Optically-free-standing InGaN microdisks with metallic reflectors

Abstract

The optical properties of free-standing thin-film microdisks with NiAg metallic reflectors are compared with those with an indium tin oxide (ITO) interfacial layer. The microdisks have been fabricated by a combination of microsphere lithography and laser lift-off processes. Optical-pumped lasing from the microdisk with NiAg reflector has been observed, with reduced threshold and higher quality factor compared those with ITO layers, attributed to improved optical confinement due to the reflectivity of the Ag coating. The results are supported by three-dimensional (3D) finite-difference-time-domain (FDTD) simulations.

Optically pumped lasing with a Q-factor exceeding 6000 from wet-etched GaN micro-pyramids

“…[13,14] show similar pyramid geometry, and a much larger size, the E th (E th 25 MW∕cm 2 ), is 10-fold higher than our reported vertical pyramid. Furthermore, the Q-factor of our vertical pyramid (∼6000) is much higher, compared with the vertical disk counterpart for WGM lasing reported by Choi [9,19], with Q-factors to be 1673 and 770 for Ag and ITO at the bottom, respectively. This should be attributed to the improved material quality of our pyramid due to the "defects' filter effect" [20], relatively smoother surface morphology, the specific isolated micro-pyramid cavity configuration via the wet-etching process, and the bottom metal reflectance for vertical confinement.…”