OPTICAL DISPLACEMENT MEASUREMENT WITH GAAS ALCAAS-BASED MONOLITHICALLY INTEGRATED MICHELSON INTERFEROMETERS/

Two monolithically integrated optical displacement sensors fabricated in the GaAs/AlGaAs material system are reported. These single-chip mic rosystems are configured as Michelson interferometers and comprise a d istributed Bragg reflector (DBR) laser, photodetectors, phase shifters , and waveguide couplers, while the use of a single Michelson interfer ometer allows measurement of displacement magnitude only, a double Mic helson interferometer with two interferometer signals in phase quadrat ure also permits determination of movement direction. In addition, thr ough the use of two 90 degrees phase-shifted interferometer signals in the latter device, a phase interpolation of 2 pi/20 is possible, lead ing to a displacement resolution in the range of 20 mn. The integratio n of these complex optical functions could be realized with a relative ly simple fabrication process.