Volume 92, Issue 3, 01 August 2002
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS (PACS 42)
Simulation of light propagation in two-dimensional photonic crystals with a point defect by a high-accuracy finite-difference time-domain method92(2002); http://dx.doi.org/10.1063/1.1490157View Description Hide Description
A high-accuracy finite-difference time-domain method based on what are called nonstandard finite differences was used to simulate optical propagation in a two-dimensional photonic crystal with a point defect. We used a photonic crystal consisting of a triangular lattice of air columns embedded in a high-refractive index medium. We found that the transmittance spectrum has four peaks in the photonic band-gap region, and that these peaks correspond to the resonant energies of light localized at the point defect. For a point defect consisting of an air hole with a radius smaller than that of the air holes of the photonic crystal, these peaks shift to higher energy. The peak shift of the resonant mode that is associated with the electric field concentrated about the center of the point defect is larger than the peak shift of the other modes.
92(2002); http://dx.doi.org/10.1063/1.1492020View Description Hide Description
We found a nontrivial metamorphosis of photonic band gaps during interpolation between two photonic crystals with two different length scales. The interpolation is parametrized by a dielectric constant of the columns inserted at the positions that are appropriately chosen in each unit cell of the starting photonic crystal. For an instance of the metamorphosis, the first band gap that is present at the beginning gradually shortens and disappears during the interpolation, while the second band gap which is initially absent begins to appear and eventually becomes a first band gap. This mechanism of opening and closing of the photonic band gaps can be used when designing tunable photonic crystals.
92(2002); http://dx.doi.org/10.1063/1.1491585View Description Hide Description
Plasma-induced damage of InGaN/GaN multiple quantum well(MQW)light-emitting diodes(LEDs) has been studied in terms of forward turn-on and reverse breakdown voltages, together with etch rate and surface morphology. The physical degradation of sidewall along with rough surface morphology of n–GaN caused by increased ion scattering induced the deterioration of the forward and reverse voltages. The forward turn-on voltage was relatively independent of the pressure up to 20 mTorr. The reverse breakdown voltage showed the worst degradation at 75% mainly because of a sidewall contamination. It was found that the turn-on voltage is sensitive to the surface roughness of the etchedn–GaN and the breakdown voltage is strongly affected by the sidewall contamination. Annealing under nitrogen after the mesa etching improved the electrical properties of the InGaN/GaN MQWLEDs.