THEORY OF GRATING-CONFINED BROAD-AREA LASERS

Angled-distributed-feedback semiconductor lasers have demonstrated 1-W diffraction-limited collimated output from a broad-area aperture. We present the first theoretical analysis of the modes of these devices, explaining their principle of operation and the reasons for their high spatial mode quality. A transfer matrix analysis is presented that ca n describe the general class of grating-guided waveguides with either finite and/or infinite grating boundaries. Lateral grating-confined br oad-area waveguides are shown to have extremely high spatial mode sele ctivity. The theory is applied to describe the new angled-grating dist ributed feedback laser (a-DFB), predicting a broad near-Gaussian near held and a collimated diffraction-limited far field, in good agreement with experiment.