中红外氟铟基玻璃及光纤激光器最新研究进展(特邀)

Recent research advances of mid-infrared fluoroindate glass and fiber lasers(invited)

3~5μm波段包含了大气的传输窗口和许多气体分子的吸收带,因而3~5μm中红外光纤激光器在大气遥感、生物医学、材料加工等领域具有广阔的应用前景。近年来,中红外光纤激光器的输出波长不断向长波长扩展,而实现中红外光纤激光输出的关键在于增益光纤材料的选择。氟铟基玻璃具有较宽的中红外透过窗口和较低的声子能量,因而氟铟基玻璃可以作为增益光纤材料应用于中红外光纤激光器领域。文中综述了从20世纪80年代至今,稀土离子掺杂氟铟基玻璃及氟铟基光纤激光器的代表性研究成果,回顾了氟铟基玻璃组分和玻璃结构的研究历程,介绍了氟铟基光纤的制备工艺,简述了稀土离子掺杂氟铟基玻璃和稀土离子掺杂氟铟基光纤激光器的最新研究进展。2018年,加拿大拉瓦尔大学的Maes等人利用Ho^(3+)掺杂氟铟基光纤作为增益介质,在中红外光纤激光器研究领域取得突破性进展,在室温下获得了输出功率接近200 mW的3.92μm光纤激光输出。最近,利用1150 nm激光作为泵浦源以及自研的Ho^(3+)/Pr^(3+)共掺杂氟铟基光纤作为增益介质,实现了~2.9μm波段中红外光纤激光输出,其最大输出功率为1.075 W,相应斜率效率为17.6%。未来,通过制备双包层氟铟基光纤和氟铟基光纤光栅,有望搭建全光纤化中红外光纤激光器,实现更高功率的3~4μm波段中红外光纤激光输出。

Significance The 3-5μm mid-infrared band contains the atmospheric transmission window and the molecular fingerprint area,and has important research significance and development prospects in the fields of remote sensing,national defense,biomedicine and materials processing.Fiber lasers have good beam quality,high lightto-light conversion efficiency,good heat dissipation characteristics,compact structure and high reliability.The output wavelength of fiber lasers is currently expanding to the mid-infrared band,however,the phonon energy of the glass matrix is an important factor affecting the generation of mid-infrared lasers.The lower the phonon energy of the matrix material,the lower the multi-phonon relaxation rate of the rare-earth ions,thus promoting the radiation transition process.Heavy metal fluoride glasses demonstrate great potential for applications in midinfrared fiber lasers due to their relatively low phonon energy,wide mid-infrared transmission window,high solubility of rare earth ions and high thresholds of laser damage resistance.With the increasing demand for 3-5μm laser sources in the mid-infrared band,the development of a relatively low phonon energy fluoride glass is essential.The most extensively investigated fluoride fibers are fluorozirconate fibers such as ZBLAN fibers.In recent years,it has attracted interest as researchers have found that fluoroindate glasses have lower phonon energy,superior physical and chemical stability compared to fluorozirconate glasses.The relatively wide mid-infrared transmission window and low theoretical loss of fluoroindate fibers indicate that fluoroindate fibers have important research significance in the field of mid-infrared fiber lasers.Progress This paper first introduces the research progress of fluoroindate glasses,including the investigation of the components,structure and luminescence properties of fluoroindate glasses.It is shown that the design of fluoroindate glass components is very complex and requires comprehensive consideration of the properties of each cation and application requirements.The structure of fluoroindate glasses is analyzed to be mainly composed of[InF_(6)]^(3−)octahedra.It is introduced the main rare earth ions that can achieve 3-5μm mid-infrared fluorescence in fluoroindate glasses are Er^(3+)ions,Dy^(3+)ions,Ho^(3+)ions and Pr^(3+)ions,indicating that fluoroindate glasses are the promising gain material to achieve mid-infrared fiber lasers.Subsequently,the preparation of low-loss fluoroindate fibers is presented,laying the foundation for the establishment of mid-infrared fluoroindate fiber lasers.The research advances in fluoroindate fiber lasers are presented.The rare earth ions that can achieve 3-5μm mid-infrared lasers in fluoroindate fibers are Er^(3+)ions,Dy^(3+)ions and Ho^(3+)ions,in which the~3.9μm laser of Ho^(3+)ions is the longest wavelength laser achievable in fluoride fibers,and the~3.9μm laser has been achieved only in fluoroindate fibers at room temperature so far,indicating that fluoroindate fibers are the potential mid-infrared fiber lasers.Conclusions and Prospects This paper reviews the latest research advances in the components and structures of fluoroindate glasses,presents the research advances of the luminescence properties of fluoroindate glasses.The preparation of low-loss fluoroindate fibers is presented,laying the foundation for the establishment of midinfrared fluoroindate fiber lasers.The research advances of fluoroindate fiber lasers is reviewed,showing that fluoroindate fibers are the most promising material to achieve mid-infrared fiber laser.The preparation of low loss double cladding fluoroindate fibers can be achieved in the future by investigating the double cladding fluoroindate glass components and the double cladding fiber drawing process,which is conducive to achieving high power mid-infrared laser output.The output performance of the midinfrared fiber laser can be further optimized by adjusting the rare-earth ion doping concentration of the fluoroindate fiber and constructing an all-fiber laser system to reduce the influence of the environment on the fiber laser system,thus achieving high power and high efficiency mid-infrared laser output.