Research On Two-Dimensional Material Transfer Technology And Its Application In Fiber Laser

Pulsed fiber laser plays key roles in communication, medical, industrial processing, national defence et al. There are mainly two ways to generate pulse lasers that are Q-switching and mode-locking, which have advantages of compact structures, good stability, easy integration, excellent pulse quality. Saturable absorption is a nonlinear loss for light as it causes relatively large loss for weak light and small loss for strong light. It is a principal way to achieve Q-switching and mode-locking by inserting saturable absorbers based on materials with the property of saturable absorption. Several materials, including dye, semiconductor saturable absorber mirror and carbon nanotubes, were successively made into saturable absorbers. Recently two-dimensional atomic crystal materials,such as graphene,topological insulator were found to have saturable absorption. Based on graphene and topological insulator saturable absorbers abundant research results have been reported on pulsed fiber laser. The specific works are as follow:1. The operational principle of Q-switching based on saturable absorber is theoretically analyzed. How to build and solve the Q-switching rate equation is described and the influence of parameters of saturable absorber on Q-switching output is discussed. On basis of nonlinear Schr?dinger equation and considering the birefringence in cavity, gain of doped fiber and saturable absorption, the Ginzburg-Landau equation, which describes how pulse propagates in fiber lasers mode locked with saturable absorber, is derivated.2. Saturable absorption theory of graphene is analyzed in detail. Graphene saturable absorber is obtained via mechanical exfoliation method by peeling highly oriented pyrolytic graphite repeatedly. A ring cavity mode-locked erbium-doped fiber laser based on graphene absorber is set up. Fundamental and high orders harmonic mode-locking output is achieved. Mechanism of multisoliton and harmonic mode-locking formation is analyzed. The variation of output power, pulse width and single pulse energy at different harmonic mode-locking orders is studied.3. The physical effects of, a method to transfer two-dimensional atomic crystal materials, is introduced and the results of this method is studied comparatively. The topological insulator nanosheets are prepared by the method of hydrothermal intercalation and exfoliation. Topological insulator saturable absorber is produced by optical deposition and inserted into linear cavity Q-switching fiber laser. How the Q-switching output changes along with pump power is studied.