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摘要:
面向极紫外光刻光源对高功率、高光束质量CO2种子激光的应用需求,本文开展了基于射频波导体制的CO2激光放大技术研究。一方面,分析了射频波导放大器的静态插入损耗与输出光束质量随入射光参数的变化关系,确定了最佳模式匹配参数。另一方面,建立了多级射频波导放大仿真模型,理论计算了工作气压与放电泵浦功率等参数对放大倍率的影响规律,在实验上,引入增益介质调控技术,实现了激光系统放大性能的优化。实验结果表明:在2.5 m的波导长度下,传输效率达到了91.4%,输出光束在水平方向与竖直方向上的光束质量因子分别为1.03与1.05;二级射频波导放大系统的总放大倍率达到了68倍,最终获得了重复频率50 kHz、脉冲宽度20 ns、平均功率17.1 W、高光束质量的CO2激光输出。
Abstract:Toward the application demand for high-power, high-beam-quality CO2 seed lasers in extreme ultraviolet lithography light sources, the amplification characteristics were investigated based on a RF waveguide architecture. The static insertion loss and output beam quality of the RF waveguide amplifier were measured as function of incident beam parameters. A numerical model was developed to simulate the multi-stage RF waveguide amplification and to evaluate the effects of the gas pressure and the discharge pumping power on gain. The technology of regulating with gain medium was implemented to optimize the amplification performance in the experiment. Experimentally, optimal mode-matching conditions were identified with a waveguide length of 2.5 m, yielding a transmission efficiency of 91.4%. The beam quality factors of the output beam in the horizontal and vertical directions were 1.03 and 1.05, respectively. An overall gain factor of 68× was achieved in a dual-stage RF waveguide amplifier. The system delivered CO2 laser emission with a repetition rate of 50 kHz, a pulse duration of 20 ns, and an average output power of 17.1 W, satisfying the design criteria and demonstrating its suitability for high-power, high-beam-quality seed laser applications.
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Key words:
- CO2 laser /
- master oscillator power amplifier /
- mode-matching /
- gain medium regulation
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图 4 光束质量因子测量结果。(a)光束质量因子随入射光束直径的变化关系;(b)入射直径为2 mm时测量结果,插图为光束强度分布图
Figure 4. Measurement results of the beam quality factor. (a) Relationship between the beam quality factor and the diameter of the incident beam; (b) Measurement results when the incident diameter is 2 mm, with the inset showing the beam intensity distribution
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