Fig. 5: Demonstration of spectrometer and scanning spectral imaging.

a Schematic diagram of the spectral imaging system. Black arrows indicate the light propagation direction. b Principle of the 2D heterojunction-based spectrometer. Especially, for spectral imaging, spectral data cubes consist of location information, and corresponding spectral information at every location point is reconstructed by the V_bg modulated photocurrents I_k according to the relationship between unknown incident light F(λ), photocurrent I_k and Responsivity R. M represents unknown non-linear function. c Reconstructed spectra from three narrowband spectra of which the peak locations are 1220 nm, 1310 nm, and 1410 nm, respectively. d Single-pixel scanning image for the logo of “Beijing University of Technology”. The Scale bar is 50 μm. Broadband white light modulated by an optical filter was applied for illumination to make sure that spectra of incident light is in the operational range of this designed spectrometer. e Spectral information of position A in d, which is matched well with a result from conventional equipment (blue-line). f Images of the logo at some selected wavelength from 1300 nm to 1470 nm are schematically shown. To clearly show the spatial information, false colors are defined for the above spectral range, and the intensities are normalized.