Optical thermometryFluorescence intensity ratioThermally coupled levelsNon-thermally coupled levelsSensitivityUP-CONVERSION LUMINESCENCETEMPERATURE SENSING BEHAVIORFLUORESCENCE INTENSITY RATIOTRANSPARENT GLASS-CERAMICSNEAR-INFRARED EMISSIONSWHITE-LIGHT EMISSIONENERGY-TRANSFERMULTICHANNEL LUMINESCENCESENSITIVITY MODULATIONGD-2(WO4)(3) PHOSPHOR