On the generation of high-quality Nyquist pulses in mode-locked fiber lasers

Nyquist pulses have wide applications in many areas,from electronics to optics.Mode-locked lasers are ideal platforms to generate such pulses.However,how to generate high-quality Nyquist pulses in mode-locked lasers remains elusive.We address this problem by managing different physical effects in mode-locked fiber lasers through extensive numerical simulations.We find that net dispersion,linear loss,gain and filter shaping can affect the quality of Nyquist pulses significantly.We also demonstrate that Nyquist pulses experience similariton shaping due to the nonlinear attractor effect in the gain medium.Our work may contribute to the design of Nyquist pulse sources and enrich the understanding of pulse shaping dynamics in mode-locked lasers.

Detection of trace metals in water by filamentand plasma-grating-induced breakdown spectroscopy

Filament-and plasma-grating-induced breakdown spectroscopy(F-GIBS)was demonstrated as an efficient technique for sensitive detection of metals in water,where plasma gratings were established through synchronized nonlinear interaction of two noncollinear filaments and an additional filament was generated with another fs laser beam propagating along their bisector.A water jet was constructed vertically to the three coplanar filaments,overcoming side effects from violent plasma explosion and bubble generation.Three distinct regimes of different mechanisms were validated for nonlinear couplings of the third filament with plasma gratings.As the third filament was temporally overlapped with the two noncollinear filaments in the interaction zone,all the three filaments participated in synchronous nonlinear interaction and plasma grating structures were altered by the addition of the third filament.As the third filament was positively or negatively delayed,the as-formed plasma gratings were elongated by the delayed third filament,or plasma gratings were formed in the presence of plasma expansion of the ahead third filament,respectively.Using F-GIBS for trace metal detection in water,significant spectral line enhancements were observed.

基于光梳的实时高分辨相位测量方法理论分析

针对液晶光学相控阵(LCOPA)调制相位分布测量实时可溯源的问题,结合空间啁啾技术与双光梳干涉测量技术,提出一种基于光梳的空间高分辨相位测量方法。针对光栅以及光梳光源的参数对系统空间分辨率以及测量视场的影响进行理论仿真分析。理论仿真结果表明,该方法的测量视场可达100 mm,空间分辨率优于2μm。实验结果表明,该方法能够在微秒时间尺度内实现LCOPA多通道驱动电极调制相位分布的快速测量,因此有望为LCOPA器件的研制和性能的评价提供有效途径。