title: Ultra-fast pulse propagation in nonlinear graphene/silicon ridge waveguide.
abstract: We report the femtosecond laser propagation in a hybrid graphene/silicon ridge waveguide with demonstration of the ultra-large Kerr coefficient of graphene. We also fabricated a slot-like graphene/silicon ridge waveguide which can enhance its effective Kerr coefficient 1.5 times compared with the graphene/silicon ridge waveguide. Both transverse-electric-like (TE-like) mode and transverse-magnetic-like (TM-like) mode are experimentally measured and numerically analyzed. The results show nonlinearity dependence on mode polarization not in graphene/silicon ridge waveguide but in slot-like graphene/silicon ridge waveguide. Great spectral broadening was observed due to self-phase modulation (SPM) after propagation in the hybrid waveguide with length of 2 mm. Power dependence property of the slot-like hybrid waveguide is also measured and numerically analyzed. The results also confirm the effective Kerr coefficient estimation of the hybrid structures. Spectral blue shift of the output pulse was observed in the slot-like graphene/silicon ridge waveguide. One possible explanation is that the blue shift was caused by the ultra-fast free carrier effect with the optical absorption of the doped graphene. This interesting effect can be used for soliton compression in femtosecond region. We also discussed the broadband anomalous dispersion of the Kerr coefficient of graphene.
authors.affiliation: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China.
authors.forename: Ken
authors.initials: K
authors.lastname: Liu
authors.affiliation: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China.
authors.forename: Jian Fa
authors.initials: JF
authors.lastname: Zhang
authors.affiliation: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China.|State key laboratory of High Performance Computing, National University of Defense Technology, Changsha, Hunan 410073, China.
authors.forename: Zhi Hong
authors.initials: ZH
authors.lastname: Zhu
authors.affiliation: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China.
authors.forename: Chu Cai
authors.initials: CC
authors.lastname: Guo
authors.affiliation: College of Science, National University of Defense Technology, Changsha, Hunan 410073, China.
authors.forename: Xiu Jian
authors.initials: XJ
authors.lastname: Li
authors.affiliation: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China.|State key laboratory of High Performance Computing, National University of Defense Technology, Changsha, Hunan 410073, China.
authors.forename: Shi Qiao
authors.initials: SQ
authors.lastname: Qin