Optical temperature measurement across IR opaque layers by means of visible excitation and photoluminescence

With the technique here proposed, we exploit the temperature variation of the photoluminescence of a direct bandgap semiconductor to achieve a full contact-less thermometry. The proposed method is based on the spectral measurement of the PL signal emitted from a red LED chip when excited by means of a 532 nm solid state laser. Both PL emission peak wavelength and FWHM are used to improve the temperature estimation. The proposed method has been demonstrated on an extended temperature range, from cryogenic (90 K) to 460 K; a +/- 1 K of uncertainty due to calibration, +/- 0.7 K of measurement accuracy and +/- 0.3 K of precision are demonstrated on a temperature range of 300 K.