Blazed Second Order Gratings In Grating Coupled Surface Emitters

Abstract

Surface gratings are useful components for integrated optic and optoelectronic circuits due to the large variety of functions they can perform [ 11. Second order gratings (SOGs) can be used to diffract a guided optical mode into a radiation mode. With the grating period identical to the wavelength in the waveguide, a counterpropagating mode is excited simultaneously and therefore the grating also provides optical feedback (resonant condition). With a slight detuning of the grating period, excitation of the reflected wave is suppressed and optical feedback is avoided (nonresonant condition). Horizontal cavity semiconductor lasers employing SOGs for surface normal emission are of great interest since they offer the prospect of beam control by varying the geometry of the grating. The surface emission efficiency (SEE) of symmetric SOGs is limited by the large fraction of the optical power that is radiated into the substrate [2]. Several methods to improve the SEE have been proposed and/or demonstrated, such as a multilayer reflector below the waveguide to redirect the substrate radiation [3] and various types of blazed gratings [2,4-61. Blazed SOGs can be made to radiate preferentially into air or substrate depending on the orientation of the grating with respect to the incident wave. Here we demonstrate, for the first time, blazing effects in grating coupled surface emitting (GSE) semiconductor lasers under both resonant and nonresonant conditions. The GSE lasers were fabricated from an InGaAdAlGaAs SQW-GRINSCH epitaxial