Miniature diode spectrometer design

Standard spectrometers involve prisms or diffraction grating to expand light spectra in space and then each spectral region is measured with a photodetector. The limit for miniaturization of such spectrometers is determined by space allocation for spectra expansion. This limit can be overcome with a proposed spectrometer design which employs the dependence of light penetration depth in semiconductor on spectral wavelength and consumes no need for optical components (prisms or diffraction grating). The principle is realized by silicon semiconductor structure with oppositely directed Schottky barrier and n-p junction, where n-region is the base. By applying external voltage U (-1V ... + 1V) on this structure, the minimum of the potential is formed in some depth x = x(U) of the semiconductor. The observed photocurrent I = I(U) depends on the integral radiation flux that penetrated the material deeper than x. Absorption coefficient ∝(λ) decreases as λ increases. Therefore by scanning the depth x, the contribution of different radiation components (with different λ) on the final signal is scanned. When Current-Voltage dependence I(U) is observed, a special algorithm can be used to extract the initial radiation spectra from these data. Proposed photodetector-spectrometer has the observation spectral range of 400-1100 nm. Reconstructed spectra show the accuracy for the spectral peak determination of 20-100 nm. Directions for improvements of the design and calculation algorithm is presented.