Abstract
The temperature-dependent green luminescence of Y3Ga5O12 nano-garnets doped with different concentrations of Er3+ ions has been measured from 300 to 850 K and, in more detail, in the biological range from 292 to 335 K.
Highlights
The temperature-dependent green luminescence of Y3Ga5O12 nano-garnets doped with different concentrations of Er3+ ions has been measured from 300 to 850 K and, in more detail, in the biological range from 292 to 335 K
The maximum value of the thermal sensitivity, 64 x 10-4 K-1 at 547 K, has been obtained for the nano-garnets doped with the lowest concentration of Er3+ ions, being one of the highest values found in the literature. These results allow concluding that a relatively low concentration of optically active ions is advisable and the changes induced by temperature on the green emissions are independent of the laser excitation radiation used, necessary to calibrate the temperature of the immediate environment of the Er3+-doped Y3Ga5O12 nano-garnets
Er3+ and Nd3+ ions have a special feature that distinguishes them from other RE3+ ions: their visible luminescence can be obtained by infrared-to-visible energy upconversion processes without co-doping with Yb3+ ions using near infrared laser radiations[11,12,13]
Summary
The emission spectrum is divided in two parts, which correspond to the emission of all the Starks of each thermalized level to the ground state In this case, the experimental ratio value RExp is equal to the ratio of the areas under the total emission profile of each part[22,24],. Room temperature diffuse reflectance spectrum, which is equivalent to the absorption one, of the YGG5Er sample was measured in the optical range (see Figure 2) In this spectrum, several bands corresponding to intra-configurational 4f11-4f11 electronic transitions between the Stark levels of the 4I15/2 ground state and those of the different excited multiplets of the Er3+ ion are identified[25]. The first involves only one optically active ion successively promoted, within the time duration of the laser pulse (~5 ns), to the upper levels by the resonant absorption of two laser photons as follows[19] (see Figure 2): ESA 1: 4I15/2+hν800nm+hν800nm→2H9/2+phonons→2H11/2,4S3/2
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