Imaging and profiling surface microstructures with noninterferometric confocal laser feedback

Exploiting the sensitivity and the self-aligning features of the confocal laser-feedback technique and the convenience of superluminescent laser diodes, we developed an optical method for imaging and profiling surface microstructures with a depth resolution as great as 20 nm. The incoherent, noninterferometric nature of the technique enables fast open-loop operation and large dynamic range. Measurements of calibrated semiconductor surface microstructures and optical ridge waveguides are demonstrated.