基于优质Yb全固态飞秒种子源结合超连续谱自差频技术获取中红外超快激光的研究

Due to the advantages of both mid-infrared laser and ultrafast laser, mid-infrared ultrafast laser has been widely applied in many fields such as scientific research, medical treatment, industry, and so on, and the generation of mid-infrared ultrafast laser has become a hot research topic. Although some theoretical and experimental researches on the generation of mid-infrared ultrafast laser have been carried out, there are still many problems to be solved. For example, the fluorescence spectrum bandwidth of gain mediums and the central wavelength of saturable absorbers limit the spectral range and pulse duration of the mid-infrared ultrafast laser generated directly from oscillators. Frequency conversion, such as optical parametric oscillator (OPO) and optical parametric amplifier (OPA), is an indirect means of obtaining ultra-fast infrared laser. However, OPO requires accurate resonators matching and OPA needs a high energy laser as pump source. In this research, the generation of mid-infrared femtosecond laser is based on a high-quality Yb all-solid-state femtosecond seed and combined with supercontinuum self-difference frequency. The specific method is as follows. Firstly, the Yb all-solid-state seed source with watt level output power and sub-thirty femtosecond pulse duration is obtained. Then the seed source is focused into the PCF to obtain the supercontinuum laser. Finally, the supercontinuum laser is injected into the nonlinear crystal to self-difference frequency and generate the mid-infrared ultrafast laser. Through this research, we hope to independently explore and master relevant experimental and technical methods for generating 5-20μm, sub-hundred femtosecond mid-infrared ultrafast laser, and then promote the development of mid-infrared ultrafast laser in related basic sciences and applications.

中红外超快激光兼具中红外波段以及超快激光二者的优势，在科研、医疗、工业等多个领域具有重要的应用，是当前的研究热点。尽管人们对于中红外超快激光的产生已经开展了卓有成效的理论和实验探究，但是依然存在一些问题亟待解决，例如增益介质的荧光光谱带宽、锁模器件的工作波长以及带宽限制了直接获取中红外超快激光的波长和脉宽；光学参量振荡、光学参量放大等非线性频率变换过程对谐振腔匹配和泵浦源要求较高；等等。基于此，本项目拟基于优质Yb固体飞秒种子源注入PCF获取超连续谱，并进一步自差频获取中红外超快激光，具体为：首先获取瓦级、亚三十飞秒Yb固体种子源；再将种子源注入到PCF中获取超连续谱；最后将超连续谱激光注入非线性晶体自差频获取中红外超快激光。通过该项目的研究，我们希望能够自主摸索并掌握获取5-20µm、亚百飞秒中红外超快激光的相关实验和技术方法，从而推动中红外超快激光在相关基础科学和应用领域的发展。

中红外超快激光兼具中红外波段以及超快激光二者的优势，在科研、医疗、工业等多个领域具有重要的应用，是当前的研究热点。本项目提出超连续谱自差频获取中红外激光的实验方案，并在实验上获得了波长可调谐的中红外激光，其波长范围为1431-1567 nm和 3289-3790 nm。摸索出谐振腔型、增益介质、可饱和吸收体等关键因素对全固态脉冲激光器的影响，实现了高功率、高重频、多波长的全固态脉冲激光器。输出激光的最大重复频率为245.04 kHz，最高输出功率为2.48 W，效率为37.1%。输出激光不仅可以运转在单波长状态，如1031 nm, 1047 nm, 1049 nm, 1051 nm, 1056 nm and 1083 nm，还可以运转在双波长状态，如 1051&1091 nm、1056&1083 nm、1375.9&1378.0 nm。构建了全固态脉冲激光器的动力学模型，理论分析了泵浦速率、腔内光子损耗、腔内光子往返时间等关键参量对系统性动力学的影响。掌握了全固态脉冲幅度混沌激光器的核心技术，实验上获取了脉冲幅度混沌激光，激光的平均输出功率达到了0.814 W。