CHARACTERIZING RESIDUAL REFLECTIONS WITHIN SEMICONDUCTOR-LASERS, INTEGRATED SOURCES, AND COUPLING OPTICS

We describe a method for analyzing reflections within or near semicond uctor lasers and more complicated integrated sources. Through Fourier transformation of an optical spectrum from the wavevector to the lengt h domain, reflections are analyzed for strength, round-trip path lengt h, and current or voltage dependence. Identification of reflections fr om within semiconductor lasers, integrated electro-absorption modulate d lasers, and from coupling optics is presented. Spatial resolution in InP of similar to 5 mu m with over two orders of magnitude in dynamic range is demonstrated. Inverse transformation of a spatially resolved feature in a transformed reflection spectrum provides an optical spec trum due to that individual feature of sufficient resolution to study wavelength dependence, for example, of coatings and gratings.