Generation of soliton molecules in mode-locked erbium-doped fiber laser by InSb saturable absorber

Abstract

Conventional solitons (CSs), and soliton molecules (SMs) consisting of two and three CSs in a passively mode-locked erbium-doped fiber (EDF) laser based on InSb saturable absorber (SA) are demonstrated. The InSb SA coated on tapered single-mode fibers by magnetron-sputtering deposition (MSD) method possesses linear transmittance of 93.39 %, modulation depth of 2.8 %, and saturation peak power of 3.18 W, respectively. In the CSs operation, the oscillating wavelength is centered at 1570.38 nm with pulse duration of 540.74 fs, pulse repetition rate of 28.38 MHz and maximum average output power of 5.51 mW. In the SMs operation, tight bound SMs consisting of two solitons, and loose bound SMs consisting of two and three solitons are achieved and analyzed in detail. It’s concluded that the initial temporal separation between neighboring solitons (TSNS) is totally decided by the cavity parameters. In the formed SMs, the ratio of TSNS to soliton pulse duration can even be as large as several hundreds of times. The adoption of real SA is more advantageous than effective one to realize the modulation of initial TSNS and hence facilitates the generation of different types of SMs. The work, for the first time, verifies the feasibility and stability of SMs generation by InSb-based SA, which not only enriches the insight of InSb two-dimensional (2D) materials, but also achieves an in-depth understanding of SMs.