Erbium-doped Random Fiber Laser By Using Random Grating And Bragg Grating

Fiber random laser is a new t ype 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 the conventional fiber random laser uses the Rayleigh scattering effect in the fiber,but because the Rayleigh scattering coefficient in the fiber is small,the feedback efficiency is low,the required fiber length(tens of kilometers or even hundreds of kilometers),The high laser threshold limits the development and application of fibe r random lasers.To solve these problems,this paper researches and proposes an erbium-doped fiber random laser based on a combination of a random grating and a Bragg grating,which is verified by experiments.A low-threshold,high-efficiency output laser is obtained,and its output characteristics are studied and analyzed.1.An erbium-doped fiber random laser based on a combination of a random grating and an erbium fiber grating is proposed.About 10,000 modulation points were written point by point on a 7 cm single-mode fiber by a femtosecond laser.A 980 nm pump laser is used to provide excitation,and a low-threshold,high-efficiency laser output with random feedback provided by a random grating and gain provided by an erbium-doped fiber is achieved.Within the bandwidth,a multi-wavelength random laser output with relatively uniform distribution is obtained,with a threshold power of 17 m W and a slope efficiency of 20.1%,and its time stability is studied.2.An erbium-doped random fiber laser based on the combination of random grating and fiber Bragg grating is proposed and implemented.A half-open cavity structure is formed by replacing the chirped fiber grating with a fiber Bragg grating to increase the stability of the output laser.Under the excitation of a 980 nm pump laser,a random laser output with a threshold of 18 m W and a slope efficiency of 13.2% was finally obtained.The output characteristics of the laser were tested and analyzed.3.The time-domain characteristics of erbium-doped random fiber laser based on the combination of random gratings and Bragg grating are studied.The pulse phenomenon of random laser was observed by oscilloscope,and its mechanism and experimental phenomenon were analyzed.At the same time,the center wavelength of the Bragg grating is changed by temperature adjustment or stress tuning,thereby realizing a tunable random fiber laser.The tuning range of the output wavelength is 2.25 nm(1548.04-1550.29 nm)and 4.45 nm(1548.04-1552.49 nm).