Recently, Su Liangbi, a researcher at the Shanghai Institute of Ceramics of the Chinese Academy of Sciences, cooperated with Shandong Normal University, Shandong University, Harbin Institute of Technology and other institutions to use trivalent rare earth ions based on the idea of ​​"rare earth luminescent ion localized lattice structure design". The fluorite-type structural crystal CaF2/SrF2 spontaneously enriches to form ion clusters, improves the interaction efficiency between activated ions through a reasonable doping mechanism, and achieves higher quantum efficiency than Stokes in the case of low concentration doping. Efficiency mid-infrared laser output.
1.8～3 μm medium-infrared laser has important applications in radar, laser communication, environmental monitoring and high-precision surgery due to its characteristics in the atmospheric window band, safety to the human eye, sensitivity to atmospheric molecules and strong absorption of liquid water molecules. value.
The research team introduced the modulation ion La3+ in the Tm:CaF2 crystal, rationally designed the composition and ratio of the crystal, and significantly improved the emission cross section and fluorescence lifetime of the Tm3+ ion 2μm band; using the 792nm laser diode as the pump source, at Tm, La:CaF2 A continuous laser output with a slope efficiency of 67.8% (Stokes quantum efficiency 41%) and a power of 4.27 W was achieved in the crystal. The laser wavelength tuning range was 190 nm (1850-2050 nm).
The research team used the characteristics of the disorder of the cationic lattice in the CaF2-SrF2 mixed crystal to reasonably design the ratio of Ca and Sr in the mixed crystal, and achieved the oblique efficiency of 41.4% in the 4 at.% Er:CaF2-SrF2 crystal (Stokes quantum efficiency). 35%), 3μm band continuous laser output with 712 mW power, and stable pulsed laser output with mode-locked laser pulse width of 1.78 ns and re-frequency 136.3 MHz in Q-switched mode. In addition, a 980 nm laser diode is used as the pump source to achieve a 3 μm band continuous laser output with a diagonal efficiency of 41% and a power of 1.06 W in a 3 at.% Er:SrF2 crystal.
The research team used a 1.94 micron Tm fiber laser as the pump source to obtain a continuous laser output of 2 μm in the 0.5 at.% Ho:CaF2 crystal with a slope efficiency of 59.8% and a power of 7.17 W. Moreover, using the acousto-optic Q-switching technology, a pulsed laser output with a pulse width of 54 ns, a single pulse energy of 1.9 mJ, and a repetition rate of 3 kHz is realized, with an average output power of 5.71 W and an oblique efficiency of 48.5%.
This research work effectively avoids a series of adverse effects due to high concentration doping in other types of laser crystal materials, thereby obtaining a high efficiency mid-infrared wave laser output. Relevant research results were published in Photonics Research, Optics Letters, Optics Express series of academic journals.
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