Fluorescence Thermometry

The fluorescence of rare-earth-doped ceramic phosphors depends on temperature. Particularly, the fluorescence lifetime is decreased by temperature. This dependence makes the fluorescence suitable for measuring temperature. This paper describes the physics of the fluorescence of these ceramics, noting the works of Forster, Dexter, Inokuti, Hirayama, and others. Next, it outlines the several advantages of fluorescence thermometry. These advantages include (a) measurement of temperature by transfer to measurement standards for time, (b) remote sensing for surface thermometry, (c) high speed of measurement relative to many physical and mechanical phenomena, (d) narrow-spectrum optical sensing suitable for hostile electrical and luminous environments, and (e) the transfer of calibration standards for precise thermometry. The paper presents engineering considerations for realizing these advantages. It presents parameter-estimation techniques that allow measurement of the temperature-dependent fluorescence parameters. It describes instrumentation techniques that transfer the measurement of temperature to measurement of units of time, with instrument calibration by atomic standards. It also discusses other measurement and instrumentation details.