Abstract
We demonstrate an optically tunable graphene saturable absorber to manipulate the laser operation in pulsed fiber laser system. Owing to the strongly enhanced evanescent field interaction with monolayer graphene, we could realize an efficient control of modulation depth in the graphene saturable absorber by optical means through cross absorption modulation method. By integrating the tunable graphene saturable absorber into the fiber laser system, we could switch the laser operation from Q-switching through Q-switched mode-locking to continuous wave mode-locking by adjusting only the optical power of the control beam. In addition, we realized a hybrid Q-switching of fiber laser by periodical modulation of the absorption of the graphene saturable absorber, where we observed that the repetition rate of the Q-switched laser could be continuously tuned according to the modulation frequency of the applied external signal.
Highlights
Graphene, a single sheet of carbon atoms arranged in a hexagonal lattice, has been intensively studied for the applications to future photonic and optoelectronic devices because of its exceptional electrical and optical properties including high carrier mobility, gapless band structure, and optical transparency over wide spectral window [1,2]
We demonstrate an optically tunable graphene saturable absorber to manipulate the laser operation in pulsed fiber laser system
Owing to the strongly enhanced evanescent field interaction with monolayer graphene, we could realize an efficient control of modulation depth in the graphene saturable absorber by optical means through cross absorption modulation method
Summary
A single sheet of carbon atoms arranged in a hexagonal lattice, has been intensively studied for the applications to future photonic and optoelectronic devices because of its exceptional electrical and optical properties including high carrier mobility, gapless band structure, and optical transparency over wide spectral window [1,2]. It has been revealed that the optically excited carriers can alternatively tune the linear optical absorption in graphene by Pauli blocking principle [22,23], which enabled all-optical modulation of the light in a graphene-based device with large bandwidth [23] In nonlinear regime, this can control nonlinear absorption properties of graphene SA (GSA), such as modulation depth and non-saturable loss. In principle, the nonlinear absorption in the GSA can be significantly manipulated through cross absorption modulation (XAM) via evanescent field interaction, optical control of fiber laser operation for different pulsed laser states has not been demonstrated to the best of our knowledge This is due to the limited nonlinear interaction of light with graphene. Experimental demonstration of different pulsed laser modes is described when the GSA was applied to a fiber ring laser with the control beam power as the only variable parameter
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