基于光纤锥形滤波结构的波长可切换掺铥光纤激光器

Wavelength switchable thulium-doped fiber laser based on fiber-tapered filter structure

摘要:

本文提出了一种基于光纤双锥滤波结构的波长可切换掺铥光纤激光器（Thulium doped fiber laser, TDFL）。通过将单模光纤（Single-mode fiber, SMF）进行拉锥处理后，级联为双锥结构制备光纤马赫-曾德干涉（Mach-Zehnder interferometer, MZI）滤波器，其自由光谱范围为4.2 nm。设计采用波长为793 nm的半导体激光器作为泵浦源，长度为3.5米的掺铥光纤作为增益介质构建TDFL，激光器阈值为126 mW。在实验中通过调整偏振控制器，所设计的激光器能够在1830.6 ~ 1881.7 nm光谱范围内实现单波长激光可切换输出，其中最小波长间隔7.1 nm；所设计的激光器能够在1841.7 ~ 1881.1 nm范围内实现双波长激光可切换输出，最小及最大波长间隔分别为4.5和35.7 nm；通过调节PC可以进一步实现三、四、五波长激光输出；在20分钟监测时间内，激光器能够分别稳定输出单波长和双波长激光，功率波动分别小于0.52和0.91 dB。本文提出的波长可切换掺铥光纤激光器具有波长切换灵活的特点，在激光传感和测试等方面具有较大的应用价值。

Abstract:

A wavelength switchable thulium doped fiber laser (TDFL) based on double fiber-tapered filter was proposed. The Mach-Zehnder interferometer (MZI) filter was constructed by tapering single-mode fiber (SMF) and cascade two tapers, and its free spectral range was 4.2 nm. In this design, a semiconductor laser with wavelength of 793 nm was used as the pump source, and a 3.5 m length thulium-doped fiber was used as the gain medium to construct a TDFL，the laser threshold was 126 mW. In the experiment, by adjusting the polarization controller, the designed laser could achieve single-wavelength laser switching output in the spectral range of 1830.6 ~ 1881.7 nm, with the minimum wavelength interval of 7.1 nm; The designed laser could realize switchable dual-wavelength laser output in the range of 1841.7 ~ 1881.1 nm, with minimum and maximum wavelength intervals of 4.5 and 35.7 nm, respectively. By adjusting PC, three, four and five-wavelength laser generation could be realized; During the 20-minute monitoring period, the laser was able to generate single- and dual-wavelength lasers steadily with power fluctuations of less than 0.52 and 0.91 dB, respectively. The proposed wavelength switching thulium-doped fiber laser in this paper has the characteristics of flexible wavelength switching, and has great application value in laser sensing and measurement.