摘要
基于加工出的Dy3+,Na+∶PbGa2S4晶体元件的吸收光谱测试以及Judd-Ofelt理论计算数据,通过互易法计算出各发光能级间的荧光吸收与发射截面.通过测试与计算得到的数据,数值模拟了采用1.3μm和1.7µm泵浦源直接抽运Dy3+,Na+∶PbGa2S4晶体产生4.3 μm中红外激光的实验方案.计算分析了激光功率、增益和吸收系数在晶体内的空间分布,分析比较了泵浦光功率、元件长度和输出镜反射率对输出功率的影响.模型中在光路中引入2.9μm级联激光振荡,以此抽运因为4.3 μm发光堆积在能级6H13/2上的粒子数,发现其可以有效降低能级6H11/2到6H13/2跃迁的自终止效应,提高激光输出功率.计算结果表明:采用1.3 μm和1.7µm泵浦源,当功率都为4 W时,最大的输出功率分别为103 mW和315 mW,斜率效率可达到2.8％和8.0％.数值模拟的结果对下一步晶体元件的改良加工以及光路搭建参数的选取提供了一定的指导意义.
Abstract
According to the absorption spectra of Dy3+,Na+∶PbGa2S4 crystal elements,as well as the theoretical calculations obtained from Judd-Ofelt analysis,we derive partial fluorescence absorption and emission cross sections.For energy levels that cannot be directly measured,we employ the reciprocal method to calculate their respective absorption cross-section and emission cross-section.Combing the experimental measurements and the calculation results,the experimental setup,which can generate a 4.3-μm mid-infrared laser through directly pumping dysprosium and Dy3+,Na+∶PbGa2S4 crystals by 1.3 μm and 1.7 μm diode lasers,is investigated through numerical simulation.The spatial distributions of laser power,gain coefficient,and absorption coefficient within the crystal are obtained through numerical calculation.Furthermore,the effects of pumping power,crystal length,and output mirror reflectance on laser performance are analyzed.In this model,a 2.9-μm laser oscillation is introduced in the optical path and the changes of output power before and after introduction are observed.Our results demonstrate that the introduction of 2.9-μm laser oscillation effectively facilitates the particle number transfer from the 6H13/2 level to the ground state 6H15/2,thereby reducing the self-terminating phenomenon during the transition between the 6H11/2 and 6H13/2 levels,and enhancing both output power and slope efficiency of the laser system.Numerical results indicate that maximum power output for the 1.3μm diode laser pumping is achieved at 103 mW with a pumping threshold of 12 mW and a slope efficiency of 2.8％,while for the 1.7-μm diode laser pumping,the power output reaches up to 315 mW with a pumping threshold of 46 mW and a slope efficiency of 8％.Additionally,the calculation results show that the optimal crystal length is 17 mm for the 1.3 μm diode laser pumping,and 32 mm for the 1.7 μm diode laser pumping.Finally,the best reflectance value for the output mirror is 0.92.These numerical results are of great significance for guiding the crystal processing and the selection of optical path structure parameters.
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