Mode-locking of Er-doped fiber laser using a multilayer MoS_2 thin film as a saturable absorber in both anomalous and normal dispersion regimes

Abstract

Application of a multilayer Molybdenum Disulfide (MoS2) thin film as a saturable absorber was experimentally demonstrated by realizing a stable and robust passive mode-locked fiber laser via the evanescent field interaction between the light and the film. The MoS2 film was grown by chemical vapor deposition, and was then transferred to a side polished fiber by a lift-off method. Intensity-dependent optical transmission through the MoS2 thin film on side polished fiber was experimentally observed showing efficient saturable absorption characteristics. Using erbium doped fiber as an optical gain medium, we built an all-fiber ring cavity, where the MoS2 film on the side polished fiber was inserted as a saturable absorber. Stable dissipative soliton pulse trains were successfully generated in the normal dispersion regime with a spectral bandwidth of 23.2 nm and the pulse width of 4.98 ps. By adjusting the total dispersion in the cavity, we also obtained soliton pulses with a width of 637 fs in the anomalous dispersion regime near the lasing wavelength λ = 1.55 μm. Detailed and systematic experimental comparisons were made for stable mode locking of an all-fiber laser cavity in both the normal and anomalous regimes.

2D Saturable Absorbers for Fibre Lasers

“…Alternatively, they can be embedded in transparent polymer films to form compact and flexible SA devices [32,[37][38][39][40][41][42][43]. Another attractive prospect is depositing TMD nano flakes along microfibres or D-shaped (side-polished) fibres [44][45][46], where the evanescent field mediates the strength of the light-matter interaction. While the light intensity on the TMD material is weaker in this case, the device interaction length can be significantly increased, which can enhance the nonlinearity, affording a higher power tolerance [44].…”

“…Using MoS 2 , such devices have been fabricated and characterized at ∼1 µm [32,44], ∼1.5 µm [34][35][36][37][39][40][41][42]45,48] and ∼2 µm [49] (corresponding to the gain bands for the principal active ions used in fibre lasers: ytterbium (Yb), erbium (Er) and thulium (Tm)), and a wide range of SA properties have been reported [30]. Saturable loss values have been reported from ∼1% [40] Figure 4 presents the optical characterization of a polymer composite including 6-7 MoSe 2 flakes.…”

“…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.…”

“…However, recent work has shown that all-normal and net-normal dispersion maps, producing dissipative solitons, can enable higher pulse energies [1,74]. Such designs have also been exploited for TMD-based mode-locked fibre lasers [33,44,45,53].…”

Tutorial on fiber-based sources for biophotonic applications

“…Pulses as short as 637 fs have been achieved with MoS 2 mode locked Er-based fiber lasers. 107 Using WS 2 , mode locking of Er 108 and Ho-Tm 109 doped fiber lasers has been successfully demonstrated, while MoSe 2 has been used to produce picosecond pulses with an Er-doped fiber laser system. 110 Other material structures have recently been introduced such as black phosphorous that has allowed the generation of pulses as short as 272 fs with an Er fiber laser 111 and from the new family of topological insulators that have recently been identified, that currently contain more [112][113][114] Consequently, there is a vast array of saturable absorbing species that can be used to mode lock fiber lasers each with distinct yet quite complementary properties.…”