高功率激光驱动器中多采用谱色散匀滑(SSD)的束匀滑技术,而SSD中的相位调制常使用等幅相位调制。为进一步改善匀滑效果,提高动态调控能力,提出一种特异性相位调制技术,即采用调制深度为时变函数的特异性调制方式来获得光谱宽度可随时间变化的信号输出。基于相位调制的频谱理论,分析了特异性相位调制后的激光频谱特性。利用任意波形发生器(AWG)整形输出的特定相位调制信号开展实验研究,通过改变AWG输出两路电信号的相对时间差,得到250 ps的信号光在3 ns内不同时间点的调制光谱,实验结果与理论模拟结果一致。这种调制方式可以完成光谱宽度的连续实时调控,这对于高功率激光驱动器的激光参数控制中实现动态的光谱色散匀滑有着重要应用。

采用光强度调制鉴相方案,使用直接数字频率合成器(DDS)和激光驱动器产生频率稳定的调制激光,注入待测光路,在待测光路后进行光电转换和放大,引入参考本振信号作为混频器相位参考信号,利用混频器测量待测光路信号与参考本振信号的相位差,获得光路延时信息。主要特点如下:提出了在本振信号链路三段移相的差分式检测方法,优化了鉴相点,提高了测量精度;采用单段短时两相位点测量模式,有效降低了光源功率波动、光路中光强波动、光电探测及放大电路增益波动、温度变化导致相位差漂移等带来的测量误差;在每个相位点多次测量采样,根据测量的平均值计算相位差,推导时间差。详细分析了测量电压和被测时延之间的函数关系,分析了影响测量精度的因素,构建验证系统,完成了实验验证。实验结果表明:本方案在4 ns的时延内的测量精度可达1 ps,大幅提升了现有高功率激光装置的同步测量精度。

在使用高功率激光装置进行物理实验时,高精度时间同步的时标系统是实现物理过程精确诊断的必要条件。为了满足物理实验需求,该系统采用任意波形发生器输出信号时分复用结合高速电光调制的技术方案,同源产生了主激光、时标光、电时标和高精度触发信号等多路信号。时标系统共可输出532,355,266 nm三种波长共10路梳状时标光信号及8路梳状电时标信号、两路快前沿高幅值触发信号。时标信号与主激光时间同步抖动峰峰值达到12.80 ps,梳状时标光信号脉冲周期峰值抖动为6.40 ps,接近目前采用的测量系统极限。完成了时标系统在高功率激光装置中的应用演示,满足了诊断设备应用要求;对条纹相机不同扫程进行时间基准标定实验,可有效校准相机大扫程的时间误差。

采用单偏振光纤远程传输待测光, 结合上升沿与顶端波形分离处理的时域恢复算法, 提出一种远程精确测量激光时间功率曲线的方法, 并对高功率激光驱动器前端系统中1 053 nm脉冲光的时间功率曲线进行了远程测量实验.结果表明, 该方法有效避免了幅频调制对激光脉冲时间功率曲线测量的影响, 获得了高保真的远程传输时间波形, 引入的误差在每1 ns范围内小于0.8%, 可用于高功率激光系统的时间功率曲线远程集中测量.

提出应用于激光脉冲高精度时间同步测量的技术方案。利用时间数字转换技术, 精确测量激光脉冲相对延时, 测量精度可小于10 ps(峰谷值)。为满足测量电路对脉冲宽度的要求, 设计针对短脉冲激光的电脉冲展宽模块, 可以将百皮秒量级的电脉冲展宽至纳秒量级, 引入时间抖动的均方根值小于2 ps。该测量方案实现了实时高精度时间同步测量, 可以作为时间同步反馈补偿的实时监测使用。

