Single fiber temperature probe configuration using anti-Stokes luminescence from Cr:GdAlO₃

Abstract

Single-photon excitation of anti-Stokes-shifted emission from a thermographic phosphor allows operation of a luminescence decay-based single fiber temperature probe with negligible interference from background fiber-generated Raman scattering. While single fiber probe configurations for luminescence-based fiber optic thermometers offer advantages of simple design, compactness, and superior emission light collection efficiency, their effective use has been limited by interference from Raman scattering in the fiber probe and excitation delivery fiber that produces distortion of the luminescence decay that follows the excitation pulse. The near elimination of interference by background fiber-generated Raman scattering was demonstrated by incorporating a Cr-doped GdAlO 3 (Cr:GdAlO 3 ) thermographic phosphor as the sensing element at the end of a single fiber luminescence decay-based thermometer and detecting anti-Stokes-shifted luminescence centered at 542 or 593 nm produced by 695 nm excitation. Measurements were performed using both silica (up to 1150 °C) and single-crystal YAG (up to 1200 °C) fiber-based thermometers. Selection of emission detection centered at 542 nm greatly benefited the YAG fiber probe measurements by practically eliminating detection of otherwise significant luminescence from Cr 3+ impurities in the YAG fiber. For both the silica and YAG fiber probes, the relative benefit of adopting single-photon excitation of anti-Stokes-shifted luminescence was evaluated by comparison with results obtained by conventional 532 nm excitation of Stokes-shifted luminescence.

Review—Photoluminescence Properties of Cr3+-Activated Oxide Phosphors

“…The experimental data are taken from Eldridge. 60 The sharp and strong PL peak can be easily found at ∼1.705 eV, which is caused by the 4 A 2g → 2 E g transition peak. Similarly, the largest PLE band peaking at ∼2.2 eV is due to the 4 A 2g → 4 T 2g excitation absorption transitions.…”

“…Figure 7. PL and PLE spectra for the GdAlO 3 :Cr 3+ phosphor measured at 300 K. The experimental data are taken from Eldridge 60. The vertical bars in the PLE spectrum show the results calculated using Eq.…”

Wall Temperature Measurements in a Full-Scale Gas Turbine Combustor Test Rig With Fiber Coupled Phosphor Thermometry

“…This is more costly than a single fiber setup and reduces collection efficiency. Also the utilization of blue-shifted phosphorescence by excitation of anti-Stokes luminescence has been demonstrated [11]. This is however not applicable for every phosphor material.…”

“…To overcome this issue excitation of the anti-Stokes shifted phosphorescence has been proposed. This way, the emission wavelength of the thermographic phosphor is shifted to a region with less influence from interference generated in the fiber [11].…”

Measurements of turbine blade temperature in an operating aero engine using thermographic phosphors

“…Thermographic phosphors applied to the thermal barrier coatings (TBCs) of turbine blades have shown promise as an alternative method of temperature measurement that may not be as prone to error [3][4][5][6][7][8][9][10]. In luminescence lifetime methods, a phosphor is excited by a light source and the time for the resulting luminescence to decay is an indicator of the temperature.…”