Wavelength-stabilized tilted wave lasers with a narrow vertical beam divergence

Abstract

We studied laser diodes grown in the tilted wave geometry with cleaved facets. In this approach a cavity with the gain medium is coupled to the second cavity, while the phase matching of the modes of the two cavities results in the wavelength stabilization. The mode separation can be controlled by the tilt angle of the leaky wave emission and the thickness of the coupled cavity. In one case a ∼100 µm thick transparent substrate with a polished and dielectric-coated back surface was used as a coupled waveguide. In the second case, a 10 µm thick GaAs layer followed by an InGaP evanescent reflector was applied. We observed an increase in the lasing mode wavelength spacing and the width of the vertical far-field lobes from ∼0.7° to 5° (full width at half maximum, FWHM) with the reduction of the thickness of the coupled cavity, in agreement with expectations. The FWHM numbers correspond to the diffraction limit for 100 and 10 µm thick coupled waveguides, respectively. A high temperature stability of the lasing wavelengths (0.1 nm K−1) was revealed. The results indicate that a new generation of wavelength-stabilized lasers for applications requiring ultrahigh brightness and wavelength stabilization can be developed.