Realization of spectrally engineered semiconductor Fabry-Perot lasers with narrow geometrical tolerances

Artikel i vetenskaplig tidskrift, 2011

Spectrally engineered semiconductor Fabry-Perot laser resonators are designed to enhance the optical feedback for selected longitudinal modes, which thereby require less gain for lasing. This is achieved by introducing refractive index perturbations along the length of the resonator. However, the physical realization of these resonators is a challenge because of very narrow tolerances; in particular the need for precise positioning of the end facets of the resonator in relation to the perturbations, and the excess propagation loss associated with the perturbations, has been a major concern. We report on a method to achieve high-quality end facet mirrors enabling precise positioning relative to the perturbations, the latter which are realized as lateral corrugations of the waveguide. Measurements show that the mirror quality is comparable to that of cleaved mirrors and that the additional loss introduced by the perturbations adds < 10 cm-1 to the overall propagation loss, provided that the perturbations are densely enough spaced along the resonator. This implies that the number of perturbations should be large, which is beneficial for the realization of strongly perturbed resonators enabling the most flexible engineering of the spectral properties of the laser.