基于异质型回音壁模微腔全光调谐的窄线宽光纤激光器研究

Tunable narrow-linewidth fiber laser has become important optical source for various applications, such as gravitational wave detection, high-precision spectral analysis, high-accuracy range detection, long-distance coherent communication, etc. However, in current fiber laser systems, drawbacks still exist in the cavity structure and material. Due to the lack of effective frequency-selection and tuning mechanism, there still need efforts as to achieve high coherence, narrow-linewidth lasing output with widely tunable wavelength. This project proposes a frequency-selection approach based on multi-material whispery-gallery-mode microcavity (MM-WGMM). The MM-WGMM offers the advantages of an ultra-narrow-band, all-optically tunable whispering-gallery-mode (WGM) spectrum. This approach is promising for achieving kHz-level narrow-linewidth fiber laser with wide tuning ability.. As to construct the high Q MM-WGMM, a highly symmetrical SiO2 microsphere is coated with a layer of TiO2 film with large thermo-optic coefficient. Preparation techniques of the MM-WGMMs are investigated and optimized. Through taped-fiber coupling method, a critical coupling condition is explored as to trigger and propagate the WGM oscillation filed. This project analyzes the optical-mode-distribution in the MM-WGMM. Furthermore, theoretical model of the multi-physics-interaction mechanism is developed to investigate the all-optical tuning property of the WGM spectrum in the MM-WGMM. Finally, a narrow linewidth fiber laser system based on the MM-WGMM as the frequency-selector is developed with performance tested and optimized. All those investigations being done to offer theoretical basis and experimental reference for developing a high performance, narrow-linewidth fiber laser with improved coherence and wavelength tunability.

可调谐窄线宽光纤激光器是引力波探测、高分辨率光谱分析和长距离相干通信等研究领域的重要光源。然而，受腔材料和结构限制，目前仍需探索实现高单色性和大波长范围的有效选频机制。本项目提出一种基于异质型回音壁模微腔(MM-WGMM)的选频新方法，利用高Q值MM-WGMM内回音壁模(WGM)共振谱的窄带宽、全光可调谐特性，实现线宽kHz及以下、大范围波长可调谐的光纤激光器。. 本项目利用高光敏感薄膜包覆高圆对称SiO2微球构造高Q值球形MM-WGMM；优化微腔制备工艺参数，掌握实现其高Q值的物性参数控制方法；探寻MM-WGMM-锥形光纤的最佳耦合条件，实现窄带WGM共振谱的高效激发；研究由材料和结构决定的MM-WGMM内多物理场互作用机制，揭示WGM共振谱在不同光场作用下的变化规律和光纤激光谐振腔内的选频特性，为获得大范围波长可调谐的窄线宽光纤激光器提供理理论和实验参考。

可调谐窄线宽光纤激光器是引力波探测、高分辨率光谱分析和长距离相干通信等研究领域的重要光源。本项目利用TiO2薄膜包覆高圆对称SiO2微球构造高Q值球形混合介质微腔；优化微腔制备工艺参数，掌握实现其高Q值的物性参数控制方法；探寻微腔-锥形光纤的最佳耦合条件，实现窄带WGM共振谱的高效激发；研究由材料和结构决定的混合介质微腔内多物理场互作用机制，揭示WGM共振谱在不同光场作用下的变化规律和光纤激光谐振腔内的选频特性。本项目通过双光路法制备获得Q>10^8的高Q值微球腔，利用ALD方法实现了微球腔的低损耗TiO2镀膜。分别搭建了基于TiO2镀膜微球腔、双微球腔、高圆度微球腔、双花生结微球的环形光纤激光器实验系统，获得了可调谐、单纵模、窄带光纤激光输出。通过特定的封装结构，最大程度地维持了微球腔的稳定性和高Q值特性。基于毛细管微腔实现了电流传感和葡萄糖传感。项目执行过程中，总计发表论文14篇，其中SCI论文11篇，申请专利14项，培养研究生5人。本项目的工作将为窄带、可调谐光纤激光器研究提供有意义的参考。