Abstract

Tm-doped pulsed fiber lasers are attractive for a number of applications in spectroscopy owing to their potential tunability, extension of the spectral band for optical communications and for pumping of mid-infrared nonlinear optical devices. Moreover, Tm-doped fiber (TDF) lasers and amplifiers can be pumped with readily available diode or Er-doped fiber lasers. Figure-8 (F8) lasers containing nonlinear amplifying loop mirror (NALM) [1] were among the first passively mode-locked ultrashort-pulsed lasers where subpicosecond pulse generation has been demonstrated using Er-doped gain fibers [2]. The geometry is attractive due to the fact that the laser is, ideally, an inherently pulsed system if a balanced 3 dB coupler is employed in the Sagnac loop (see Fig.1(a)). The F8 cavity configuration is therefore attractive for demonstrating passive mode-locking in 2 μm range where low-loss fiber components and saturable absorber mirrors are still under active development. F8 cavities are well known for their rich dynamics where targeting a specific operational mode can be far from trivial. For instance, F8 cavities with TDF have been shown to operate in fundamental soliton, multiple-pulse, noise-like long pulse regimes [3,4].

© 2015 IEEE