An evanescent wave microspectrometer includes a planar diopter separating two transparent media, an optical sensor with a pixel array, and disposed in the second transparent medium, and an interference device disposed such that at least a part of the interference device is in contact with evanescent waves generated at the surface of the diopter. The micro-spectrometer also includes a memory storing a map having a set of set of data grids including the optical response of said sensor for a set of quasi-monochromatic wavelengths of a calibration light source, and a calculator configured to determine the spectrum (ψ) of a test light source configured to generate evanescent waves at the surface of the diopter, on the basis of the map and the optical response of the sensor.