极紫外光学频率梳的频谱拓展与功率提升(特邀)  

Spectrum Expansion and Power Enhancement of an Extreme Ultraviolet Optical Frequency Comb(Invited)

作　　者：张恒之 朱穆峰 肖峥嵘 华林强 许松坡 刘阳妮 柳晓军 Zhang Hengzhi;Zhu Mufeng;Xiao Zhengrong;Hua Linqiang;Xu Songpo;Liu Yangni;Liu Xiaojun(State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430071,Hubei,China;University of Chinese Academy of Sciences,Beijing 100049,China;Chongqing College of Electronic Engineering,Chongqing 401331,China)

机构地区：[1]中国科学院精密测量科学与技术创新研究院波谱与原子分子物理国家重点实验室,湖北武汉430071 [2]中国科学院大学,北京100049 [3]重庆电子工程职业学院,重庆401331

出　　处：《光学学报》2024年第17期291-298,共8页Acta Optica Sinica

基　　金：国家自然科学基金(U21A20435,12393823,92265206);中国科学院稳定支持基础研究领域青年团队计划(YSBR-055)。

摘　　要：频谱覆盖范围和输出功率是衡量极紫外光学频率梳(简称“极紫外光梳”)性能和实现其广泛应用的重要参考依据。本研究利用固体芯光子晶体光纤展宽驱动光光谱,采用啁啾镜精确补偿色散,以实现驱动光源脉宽的压缩,进而提升飞秒共振增强腔内峰值功率,达到拓展极紫外光梳频谱覆盖范围与提升其输出功率的目的。最终实现了重复频率约为80 MHz、平均功率约为50 W、脉宽约为56 fs的驱动光脉冲,以及高达9.3×10^(13)W/cm^(2)的峰值光强。结合Xe、Kr以及Ar的高次谐波产生过程,实现了最短波长约为30 nm(对应35阶谐波)的极紫外光梳,其61 nm(对应17阶谐波)处的耦合输出功率可达9.3μW。本研究为后续利用极紫外光梳实现少电子原子分子的精密光谱测量奠定了窄线宽光源方面的基础。Objective Extreme ultraviolet(XUV)optical frequency combs have significant applications in precision measurement physics and ultrafast science.They are essential tools for high-resolution XUV spectroscopy,such as precise spectroscopic measurements of few-electron atomic or ionic systems(e.g.,He+and Li+),which probe the limits of quantum electrodynamics(QED)theory.Combining XUV frequency comb spectroscopy with thorium-229 nuclear transition could advance the development of a novel optical clock-the nuclear optical clock.In ultrafast science,utilizing the high-order harmonic generation(HHG)process inherent in XUV frequency comb generation reveals ultrafast phenomena under conditions of extremely high repetition rates(>50 MHz).In addition,XUV frequency combs provide high-repetition-rate and low-flux XUV light sources,which facilitate time-and angle-resolved photoelectron spectroscopy studies.The spectral coverage and output power are critical parameters for assessing the performance of an XUV comb and realizing its broad applications.Extending its spectral coverage and increasing the output power are core objectives in developing XUV combs and in the present study.Methods To optimize the key parameters of an XUV comb,we enhance the peak power within the femtosecond enhancement cavity(fsEC)by compressing the pulse duration of the driving laser source.Firstly,we utilize a solid-core photonic crystal fiber for spectral broadening.The driving laser,assisted by our self-constructed beam stabilization system,is coupled into the solid-core photonic crystal fiber.The fiber’s photonic bandgap structure enables high-efficiency transmission of specific wavelengths through the solid fiber core,resulting in spectral broadening via the self-phase modulation(SPM)effect.We then use multiple chirped mirrors for compressing pulse duration.The multilayer structure of the chirped mirrors ensures precise dispersion compensation by providing different group delays for different frequency components.Finally,in the high-order harmonic ge

关 键 词：超快光学 极紫外光学频率梳 飞秒共振增强腔 脉宽压缩 

分 类 号：O437[机械工程—光学工程]