Solution Processed Graphene-PVA Composite for mode-locked ultrafast Er-doped all fiber laser
Chih-Yuan Wen1*, Hou-Ren Chen1, Wen-Feng Hsieh1
1Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan
* presenting author:Chih-yuan Wen,
Ultrafast lasers provided a valuable and dependable radiation source for various applications, from basic research, material processing to medicine applications. In comparison to the solid state lasers, fiber lasers have the advantages of compactness, efficient heat dissipation, high beam quality. We use in this presentation a solution processed graphene-PVA composite as a saturable absorber to mode lock an Er-doped all fiber laser system.

Recently, Graphene is the main 2D-material as the ultra-broadband saturable absorbers (SAs) due to its linear dispersion of the Dirac electrons, fast carrier dynamics, and large saturable absorption. [1].

Graphene can be obtained through mechanical cleavage [2], solution-based methods [3], or grown directly by CVD [4]. Mechanical cleavage produces high quality flakes ideal for fundamental studies, but is not scalable, making it unsuitable for realistic applications. CVD can grow scalable mono or few -layer graphene, but it relies on high temperatures, and requires additional processing steps to transfer the as-grown material on to the desired substrate. In contrast, solution processing of graphene can be carried out under ambient condition, and produce dispersion of mono or few -layer flakes. For example, the solution processing liquid phase exfoliation (LPE) method just needs graphite powder and solvent (Sodium deoxycholate, SDC) dissolved in DI water by sonication technique [5], which offers a simple and cost-effective pathway to obtain graphene flakes.

In this paper we demonstrated passively mode-locked ultrafast Er-doped fiber laser using solution processed graphene-PVA (polyvinyl alcohol) composite as a SA. Using this SA, it is shown that stable, ultrafast pulses with a temporal width of ~564 fs can be generated with maximal output power of 232 μW, spectral bandwidth of 3.04nm at wavelength of 1558.3 nm and 5.43MHz repetition rate from a Er-doped fiber ring cavity.

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Keywords: graphene, liquid phase exfoliation, ultrafast laser