基于NPR效应的可调谐多波长被动锁模光纤激光器

A tunable multi-wavelength mode-locked fiber laser based on NPR effect

提出了一种基于非线性偏振旋转(NPR)效应的被动锁模光纤激光器,以980 nm半导体光源作为泵浦源,5 m长的掺铒光纤(EDF)作为增益介质,利用两个偏振控制器(PC1和PC2)和一个偏振相关隔离器(PDI)产生NPR效应,作为等效可饱和吸收体,实现对脉冲的窄化,产生稳定的锁模脉冲输出,脉冲宽度为36.02 ns,并通过改变腔中单模光纤的长度探究激光器的输出与腔长的关系,当腔长较长时,实现锁模需要的阈值功率降低,锁模脉冲稳定性较好。通过结合一个3 dB耦合器、1 m保偏光纤(PMF)和一个偏振控制器(PC3)构成的Sagnac环结构,作为梳状滤波器,实现了C波段从单波长到五波长的多波长可调谐激光输出,并对输出光谱的稳定性进行了测试,光谱稳定性在室温条件下表现良好。实验结果说明该激光器在电域可以产生稳定的锁模脉冲,在光域可以产生C波段从单波长至五波长的可调谐的激光输出,具有广阔的应用前景和较高的研究价值,例如生物医疗领域和波分复用领域。

A passive mode-locked fiber laser based on nonlinear polarization rotation(NPR)effect was reported and demonstrated,the pump source of this cavity is 980 nm diode and the gain medium is a 5 m long erbium-doped fiber.Two polarization controllers(PC1 and PC2)combine with a polarization dependent isolator(PDI)were used to generate NPR effect,as the equivalent saturable absorber,generate stable mode-locked pulse output with the pulse width is 36.02 ns.And the influences of different cavity length on laser’s output were investigated,the threshold value of pump power will decrease with the increase of the length of the cavity.The laser combine with a Sagnac ring,which was consist of a 3 dB coupler,a 1 m polarization-maintain-fiber(PMF)and a PC,used as a comb filter.Through experiments,tunable multi-wavelength output from single to five wavelengths in C-band is realized.The long-term stability of the output spectrum was also tested,the output spectrum of the laser shows little change at room temperature,so it exhibits excellent stability.The results show that the laser could generate mode-locked pulses and tunable multi-wavelength.The laser will have broad application prospect and high research value,such as biomedical field and wavelength multiplexing system.