Under strong laser illumination, few-layer graphene exhibits both a transmittance increase due to saturable absorption and a nonlinear phase shift. Here, we unambiguously distinguish these two nonlinear optical effects and identify both real and imag
inary parts of the complex nonlinear refractive index of graphene. We show that graphene possesses a giant nonlinear refractive index n2=10-7cm2W-1, almost nine orders of magnitude larger than bulk dielectrics. We find that the nonlinear refractive index decreases with increasing excitation flux but slower than the absorption. This suggests that graphene may be a very promising nonlinear medium, paving the way for graphene-based nonlinear photonics.
Solitons, as stable localized wave packets that can propagate long distance in dispersive media without changing their shapes, are ubiquitous in nonlinear physical systems. Since the first experimental realization of optical bright solitons in the an
omalous dispersion single mode fibers (SMF) by Mollenauer et al. in 1980 and optical dark solitons in the normal dispersion SMFs by P. Emplit et al. in 1987, optical solitons in SMFs had been extensively investigated. In reality a SMF always supports two orthogonal polarization modes. Taking fiber birefringence into account, it was later theoretically predicted that various types of vector solitons, including the bright-bright vector solitons, dark-dark vector solitons and dark-bright vector solitons, could be formed in SMFs. However, except the bright-bright type of vector solitons, other types of vector solitons are so far lack of clear experimental evidence. Optical solitons have been observed not only in the SMFs but also in mode locked fiber lasers. It has been shown that the passively mode-locked erbium-doped fiber lasers offer a promising experimental platform for studying the scalar optical solitons. Vector solitons can also be formed in mode locked fiber lasers. In this dissertation, the author presents results of a series of theoretical and experimental investigations on the vector solitons in fiber lasers.
A recent communication [Opt. Commun. doi:10.1016/j.optcom.2010.06.076 (2010)] presents experimental results in which dark pulses are observed in a dispersion-managed (DM) net-anomalous dispersion fiber laser. Disagreement on the formation mechanism p
roposed in this communication, we would like to indicate a more accurate explanation in order to clarify some potential misunderstanding on dark pulses in fiber lasers.
We report on the observation of dispersion-managed (DM) dark soliton emission in a net-normal dispersion erbium-doped fiber laser. We found experimentally that dispersion management could not only reduce the pump threshold for the dark soliton format
ion in a fiber laser, but also stabilize the single dark soliton evolution in the cavity. Numerical simulations have also confirmed the DM dark soliton formation in a fiber laser.
We report on the experimental observation of a new type of dark soliton in a fiber laser made of all normal group velocity dispersion fibers. It was shown that the soliton is formed due to the cross coupling between two different wavelength laser bea
ms and has the characteristic of separating the two different wavelength laser emissions. Moreover, we show experimentally that the dual-wavelength dark solitons have a much lower pump threshold than that of the nonlinear Schrodinger equation dark solitons formed in the same laser.
We reply to S. Coen and T. Sylvestres comment on our paper [Phys. Rev. A 80, 045803 (2009)] and make some additional remarks on our experimental results.
We demonstrate that the intrinsic properties of monolayer graphene allow it to act as a more effective saturable absorber for mode-locking fiber lasers compared to multilayer graphene. The absorption of monolayer graphene can be saturated at lower ex
citation intensity compared to multilayer graphene, graphene with wrinkle-like defects, and functionalized graphene. Monolayer graphene has a remarkable large modulation depth of 95.3%, whereas the modulation depth of multilayer graphene is greatly reduced due to nonsaturable absorption and scattering loss. Picoseconds ultrafast laser pulse (1.23 ps) can be generated using monolayer graphene as saturable absorber. Due to the ultrafast relaxation time, larger modulation depth and lower scattering loss of monolayer graphene, it performs better than multilayer graphene in terms of pulse shaping ability, pulse stability and output energy.
Soliton operation and soliton wavelength tuning of erbium-doped fiber lasers mode locked with atomic layer graphene was experimentally investigated under various cavity dispersion conditions. It was shown that not only wide range soliton wavelength t
uning but also soltion pulse width variation could be obtained in the fiber lasers. Our results show that the graphene mode locked erbium-doped fiber lasers provide a compact, user friendly and low cost wavelength tunable ultrahsort pulse source.
Atomic layer graphene possesses wavelength-insensitive ultrafast saturable absorption, which can be exploited as a full-band mode locker. Taking advantage of the wide band saturable absorption of the graphene, we demonstrate experimentally that wide
range (1570 nm - 1600nm) continuous wavelength tunable dissipative solitons could be formed in an erbium doped fiber laser mode locked with few layer graphene.
We report on the experimental observation of induced solitons in a passively mode-locked fiber ring laser with birefringence cavity. Due to the cross coupling between the two orthogonal polarization components of the laser, it was found that if a sol
iton was formed along one cavity polarization axis, a weak soliton was also induced along the orthogonal polarization axis, and depending on the net cavity birefringence, the induced soliton could either have the same or different center wavelengths to that of the inducing soliton. Moreover, the induced soliton always had the same group velocity as that of the inducing soliton. They form a vector soliton in the cavity. Numerical simulations confirmed the experimental observations.
