Low-cost chip-scale spectrometer enabled by equal-thickness interference spectral encoding

We present a low-cost, chip-scale spectrometer based on the principle of equal-thickness interference for spectral encoding. The design features a particularly simple structure, consisting of a plano-convex lens and a flat glass plate, both coated with silver on one side, while a charge-coupled device (CCD) captures the interferograms. The active chip is a square with a side length of 8.6 mm, and the overall spectrometer form factor is 7 cm. By employing an accompanying physics-constrained neural network (PCNN) to decode the interference images, the proposed micro-spectrometer achieves a spectral resolution of better than 4.8 nm across the 400-800 nm wavelength range. Calibration is significantly simplified by capturing the interferogram at 400 nm and using the scaling relationship. This approach offers a compact and practical solution for miniaturized spectral sensing.