Carrier-induced lensing in broad-area and tapered semiconductor amplifiers

Wavefront lensing due to nonuniform carrier saturation in rectangular (broad-area) and tapered GaAlAs amplifiers is described. Lensing dependence on current and input power, measured interferometrically and by a lens displacement method, agree with calculations based on a beam propagation model. Lensing induced astigmatism, calculated for a representative optical focusing system, exhibited minimal variation of less than 0.3 μm/A under saturated high power conditions in both amplifier types.