We present a grating model of two-dimensional (2D) rigorous coupled wave analysis (RCWA) to study top diffraction gratings on light-emitting diodes (LEDs). We compare the integrated-transmission of the non-grating, rectangular-grating, and triangular-grating cases for the same grating period of 6 \mum, and show that the triangular grating has the best performance. For the triangular grating with 6-\mm period, the LED achieves the highest light transmission at 6-m grating bottom width and 2.9-\mum grating depth. Compared with the non-grating case, the optimized light transmission improvement is about 74.6%. The simulation agrees with the experimental data of the thin polymer grating encapsulated flip-chip (FC) GaN-based LEDs for the light extraction improvement.

We investigate the transverse mode pattern in GaN quantum-well (QW) laser diode (LD) by numerical calculation. We optimize the current GaN LD structure by varying the n-GaN layer thickness. The n-type GaN layer is an important factor to determine the optical mode. Finally, we discuss the lasing performance of the GaN LD based on the transverse optical modes.

We have theoretically investigated the guiding mode patterns of hollow nanowires. Two types of nanowires, round shape and hexagonal shape, are examined with different combination of outer and inner radii. Because of electric field discontinuity at hollow interfaces and evanescent modes overlap in low refractive index region, strong light guiding and confinement are achieved in both hollow wire structures.