搭建了基于半导体可饱和吸收镜（SESAM）锁模的全保偏皮秒脉冲光纤激光器，对比分析了以多量子阱和体材料作为可饱和吸收层的SESAM对锁模激光器输出特性的影响。实验结果表明，多量子阱和体材料SESAM均可实现稳定的自启动锁模。随着量子阱周期数的增加，SESAM调制深度增大，激光器输出脉冲宽度变窄，具有更高的输出功率和更大的锁模区间。但量子阱周期数过高的SESAM具有较大非饱和损耗，使得相同泵浦功率下输出功率降低。在相同调制深度下，体材料SESAM的非饱和损耗偏大，降低了输出功率和光光转化效率，但对脉冲的窄化作用更显著。SESAM对输出脉冲的波长和光谱宽度无显著影响，主要受光纤布拉格光栅（FBG）控制。本文对SESAM的设计与选型具有一定指导意义。

Spatiotemporal shaping of ultrashort pulses is pivotal for various technologies, such as burst laser ablation and ultrafast imaging. However, the difficulty of pulse stretching to subnanosecond intervals and independent control of the spatial profile for each pulse limit their advancement. We present a pulse manipulation technique for producing spectrally separated GHz burst pulses from a single ultrashort pulse, where each pulse is spatially shapable. We demonstrated the production of pulse trains at intervals of 0.1 to 3 ns in the 800- and 400-nm wavelength bands and applied them to ultrafast single-shot transmission spectroscopic imaging (4 Gfps) of laser ablation dynamics with two-color sequentially timed all-optical mapping photography. Furthermore, we demonstrated the production of pulse trains containing a shifted or dual-peak pulse as examples of individual spatial shaping of GHz burst pulses. Our proposed technique brings unprecedented spatiotemporal manipulation of GHz burst pulses, which can be useful for a wide range of laser applications.

论证了单晶体光参量放大（OPA）过程在特定边界条件下满足频域宇称-时间（PT）反对称性。归一化的数值求解结果显示，OPA系统PT对称阈值点附近呈现增益跃变性质。对于存在位相失配的OPA，通过实时调控泵浦光强，即可控制系统PT对称性，论文基于相位失配OPA中可超快调控PT对称性的特性构建了超快光开关，一方面光开关与周期性幅度调制的泵浦光联合使用，可直接将连续激光转换为超短脉冲序列输出；另一方面，构建的光开关也可用于脉冲激光再压缩，有望用于中红外波等长波段超短种子源。论文提出的基于超快光开关直接产生超短脉冲序列的方案，由于不需要光学谐振腔，易于实现大于10 GHz的超高重复频率。

Ultrashort pulses at 920 nm are a highly desired light source in two-photon microscopy for the efficient excitation of green fluorescence protein. Although Nd^{3 +} -doped fibers have been utilized for 920-nm ultrashort pulse generation, the competitive amplified spontaneous emission (ASE) at 1.06 μm remains a significant challenge in improving their performance. Here, we demonstrate a coordination engineering strategy to tailor the properties of Nd^{3 +} -doped silica glass and fiber. By elevating the covalency between Nd^{3 +} and bonded anions via sulfur incorporation, the fiber gain performance at 920 nm is enhanced, and 1.06-μm ASE intensity is suppressed simultaneously. As a result, the continuous-wave laser efficiencies and signal-to-noise ratio at 920 nm by this fiber are significantly enhanced. Importantly, the stable picosecond pulses at 920 nm are produced by a passive mode-locking technique with a fundamental repetition rate up to 207 MHz, which, to the best of our knowledge, is the highest reported repetition rate realized by Nd^{3 +} -doped silica fibers. The presented strategy enriches the capacity of Nd^{3 +} -doped silica fiber in generating 920-nm ultrashort pulses for application in biophotonics, and it also provides a promising way to tune the properties of rare-earth ion-doped silica glasses and fibers toward ultrafast lasers.