摘要
设计并搭建了一台具有高重复频率(1 MHz)和低泵浦阈值的飞秒光参量放大器(OPA)。该OPA使用掺镱飞秒光纤激光器进行泵浦,超连续白光作为种子在β-偏硼酸钡(BBO)晶体内被515 nm倍频光放大,实现了650~950 nm范围内的可调谐输出。该OPA的最高转换效率超过20%,功率稳定性可以达到0.22%,压缩后的最短脉宽小于34 fs,当1030 nm波段的脉冲能量为300 nJ时即可实现稳定输出。相比于飞秒光参量振荡器,该系统更加简单稳定;相比常规飞秒光参量放大器,该OPA具有更低的阈值,更适合高重复频率低能量的应用场景,例如多光子成像、显微瞬态吸收光谱等。
Objective High repetition tunable femtosecond light sources are widely used in time-resolved spectroscopy,nonlinear spectrosco py,and bioimaging,and other fields.Optical parametric oscillators(OPO)and optical parametric amplifiers(OPA)are the most frequent equipment to generate tunable femtosecond pulses and the high pump energy in single pass amplification.The threshold of OPA is limited by the minimum pulse energy to create a supercontinuum seed.OPA is usually applied in low repetition and high-energy laser systems.For high repetition system,a high average power pump laser source is required.OPO is applied in high repetition systems,where the threshold is much lower.However,the complex cavity and poor stability constrain its application.OPA with an extremely low threshold is a possible solution for a stable high repetition tunable ultrafast laser source.In earlier studies,various techniques were used to lower the OPA threshold.These techniques fall into two categories:lowering the threshold of seed generation through supercontinuum generation in highly nonlinear optical fibers,and replacing the gain medium with crystals with high nonlinear coefficients like PPLN.The cost of these OPAs is much higher,and the stability is also poor.The article reports a femtosecond OPA design with an extremely low threshold and excellent stability.The threshold of our setup is only 300 n Jat 1030 nm and the long-time stability for 6 h is approximately 0.22%.Our design is possible to replace femtosecond OPOs.Methods To reduce the OPA threshold,a YVO4crystal,the nonlinear refractive index of which is much higher than that o f common crystals,is used as the medium of supercontinuum generation.The calculated threshold of the YVO4crystal is 0.54 MW at 1030 nm.Details of the setup of OPA are shown in Fig.1.The pump laser source is a femtosecond fiber laser with a central wavelength of 1030 nm,a repetition rate of 1 MHz,an average power of 10 W,and a pulse width of 300 fs.The 0.3 W power is used to pump the OPA.The pump laser is split b
作者
曾文
李博瀚
李煌
任泽峰
Zeng Wen;Li Bohan;Li Huang;Ren Zefeng(State Key Laboratory of Molecular Reaction Dymamics,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116650,Liaoning,China;University of Chinese Academy of Science,Beijing 100049,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2022年第23期20-25,共6页
Chinese Journal of Lasers
基金
国家重点研发计划(2018YFA0208700)
国家自然科学基金(22073097)。
关键词
激光器
飞秒光参量放大器
低阈值
可调谐激光
高稳定性
lasers
femtosecond optical parametric amplifier
low threshold
tunable laser
high stability
