Fig. 4: 2D chirped grating for polarimetric spectroscopy.

a SEM image of a preliminary sample with the period varying from 439 to 739 nm along two directions. Scale bar is 10 µm. b, c Zoom-in images at two corners of the chirped grating. Zoom-in regions correspond to squared off areas of matching color in (a). Scale bars are 2 µm. d Reflection images of the grating under the illumination of 490, 595, 635, and 660 nm light. e, f Reconstructed spectra of vertically polarized (e) and horizontally polarized (f) light with peak wavelengths at 490, 595, and 635 nm. Dark blue lines are reconstructions from the proposed intelligent spectrometer, while red lines resemble reconstruction from a conventional benchtop spectrometer.