The measurement of lateral index variations in unstable resonator semiconductor lasers from spectrally resolved near-field images

We show that the spatially and spectrally resolved near-field images of unstable resonator semiconductor lasers (URSL) can be used to measure the lateral refractive index variation that is intentionally incorporated into these devices. Several URSL lasers, with different lateral index profiles, were measured using this technique and good agreement was found between the designed and actual index variation. This technique also allows the measurement of index changes due to other processes such as thermal effects, nonuniform carrier distribution and material defects.