Reflectivity measurements of intracavity defects in laser diodes

A method for measuring the complex reflectivity associated with a localized defect existing inside a laser diode cavity is presented. It relies on analyzing the magnitudes of resonant peaks in the Fourier transform of a subthreshold laser spectrum. Reflectivities between 0.01 and 0.02 with zero phase have been measured in a laser with a deliberately induced scattering center produced by standard lithographic techniques.