Scanning micro-mirrors: From bar-code-scanning to spectroscopy

Micro Opto Electro Mechanical Systems (MOEMS) reach more and more importance in technical applications. They are smaller than conventional devices, less expensive when fabricated in higher numbers and offer new options concerning reliability and measuring methods. Resonant movable micro-mirrors produced as single crystalline chips with CMOS-compatible technologies provide a broad field of applications. They can be used as fast scanning devices, for display and endoscopy applications and as grating for spectroscopy when a structured surface is applied. Therefore, special designs have been developed and tested by Fraunhofer IPMS. The resonant electrostatic driven micro-mirrors presented here have diameters of 0.5 mm up to 3 mm, with moving frequencies of 125 Hz to several kHz and mechanical deviation of ± 16° and more. Devices with one and two rotational axes have been fabricated and tested. Focusing on spectroscopic applications, micro-scanning grating chips with a diffractive surface of 300 and 500 lines/mm have been designed. Working in a wavelength range between 900 nm and 2200 nm, the scanning grating chips have been built in a micro-spectrometer with a size of 90 x 60 x 50 mm. Due to the Czerny-Turner setup, only one fast single InGaAs-photodiode is required. To improve the signal-to-noise-ratio of the system, special high efficient grating structures have been developed. The CMOS-compatible fabrication process and first investigations of these new micro-scanning grating chips will be presented.