Modeling and fabrication of mirrors used in micro-spectrometers for infrared analysis of biofluids

The spectrometers in general are used to detect the chemical composition of a sample by measuring its absorption or emission spectra. The intended application of the device is for doing the qualitative and quantitative analysis of liquids. The design, fabrication and characterization of micro-mirrors used in the Fabry-Perot interferometer (FPI) operating in the infrared (IR) region are discussed. The miniaturized spectrometer basically comprises three components: infrared emitter, FPI and a photo-detector. The FPI is critical, as it is the wavelength-selecting component. Mirrors in the FPI should have low loss, high and broadband reflectance in the infrared region to operate the FPI in ER region. Mirrors were modeled and optical properties were observed for varying mirror thickness. The mirrors were microfabricated and tested using FTIR. Experimental results of mirror transmittance closely agree with the modeling results.