title: Whispering-gallery mode lasing from optically free-standing InGaN microdisks.
abstract: 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 ∼6.6  μm 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 ∼9.06  mJ/cm2, with a quality factor Q of ∼770 evaluated from the dominant mode at λ=430.2  nm, and a free space range (FSR) of 3.17 to 2.16 nm, which is mode-dependent.
authors.forename: Xuhui
authors.initials: X
authors.lastname: Zhang
authors.forename: Yuk Fai
authors.initials: YF
authors.lastname: Cheung
authors.forename: Yiyun
authors.initials: Y
authors.lastname: Zhang
authors.forename: H W
authors.initials: HW
authors.lastname: Choi