Optical gain and optical internal loss of GaN-based laser diodes measured by variable stripe length method with laser processing

We demonstrate a new technique for the variable stripe length (VSL) method by which the optical gain and optical internal loss of GaN-based laser diod es (LDs) can be directly measured. In the technique, the laser processing i s utilized for varying the excitation length. The excitation length of GaN- based LDs can be varied by directly processing its p-electrode with high-po wer laser irradiation. From the results of the measurements, it was reveale d that the optical internal loss of GaN-based LDs was strongly affected by the layer structure.