Photonic crystals were fabricated by focused ion beam etching into an ion-implanted VCSEL. Although the photonic crystal structure pictured below fails the theoretical single mode test if a simple equivalent refractive index model is used, our theory shows single mode operation with finite etch depth. Lasing is in the fundamental mode as pictured below. Since light is not visible from under the holes, this suggests that the light is confined within the defect region of the photonic crystal, and that the confinement is not caused by extra loss from the change in reflectivity or scattering from the etched holes. Spectra taken under pulsed conditions is shown in the bottom figure. The reference sample shows multimode operation, whereas the photonic crystal device shows single mode operation at the highest currents tested.
Fig. 1. Fundamental photonic crystal mode appearing in defect region
Fig. 2. Spectra showing single fundamental mode operation from photonic crystal device versus reference VCSEL