Interferometric measurement of lateral phase profile and thermal lensing in broad-area diode amplifiers

A Mach-Zehnder imaging interferometric is used to directly measure the lateral phase profile in the near field of broad-area semiconductor optical amplifiers with lambda /25 phase resolution, or 0.1 degrees C in temperature. The quadratic thermally induced phase distortion and its equivalent thermal lens focal length are characterized. Anomalous localized phase variations are correlated to thermal bond nonuniformities in devices mounted under nonoptimal conditions. It is demonstrated for an unbiased 600- mu m-wide by 1000- mu m-long amplifier device that a phase uniformity across the stripe of better than lambda /25 can be obtained.<
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