基于绝热通道方式的宽带三倍频  

Broadband Third-Harmonic Generation Based on Adiabatic Passage

作　　者：尹立 季来林[1] 刘栋[1] 贺瑞敬 张天雄 冯伟[1] 单翀 赵晓晖 崔勇[1] 高妍琦[1] 隋展 Yin Li;Ji Lailin;Liu Dong;He Ruijing;Zhang Tianxiong;Feng Wei;Shan Chong;Zhao Xiaohui;Cui Yong;Gao Yanqi;Sui Zhan(Shanghai Institute of Laser Plasma,China Academy of Engineering Physics,Shanghai 201800,China)

机构地区：[1]中国工程物理研究院上海激光等离子体研究所,上海201800

出　　处：《光学学报》2024年第19期282-288,共7页Acta Optica Sinica

摘　　要：提出基于绝热通道方式的宽带三倍频方案,采用渐变折射率的非线性晶体,在室温下可同时满足高效频率转换和大接收带宽。理论与模拟表明,宽带529 nm激光与窄带1053 nm激光可高效地通过渐变折射率II类相位匹配磷酸二氢钾(KDP)晶体和频,倍频光几乎完全转换成三倍频光,产生的三倍频带宽接近2 nm(5 THz),转换效率对泵浦光强以及失谐角不敏感,具有极佳的鲁棒特性。Objective Nonlinear frequency conversion,which leverages nonlinear optical effects to transform light from one frequency to another,is a crucial approach for obtaining light across various spectral bands.The efficiency of this conversion depends on satisfying phase-matching conditions,which are typically achieved through either birefringence in nonlinear crystals or quasi-phase matching in periodically poled crystals.These methods ensure coherent interaction among the interacting light waves.In the context of laser-driven inertial confinement fusion research,efforts are focused on minimizing laser-plasma instabilities by shortening laser wavelengths and reducing spatial and temporal coherence.Highpower laser drivers usually employ cascaded frequency conversion schemes to convert narrowband neodymium glass lasers to third harmonics.However,this conventional approach is notably sensitive to fluctuations in pump wavelength,crystal temperature,and beam propagation angles.Consequently,there is a trade-off between achieving high conversion efficiency and maintaining a broad acceptance bandwidth.To reconcile both high efficiency and broad bandwidth,we propose a frequency conversion methodology inspired by adiabatic passage theory,similar to population control in two-level atomic systems.In our study,we implement a gradient deuteration technique to induce a refractive index gradient within the crystal.This approach fulfills the criteria for adiabatic passage and enables efficient broadband frequency conversion.Methods In this study,we use gradient-deuterated KDP crystals and a dual-frequency mixing technique to achieve triply frequency-converted light,combining both broadband and narrowband sources.First,we direct a low-coherence broadband fundamental wave with a central wavelength of 1058 nm and a bandwidth of 10 nm onto the KDP crystal at the phase-matching angle.The 18-mm-thick KDP crystal,which acts as the frequency-doubling crystal,produces broadband frequency-doubled light.Next,we introduce a narrowband fundamental

关 键 词：非线性光学 宽带激光 三倍频 相位匹配 绝热通道 

分 类 号：O437.1[机械工程—光学工程]