Fluorescence decay characteristic of Tm-doped YAG crystal fiber for sensor applications, investigated from room temperature to 1400 °C

Abstract

A Yttrium aluminum garnet (YAG) crystal fiber with a thulium-doped end tip was specially grown by means of the laser heated pedestal growth approach and designed to be incorporated in a fiber-optic temperature probe. The fluorescence decay characteristics of the crystal fiber, including the temperature dependence of both the fluorescence lifetime and intensity, were comprehensively investigated. Experimental results indicated that the crystal fiber showed a monotonic relationship between the fluorescence lifetime and temperature with an average lifetime sensitivity of 3 s C over a wide temperature range, taking measurement from room temperature to 1200 C. Good stability (up to 1400 C) was observed with high repeatability of the fluorescence lifetime during the annealing process carried out on the fiber over this temperature range. The fiber was found to be an excellent candidate material to be used as a fluorescence decay-based fiber thermometer probe and the results are presented on its performance.Index Terms-Crystal fiber, fiber thermometer, fluorescence lifetime.

Fiber optic thermometer using Cr-doped GdAlO3broadband emission decay

“…Thermometers based on optical fibers have generated much interest because of their suitability for making remote temperature measurements in harsh environments such as turbine engines where interference from electromagnetic radiation and high-temperature chemical attack make discrete, wired temperature sensors such as thermocouples and thermistors unacceptable [1]. Typically, sapphire fiber optic thermometers using blackbody radiation have been employed at higher hermistors (above ~1200 °C) [2], while luminescence-based silica (for temperatures below 1000 °C) [3][4][5][6][7][8], or either sapphire [9] or Y 3 Al 5 O 12 (YAG) [10][11][12] (for temperatures above 1000 °C) fiber optic thermometers incorporating thermographic phosphors have been used at lower temperatures where blackbody radiation is weak. A wider temperature range can be covered by hybridizing both techniques in one probe [13,14].…”

“…An attractive feature of the luminescence decay-based thermometers in contrast to the blackbody radiation thermometers is that the temperature is determined by the intrinsic decay rate of the thermographic phosphor, and because the measurement is not intensity-based, the thermometer will not require re-calibration. For this reason, significant effort has been made towards extending the operating range of luminescence decay-based fiber optic thermometers to higher temperatures [1,10,12].…”

A suitable (wide-range + linear) temperature sensor based on Tm3+ ions

“…In this last case, however, the T-sensor was based on the lifetime decay of the Tm 3+ -related integrated signal in the 1000–1700 nm NIR region, after excitation with 800 nm photons. According to the experimental results, excellent fluorescence stability and good temperature sensitivity (~3 μs K −1 ), in the ~298–1675 K range, were achieved from a Tm 3+ -doped YAG (or Y 3 Al 5 O 12 ) optical fiber 25,26 .…”

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

“…Luminescence decay-based fiber optic thermometers have attracted considerable interest for their ability to probe temper atures in harsh environments where their immunity to chemical attack and electromagnetic interference as well as minimal intrusiveness are significant advantages over either thermocouples or electrical-resistance based thermometers [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. While single fiber probe configurations for luminescence-based fiber optic thermometers as well as for fluorescence and Raman probes have been recognized to offer advantages of simple design, compactness, perfect excitation/ collection zone alignment, and high light collection efficiency, their effective use has been greatly limited by background interference by emission or scattering generated in the fiber probe itself as well as the excitation and collection fibers coupled to the probe [15][16][17][18][19][20].…”