Whispering-gallery mode lasing from optically free-standing InGaN microdisks

Optically pumped multi-mode whispering-gallery mode (WGM) lasing has been observed in optically free-standing InGaN/GaN quantum well microdisks at room temperature. The similar to 6.6 mu m optically isolated microdisks are patterned by microsphere lithography on GaN thin-films prepared by laser lift-off of the sapphire substrate, enabling superior optical confinement. The modes are determined to be of second order according to simulations. The lasing threshold is found to be similar to 9.06 mJ/cm(2), with a quality factor Q of similar to 770 evaluated from the dominant mode at lambda = 430.2 nm, and a free space range (FSR) of 3.17 to 2.16 nm, which is mode-dependent. (C) 2014 Optical Society of America