Gain- and feedback-channel matching in lasers based on radiative-waveguide gratings

Angle-resolved emission spectroscopy is employed to investigate the distributed feedback (DFB) mechanisms in active waveguide grating structures with the DFB cavity consisting of a dielectric grating on an active waveguide layer. Laser emission can be achieved at the perfect matching between the resonance mode and the gain spectrum of the DFB cavity. This requires vertical surface-emitting resonance mode and its overlap with the peak of the gain spectrum that is determined by the photoluminescence spectrum of the active medium and the structural parameters of the DFB cavity.