Microfiber-based WS_2-film saturable absorber for ultra-fast photonics

Abstract

In this paper, we demonstrated a passively mode-locked erbium-doped fiber (EDF) laser by incorporating a tungsten disulfide (WS2) film SA fabricated by pulsed laser deposition (PLD) method. The WS2 film was thickness-dependent, which had two different states: the bulk WS2 [faced to plasma plume] and tiny WS2 flakes [in the shadow of plasma plume]. This SA device demonstrated low insertion loss (IL) and high power tolerance ability. Interestingly, the SA device possessed different nonlinear absorption regimes related with the film states. By employing this new type of SA, we obtained stable fundamental mode-locking (FML) at pump power of 54 mW, and the generated soliton pulse had pulse duration of 675 fs and signal-to-noise ratio (SNR) of 65 dB. At the maximum pump power of 395 mW, we also obtained up to 1 GHz repetition rate of harmonic mode-locking (HML) with pulse duration of 452 fs and SNR of 48 dB. The experimental results show that WS2-PLD film can serve as a promising SA for ultrafast laser systems.