Interaction Length-Dependent Saturable Absorption of MoS2-Coated Planarized Waveguide and its Effect on the Performance of Q-Switched Pulse Laser Generation

The performance of Q-switched erbium doped fiber laser using monolayer molybdenum disulfide (MoS
₂
)-coated planarized optical waveguides with different MoS
₂
coating lengths is studied in this work. Monolayer MoS
₂
thin film is integrated onto a planarized optical waveguide using dry transfer technique. As the MoS
₂
thin film interacts with the evanescent field only, the MoS
₂
-coated planarized waveguide saturable absorber provides advantages in terms of high damage threshold and controllable interaction length between the MoS
₂
thin film and the light propagating in the waveguide. With a MoS
₂
coating length of 7.2 mm, the laser shows a widely tunable wavelength range of 38.6 nm. The wavelength tunability of the Q-switched fiber laser reduces to 5.9 nm when the interaction length between light propagating in the waveguide and the MoS
₂
monolayer is reduced to 2.5 mm. This effect is attributed to the reduction in the number of vacancy states of MoS
₂
in shorter length coatings. The results obtained contribute valuable information towards the development of all-planar waveguide pulsed laser source.