Abstract
The ultrafast saturable absorption in graphene is experimentally and theoretically investigated in the femtosecond (fs) time regime. This phenomenon is well-modeled with valence band depletion, conduction band filling and ultrafast intraband carrier thermalization. The latter is dominated by intraband carrier-carrier scattering with a scattering time of 8 ( +/- 3) fs, which is far beyond the time resolution of other ultrafast techniques with hundred fs laser pulses. Our results strongly suggest that graphene is an excellent atomic layer saturable absorber.
Highlights
Graphene is new class of single atom thick materials which possesses a unique smooth-sided conical band structure that converges to a single Dirac point [1,2,3,4]
Within the model of the non-interacting, massless Dirac fermions [1,2], the weak light absorption is calculated to be independent of frequency and to have a universal opacity, π·α = 2.3% [5,6,7]
During the accumulation of carriers in the valence band (VB) and conduction band (CB): photo absorption of incoming photons at the same energy and the intraband c-c scattering
Summary
Graphene is new class of single atom thick materials which possesses a unique smooth-sided conical band structure that converges to a single Dirac point [1,2,3,4]. Within the model of the non-interacting, massless Dirac fermions [1,2], the weak light absorption is calculated to be independent of frequency and to have a universal opacity, π·α = 2.3% (where α is the fine structure constant) [5,6,7]. This theoretical prediction has been confirmed by recent infrared to visible reflectivity and transmission measurements [8,9,10,11]. Key to the development of practical graphene-based optoelectronic devices is through a clear understanding of its intrinsic optical properties
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