Feedback effects in tapered broad-area semiconductor lasers and amplifiers

A detailed experimental investigation of the effect of optical feedback upon the operation of high-power broad area InGaAs strained quantum well semiconductor lasers is presented. In particular, we examine the effect optical feedback has upon the beam quality of high-brightness lasers employing a tapered electrical contact. The far-field of such lasers is shown to degrade rapidly with power feedback ratios exceeding -30 dB, leading to a significantly reduced power in the central diffraction-limited far-field lobe. Far-field degradation is accompanied by dynamic instability and spectral broadening. Good beam quality and low intensity noise can be recovered, however, by rotating the feedback polarization.<>