Towards On-Chip MEMS-Based Optical Autocorrelator

We propose a compact MEMS-based optical autocorrelator based on a micromachined Michelson interferometer in silicon and the two-photon absorption non-linearity in a photodetector. The miniaturized autocorrelator has a scanning range of 1.2 ps and operates in the wavelength range of 1100-2000 nm. The device measures the interferometric autocorrelation due to its collinear nature, from which the intensity autocorrelation can be calculated. The field autocorrelation can also be measured, from which the optical pulse spectrum can be calculated. A theoretical model based on Gaussian beam propagation is developed to study the effect of optical beam divergence, pulse dispersion, tilt angle between the interferometer mirrors, and amplitude mismatch between the interfering pulses. This model explains many of the effects observed in experimental measurements due to the use of a MEMS interferometer. The experimental results of autocorrelation signals for several pulses in the order of 100 fs are compared to a commercial autocorrelator and a good match is found.