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为满足13.5 nm极紫外光刻(EUVL)等领域的应用需求,研制了高重复频率、高稳定性的声光调Q CO2激光器。首先,对声光Q开关的工作原理进行了分析,并实验研究了调制信号电压与衍射效率的关系。接着,研究了调制信号占空比对脉冲波形的影响,通过选择适当的占空比消去了脉冲拖尾。然后,对不同重复频率下的脉冲宽度、功率和脉冲幅值稳定性进行了测量和分析。最后,对激光器的光束指向稳定性进行了测量。实验结果表明:该激光器实现了重复频率1~100 k Hz连续可调的脉冲输出,在重复频率1 k Hz时,获得最小脉冲宽度252 ns和最大峰值功率7 579 W的激光脉冲输出。通过设计以殷钢管为主体的支撑架,使得激光器的脉冲幅值不稳定性小于3%,光束指向稳定性为46.6μrad。该声光调Q CO2激光器可作为高性能种子源在EUVL等领域中得到应用。
In order to meet the application requirements in the field of 13.5 nm EUVL, an acousto-optic Q-switched Q CO2 laser with high repetition rate and high stability has been developed. First of all, the working principle of the acousto-optic Q-switch is analyzed, and the relationship between the modulated signal voltage and the diffraction efficiency is experimentally studied. Next, we study the influence of the duty cycle of the modulated signal on the pulse waveform and eliminate the pulse trailing by selecting the proper duty cycle. Then, the stability of pulse width, power and pulse amplitude under different repetition frequency were measured and analyzed. Finally, the laser beam pointing stability was measured. The experimental results show that the laser achieves a pulse output with a continuously adjustable repetition rate of 1 ~ 100 k Hz and a laser pulse output with a minimum pulse width of 252 ns and a maximum peak power of 7 579 W at a repetition rate of 1 k Hz. By designing the support frame with Invar tube, the pulse instability of the laser is less than 3% and the beam pointing stability is 46.6μrad. The acousto-optic Q-switched Q-switched laser can be used as a high-performance seed source in EUVL and other fields.