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Articles you may be interested inHighly-directional emission patterns based on near single guided mode extraction from GaN-based ultrathin microcavity light-emitting diodes with photonic crystals Appl. Phys. Lett. 97, 013108 (2010); 10.1063/1.3459970 Enhancement of light extraction from GaN-based green light-emitting diodes using selective area photonic crystal Appl. Phys. Lett. 96, 251103 (2010); 10.1063/1.3454240 Measurement of extraction and absorption parameters in GaN-based photonic-crystal light-emitting diodes

This article presents a new time domain approach to treat the active stabilization (active vibration control) problem of flexible mechanical systems under (1) mode truncation, (2) nonlinear/linear timevarying parameter perturbations, (3) noise (input noise and measurement noise), and (4) noise uncertainties. In the proposed approach, the residual model is viewed as an additive perturbation to the controlled dynamics. A new robust stability condition is derived for the flexible mechanical system that is controlled by a linear-quadratic-Gaussian (LQG)-based controller and subject to mode truncation, noise uncertainties, and nonlinear/linear time-varying parameter perturbations. The proposed new condition gives an insight into the relationship between the stability margins of the controlled and residual mode subsystems, spillover effect, and additive time-varying parameter perturbations. Finally, two examples are given to confirm the presented approach.

The authors demonstrate, using finite-difference time-domain modeling, an enhancement in the extraction efficiency of flip-chip GaN light-emitting diodes (LEDs) using photonic crystals. The authors compare the extraction efficiencies of four configurations of a flip-chip GaN LED: with and without photonic crystal (PhC) layers, with a perfect reflecting mirror, and a bottom PhC reflector on GaN in combination with a top PhC extractor on sapphire. The authors show that, by using a photonic crystal layer as a bottom reflector, they can enhance the extraction efficiency similar to that of a mirror, yet the PhC reflector has the advantage that the metallic mirror loss can be avoided.

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