Mode and Lasing Characteristics for Hybrid Square-Rectangular Lasers

Abstract

Whispering-gallery mode (WGM) microlasers are potential light sources for monolithic photonic integration circuits and optical interconnects. In this study, stable single-mode hybrid square-rectangular lasers (HSRLs) are reported, based on mode coupling between WGM and Fabry-Pe&x0301;rot (FP) modes. Mode selection mechanisms are explained based on numerical results of the resonant reflection of the square microcavity and energy distributions of coupled mode in the two cavities, and the reduction of effective linewidth enhancement factor is expected as two cavities are modulated individually. HSRLs with different sizes are fabricated by contact photolithography and dry-etching techniques. For a hybrid laser with a square-side length a = 15 &x03BC;m and the FP cavity length and width of L = 300 &x03BC;m and d = 2 &x03BC;m, stable single-mode operation with a side-mode suppression ratio up to 47 dB is obtained, and a small-signal modulation bandwidth of 13.3 GHz is realized by modulating the current of the FP cavity. The dynamic characteristics are further investigated for the hybrid laser. Furthermore, threshold currents and tunable behaviors are compared for HSRLs with a = 10, 15, and 20 &x03BC;m and d = 1.5 and 2 &x03BC;m.