Micro-turbomachine driving an infrared polarization modulator for Fourier transform infrared spectroscopy

This paper describes the development of a micro-air-turbine-driven polarization modulator (MPM) for double modulation Fourier transform infrared spectroscopy (FT-IR). The MPM has a Au/Cr wire grid polarizer on the backside of a /spl phi/ 5 mm n-type silicon turbine rotor. The MPM was fabricated using silicon bulk micromachining techniques such as photolithography and deep reactive ion etching (deep RIE). We completed first and second generation MPMs. The second generation MPM has an improved blade shape, a narrower radial bearing gap of 10 /spl mu/m and a better rotor balance compared to those of the first generation MPM. The first generation MPM rotated at about 10,000 rpm using 0.44 MPa compressed air, and realized IR light modulation frequency of 0.3 kHz.