Without discrete optical components influencing the fiber format, all-fiber mode-locked laser has tremendous potential practical applications due to its advantages of better stability, alignment free, and better compaction. All-fiber laser mode-locked by nonlinear polarization evolution (NPE) can obtain good performances in terms of pulse duration and spectrum. But the effective saturable absorption mirror can be overdriven at high peak power, which leads to multiple pulses, limiting the output pulse energy. And there is a trade-off between avoiding overdriving the NPE and ease of self-starting. In addition, the polarization of the pulse propagating in a long fiber is so sensitive to the environment vibration that it is difficult to implement a stable lone-time operation. All-fiber ring laser mode-locked by NPE alone is analyzed and realized. The simulation results show that even a polarization vibration of /38 can break the mode-locking completely. Experimentally, after carefully adjusting, singlepulse mode-locking is achieved with the spectrum centered at 1053.4 nm and a maximum pulse energy of 82 pJ. But the output parameters change continually during operating. After 60 min, the mode-locking is broken. The conclusion is obtained that instability and unreliability of self-starting are inevitable for such a laser. Here, we show significant improvements of the pulse energy, operating stability, and self-starting reliability from an all-fiber Yb-doped mode-locked fiber laser. The laser is mode-locked by NPE combined with chirped pulse spectral filtering (CPSF). In order to easily self-start and stabilize mode locking, a spectral filter is employed in the all-normal group velocity dispersion NPE cavity to provide additional amplitude modulation. Combined effects of NPE and CPSF result in desirable pulse output, desirable operating stability, and reliable self-starting simultaneously. Stable mode-locking centered at 1053 nm is achieved with a 3 dB spectral bandwidth of 9.1 nm and pulse duration of 17.8 ps. The average output power is 66.9 mW at a repetition rate of 15.2 MHz, corresponding to a pulse energy of 4.25 nJ. Especially, high operating stability and easily one-button self-starting are achieved simultaneously. The fluctuations of output parameters including pulse energy, pulse duration, and spectrum are within 0.3% during 150-min operation. Self-starting reliability is tested. The testing time lasts two weeks. During the two weeks, the laser is turned off and turned on 48 times by using a power supplying button, without any adjustment. And the re-turned on intervals change randomly. Each time, the mode-locking can start itself. The repeatabilities of output parameters including pulse energy, pulse duration, and spectrum are within 0.55%.

A method of controlling spectrum based on all-fiber multi-pass phase modulation is demonstrated experimentally and theoretically. Numerical simulation results indicate that modulation times, modulation depth, shape and width of the modulation signal and synchronized precision between optical pulse and modulation signal have influences on the central wavelength, bandwidth as well as the shape of the output spectrum. The input spectrum with bandwidth of 0.03 nm is broadened into 2.238 nm after multi-pass phase modulation, and the experimental results match well with the simulation results. The corresponding relationship between the modulation signal waveforms with different phases and the output spectra is obtained, and the feasibility of the spectral characteristics control is verified.

提出应用于神光Ⅱ装置中的拍瓦短脉冲与主压缩脉冲高精度同步方案。在该方案中，通过与门技术实现了锁模激光器输出的短脉冲序列与主激光总控触发信号时间的初步锁定，该技术是实现惯性约束核聚变高功率激光装置中长短脉冲精确同步的关键。由总控系统的触发信号作为与门中可编程现场门阵列(FPGA)电路的触发信号，锁模激光器输出的百皮秒激光脉冲通过光电转换放大,并由同步展宽装置进行处理之后，作为FPGA电路的时钟信号，能够实现系统主激光门脉冲触发信号与短脉冲激光之间均方根值为26.3 ps的同步精度，这一技术可有效提升装置中同步系统的稳定性。

提出了一种基于全光纤多程相位调制的光谱控制方法，并对其进行了理论模拟和实验研究。理论模拟结果表明，调制次数、调制深度、调制信号形状和宽度以及调制信号和光脉冲的时间同步均会对输出光谱的中心波长、光谱宽度和形状产生影响。在实验上对光谱宽度为0.03 nm的注入信号进行多程相位调制，得到了带宽为2.238 nm的输出光谱，实验结果与理论模拟结果相符合。并从实验上研究了不同相位调制信号波形与输出光谱的对应关系，验证了通过控制调制信号波形进行光谱特性控制的可行性。

A method to broaden the spectrum by direct phase modulation is proposed. The effects on the spectrum of modulation depth,modulation signal width, synchronization precision and different signal forms are investigated by numerical simulations. The results show that deeper modulation and more narrow modulation signal width lead to a more obvious effect and a broader spectrum of single modulation; different modulation signal widths require different synchronization precisions, and the narrow signals need a high-precision synchronization; compared to the parabolic signal, sinusoidal signal can lead to an obvious frequency modulation to amplitude modulation, which can bring down the compressibility and the signal to noise ratio. The experiment results of the central wavelength match well the simulation results.