Shenhe Fu

Discrete solitons and vortices on two-dimensional lattices of 𝒫𝒯 -symmetric couplers

We introduce a 2D network built of 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 PT-symmetric dual-core waveguides embedded into a photonic crystal. The system supports 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 systems 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.

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 μm thick sample, the pulse duration could be compressed from 100 to 48 fs. Coupled-mode equations for forward and backward waves were employed to simulate the dynamics therein, and good agreement between theory and experiment was obtained.

Discrete Solitons in Waveguide Arrays with Long-Range Linearly Coupled Effect

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 bynon-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.

THE TRANSMISSION OF QUASI-DISCRETE SOLITONS IN RESONANT WAVEGUIDE ARRAYS ACTIVATED BY THE ELECTROMAGNETICALLY INDUCED TRANSPARENCY

We introduce a model of resonant optical systems: a waveguide array doped periodically with resonant four-level N-type atoms. The dopant atoms are driven by external fields which induce the effect of the electromagnetically induced transparency (EIT). In this resonant waveguide arrays (RWA) system, the optical field propagates as quasi-discrete diffraction, breathing beam or stable spatial soliton when different initial amplitude and width of the probe are given. The critical values representing these transformations are obtained by the numerical simulations. In a further study of the oblique incidence, the soliton loses a portion of its energy while a kick (i.e., a transverse wave vector) is initially introduced. As the value of the kick becomes larger than a critical value, the soliton collapses.

Two-dimensional dipolar gap solitons in free space with spin-orbit coupling

We present gap solitons (GSs) that can be created in free nearly two-dimensional (2D) space in dipolar spinor Bose-Einstein condensates with the spin-orbit coupling (SOC), subject to tight confinement, with size

Two-dimensional solitons and quantum droplets supported by competing self- and cross-interactions in spin-orbit-coupled condensates

a_{\perp }

Buffering and trapping ultrashort optical pulses in concatenated Bragg gratings

, in the third direction. For quasi-2D patterns, with lateral sizes

Slow-light all-optical soliton diode based on tailored Bragg-grating structure

l\gg a_{\perp }

Tunable storage of optical pulses in a tailored Bragg-grating structure

, the kinetic-energy terms in the respective spinor Gross-Pitaevskii equations may be neglected in comparison with SOC. This gives rise to a bandgap in the systems spectrum, in the presence of the Zeeman splitting between the spinor components. While the present system with contact interactions does not produce 2D solitons, stable gap solitons(GSs), with vorticities

Dipolar bright solitons and solitary vortices in a radial lattice

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