Fig. 1. (a) Schematic diagram of the proposed on-chip computational spectrometer. (b) Schematic of a metasurface unit. Period P = 1600 nm and thickness of a-Si d = 200 nm. (c) Scanning electron microscope (SEM) images of metasurface filters and their corresponding transmission (after calibration). (d) Correlation heatmap of the 25 filters. A threshold of 0.5 is selected. (e) Fabrication process for the proposed on-chip spectrometer.

Fig. 2. Overview of metasurface filter selection and the spectral reconstruction algorithm based on the least squares method, introducing regularization and utilizing GA to optimize regularization coefficients.

Fig. 3. (a) Schematic diagram of experimental setup for reconstruction experiments. BS, beam splitter. (b) Reconstruction result of broadband spectrum (630–730 nm). (c) Broader broadband spectrum. (d) Reconstruction of large bandwidth complex broadband spectrum. (e) Broadband spectrum (550–850 nm).

Fig. 4. (a) Reconstruction results of monochromatic spectra (colorful solid lines) and reference spectra measured by a commercial spectrometer (dashed lines). (b) F and RMSE of each reconstructed monochromatic spectrum with different center wavelengths. (c) Reconstruction errors of each reconstructed monochromatic spectrum.

Fig. 5. (a), (b) Reconstruction of dual-narrow peaks at 595 and 596.5 nm (1.5 nm separation); (c), (d) at 691.5 and 694 nm (2.5 nm separation); and (e), (f) at 791.5 and 796 nm (4.5 nm separation).

Fig. 6. (a) Reconstruction result of a discrete spectrum with four wavelengths spaced 60 nm apart. (b) Five wavelengths (50 nm apart). (c) Six wavelengths (40 nm apart). (d) Eight wavelengths (30 nm apart).