Heterodyne laser Doppler vibrometers integrated on silicon-on-insulator based on serrodyne thermo-optic frequency shifters

Miniaturized laser Doppler vibrometers (LDVs) have many advantages over conventional bulk LDVs. In this paper, the realization of a miniaturized heterodyne LDV integrated on silicon-on-insulator substrate is reported. The optical frequency shifters in these on-chip LDVs employ a serrodyne technique, and they generate a frequency shift at 2 kHz. Vibrations of a mirror for the frequency range between 1.1 and 123 Hz and the velocity range between 0.8 and 400 μm/s are measured by both an on-chip LDV and a commercial LDV. The measurement results agree well. A compensation method for the influence of on-chip spurious reflections is also demonstrated.