WS_2 as a saturable absorber for ultrafast photonic applications of mode-locked and Q-switched lasers

Abstract

Two-dimensional (2D) nanomaterials, especially the transition metal sulfide semiconductors, have drawn great interests due to their potential applications in viable photonic and optoelectronic devices. In this work, 2D tungsten disulfide (WS2) based saturable absorber (SA) for ultrafast photonic applications was demonstrated. WS2 nanosheets were prepared using liquid-phase exfoliation method and embedded in polyvinyl alcohol (PVA) thin film for the practical usage. Saturable absorption was discovered in the WS2-PVA SA at the telecommunication wavelength near 1550 nm. By incorporating WS2-PVA SA into a fiber laser cavity, both stable mode locking operation and Q-switching operation were achieved. In the mode locking operation, the laser obtained femtosecond output pulse width and high spectral purity in the radio frequency spectrum. In the Q-switching operation, the laser had tunable repetition rate and output pulse energy of a few tens of nano joule. Our findings suggest that few-layer WS2 nanosheets embedded in PVA thin film are promising nonlinear optical materials for ultrafast photonic applications as a mode locker or Q-switcher.

WS_2 saturable absorber for dissipative soliton mode locking at 106 and 155 µm

“…Several groups also found that WS 2 nanosheets exhibit nonlinear saturable absorption property at 1.55 µm, and observed soliton mode-locking or Q-switching operations in erbium-doped fiber (EDF) lasers [28][29][30]. The aforementioned studies were mainly concentrated on the anomalous-dispersion regime, and mode-locking operation based on WS 2 SA has not been reported in normaldispersion fiber lasers.…”

2D Saturable Absorbers for Fibre Lasers

“…For example, WS 2 [42,50,66,67] and WSe 2 [42] have been demonstrated in passively Q-switched Er:fibre lasers. Additionally, a single MoSe 2 SA was used to Q-switch Yb, Er and Tm-doped fibre lasers [55].…”

“…The laser produced 800 ps pulses at a 6.6 MHz pulse repetition frequency, with an average output power of 9.3 mW [33]. Further work through cavity dispersion engineering resulted in sub-picosecond pulse generation [39,45,66,73], down to 637 fs [45]. These ultrafast lasers operated in the net anomalous dispersion regime, generating solitons.…”

Delivering dispersion-managed soliton and Q-switched pulse in fiber laser based on graphene and nonlinear optical loop mirror

“…DMS and DS were formed from opposite direction in a fiber laser, respectively [37]. In addition, Q-switched pulse and mode-locked pulse can be achieved through WS 2 saturable absorber (SA) in a fiber laser, respectively [38]. Q-switched mode-locked pulse was acquired in Tm: LiLuF 4 laser [39] and erbium-doped fiber (EDF) laser based on gold nanorod-PVA [40].…”