Imaging and vibrational analysis with laser-feedback interferometry

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Abstract
We have constructed a scanning confocal laser-feedback microscope that determines surface profiles in the range of 5 nm to 3 μm with ~200-nm lateral discrimination. A direct comparison is made with scanning electron microscopy, and an image of a silicon resolution standard with 40-nm-high structures is shown. The device is also capable of characterizing surface motion with a sensitivity of −1/2 across a bandwidth of several megahertz. Vibrational analysis of a miniature piezoelectric microphone is demonstrated from 50 Hz to 50 kHz. An operational description of the device is presented in addition to a generalization of laser-feedback theory that includes gas-laser dynamics.