Suppression and hopping of whispering gallery modes in multiple-ring-coupled microcavity lasers

Abstract

We report on single whispering gallery mode lasing generation and hopping in multiple-ring-coupled microcavities. A side-mode-suppression ratio (SMSR) of 28 dB is obtained in a four-ring-coupled cavity laser, and the ratio of the side- and main-mode lasing threshold (Isth/Ith) is as large as 2.5. Both of the values are obviously higher than that of a two-ring-coupled cavity laser. We also find that the single-laser mode hops in steps of the mode spacing when the temperature of the coupled microcavity changes gradually. The mechanisms of side-mode suppression and mode hopping are investigated experimentally and theoretically.