基于黑磷可饱和吸收体的色散管理锁模光纤激光器研究

Two-dimensional nanomaterial black phosphorus (BP) being saturable absorbers (SAs) applied in mode-locked fiber lasers has attracted much attention in recent years. The project proposes BP-fiber based SAs that BP is integrated on tapered fibers as well as the end-facets of the standard fiber by optically-driven deposition method. By using the broadband BP-fiber based SAs with large modulation depth, the project aims to solve the problem of the instability of dispersion-managed mode-locked (DMML) fiber lasers at near-zero net cavity dispersion and achieve the excellent performance of DMML fiber lasers. The main contents include: reveal the physical mechanism of BP-light interaction and the controllable technique in optically-driven deposition process; fabricate highly-integrated and broadband BP-fiber based SAs with large modulation; solve the problems faced by the existing BP-fiber based SAs including low thermal damage threshold, polarization dependence, and poor stability; by using BP-tapered fiber based SAs, the ring-configuration DMML fiber lasers are optimized to produce pulses with wide spectral bandwidth, ultrashort pulse duration and low noise; by using BP-fiber end-facet based SAs, the linear-configuration DMML fiber lasers are optimized to produce high-quality pulses with high repetition rate. The expected results are believed to promote the performance of DMML fiber lasers by the breakthrough in the structure and optical properties of BP-fiber based SAs, which aims to fulfill the requirements of light sources by the modern fiber communication and fiber sensing systems.

基于二维纳米材料黑磷可饱和吸收体在锁模激光器中的应用近年来受到极大关注。本项目提出基于光驱动沉积法将黑磷集成在拉锥光纤锥区和普通光纤端面上，利用黑磷-光纤可饱和吸收体的宽带和大调制深度光学特性，解决色散管理锁模光纤激光器在近零色散处不稳定的难题，实现高性能锁模光纤激光器。项目主要内容包括：探索光驱动沉积黑磷的物理机制及调控技术；实现黑磷与光纤高集成、宽带、大调制深度的可饱和吸收体，拟解决现有黑磷-光纤可饱和吸收体的低热损伤阈值、偏振相关、稳定性差等问题；基于黑磷-拉锥光纤可饱和吸收体研究环形锁模光纤激光器在近零色散处的工作特性，实现宽光谱、窄脉宽、低噪声脉冲输出；基于黑磷-光纤端面可饱和吸收体研究线形近零色散锁模光纤激光器，实现高质量、高重复频率脉冲输出。预期成果将有望从黑磷可饱和吸收体结构和性能上突破，实现优化的色散管理锁模光纤激光器，从而满足现代光通信和光传感发展对激光光源的要求。

本项目在基于黑磷饱和吸收体制备、色散管理锁模光纤激光器、及其超连续谱应用三个方面开展了理论和实验研究。在基于黑磷饱和吸收体光控机理及制备技术研究方面，基于液相剥离技术制备了少层黑磷（BP）样品，并将BP与聚合物（PVA）薄膜集成到一起，制备了BP-PVA薄膜饱和吸收体，改善了黑磷在空气中的不稳定性。在基于纳米材料光纤激光器的脉冲产生技术方面，开展了1.5微米和2微米波段光纤激光器的理论和实验研究。理论上，基于金兹堡朗道方程研究了脉冲演化过程，指出了当腔内净色散值小于-0.2ps2时，调制深度为2%的可饱和吸收体就可以输出稳定的孤子，但当净色散值继续趋于零时，锁模所需最小调制深度增加到15%左右。实验上，分别实现了（1）1.5微米波段调Q脉冲输出，最高脉冲能量可达468.03nJ;（2）1572.3nm和1597.1nm双波长锁模脉冲输出；（3）C+L波段、从负色散到正色散的稳定锁模脉冲输出，脉冲宽度可达837fs；（4）在2微米波段实现了锁模脉冲输出，中心波长1919nm，3dB带宽3.3nm。在基于超快脉冲光泵浦的超连续产生技术研究方面，通过将超快脉冲抽运到氟化物光纤，光谱可延伸到2160nm，且在1571.8-1803.1nm波长范围内平坦度抖动小于1.29dB。由于超连续光源具有良好的光束质量和较高的光谱稳定性，实现的超连续谱可在光学成像、传感中具有潜在的应用。