Single Transverse Whispering-Gallery Mode AlGaInAs/InP Hexagonal Resonator Microlasers

AlGaInAs/InP hexagonal resonator microlasers with an output waveguide connected to one vertex of the hexagon are fabricated using standard photolithography and inductively coupled plasma (ICP) etching process. Room-temperature continuous-wave electrically injected operation with a threshold current of 18 mA is realized for a hexagon laser with an edge length of 16 μm and an output waveguide width of 2 μm. Single-mode operation is achieved with a side mode suppression ratio of 21 and 33 dB at the injection current of 30 and 60 mA, respectively. The peak wavelength intervals of the laser spectrum agree very well with the longitudinal mode intervals of the whispering-gallery modes, which indicates single transverse mode operation. The mode Q factor of 6.53 × 10³ is measured for the lasing mode at 1547 nm at the threshold current, which is in the same magnitude as the Q factor obtained by finite-difference time-domain (FDTD) simulation. The numerical simulations also indicate that the hexagonal resonator with an output waveguide is suitable to realize single transverse mode operation.