1.7μm可调谐自相似掺铋飞秒光纤激光研究

Femtosecond tunable lasers at 1.7μm are important research topic because a lot of special applications demand of the lasers, such as multi-photon deep microscopic imaging in biological tissue. Presently, it is still a challenge topic to generate these lasers system. In order to resolve the issues of the low efficiency, complicated technology and poor performance in current laser system, this research proposal will focus on the investigation of 1.7μm tunable self-similar bismuth-doped femtosecond fiber laser based on two-dimensional material as saturable absorber. Firstly, our research will investigate and reveal the dependence of the performance and structure of two-dimensional material, and then obtain excellent saturable absorber. Secondly, we will study the generation mechanism of tunable self-similar bismuth-doped femtosecond fiber laser based on two-dimensional material. The problems of low pulse energy and long pulse width are solved by using the dispersion-management and nonlinear-control technology. And on this basis, we will systematically study spectral modulation characteristic of fiber Bragg grating, and get the tunable femtosecond fiber laser at 1.7μm. Finally, we propose to pre-chirp non-linear amplification method and pulse compression technology to get more than 500-mW femtosecond pulse. The above mentioned research works will not only get an innovation of femtosecond optical fiber laser, and will also fill the blank of the 1.7 um band of femtosecond laser. It will provide necessary technical reserves for laser needed by deep-tissue multiphoton microscopy.

1.7μm波段可调谐飞秒激光由于在生物组织多光子深层显微成像等方面的特殊应用需求，是具有重要意义的研究课题。本项目针对目前该波段激光仍面临的效率低、技术复杂、性能差等挑战性问题，拟开展基于二维材料的1.7μm可调谐自相似掺铋飞秒光纤激光器研究。主要研究内容包括：（1）通过研究二维材料性能与结构的依赖规律，制备适合1.7μm波段的高质量宽带可饱和吸收体；（2）研究基于二维材料的可调谐自相似掺铋飞秒光纤激光产生机制，采用色散管理和非线性控制技术，解决脉冲能量低、脉宽宽等问题，同时结合理论与实验研究光纤布拉格光栅的光谱调制特性，实现1.7μm可调谐自相似激光输出；（3）进行预啁啾非线性光学放大和脉冲压缩技术的研究，得到平均功率大于500mW飞秒激光脉冲放大输出。上述研究结果不仅将实现一种创新的飞秒光纤激光器件，填补1.7μm波段飞秒激光的空白，也将为多光子成像系统的发展提供坚实的理论技术基础。

1.7μm波段可调谐飞秒激光由于在生物组织多光子深层显微成像等方面的特殊应用需求，是具有重要意义的研究课题。项目执行过程中，为解决1.7μm超短脉冲光纤激光器的产生，完成了对超短脉冲光纤激光产生和非线性光谱扩展进行理论仿真，通过理论优化选择合适的增益光纤、光纤色散、非线性效应的等参数，为获得超短脉冲光纤激光提供理论指导；为了实现超短脉冲光纤激光，完成了对饱和吸收体进行了制备和表征，并利用制备的碳纳米管和氧化石墨烯作饱和吸收体，分别实现超短脉冲光纤激光的稳定输出；实现了1.7μm 可调谐超短脉冲光纤激光稳定输出，重复频率102 MHz，中心波长1.7 µm，脉冲宽度384 fs，平均功率35 mW。在此基础上，通过全保偏光纤放大器对功率进行放大，输出功率可达350 mW，脉冲宽度~80 fs，利用高非线性光纤，最终获得1650-2080nm范围的宽谱调谐输出；此外，实现了1400-2000nm 宽谱自相似超短脉冲激光输出，在最大泵浦功率下得到了最窄脉宽59 fs，输出功率250 mW, 光谱覆盖范围从1400-2000 nm，20 dB的光谱带宽为553 nm的输出。总之，本项目基本完成了申请书中的研究内容，没有进行大的调整，实现了项目的研究目标。发表正式SCI期刊论文7篇，申请专利1项，参与项目研究生6名。