液芯光子晶体光纤中高能量2-5微米超连续谱的产生和光谱控制研究

Laser sources in the 2-5 μm wavelength range have important applications in such diverse fields as scientific research, industry and national defense. Supercontinuum generation is an important way for achieving mid-infrared laser with extremely large continuous spectral bandwidth. Currently, supercontinuum generation spanning the region from 2 to 5 μm in non-silica fiber is commonly used. But its high requirement of the wavelength of pump laser and high absorption loss limit the conversion efficiency of supercontinuum. Aim at these disadvantages, this proposal will design a highly nonlinear liquid-core photonic crystal fiber (LC-PCF), which is suitable for the generation and propagation of mid-infrared supercontinuum laser, by filling the central core of conventional silica hollow-core photonic crystal fiber (HC-PCF) with transparent liquids endowed with low absorption loss and high nonlinearity. The optical characteristics of LC-PCF can be tailored by combining the flexible design of PCF with the optionality of liquids filled. The generation mechanism and law of the 2-5 μm supercontinuum in LC-PCF will be revealed. On the basis of these findings, the selective excitation and high efficient conversion of 2-5 μm supercontinuum will be studied and achieved.

2-5微米中红外激光光源在科学研究、工业和国防等领域有重要应用。超连续谱产生是获得宽光谱中红外激光的重要途径之一，但目前普遍采用的非石英光纤产生2-5微米超连续谱的方法对泵浦源的工作波长要求高、损耗大等不利因素限制了超连续谱的转换效率。针对上述不利因素，本项目通过在石英空芯光子晶体光纤的中心孔中填充低吸收高非线性液态透明介质，设计适合中红外超连续激光产生和传输的液芯光子晶体光纤；结合光子晶体光纤灵活的结构设计和填充介质的可选择性，调控液芯光子晶体光纤的光学特性；揭示液芯光子晶体光纤中2-5微米超连续谱产生的机理和规律；在此基础上，研究并实现2-5微米超连续谱激光的高效转换与选择性激发。

本项目研究了超短脉冲激光在液芯光子晶体光纤中的非线性传输，着重研究了2-5微米超连续谱产生的机理和规律。我们利用光谱相位调制技术获得非对称的整形脉冲，这种脉冲具有独特的线性特性：抗色散、自愈以及自加速或自减速特性。我们研究了这种整形脉冲激发超连续谱的特性与规律，重点研究了超连续谱产生过程中两个重要机制：拉曼孤子自频移和色散波辐射。我们研究发现非对称的整形脉冲能够有效操控拉曼自频移和色散波辐射过程，不仅能够控制频率而且能够提高能量。另外，我们研究了艾里和孤子脉冲相互作用下增强拉曼自频移的过程以及非线性自加速艾里脉冲激发超宽频谱的色散波辐射过程。此外，我们研究了分数薛定谔方程中的调制不稳定特性和超高斯光束在这种系统系下线性传输特性以及经典的Fermi-Pasta-Ulam-Tsingou回归现象。本项目三年间共公开发表论SCI文10篇。