基于氟化物晶体中Er3+团簇效应实现3μm波段高效激光输出的研究

The Er3+ ion-based lasers, operating at around 3μm, have attracted great interest because of their potential applications in medicine, communication, remote sensing, biology processing and pollution monitor. The search for such new efficient laser materials which can generate high efficiency lasers has been continued. This project foucuses on Er3+ ions doped fluoride materials which have potential applications in 3μm laser output. The main contents are listed as follow: 1) realizing laser output with low Er3+ ion concentration by increasing the possibility of energy transfer within Er3+ clusters in the lattice; 2）overcoming the self-terminating “bottleneck” effect of the lower laser level in the four-level laser system of Er3+（4I11/2→4I13/2）by decreasing the lifetime of lower laser level 4I13/2 with co-doping de-excitation ions Pr3+. We will solve the self-terminating transition and the serious thermal problem in the lasers and develop valuable 3μm mid-infrared laser materilals and lasers with independent intellectual property rights.

3μm波段Er激光在医疗、通信、遥感、生物工程、污染监测等领域有重要应用，是目前固体激光领域研究的热点。“一代材料、一代器件”，该波段激光器的实用化发展瓶颈关键在材料。本项目针对目前具有应用潜力的掺Er氟化物激光材料，提出：1）利用Er3+在晶格中的“团簇”结构,提高离子间的能量传递,实现低Er3+浓度3μm激光输出；2）共掺去激活离子Pr3+,降低下能级4I13/2寿命，解决Er3+（4I11/2→4I13/2）四能级系统激光通道下能级的阻塞。有效解决抑制掺铒激光器发展的激光振荡自终止现象和激光运转热效应等问题。发展具有实用价值和自主知识产权的3μm波段中红外激光材料和激光器。

基于Er3+的2.8μm激光是固体激光领域的研究热点。本项目选择低声子能量的氟化钙、氟化锶晶体作为Er3+掺杂基质，开展 2.8μm光谱及激光性能的研究。采用坩埚下降法生长了Er:CaF2晶体，晶体具有较好的光学质量。通过计算不同掺杂浓度晶体的光谱参数，得出最佳掺杂浓度晶体。采用LD泵浦，4at.% Er:CaF2晶体实现了最佳的斜效率17.3%，输出功率0.342W的2.79μm连续激光。采用坩埚下降法生长了Er,Pr:CaF2晶体。极少量（0.03at.%）的Pr3+，即可有效猝灭不利的近红外发光，极大缩小激光上下能级寿命差值（从7ms缩小到1ms）。在LD泵浦下，3at.%Er, 0.03at.% Pr:CaF2晶体的2.79μm连续激光斜效率与输出功率较3at.% Er:CaF2晶体均提高一倍，达到15.8%，0.268 W。采用坩埚下降法生长了Er:SrF2晶体。在3at.% Er:SrF2晶体中实现了低阈值0.058W，高斜效率30.7%（已接近斯托克斯效率），高平均输出功率0.614W的2.8μm连续激光。通过调整激光谐振腔，该晶体的最高平均输出功率达到1.05W。在SCI期刊上发表论文5篇。