Abstract

Tm-doped fibre pulse lasers covering the spectral range of 1.8 to 2.0 mm are currently developing with great interest because of their potential applications in various fields including remote sensing, spectroscopy, bio-medicine as well as efficient pump sources for nonlinear conversion of light to mid-infrared wavelength of few mm. In recent years, passively mode-locked Tm-doped fibre laser have been demonstrated by using various saturable absorbers (SAs) based on semiconductor saturable absorbers (SESAMs), carbon nanotubes, graphenes and topological insulators. Among these, graphene SAs is being regarded as a promising SA owing to its outstanding optical features such as ultra-broadband spectral operation range without chirality control, huge third-order nonlinearity, and fast recovery time [1]. Several previous efforts have been made for mode-locking of Tm-doped fibre lasers by using a SA with graphene flake/polymer composite [2]. More uniform and well-defined graphene layer synthesized by chemical vapour deposition (CVD) method was also employed as a mode-locker for Tm-doped fibre laser by transferring CVD graphene/PMMA layer to optical fibre ferrule [3]. However, this ferrule type graphene SA exhibits limited nonlinear interaction length (and strength) due to the low optical absorption (~ 2.3%) and very thin thickness (~0.34 nm) of a mono-layer graphene, which potentially causes an optical damage of the SA for high power operation.

© 2015 IEEE