Despite their great promise, small experimental thermophotovoltaic (TPV) systems at 1000 K generally exhibit extremely low power conversion efficiencies (approximately 1%), due to heat losses such as thermal emission of undesirable mid-wavelength infrared radiation. Photonic crystals (PhC) have the potential to strongly suppress such losses. However, PhC-based designs present a set of non-convex optimization problems requiring efficient objective function evaluation and global optimization algorithms. Both are applied to two example systems: improved micro-TPV generators and solar thermal TPV systems. Micro-TPV reactors experience up to a 27-fold increase in their efficiency and power output; solar thermal TPV systems see an even greater 45-fold increase in their efficiency (exceeding the Shockley-Quiesser limit for a single-junction photovoltaic cell).

Abstract-Planar magnetic components using printed-circuitboard windings are attractive due to their high repeatability, good thermal performance and usefulness for realizing intricate winding patterns. To enable higher system integration at high switching frequency, more sophisticated methods that can rapidly and accurately model planar magnetics are needed. This paper develops a lumped circuit model that captures the impact of skin and proximity effects on current distribution and electromagnetic fields in planar magnetics. This enables accurate predictions of impedances, losses, stored reactive energy and current sharing among parallel windings. This lumped model is also a circuit domain representation of electromagnetic interactions. It can be used to simulate circuits incorporating planar magnetics, to visualize the electromagnetic fields, and to extract parameters for magnetic models by simulations. The modeling results match with previous theories and finite-element-modeling results. A group of planar magnetic devices, including transformers and inductors with various winding patterns, are prototyped and measured to validate the proposed approach.

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Abstract-The PowerChip research program is developing technologies to radically improve the size, integration, and performance of power electronics operating at up to grid-scale voltages (e.g., up to 200 V) and low-to-moderate power levels (e.g., up to 50 W) and demonstrating the technologies in a high-efficiency light-emitting diode driver, as an example application. This paper presents an overview of the program and of the progress toward meeting the program goals. Key program aspects and progress in advanced nitride power devices and device reliability, integrated highfrequency magnetics and magnetic materials, and high-frequency converter architectures are summarized.Index Terms-Gallium nitride, high frequency (HF), integrated magnetics, integrated power converter, light-emitting diode (LED) driver, PwrSoC.

A new, efficient adiabatic in-plane fiber-to-chip coupler design is proposed. In this design, the light from the fiber is coupled into a low-index waveguide with matching mode size. The mode is first adiabatically reduced in size with a rib taper, and then transferred into a high-index (e.g. silicon) waveguide with an inverse taper. The two-stage design allows to reduce the coupler length multiple times in comparison with pure inverse taper-based couplers of similar efficiency. The magnitude of length reduction increases with the refractive index of the low-index waveguide and the fiber mode size.

Abstract-Planar magnetic components using printed-circuitboard windings are attractive due to their high repeatability, good thermal performance and usefulness for realizing intricate winding patterns. To enable higher system integration at high switching frequency, more sophisticated methods that can rapidly and accurately model planar magnetics are needed. This paper develops a lumped circuit model that captures the impact of skin and proximity effects on current distribution and electromagnetic fields in planar magnetics. This enables accurate predictions of impedances, losses, stored reactive energy and current sharing among parallel windings. This lumped model is also a circuit domain representation of electromagnetic interactions. It can be used to simulate circuits incorporating planar magnetics, to visualize the electromagnetic fields, and to extract parameters for magnetic models by simulations. The modeling results match with previous theories and finite-element-modeling results. A group of planar magnetic devices, including transformers and inductors with various winding patterns, are prototyped and measured to validate the proposed approach.

Photonic Analog-to-Digital Conversion (ADC) has a long history. The premise is that the superior noise performance of femtosecond lasers working at optical frequencies enables us to overcome the bottleneck set by jitter and bandwidth of electronic systems and components. We discuss and demonstrate strategies and devices that enable the implementation of photonic ADC systems with emerging electronic-photonic integrated circuits based on silicon photonics. Devices include 2-GHz repetition rate low noise femtosecond fiber lasers, Si-Modulators with up to 20 GHz modulation speed, 20 channel SiN-filter banks, and Ge-photodetectors. Results towards a 40GSa/sec sampling system with 8bits resolution are presented.

This paper presents the derivation and verification of a sinusoidal steady-state equivalent-circuit model for microfabricated inductors developed for use in integrated power electronics. These inductors have a low profile, a toroidal air core, and a single-layer winding fabricated via high-aspect-ratio molding and electroplating. Such inductors inevitably have a significant gap between winding turns. This makes the equivalent resistance more difficult to model. The low profile increases the significance of the energy that is stored in the winding, which together with the winding gap makes the equivalent inductance more difficult to model. The models presented here account for these effects. Finally, the models are verified against results from 2-D and 3-D finiteelement analysis (2-D FEA and 3-D FEA) direct measurement, and from in-circuit experimentation. In all cases, the equivalent-circuit model is observed to be accurate to within several percentage.