Far-field pattern simulation and measurement for unidirectional-emission circular microlasers

Abstract

Three-dimensional circular resonators connected with an output waveguide were simulated by the three-dimensional finite-difference time-domain (FDTD) technique. For the microcircular resonator with vertical waveguiding consisted of active layer confined by upper and lower cladding layers with the refractive indices of 3.4 and 3.17, the mode Q factors are greatly influenced by the thickness of the upper cladding layer. The numerical results of the near field and the farfield patterns indicate that the vertical waveguide with semiconductor materials does not provide enough optical confinement for the confined modes in the resonator. Furthermore, the lasing spectra and far-field patterns are measured for a circular microlaser with a radius of 15 μm and a 2-μm-width output waveguide. Single mode operation with the side mode suppression ratio up to 33 dB is realized at room temperature, and multiple peaks are observed in the vertical far-field pattern due to the vertical radiation of the mode field.