饱和吸收体锁模掺铥光纤激光器的时间抖动研究

Ultralow-timing jitter mode-locked lasers can be used for precise spectroscopy, scientific facilities synchronization, low phase noise microwave generation, analog to digital conversion, coherent optical communications and etc. At present, most of the research on ultralow timing jitter of mode-locked fiber laser were at 1 μm and 1.5 μm. There are few reports on the studying the timing jitter of fiber laser at 2 μm. Based on mode-locked thulium fiber laser by carbon nanotubes and cadmium arsenide saturable absorber, this project will study the relationship between the timing jitter and absorber parameters (recovery time, modulation depth, saturable intensity and etc) as well as the relationship between the timing jitter and laser parameters (dispersion, pulse energy, width, bandwidth, repetition rate and etc.). Furtherly, 2 μm ultrashort pulse laser with time jitter of < 10 fs will be achieved by controlling the above mentioned parameters. .The project can not only get the timing jitter characteristics of mode-locked thulium fiber laser, but also systematically reveal the impact of saturable absorber parameters on the timing jitter performance. This research result will lay a foundation for studying other low noise and timing jitter fiber lasers with novel saturable absorbers in the future.

超低时间抖动的锁模激光器可以应用于精密光谱测量，光学原子钟，大型科学设施的时间精密同步，低噪声微波产生，光子模数转换器，相干光通信等。目前，有关超低时间抖动锁模光纤激光器的研究主要集中于1μm和1.5μm波段。而关于2μm波段锁模掺铥光纤激光器的时间抖动研究还鲜有报道。本项目以碳纳米管CNT、砷化镉Cd3As2饱和吸收体锁模掺铥光纤激光器为研究对象，获取其非线性参数（恢复时间，调制深度，饱和光强等）及所在激光的运转参数（色散，能量，脉宽，带宽，重复频率等）与时间抖动的关联。进一步通过相关参数调控获得超低时间抖动（<10fs）的2μm超短脉冲激光输出。.本项目的实施不仅能获得2μm锁模脉冲光纤激光的时间抖动特征，还将系统的获得饱和吸收体参数对时间抖动的影响，为将来其它新型饱和吸收体锁模的低噪声光纤激光产生奠定了基础。

超短脉冲激光器在科学研究领域及工业生产中都有广泛应用。本项目首先研究了新型半导体材料Bi2O2Se的饱和吸收特性，并成功应用于1.5µm波段的锁模掺铒光纤激光器和2µm波段的调Q掺铥光纤激光器。利用单壁碳纳米管及自制滤波器实现了中心波长及脉冲宽度可调谐的2µm波段锁模掺铥光纤激光器，300nm的波长调谐范围为业界最大宽度。其次，本项目通过非线性的波长转化过程，将饱和吸收体锁模光纤激光扩展为1-2µm多波长范围覆盖的双光梳脉冲激光，3-5µm波段的中红外超短脉冲激光及极紫外光波段的超短脉冲激光。最后，本项目对锁模超短脉冲光纤激光器的噪声进行了研究。对于全正色散的锁模光纤激光器，实验证明非线性放大压缩器对脉冲激光强度噪声的影响很小。对于10GHz高重复频率的再生锁模2µm掺铥光纤激光器，通过反馈机制可以将低频段的时间抖动值降低到至1ps左右，同时低频段的强度噪声也被较好的抑制。进一步，通过平衡光交差的时间抖动测量装置测得饱和吸收体锁模光纤激光的最小时间抖动值仅为48as，抖动主要来源于腔内剩余色散引入的中心波长漂移。本项目研究所获得的宽波长覆盖范围、低噪声锁模脉冲光纤激光器可以应用于精密光谱测量，光学原子钟，时间同步，微波产生，光子模数转换器，光电子能谱等领域。