We propose a spatially chirped quasi-phase-matching (QPM) scheme that enables ultrabroadband second-harmonic-generation (SHG) by using a fan-out QPM grating to frequency-convert a spatially chirped fundamental wave. A “zero-dispersion” 4f system maps the spectral contents of ultrabroadband fundamental onto different spatial coordinates in the Fourier plane, where the fundamental is quasi-monochromatic locally in picosecond duration, fundamentally canceling high-order phase mismatch. A fan-out QPM grating characterized by a linear variation of the poling period along the transverse direction exactly supports the QPM of the spatially chirped beam. We theoretically demonstrate the SHG of an 810-nm, 12.1-fs pulse into a 405-nm, 10.2-fs pulse with a conversion efficiency of 77%.

在间接驱动激光聚变研究中，平响应X射线二极管是X射线辐射能流测量的主要探测器。为了获得理想的平响应效果，采用传统方法需要花费大量时间优化二极管的复合滤片参数，为此引入了粒子群优化算法，将之用于平响应X射线二极管复合滤片参数的优化，该方法可更快捷、更准确地得到复合滤片的优化参数。提出了新的滤片组合方式，并优化其平响应特性，得到了比传统滤片组合更优的参数配比。该项工作为平响应X射线二极管复合滤片参数的寻优提供了一种更高效的方法。

Spatiotemporal mode-locking creates great opportunity for pulse energy scaling and nonlinear optics research in fiber. Until now, spatiotemporal mode-locking has only been realized in normal-dispersion dissipative soliton and similariton fiber lasers. In this paper, we demonstrated the first experimental realization of a spatiotemporally mode-locked soliton laser in mid-infrared fluoride fiber with anomalous dispersion. The mode-locked fluoride fiber oscillator directly generated a record pulse energy of 16.1 nJ and peak power of 74.6 kW at 2.8 μm wavelength. This work extends the spatiotemporal mode-locking to soliton fiber lasers and should have a wide interest for the laser community.

Parametric interaction allows both forward and backward energy transfers among the three interacting waves. The back-conversion effect is usually detrimental when unidirectional energy transfer is desired. In this theoretical work, we manifest that the back-conversion effect underpins the direct generation of the picosecond pulse train without the need for a laser resonator. The research scenario is an optical parametric amplification (OPA) that consists of a second-order nonlinear medium, a quasi-continuous pump laser and a sinusoidal amplitude-modulated seed signal. The back-conversion of OPA can transfer the modulation peaks (valleys) of the incident signal into output valleys (peaks), which inherently induces spectral sidebands. The generation of each sideband is naturally accompanied with a phase shift of ±π. In the regime of full-back-conversion, the amount and amplitude of the sidebands reach the maximum simultaneously, and their phase constitutes an arithmetic sequence, leading to the production of a picosecond pulse train. The generated picosecond pulse train can have an ultrahigh repetition rate of 40 GHz or higher, which may facilitate ultrafast applications with ultrahigh speed.

In strong-field physics experiments with ultraintense lasers, a single-shot cross-correlator (SSCC) is essential for fast optimization of the pulse contrast and meaningful comparison with theory for each pulse shot. To simultaneously characterize an ultrashort pulse and its long pedestal, the SSCC device must have both a high resolution and a large temporal window. However, the resolution and window in all kinds of single-shot measurement contradict each other in principle. Here we propose and demonstrate a novel SSCC device with two separate measurement channels: channel-1 for the large-window pedestal measurement has a moderate resolution but a large window, while channel-2 for the ultrashort pulse measurement has a small window but a high resolution; this allows the accurate characterization of the pulse contrast in a single shot. A two-channel SSCC device with a 200-fs resolution and 114-ps window has been developed and tested for its application in ultraintense lasers at 800 nm.

Optical parametric chirped-pulse amplification is inevitably subject to high-order spatial chirp, particularly under the condition of saturated amplification and a Gaussian pump; this corresponds to an irreversible spatiotemporal distortion and consequently degrades the maximum attainable focused intensity. In this paper, we reveal that such spatial chirp distortion can be significantly mitigated in quasi-parametric chirped-pulse amplification (QPCPA) with idler absorption. Simulation results show that the quality of focused intensity in saturated QPCPA is nearly ideal, with a spatiotemporal Strehl ratio higher than 0.98. As the seed bandwidth increases, the idler absorption spectrum may not be uniform, but the Strehl ratio in QPCPA can be still high enough due to stronger idler absorption.

提出并研究了一种宽带、大量程、方向可控的超短脉冲群速度调控方法。利用级联光参量放大，将泵浦光时域的线性强度调制转移至啁啾信号光频域的线性位相调制，压缩后信号光脉冲将获得延时或提前。通过调控泵浦时域强度调制的斜率大小和符号，可对信号光群速度调控的量程和方向进行灵活操控。级联光参量放大过程不需要满足位相匹配，响应带宽很大，原理上支持周期量级脉冲的群速度调控。分别研究了锯齿型和高斯型脉冲泵浦的级联光参量放大过程，演示验证了该方法的调控效果。该方法可在常规非线性晶体中实施，具备应用价值。

提出了一种可同时实现高效率和大带宽的频率上转换技术，可将高能钕玻璃基频激光（波长1 054 nm）高效率地转换为紫蓝光波段的宽带2.5倍频激光（波长421.5 nm）.将窄带钕玻璃的倍频激光与中心波长为2 100 nm的宽带中红外激光以能量比4∶1进行非线性和频，并通过非共线构型实现位相匹配和群速度匹配，实验产生了能量为12.4 J、带宽为10.4 nm（相对带宽大于2%）的宽带2.5倍频激光.实验结果能够支撑紫蓝光波段百太瓦强激光的产生，为未来开发短波长的超短超强激光提供借鉴.