Abstract The present work concerns the upconversion luminescence in Cr3+:YAG single crystal under infrared laser irradiation. During the experiment, 404 nm, 808 nm, 980 nm, and 1064 nm laser excitation sources in range of −150 °C–600 °C were employed. A strong red light emission was detected in the bulk of the samples under the infrared excitation. The red emission originated from 4T2g→4A2g transition of Cr3+ ions and are only observed at temperatures higher than 150 °C; the profile of the emission curve is Gaussian-type with maxima at 500 °C, 600 °C, and 620 °C for λexc 808 nm, 980 nm, and 1064 nm respectively. This is attributable to the high-temperature nature of the upconversion luminescence, where the energy gap between the energy of a laser photon and the 4T2g state is compensated by simultaneous absorption of two photons.

中文翻译：

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Cr3+:YAG 单晶在红外激发下的上转换发光

摘要 目前的工作涉及在红外激光照射下 Cr3+:YAG 单晶的上转换发光。在实验过程中，采用了 -150 °C–600 °C 范围内的 404 nm、808 nm、980 nm 和 1064 nm 激光激发源。在红外激发下，在大部分样品中检测到强烈的红光发射。红色发射源自 Cr3+ 离子的 4T2g→4A2g 跃迁，仅在高于 150 °C 的温度下观察到；发射曲线的轮廓为高斯型，λexc 808 nm、980 nm 和 1064 nm 的最大值分别在 500 °C、600 °C 和 620 °C。这归因于上转换发光的高温性质，其中激光光子能量与 4T2g 状态之间的能隙通过同时吸收两个光子来补偿。