Monolithically integrated interferometer for optical displacement measurement

A monolithically integrated optical displacement sensor in the GaAs/AlGaAs material system has been developed, fabricated and characterized. The device was a double Michelson interferometer with an integrated light source, photodetectors, couplers and phase shifters. A key point of the work was the development of a single growth-step distributed Bragg reflector laser which served as the light source of the interferometer circuit. Special attention was also directed at the establishment of a bandgap-engineering technique (vacancy-enhanced disordering) allowing the definition of absorbing areas for the pumped laser section and the photodetector and transparent areas for the waveguiding sections and the grating section of the laser. The combination of the vacancy-enhanced disordering and the laser process enabled the fabrication of a fully integrated optical Michelson interferometer with quadrature signal detection. The maximal measurement distance with this double Michelson interferometer was 25 cm, and a maximal resolution of 20 nm was seen. Although using relatively simple standard processes, complex optical functions could be realized on a single chip.

Thèse de doctorat : Université de Neuchâtel, 1996