arXiv subjects

Shenhe Fu

Publications and source records attributed to Shenhe Fu.

23 records · Page 2Linked to original sources

arXiv2014

Control of the stability and soliton formation of dipole moments in a nonlinear plasmonic finite nanoparticle array

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.

physics.optics↗

arXiv2014

Discrete solitons and vortices on two-dimensional lattices of $\mathcal{PT}$-symmetric couplers

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.

physics.optics↗

arXiv2013

Direct femtosecond pulse compression with miniature-sized Bragg cholesteric liquid crystal

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.

physics.optics↗

arXiv2013

Buffering and Trapping Ultrashort Optical Pulses in Concatenated Bragg Gratings

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.

nlin.PS↗

arXiv2012

Two-component solitons under a spatially modulated linear coupling: Inverted photonic crystals and fused couplers

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 Schrödinger (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.

physics.optics↗