【作者】 秦鹏；

【导师】 王清月； 宋有建；

【作者基本信息】 天津大学 ， 光学工程， 2016， 博士

【摘要】 光纤飞秒激光器输出的超短脉冲序列具有极低的时间抖动,同时结构紧凑,价格低廉,对工作环境不敏感,易于操作和维护,是前沿应用中低噪声脉冲激光源的首选。随着飞秒激光器噪声理论的发展,相关领域的研究者对时间抖动的特点及影响有了更加深入的认识。平衡光学互相关方法的出现,使得光纤飞秒激光器时间抖动在实验中的精确测量和优化成为了可能。本论文以降低掺镱光纤飞秒激光器的量子极限时间抖动水平为目的,围绕激光器腔内动力学过程对输出脉冲序列时域位置的影响进行了一系列理论和实验的研究,并在此基础上进行了基于掺镱光纤飞秒激光器的飞行时间法绝对距离测量和低抖动时钟信号提取研究。论文主要内容概括如下:一、从非线性薛定谔方程和金兹伯格-朗道方程入手,结合准三能级增益介质中放大自发辐射噪声的半经典理论模型,建立了计算掺镱单模光纤飞秒激光器时间抖动水平的数值模型。在此基础上,通过改变飞秒激光器腔内净色散、滤波情况及滤波器带宽等主要参数,结合不同状态下脉冲在腔内的演化过程,对影响飞秒激光器时间抖动水平的主要因素进行了系统地计算与分析。二、在实验中搭建了基于平衡光学互相关方法的时间抖动测量系统,以低时间抖动的呼吸孤子锁模飞秒激光器为参考,通过将待测激光器的重复频率同步到参考激光器,对前者在不同参数下的时间抖动水平进行了系统地测量,分辨率达到了阿秒量级。在此基础上,通过在腔内加入带宽7.7 nm的窄带光谱滤波器,实现了放大自发辐射噪声间接耦合时间抖动成分的抑制,将光纤飞秒激光器在不同净色散下的时间抖动水平稳定在0.6 fs~1.1 fs的范围内,相应的积分区间为[10kHz,10 MHz]。三、以单台掺镱光纤飞秒激光器为光源,结合平衡光学互相关系统,搭建了基于迈克尔逊干涉仪结构的飞行时间法任意长绝对距离测量系统,并通过将激光器腔长锁定到待测距离的整数倍分之一来获得待测距离信息。在实验室环境内,对约为52 m的待测距离进行了测量,在1 s的平均时间内获得了12 nm的测量精度。当待测距离为零时,上述系统在1 s平均时间内的极限精度为4 nm。四、搭建了基于低时间抖动飞秒激光器和平衡光学互相关的高精度时钟信号接收系统,以参考激光器输出的脉冲序列模拟低噪声的“主时钟”信号,在本地进行了低抖动时钟信号提取的原理性演示实验。在优化接收系统中飞秒激光器腔内色散和锁模状态的基础上,通过电光调制器进一步抑制了激光器时间抖动引入的残余时间误差,锁定带宽达到了400 kHz。在[1 Hz,10 MHz]的频率区间内,整个信号接收系统的分辨率达到了13 as,其相对于“主时钟”信号的残余时间误差降低到了109 as,在1μm波段对应载波周期的1/30。更多还原

【Abstract】 Femtosecond fiber lasers exhibit inherently low timing jitter.They are compact,low in price,insensitive to environmental perturbations,easy to operate and maintain,and thus an ideal choice for pulsed laser source in advanced applications.Along with the development of the noise theory in femtosecond lasers,properties and corresponding impacts of timing jitter have been better understood in relevant fields.The balanced optical cross-correlation method has made it possible to characterize and optimize the timing jitter in femtosecond lasers with unprecedented resolution.This thesis is aimed at quantum-limit timing jitter optimization in femtosecond Ytterbium-doped fiber lasers,and the impact of intra-cavity dynamics is systematically studied with both numerical simulation and experimental setups.Furthermore,time-of-flight metrology and low-jitter timing signal extraction experiments based on femtosecond fiber lasers are carried out.This thesis is basically structured as follows:1.Numerical model of timing jitter characterization in femtosecond Yb-fiber lasers is developed based on the nonlinear Schr?dinger equation,the Ginzburg-Landau equation,and the semi-classical amplified spontaneous emission noise model in the quasi-three-level gaining medium.The timing jitter level and corresponding leading influence factors in conditions with various intra-cavity net dispersion and filter parameters are simulated and then analyzed according to the intra-cavity dynamics of each condition.2.A timing jitter characterization system is built upon the balanced optical cross-correlation method.The reference laser is a femtosecond Yb-fiber laser operating in the stretched-pulse regime and the laser under test has the same structure with varying net dispersion and filtering conditions.By synchronizing the repetition rate of the laser under test to the reference,the timing jitter can be characterized with attosecond resolution.Upon insertion of a 7.7-nm narrow band-pass filter,the timing jitter component indirectly coupled from the amplified spontaneous emission is sufficiently suppressed.When integrated from 10 kHz to 10 MHz,the jitter level with different net dispersion is stabilized between 0.6 fs and 1.1 fs.3.The jitter-stabilized femtosecond Yb-fiber laser is utilized in a time-of-flight metrology system with Michelson interferometer structure.Armed with the attosecond resolution of the balanced optical cross-correlation method,the timing offset between target-reflected pulses and reference pulses is precisely characterized and tightly locked to zero.The distance under test can then be calculated with the repetition rate information of the femtosecond laser.A 52 m free space distance is measured in laboratory environment,and the resolution is 12 nm in 1 s averaging time.When the distance under test is zero,the resolution limit of the metrology system reaches 4 nm in 1 s averaging time.4.A timing reception system is built upon a femtosecond fiber laser with ultra-low timing jitter and a balanced optical cross-correlation system with attosecond-level timing resolution.Then,a demonstrative low-jitter timing signal extraction experiment is carried out,together with the reference laser as the master clock signal.Besides quantum-limit timing jitter suppression,the residual timing error between the master clock and the reception system is further suppressed via an intra-cavity electro-optic modulator.The locking bandwidth is increased to 400 kHz,and the timing resolution of the entire reception system is 13 as,when integrated from 1 Hz to 10 MHz.The lowest residual timing error between the master clock and the reception system is measured to be 109 as,which is less than one-thirtieth of the carrier cycle in the 1 micron range.更多还原