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.
Applications of photobiological studies and photochemical reactions are unlocking innovative results both for research and industrial fields. With this work we report on the optical, electronic and thermal design of extreme irradiance incoherent solid-state light sources. State of the art GaN (Gallium Nitride) and AlInGaP (Aluminum Indium Gallium Phosphide) LEDs have been analyzed and selected in order to achieve 450 nm and 940 nm radiation. Different optical approaches have been evaluated: i) geometric lenses, ii) TIR lenses and iii) reflectors. Lighting unit prototypes demonstrate a global efficiency (optical power vs electrical power) of up to 50% and an irradiance over an area of 100x100 mm in excess of 10 W/cm2.
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