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Two-component solitons under a spatially modulated linear coupling: Inverted photonic crystals and fused couplers
Yongyao Li,Wei Pang,Shenhe Fu,Boris Malomed
Physics , 2012,
Abstract: We study two-component solitons and their symmetry-breaking bifurcations (SBBs) in linearly coupled photonic systems with a spatially inhomogeneous strength of the coupling. One system models an inverted virtual photonic crystal, built by periodically doping the host medium with atoms implementing the electromagnetically induced transparency (EIT). In this system, two soliton-forming probe beams with different carrier frequencies are mutually coupled by the EIT-induced effective linear interconversion. The system is described by coupled nonlinear Schr\"{o}dinger (NLS) equations for the probes, with the linear-coupling constant periodically modulated in space according to the density distribution of the active atoms. The type of the SBB changes from sub- to supercritical with the increase of the total power of the probe beams, which does not occur in systems with constant linear-coupling constants. Qualitatively similar results for the SBB of two-component solitons are obtained, in an exact analytical form, in the model of a fused dual-core waveguide, with the linear coupling concentrated at a point.
Discrete solitons in waveguide arrays with long-range linearly coupled effect
Zhijie Mai,Shenhe Fu,Jianxiong Wu,Yongyao Li
Physics , 2014, DOI: 10.7566/JPSJ.83.034404
Abstract: We study the influences to the discrete soliton (DS) by introducing linearly long-range nonlocal interactions, which give rise to the off-diagonal elements of the linearly coupled matrix in the discrete nonlinear schrodinger equation to be filled by non-zero terms. Theoretical analysis and numerical simulations find that the DS under this circumstance can exhibit strong digital effects: the fundamental DS is a narrow one, which occupies nearly only one waveguide, the dipole and double-monopole solitons, which occupy two waveguides, can be found in self-focusing and -defocusing nonlinearities, respectively. Stable flat-top solitons and their stagger counterparts, which occupy a controllable number of waveguides, can also be obtained through this system. Such digital properties may give rise to additional data processing applications and have potential in fabricating digital optical devices in all-optical networks.
Slow-light all-optical soliton diode based on tailored Bragg-grating structure
Hongji Li,Zhigui Deng,Jiasheng Huang,Shenhe Fu,Yongyao Li
Physics , 2015,
Abstract: An all optical soliton diode (AOSD) is proposed based on a sandwich nonlinear Bragg-grating structure: a linearly chirped Bragg-grating linked to a uniform Bragg-grating and again to a chirped Bragg-grating. The nonreciprocity is achieved by introducing two spatially asymmetric chirped Bragg-gratings with optical nonlinearity. High transmission ratio up to 150 is obtained when launching a picosecond Gaussian pulse into the setting. We find that such pulses in a form of solitons propagate at a rather small velocity ($<0.03c$) when pulse wavelength is selected in the vicinity of photonic bandgap.
Buffering and Trapping Ultrashort Optical Pulses in Concatenated Bragg Gratings
Shenhe Fu,Yikun Liu,Yongyao Li,Liyan Song,Juntao Li,Boris A. Malomed,Jianying Zhou
Physics , 2013, DOI: 10.1364/OL.38.005047
Abstract: Strong retardation of ultrashort optical pulses, including their deceleration and stoppage in the form of Bragg solitons in a cascaded Bragg-grating (BG) structure, is proposed. The manipulations of the pulses are carried out, using nonlinear effects, in a chirped BG segment which is linked, via a defect, to a uniform grating. The storage of the ultrashort pulses is shown to be very robust with respect to variations of the input field intensity, suggesting the feasibility of storing ultrafast optical pulses in such a structure. Physical estimates are produced for the BGs written in silicon.
Tunable storage of optical pulses in a tailored Bragg-grating structure
Shenhe Fu,Yongyao Li,Yikun Liu,Jianying Zhou,Boris A. Malomed
Physics , 2015, DOI: 10.1364/JOSAB.32.000534
Abstract: Scenarios for controllable creation, trapping and holding of single and multiple solitons in a specially designed nonlinear Bragg grating (BG) are proposed. The setting includes a chirped BG segment, which is linked via a local defect to a uniform BG with a built-in array of defects. A parabolic relation between the trapping position of the incident soliton and its power is obtained. Simultaneous trapping of two and three solitons at different locations is demonstrated too.
Direct femtosecond pulse compression with miniature-sized Bragg cholesteric liquid crystal
Liyan Song,Shenhe Fu,Yikun Liu,Jianying Zhou,Vladimir G. Chigrinov,Iam Choon Khoo
Physics , 2013, DOI: 10.1364/OL.38.005040
Abstract: Direct compression of femtosecond optical pulses from a Ti:sapphire laser oscillator was realized with a cholesteric liquid crystal acting as a nonlinear 1D periodic Bragg grating. With a 6-um thick sample, the pulse duration could be compressed from 100 to 48 femtoseconds. Coupled-mode equations for forward and backward waves were employed to simulate the dynamics therein and good agreement between theory and experiment was obtained.
Control of the stability and soliton formation of dipole moments in a nonlinear plasmonic finite nanoparticle array
Zhijie Mai,Shenhe Fu,Yongyao Li,Xing Zhu,Yikun Liu,Juntao Li
Physics , 2014, DOI: 10.1016/j.photonics.2014.10.001
Abstract: We perform numerical analysis of a finite nanoparticle array, in which the transversal dipolar polarizations are excited by a homogenous optical field. Considering the linearly long-range dipole-dipole interaction and the cubic dipole nonlinearity of particle, the characteristics of stability of a finite number nanoparticle array should be revised, compared with that of an infinite number nanoparticle array. A critical point in the low branch of the bistable curve is found, beyond which the low branch becomes unstable for a finite number of nanoparticles. The influence of the external field intensities and detuning frequencies on this critical point are investigated in detail. When the total number of particles approaches infinity, our results become similar to that of an infinity number particle system [cf. Ref.32]. Notably, with appropriate external optical field, a dark dipole soliton is formed. Moreover, when the scaled detuning is set to an appropriate value, a double monopole dark soliton (DMDS) consisting of two particles is formed. The DMDS may have potential applications in the subwavelength highly precise detection because of its very small width.
