Lasing from slab edge mode of free-standing two-dimentional photonic crystal

Abstract

We study the electromagnetic surface waves that can exist in the edge of the two-dimensional photonic crystal slab structures. Free-standing photonic crystal slab edge structures with InGaAsP quantum wells emitting near 1550 nm are fabricated using the electron-beam lithography, the chemically-assisted ion-beam etching, and the undercut wet etching techniques. Two types of the lasing actions are observed from the fabricated samples by pulsed optical pumping with a 980 nm laser diode at room temperature. By varying the pumping condition, the lasing wavelength can be tuned in the wide range from 1477 nm to 1589 nm. The threshold of a typical laser sample is about 2 mW, which is similar to the value of the conventional photonic crystal laser. In order to investigate the observed results, we also perform the computational simulations. The dispersion relations from the plane wave expansion method show that the slab edge structures should have the special cutting parameters for the existence of the slab edge modes near the center of the bandgap. The finite-difference time-domain calculations show that the quality factor of the slab edge mode can be sensitively changed by the cutting parameters. These results imply that the cutting parameters are critical to the actual lasing action from the slab edge mode.