Publications

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We describe and experimentally demonstrate a method for active control of resonant modulators and filters in an integrated photonics platform. Variations in resonance frequency due to manufacturing processes and thermal fluctuations are corrected by way of balanced homodyne locking. The method is compact, insensitive to intensity fluctuations, minimally disturbs the micro-resonator, and does not require an arbitrary reference to lock. We demonstrate long-term stable locking of an integrated filter to a laser swept over 1.25 THz. In addition, we show locking of a modulator with low bit error rate while the chip temperature is varied from 5 to 60° C. © 2014 Optical Society of America.

Adoption of on-chip optical interconnects with silicon photonics requires addressing wavelength stabilization of resonant modulators and filters. We have developed low-power integrated photonic and electronic control circuits, with progress toward minimizing circuit footprint. © 2014 OSA.

We demonstrate and investigate concurrent switching of twenty 10-Gbps channels using a silicon Mach-Zehnder interferometer switching structure with low on-state loss, low power, and microsecond-scale switching time. © 2014 IEEE.

A compact silicon photonic channelized optical spectrum monitor is designed and realized, which can replace a large rack-mounted OSA's channel power monitoring functionality, and the signal processing algorithm underlying its operation is described. © 2014 OSA.

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Microsystem technologies have the potential to significantly improve the performance, reduce the cost, and extend the capabilities of solar power systems. These benefits are possible due to a number of significant beneficial scaling effects within solar cells, modules, and systems that are manifested as the size of solar cells decrease to the sub-millimeter range. To exploit these benefits, we are using advanced fabrication techniques to create solar cells from a variety of compound semiconductors and silicon that have lateral dimensions of 250 - 1000 μm and are 1 - 20 μm thick. These fabrication techniques come out of relatively mature microsystem technologies such as integrated circuits (IC) and microelectromechanical systems (MEMS) which provide added supply chain and scale-up benefits compared to even incumbent PV technologies. © The Electrochemical Society.

In this paper we propose a stacked multi-junction solar cell design that allows the intimate contact of the individual cells while maintaining low resistive losses. The cell design is presented using an InGaP and GaAs multi-junction cell as an illustrative example. However, the methodologies presented in this paper can be applied to other III-V cell types including InGaAs and InGaAsP cells. The main benefits of the design come from making small cells, on the order of 2×10-3 cm2. Simulations showed that series resistances should be kept to less than 5 ω for devices up to 400 μm in diameter to keep resistance power losses to less than 1%. Low resistance AuBe/Ni/Au ohmic contacts to n-type InGaP are also demonstrated with contact resistivity of 5×10-6 ωcm-2 when annealed at 420°C. © 2013 IEEE.

We calculate voltage-matching considerations for stacked independent cells. The calculations show that designs using independent junctions that are voltage matched can achieve better efficiency across temperature, spectrum, and a yearly metric compared to traditional monolithic cells. Voltage matching is shown to be relatively insensitive to temperature and spectrum, but dependent on open circuit voltage as a measure of cell efficiency. Voltage matching can usually yield yearly efficiencies of 98%-99% of the efficiency of a system with each junction operating at its own maximum power point. © 2013 IEEE.

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