基于全光栅光纤的超窄线宽随机光纤激光器

Ultra-Narrow Linewidth Random Fiber Laser Based on All Grating Fiber

设计并验证了一种采用全光栅光纤(AGF)作为随机反馈介质的窄线宽随机光纤激光器(RFL)。基于相位掩模法在利用拉丝塔在线制作的单模光纤纤芯上连续刻写长度为0.3mm的布拉格光栅(FBG)约4.3×105支,制作了长度为130m的AGF。利用光学环形器将AGF接入由掺铒光纤放大器、光纤隔离器和窄带光滤波器组成的环形激光腔中,构成环形RFL。结果表明,通过窄带光滤波器选模,基于AGF的RFL输出连续单模激光的最大功率为1.26mW,阈值电流为75mA,斜率效率为56%。抽运电流恒定为100mA时,基于AGF的RFL线宽为1.25kHz,光信噪比为75dB。当频率为1kHz以上时,激光器输出的相对强度噪声达到-90dB。相较于传统基于分立FBG的RFL反馈腔,基于AGF的RFL反馈腔具有更多的随机反馈点和更均匀的随机性,有利于RFL获得更窄的线宽。

A narrow linewidth random fiber laser （RFI,） using all grating fiber （AGF） as the random feedback media is designed and verified. A 130 m AGF is fabricated on the single mode optical fiber core which is made online by the drawing tower based on the phase mask method. Total 4.3× 10s fiber Bragg gratings （FBG） with 0.3 mm grating length are made on the 130 m AGF. The AGF is incorporated into a ring laser cavity consisting of an erbium-doped fiber amplifier, a fiber isolator and a narrow band optical filter via an optical circulator, and then a ring RFL is established. Results show that the RFL based on AGF can output continuous single mode laser with the maximum power of 1.26 mW when the RFL mode is selected by the narrowband optical filter. The threshold current is 75 mA and the slope efficiency is 56%. The RFL based on AGF with the narrow linewidth of 1.25 kHz and the optical signal-noise-rate of 75 dB is achieved with a 100 mA pump current. The relative intensity noise is --90 dB when the frequency is beyond 1 kHz. Compared with the traditional RFL feedback cavity which is based on discrete FBG, the RFL feedback cavity based on AGF can provide more random feedback points and more uniform randomness, which contributes to obtaining narrow linewidth for RFL.