Circular-side square microlasers with shifted output waveguide positions for mode and lasing spectrum control

Abstract

Circular-side square microlasers with shifted output waveguide positions are demonstrated to realize mode and lasing spectrum control. Numerical simulation results indicate that the mode Q factors of the fundamental, first- and second-order transverse modes are modulated, and the output coupling efficiency of the output waveguide can be greatly improved by introducing the translation of the output waveguide. Single-mode lasing, dual-mode lasing, and three-mode lasing are experimentally realized by changing the output waveguide positions. At the optimized shifted output waveguide position, a microlaser exhibits tunable single-mode behavior with a maximum output power of 120 µW, a side-mode suppression ratio of 31 dB, and a linewidth of 42 MHz. Furthermore, the lasing characteristics of microlasers with different circular sides are compared.