Characterization of heterojunction laser diodes by near field optical scanning microscopy: layer composition and mode structure analysis

We report mode structure and semiconductor layer composition analysis of strained (In,Ga)As quantum well lasers using the super-resolution capabilities of near field scanning optical microscopy (NSOM). Submicron collection mode imaging of the emission mode structure easily identifies high order transverse modes as well as mode leakage into the substrate. Using the tip as a localized, tunable source of photons, near field optical beam induced current (NOBIC) measurements reveals the compositional profile of the layer structure. The active region is very sensitive to the excitation wavelength due to the effect of a changing optical absorption in near field coupling to a thin layer