Photothermal modulation of laser diode wavelength: application to sinusoidal phase-modulating interferometer for displacement measurements

In this paper, a novel laser-diode (LD) sinusoidal phase-modulating (SPM) i nterferometer, which utilizes a photothermal technique for LD wavelength mo dulation, is proposed to measure displacements with a nanometer accuracy. I n conventional LD-SPM interferometers, the LD intensity modulation is concu rrent with the wavelength modulation, which increases measurement errors. U sing the photothermal technique, the LD wavelength modulation can be accomp lished with negligible concomitant intensity modulation, and the measuremen t errors are thus eliminated. The computer simulations and experiment resul ts verify the usefulness of this novel interferometer. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.