“9”字腔锁模的1.5µm高重频飞秒光纤激光器

1.5µm High Repetition Rate Femtosecond Fiber Laser Based on Figure-9 Mode-locking

高重频飞秒激光在医疗、成像、微波产生、微纳加工等领域有着重要应用。随着技术的发展,人们对1.5µm飞秒激光器的重复频率、光谱、脉宽、稳定性等也提出了更高的要求。为了得到高重复频率、宽光谱、窄脉冲、高稳定性的1.5µm飞秒光纤激光器,设计了一种基于“9”字腔锁模的1560 nm高重频飞秒光纤激光器,利用Semi-wdm和自主设计的双波片架等机械器件,搭建并实现347.4 MHz高重复频率脉冲序列输出,在2100 mA 980 nm泵浦下实现锁模自启动。锁模激光中心波长为1560 nm,光谱半高全宽度最宽为42 nm,激光脉宽最窄可以到58 fs,功率最高可到96.4 mW,单脉冲能量大于0.277 nJ。在光斑分析仪上测到,激光光斑圆度整体优于90%,具有优良的光束质量。输出的脉冲激光,偏振消光比大于25 dB。经测试,激光器具有良好的锁模自启动特性和稳定性,为以后在激光医疗、光学频率梳、成像等应用提供了可能。

High repetition rate femtosecond fiber laser has important applications in medical treatment,imaging,microwave generation,micronano machining and so on.With the development of technology,higher requirements are put forward for the repetition rate,spectrum,pulse width and stability of 1.5µm femtosecond laser.In order to obtain a 1.5µm femtosecond fiber laser with high repetition rate,wide spectrum,narrow pulse width and high stability,a 1560 nm high repetition rate femtosecond fiber laser based on figure-9 mode-locking is designed.Using Semi-wdm and the self-designed double-wave plate and other mechanical devices,the output of 347.4 MHz high repetition rate pulse sequence is constructed and realized,and the mode-locking self-starting is realized under the 2100 mA 980 nm pump.The central wavelength of the mode-locked laser is 1560 nm and the maximum spectral half-height full width is 42 nm.The pulse width can be as narrow as 58 fs,and the power can be as high as 96.4 mW.The signal pulse energy is greater than 0.277 nJ.Measured on the spot analyzer,the roundness of the laser spot is better than 90%,and it has excellent beam quality.The polarization extinction ratio of pulsed laser is greater than 25 dB.The test results show that the laser has good mode-locking self-starting characteristics and stability,which provides possibilities for future applications in laser medicine,optical frequency comb,and imaging.