Low-Threshold, Multiple High-Order Harmonics Fiber Laser Employing Cr 2 Si 2 Te 6 Saturable Absorber.

Abundant research findings have proved the value of two-dimensional (2D) materials in the study of nonlinear optics in fiber lasers. However, there remains two problems: how to reduce the start-up threshold, and how to improve the damage threshold, of fiber lasers based on 2D materials. A 15.1 mW low-threshold mode-locked fiber laser, based on a Cr 2 Si 2 Te 6 saturable absorber (SA) prepared by the liquid-phase exfoliation method, is demonstrated successfully in this work. This provides a useful and economical method to produce SAs with low insertion loss and low saturation intensity. Besides, multiple high-order harmonics, from the fundamental frequency (12.6 MHz) to the 49th-order harmonic (617.6 MHz), mode-locked operations are recorded. The experimental results indicate the excellent potential of Cr 2 Si 2 Te 6 as an optical modulator in exploring the soliton dynamics, harmonic mode locking, and other nonlinear effects in fiber lasers.