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.