Discrete solitons and vortices on two-dimensional lattices of $\mathcal{PT}$-symmetric couplers
Zhaopin Chen,Jingfeng Liu,Shenhe Fu,Yongyao Li,Boris A. Malomed
Physics , 2014, DOI: 10.1364/OE.22.029679
Abstract: We introduce a 2D network built of $\mathcal{PT}$-symmetric dimers with on-site cubic nonlinearity, the gain and loss elements of the dimers being linked by parallel square-shaped lattices. The system may be realized as a set of $\mathcal{PT}$-symmetric dual-core waveguides embedded into a photonic crystal. The system supports $\mathcal{PT}$-symmetric and antisymmetric fundamental solitons (FSs) and on-site-centered solitary vortices (OnVs). Stability of these discrete solitons is the central topic of the consideration. Their stability regions in the underlying parameter space are identified through the computation of stability eigenvalues, and verified by direct simulations. Symmetric FSs represent the system's ground state, being stable at lowest values of the power, while anti-symmetric FSs and OnVs are stable at higher powers. Symmetric OnVs, which are also stable at lower powers, are remarkably robust modes: on the contrary to other PT-symmetric states, unstable OnVs do not blow up, but spontaneously rebuild themselves into stable FSs.
NeogenePaleoseismicEventsandtheShanwangBiota’sBurialintheLinquArea,ShandongProvince,China
TIAN,Hongshui,A.,J.,(Tom),VAN,LOON,*ZHANG,Zengqi,ZHANG,Shenhe,ZHANG,Banghua,L?,Mingying,LI,Fuchang,and,MA,Xuemin
地质学报 , 2015,
Abstract: SeveralpaleoseismiceventsarerecordedintheNeogeneLinquGroup,exposedintheLinquarea,ShandongProvince,China.Theeventswereinterpretedonthebasisoffieldworkandlaboratoryanalysis,whichshowedthepresenceofseismiteswithplasticallydeformedsoft-sedimentdeformationstructuresintheShanwangFormation,andofseismicvolcanicrocksintheYaoshanFormationwhichshowbrittledeformation.Theearthquake-triggeredsoft-sedimentdeformationsintheseismitesincludeloadstructures,ball-and-pillowstructures,flamestructures,pillow-likebeds,boudinagestructures,slumpfolds,syn-depositionalfaults,veinsofliquefiedsand,anddikesofliquefiedsandylime-mud.Theseismicactivityisalsoreflectedinwhatmightbecalled‘brittleseismites’;theseoriginatedwhen,undertheinfluenceofseismicvibrations,semi-consolidatedconglomeratewasshattered.Moreover,volcanicactivityisrelatedtointenseearthquakesthataffectedbasaltsintercalatedwithsandlayers;thesesuccessionsareknownas‘seismicvolcanicrocks’,whicharecharacterizedbyveinsofliquefiedsandintrudingthebasalts.Allabovetracesofpaleoseismicactivitywereleftfromonesingletimespanof4Mawithactiveseismicitythattookplace14?10Ma.Thistimespanisknownas‘theLinquNeogenePaleoseismicActivePeriod’,whichisdividedintofourpaleoseismicepisodes,whichwereresponsestotectonicextensionandbasinriftinginthisarea.ItevenincludestheactivityoftheYishuFaultZoneduringtheMioceneandtheNeogene.Theratiosoftraceelementsintheseismites,w(La)/w(Sc)andw(La)/w(Th)arehigherthantheaveragevalueoftheuppercrust,butw(Th)/w(Sc)islower;thisisgeochemicalevidenceforthebasinriftingthatresultedinahighsedimentationrate.Theintenseandfrequentpaleo-earthquakesareheldresponsiblefortherapidburialoftheShanwangBiota.Secondaryearthquake-inducedprocesses(e.g.slumpingofalakeshoreandthestronglyincreasedlacustrinesedimentationrate)contributedtotherapidburialofthebiota.
Nonlinear light propagation in cholesteric liquid crystals with a helical Bragg microstructure
Yikun Liu,Shenhe Fu,Xing Zhu,Xiangsheng Xie,Mingneng Feng,Jianying Zhou,Yongyao Li,Ying Xiang,Boris A. Malomed,Gershon Kurizki
Physics , 2015,
Abstract: Nonlinear optical propagation in cholesteric liquid crystals (CLC) with a spatially periodic helical molecular structure is studied experimentally and modeled numerically. This periodic structure can be seen as a Bragg grating with a propagation stopband for circularly polarized light. The CLC nonlinearity can be strengthened by adding absorption dye, thus reducing the nonlinear intensity threshold and the necessary propagation length. As the input power increases, a blue shift of the stopband is induced by the self-defocusing nonlinearity, leading to a substantial enhancement of the transmission and spreading of the beam. With further increase of the input power, the self-defocusing nonlinearity saturates, and the beam propagates as in the linear-diffraction regime. A system of nonlinear couple-mode equations is used to describe the propagation of the beam. Numerical results agree well with the experiment findings, suggesting that modulation of intensity and spatial profile of the beam can be achieved simultaneously under low input intensities in a compact CLC-based micro-device.
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