This paper presents theory, design, fabrication, and optical characterization of two-dimensional (2D) tungsten (W) photonic crystals (PhC) as selective thermal emitters. We use the photonic band gap of a 2D W PhC, radiating out of a plane of periodicity, to design a selective infrared thermal radiation source that exhibits close to blackbody emittance near the the band gap wavelength and relatively sharp cutoff for wavelengths above the band gap. In addition, we present simple design rules and detailed simulation results for several representative geometries. Microfabrication steps are also presented. Finally, we present detailed experimental results of the optical characterization of three fabricated prototypes that exhibit good agreement with simulation results.

In this paper we present a vertical-cavity enhanced resonant thermal emitter-a highly directional, narrowband, tunable, partially coherent thermal source. This device enhances thermal emittance of a metallic or any other highly reflective structure to unity near a cavity resonant frequency. The structure consists of a planar metallic surface ͑e.g., silver, tungsten͒, a dielectric layer on top of the metal that forms a vertical cavity, followed by a multilayer dielectric stack acting as a partially transparent cavity mirror. The resonant frequency can easily be tuned by changing the cavity thickness ͑thus shifting resonant emission peak͒, while the angle at which the maximum emittance appears can be tuned as well by changing the number of dielectric stack layers. The thermal emission exhibits an extremely narrow angular emission lobe, suggesting increased spatial coherence. Furthermore, we show that we can enhance the thermal emission of an arbitrarily low-emittance material, choosing a properly designed thermal cavity, to near unity.

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This article presents a detailed exploration of the optical characteristics of various one-dimensional photonic crystal structures designed for use as a means of improving the efficiency and power density of thermophotovoltaic ͑TPV͒ devices. The crystals being investigated have a ten-layer quarter-wave periodic structure, and are based on Si/ SiO 2 and Si/ SiON material systems. For TPV applications the crystals are designed to act as filters, transmitting photons with wavelengths below 1.78 m to a GaSb photodiode, while reflecting photons of longer wavelengths back to the source of thermal radiation. In the case of the Si/ SiO 2 structure, the Si and SiO 2 layers were designed to be 170 and 390 nm thick, respectively. This structure was fabricated using low-pressure chemical vapor deposition. Reflectance and transmittance measurements of the fabricated Si/ SiO 2 photonic crystals were taken from 0.8 to 3.3 m for both polarizations and for a range of incident angles. Measurement results were found to correlate well with simulation results for the ideal structure. Measurement results were used to predict the TPV system efficiency, power density and spectral efficiency using an ideal thermodynamic model of a TPV system.

These capacitors can store large amounts of energy and deliver very high peak power; they are used in electric vehicles and may have applications in linear motor drives.

This paper introduces a distributed approach to interleaving paralleled power converter cells. Unlike conventional methods, the distributed approach requires no centralized control, automatically accommodates varying numbers of converter cells, and is highly tolerant of subsystem failures. A general methodology for achieving distributed interleaving is proposed, along with a specific implementation approach. The design and experimental verification of a 50 kHz prototype system is presented, and quantitative performance comparisons are made between synchronized clocking, independent clocking, and interleaved clocking of the converter cells. The experimental results corroborate the analytical predictions and demonstrate the tremendous benefits of the distributed interleaving approach.

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