基于β⁃BBO晶体级联倍频的深紫外可调谐激光数值模拟  

Numerical Simulation in Deep⁃Ultraviolet Tunable Laser Based on Cascaded Frequency Doubling inβ⁃BBO Crystals

作　　者：张一凡[1] 张泽亮 齐鹏飞[1,2] 孙陆 张楠[1,2] 林列 刘伟伟[1,2] Zhang Yifan;Zhang Zeliang;Qi Pengfei;Sun Lu;Zhang Nan;Lin Lie;Liu Weiwei(Institute of Modern Optics,Eye Institute,Nankai University,Tianjin 300350,China;Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology,Tianjin 300350,China;Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network,Tianjin 300350,China)

机构地区：[1]南开大学现代光学研究所眼科研究所,天津300350 [2]天津市微尺度光学信息技术科学重点实验室,天津300350 [3]天津市光电传感器与传感网络重点实验室,天津300350

出　　处：《中国激光》2024年第18期47-53,共7页Chinese Journal of Lasers

基　　金：国家自然科学基金(12074198)。

摘　　要：紫外光具有短波长、高光子能量等优点,然而200 nm以下的深紫外激光很难直接产生,且常用的光学材料对深紫外激光都有很高的吸收。利用非线性频率转换方法可以获得深紫外宽带光源,但现有的方法无法兼顾高效率与宽调谐范围。通过模拟计算,验证了级联β-BBO晶体可以实现高效率、宽范围的深紫外光转换。在激光器输出波长为650~1050 nm、基频功率为3.5 W、重复频率为80 MHz、脉冲宽度为150 ps的条件下,级联β-BBO晶体四次谐波可实现186.0~262.5 nm的深紫外光输出,在227 nm处的最大转换效率可达28.6%,满足宽调谐范围与高转换效率的要求。Objective Ultraviolet and deep-ultraviolet lasers offer short wavelengths and high photon energies.Thus,they are applicable to diverse fields such as fine processing,damage detection,and atomic spectral analysis.Deep-ultraviolet light-generation methods include synchrotron radiation,gas discharge lamps,excimer lasers,free-electron lasers,and nonlinear frequency conversion.Nonlinear frequency conversion uses nonlinear optical crystals to realize the output of deep-ultraviolet light via frequency doubling and frequency summing.Compared with other methods,it offers the advantages of low cost,simple structure,and continuous tuning.However,deep-ultraviolet lasers below 200 nm cannot be easily generated directly.Meanwhile,commonly used optical materials readily absorb deep-ultraviolet lasers,and the existing methods cannot offer both high efficiency and a wide tuning range.Methods By analyzing the coupled wave equation,the conversion efficiencies of the second,third and fourth harmonics in cascadedβ-BBO crystals are discussed herein.The efficiency of nonlinear frequency conversion is positively correlated with the nonlinear polarization coefficient,and the nonlinear polarization coefficients of the third harmonic and above are much smaller than that of the second harmonic.Moreover,the shortest phase-matching range of the second harmonic of theβ-BBO crystal is 409.6 nm,and the wavelength of deep-ultraviolet light is halted at 205 nm via direct frequency doubling.Therefore,we perform cascaded second-order nonlinear frequency conversion to achieve a high conversion efficiency for higher harmonics.The fundamental frequency light converges in theβ-BBO crystal through the convex lens,and the second-harmonic wave perpendicular to the polarization direction of the fundamental frequency light is obtained.The two beams are collimated into parallel light using an off-axis parabolic mirror to avoid chromatic and spherical aberrations.After passing through a dual-wavelength waveplate(DWP),the polarization direction of the fundam

关 键 词：非线性光学 深紫外 级联 相位匹配 四次谐波 

分 类 号：O437[机械工程—光学工程]