基于飞秒激光直写FBG的C+L波段掺铒光纤激光器

提出并设计了一种基于飞秒激光直写制备光纤布拉格光栅阵列的C+L波段掺铒光纤激光器，实现了波长可切换的单波长及双波长激光输出。采用飞秒激光透过聚酰亚胺光纤保护层在纤芯直写的方法，分别实现周期为538、542、547 nm的光纤布拉格光栅刻写，单个光栅栅区长度3 000 m。作为选频器件的光栅阵列反射波长分别为1 555.5、1 569.6、1 583.8 nm；选用长度为3 m的C波段和10 m的L波段掺铒光纤组合作为激光器增益介质，结合泵浦源、光纤布拉格光栅偏振控制器及宽带全反镜构成线形腔结构光纤激光器。实验结果表明:激光器工作阈值为35 mW，通过调节偏振控制器能够实现1 555.4、1 569、1 583.2 nm单波长激光可切换输出，激光3 dB线宽0.05 nm，边模抑制比大于35 dB；实验中分别对单波长激光的光谱稳定性进行了测试，10 min内最大功率波动小于0.98 dB；通过调节偏振控制器可分别实现1 569、1 583.2 nm以及1 555.4、1 569 nm双波长激光同时输出，在10 min监测时间内，输出激光功率变化分别小于1.14 dB和4.48 dB。

C+L band Erbium-doped fiber laser based on FBG fabricated by femtosecond laser

A switchable and stable single- and dual-wavelength C+L band Erbium-doped fiber laser based on FBG array fabricated by femtosecond laser was proposed and experimentally demonstrated. Fiber grating period of 538, 542, 547 nm was realized on polyimide fiber core through fiber protection and cladding by femtosecond laser, grating length was 3 000 m, and reflection spectrum of each FBG was 1 555.5, 1 569.6, 1 583.8 nm, respectively; the length of 3 m C-band Erbium-doped fiber and 10 m L-band were used as the gain medium, and the proposed fiber laser was composed of gain medium, pump source, FBG, PC and broadband reflection mirror. In the experiment, the laser working threshold was 35 mW, through adjusting the polarization controller, a switchable single-wavelength of 1 555.4, 1 569, 1 583.2 nm laser was obtained, 3 dB linewidth was 0.05 nm, and SNR was more than 35 dB; The spectral stability of single-wavelength laser was tested in the experiment, and it was found that the power fluctuation of each single-wavelength laser was less than 0.98 dB over 10 min; by adjusting the polarization controller, the proposed fiber laser had the capability to produce switchable 1 569, 1 583.2 nm and 1 555.4, 1 569 nm dual-wavelength laser simultaneously, and the power shift was less than 1.14 dB and 4.48 dB, respectively over 10 min monitoring time.