A temperature sensor includes a photon source, a fluorescent element and a photodetector. The fluorescent element includes a temperature-insensitive first fluorophore and a temperature-sensitive second fluorophore. The photodetector includes a first photosensor exhibiting a first spectral responsivity and a second photosensor exhibiting a second spectral responsivity. To measure a temperature of a surface, the fluorescent element may be placed adjacent to the surface and irradiated with a photon beam. First photons emitted from the first fluorophore and second photons emitted from the second fluorophore are collected. The first and second photons may be transmitted as a single dichromatic beam to the photodetector. The photosensors generate two different photodetector output signals, the ratio of which may be correlated to temperature.