Interferometric sensors for spectral imaging

An interferometric sensor based on a partly transparent amorphous silicon n-i-p diode was realized. The combination of the sensor with a tunable micromirror facilitates the realization of a novel microspectrometer. The working principle of the sensor based on the sampling of a standing wave created in front of the tunable mirror. To sample a standing wave the active region of the sensor has to be thinner than the wavelength of the incoming light. Varying the position of the mirror results in a shift of the phase of the standing wave, in a variation of the generation profile within the diode and, thus, in a modulation of the photocurrent. The spectral information of the incoming light can be determined by the Fourier transform of the sensor signal. The spectral resolution of the integrated spectrometer scales reciprocally with the displacement of the mirror. A spectrometer resolution down to 6 nm was achieved.