Ultraviolet single whispering-gallery mode lasers in a pair of parallel ZnO microrods with different juxtaposed microresonators

Abstract

Ultraviolet single-mode lasing was achieved by optically pumping coupled microcavities formed from two ZnO microrods, which were intentionally placed edge- to-edge and face-to-face to form two different coupling microcavities. Unlike single ZnO microlasers in multiple longitudinal modes, mode selection was achieved through the Vernier effect in coupled microcavities, significantly expanding the free space range. Numerical analysis of coupling cavity resonance revealed that only one mode could exist in coupled ZnO microrods. The side-by-side coupled microcavities provided a specific side-mode suppression ratio and line width, indicating an accessible route to realizing single-frequency lasers using microcavity lasers.