The Research Of Graphene-based Mode-locked Erbium-doped Fiber Laser

Erbium-doped fiber laser is a hot research field of optical communication since the early 80th year. The output characteristics went through several stages from continuous operation to single-longitudinal-mode output and so on. It is playing an increasingly important role in the optical fiber communication, fiber optic sensing, bio-medical and other fields. Erbium-doped fiber laser in recent years has become a hot research because of its extremely short pulse duration and high peak power, etc. Ultrafast pulsed laser mainly through Q-and clamp technique to achieve. Passively mode-locked picosecond technology to produce even ultrafast femtosecond pulse, and therefore favored. Passive mode-locking using nonlinear absorption or nonlinear phase change material properties to generate ultrafast laser pulses. At present, more mature nonlinear material semiconductor saturable absorber mirror and carbon nanotube saturable absorber. Currently mature nonlinear materials include semiconductor saturable absorption mirror and carbon nanotubes. However fabricating a semiconductor saturable absorber mirror requires a relatively complex and costly clean manufacturing system. Typical recovery time for such devices is about a few nanoseconds. Carbon nanotubes are direct bandgap material, the band gap size is determined by the diameter and properties of carbon nanotubes. Mixing carbon nanotubes with different diameters can achieve a wide nonlinear absorption band covering common 1.0-1.6 um emission band laser gain. However, due to the tubular form of carbon nanotubes will have great scattering losses and improve the clamping threshold limit of laser output power and efficiency. So, researchers have been looking for a saturated absorbent material with high damage threshold, ultra-fast recovery time, wide bandwidth and inexpensive price, etc. In recent years, researchers found that graphene due to its unique zero band gap structure, all bands are non-selective absorption of light, and has a fast recovery time and high damage threshold. So take advantage of the unique graphene nonlinear saturable absorption characteristics to make a saturable absorber and applied to passively mode-locked fiber laser ultrafast pulsed laser has become a hot research area. This article specifically as follows:We give a simple introduction of research progress of erbium-doped fiber laser and give a theoretical analysis of erbium-doped fiber amplifiers and erbium-doped fiber laser. Study the correspondence between the output characteristics of the erbium-doped fiber laser pump source and power, gain fiber length and other factors experimentally. The spectral output characteristics of erbium-doped fiber fluorescence light experiment to find the best erbium-doped fiber laser gain fiber length. On the other hand, we have also introduced the working principle of fiber lasers, taking laser experiments and obtain stable continuous laser output.This paper analyzes the mechanism of ultrafast pulse generation, and introduced the Q-technology and clamping technology. Three common saturable absorbers include semiconductor saturable absorber mirror, carbon nanotubes and graphene saturable absorber. It’s production methods, production costs, absorption bandwidth, damage threshold, recovery characteristic aspects of time and modulation depth were compared.In this paper, the structure of the energy levels of graphene were studied; analysis of the ultrafast relaxation processes graphene and related saturable absorption mechanism; analysis of the physical mechanisms of graphene has extremely low resistivity. We use chemical vapor deposition method to obtain a high-quality graphene films. Respectively by wet and dry graphene film transferred to fiber jumper zirconia ferrule end surface. Because the process is controllable layers, we were transferred to one, two, and six to three different fiber jumpers zirconia ferrule end surface.Finally got three layers of different graphene saturable absorber and experimentally studied saturable absorption characteristics.In this paper, experimental studies based on the optical output characteristics of the different parameters of graphene saturable absorber of erbium-doped fiber laser pulses. We got picosecond mode-locked pulse train output. To establish a correspondence between the graphene saturable absorber between body and clamping pulse output parameters, and the laser cavity parameters were optimized.