in thermal detection.

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A silicon photonics based integrated optical phase locked loop is utilized to synchronize a 10.2 GHz voltage controlled oscillator with a 509 MHz mode locked laser, achieving 32 fs integrated jitter over 300 kHz bandwidth.

Micro-optical 5mm lenses in 50mm sub-arrays illuminate arrays of photovoltaic cells with 49X concentration. Fine tracking over ±10° FOV in sub-array allows coarse tracking by meter-sized solar panels. Plastic prototype demonstrated for 400nm<λ<1600nm. © 2010 Copyright SPIE - The International Society for Optical Engineering.

A novel silicon microdisk modulator with "error-free" ∼3 femtojoule/bit modulation at 12.5Gbs has been demonstrated. Modulation with a 1 volt swing allows for compatibility with current and future digital logic CMOS electronics. ©2010 IEEE.

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A low power modulator is monolithically integrated with a radiation hardened CMOS driver. This integrated optoelectronic device demonstrates 1.68mW power consumption at 2Gbps.

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