Fabrication of ruby sensor probe for the fiber-optic thermometer using fluorescence decay

Abstract

Ruby single crystals have been grown successfully from the melt droplet on the sapphire crystal fibers as the sensor head directly coupled with optical fiber for the thermometer applications using fluorescence decay. In this fabrication process, droplets of slurry of ruby powders are formed on the end of the sapphire crystal fiber and are dried, sintered, and then melted and solidified in a floating-zone furnace. The photoluminescence (PL) lifetime of the ruby sensor head varies from τ=3.8 to 2.5 ms with the Cr3+ concentrations from 0.07 to 1.0 at. %. The ruby crystal with a Cr3+ concentration of 0.35 at. % is found to be the most suitable sensor head having the longest PL lifetime. The temperature coefficient of the fiber-optic thermometer equipment using the directly coupled ruby sensor head with a Cr3+ concentration of 0.35 at. % is −12.4 μs/K.

Photoluminescence and transformation of dense Al2O3:Cr3+ condensates synthesized by laser-ablation route

“…The y fluorescence and the R 1 /R 2 lines could also be a sensitive sensor of the g-d-y-a transformation and the accompanied lattice mismatch stress for the gAl 2 O 3 :Cr 3+ condensates. The g-Al 2 O 3 :Cr 3+ condensates when accumulated as coating on suitable semiconducting materials could also act as a photon sensor, taking advantage of its g-d-y-a transformations at an optimized excitation pulse energy under visible light and a long lifetime of y and ruby luminescence [22,35]. (The radiation lifetime of the excited 2 E state at room temperature is 12 ms for y-Al 2 O 3 [35], 4-5.8 ms for ruby [22,35], and varied lifetimes to exhibit nonexponential behavior for less ordered g-and d-Al 2 O 3 [35].)…”

“…The g-Al 2 O 3 :Cr 3+ condensates when accumulated as coating on suitable semiconducting materials could also act as a photon sensor, taking advantage of its g-d-y-a transformations at an optimized excitation pulse energy under visible light and a long lifetime of y and ruby luminescence [22,35]. (The radiation lifetime of the excited 2 E state at room temperature is 12 ms for y-Al 2 O 3 [35], 4-5.8 ms for ruby [22,35], and varied lifetimes to exhibit nonexponential behavior for less ordered g-and d-Al 2 O 3 [35].) Note that the PL of Cr 4+ in the visible and near infrared regions is of concern, respectively, to brownish color and wideband light source for optical communications of Cr 4+ :YAG fiber with silicate glass cladding [36].…”

CVD of Thin Ruby Films on Si(100) and Stainless Steel for Surface Temperature Sensor Applications

“…[7,10,11] The temperature dependence of the 420 emission spectrum, [8,9] and the phosphorescence decay time, [10,11] were studied extensively in a wide temperature range. Thus, the application of ruby as a temperature sensor has already been proposed and some experiments described in the literature, mainly the use of ruby crystals in combination with fiber optics, [12][13][14][15][16][17] but some work on ruby films has also been published. [18][19][20] Although the basics of the temperature measurement using thermographic phosphors (including the use of ruby films) are well understood, less attention has been paid on the fabrication of such films.…”

Evaluation of Cr-doped yttrium aluminum garnet crystals for hybrid fiber-optic thermometer application

“…The sensitivity and the accuracy of the measurement, therefore, depends greatly on the properties of the sensor materials. Various phosphors, such as ruby (Cr-doped Al 2 O 3 ) [5,6], spinel (Cr-doped MgAl 2 O 4 ) [7], alexandrite (Cr-doped BeAl 2 O 4 ) [8] and emerald (Cr-doped Be 3 Al 2 Si 6 O 18 ) [9] have been reported for the sensor head of the fiber-optic thermometer. Among other phosphors, rare-earth garnet crystals have the advantages of chemical and thermal stability for use as the sensor material of a thermometer.…”

“…A wide variety of fiber-optic thermometers have been demonstrated [2][3][4][5][6][7][8][9][10]. Among these fiber-optic thermometers, blackbody radiation thermometry [3] and fluorescent thermometry [4][5][6][7][8][9][10] are recognized as a practical measurement technique. Shen et al [3] have reported that the fiber-optic thermometer which combines the blackbody radiation thermometry and fluorescent thermometry is useful system to measure wide temperature range from 290 K to 2000 K. They used a sapphire-fiber doped in its end parts with Cr 3+ ions as sensor materials.…”