Two-dimensional photonic crystal ring laser

Abstract

This study describes lasing action in ring-type resonators defined by two-dimensional photonic crystals on a free-standing slab with InGaAsP active layers emitting at 1.55㎛. Free-standing photonic crystal slab structures are fabricated by using electron-beam lithography, chemically-assisted ion-beam etching, and undercut wet etching. The fabricated structures are pulse-pumped by a 980-nm laser diode at room temperature. Lasing actions from samples with various ring sizes are observed. A spectrum of a typical ring laser at above threshold shows the lasing wavelength of 1620 nm. An L-L curve shows a threshold pump power of ~3 mW. The lasing mode of the photonic crystal ring resonator originates from the true ring-type mode, which is confirmed by the observation of spectra and near-field images. The quality factor of the ring resonator is measured from the below threshold linewidth, which sets the lower bound as ~2000. The photonic crystal ring laser consists of 6 waveguides and 6 bent regions. Therefore, this structure is used to estimate the propagation loss in a photonic crystal waveguide. Using the reasonable value of group index of waveguide, propagation loss is less than $60 cm^{-1}$.