Design and fabrication of a metallic irregular F–P filter array for a miniature spectrometer

Here we report our study on methods proposed for the design and fabrication of a metallic irregular Fabry–Perot (F–P) filter array for a miniature spectrometer to improve its performance and convenience in implementation. The method in designing suggests including both types of unit-cell filters that have broader single passband peaks of lower-order resonance modes and narrower multiple passband peaks of higher-order resonance modes in the F–P filter array for improved performance in reconstructive measurement of a spectrum with both finer and broader features in a wide spectral range. The fabrication method suggests using fewer film-deposition steps to form a larger number of different film thicknesses for the interspacing dielectric layers in the arrayed F–P filters. The processes involve inexpensive facilities and low-resolution patterning techniques in defining the unit cells of the filter array and can be conveniently fabricated using standard planar processing technologies. Resonant transmission spectrum profiles and passband peak positions of unit-cell filters are irregularly distributed in as-designed and -fabricated filter arrays. Based on the route of acquiring spectrum via computational reconstruction, such irregularities can facilitate designing and fabrication of F–P-type filter arrays for miniature spectrometers to achieve both high performance and low cost.