Erbium-Doped Fiber Random Laser Based On Chirped Fiber Grating Array

Fiber random laser is a new type of fiber laser.Its working principle is mainly to realize the gain amplification and random distribution feedback of light in the fiber medium.It does not need a fixed cavity,so it has the characteristics of simple structure and low laser coherence,and has broad application prospects in biomedical imaging,sensing,non-linear optics,optical communication and other fields.The random distributed feedback mechanism in conventional random fiber lasers is Rayleigh scattering in optical fibers.However,due to the small Rayleigh scattering coefficient of the optical fiber,the shortcomings of low feedback efficiency,long fiber length(tens of kilometers),and high laser threshold limit the development and application of the random fiber laser.To solve the above problems,a random laser based on erbium-doped fiber chirped grating string is studied and optimized in this paper.A new design of feedback-enhanced erbium-doped fiber chirped grating string random laser is proposed,which is verified by experiments,and a lower pump threshold is obtained.1.The erbium-doped fiber random laser based on chirped fiber grating is optimized.The length of the erbium-doped fiber was optimized to 5 m by measuring the amplified spontaneous emission spectrum.And 22 randomly spaced weak-reflectively chirped fiber Bragg gratings were written in the erbium-doped fiber by the phase mask method.Low-threshold fiber random laser based on erbium-doped fiber amplification and random distribution feedback of chirped-fiber Bragg gratings are realized by 980 nm laser pumping.In the 8.1nm bandwidth,a multi-wavelength random lasers output with uniform distribution was obtained.The threshold power was 10.3 mW and the slope efficiency was 9.8%.The stability was tested and analyzed.2.A erbium-doped fiber chirped grating random laser based on single-ended high reflection is proposed and realized.Connecting a high-reflectively wavelength-matching chirped fiber Bragg grating at one end of the weak-reflectively chirped fiber Bragg grating array,and the light emitted from the end is reflected back into the erbium-doped fiber chirped Bragg grating array to increase the random feedback length and improve the laser conversion efficiency.Pumped by 980 nm laser diode,a random laser output with a threshold of 4.3 mW and a slope efficiency of 20.3% is achieved.3.A erbium-doped fiber chirped grating array random laser based on double-ended high-reflectively is proposed and realized.By connecting a wavelength-matched chirped fiber Bragg grating with high-reflectively at both ends of the chirped fiber Bragg grating array with weak-reflectively,the feedback probability of the light in the erbium-doped fiber chirped Bragg grating array is further enhanced,and the threshold of the laser is further reduced to 3.1 mW.