Stable new bound soliton pairs in a 10 GHz hybrid frequency modulation mode-locked Er-fiber laser

We report what is, to our knowledge, the first experimental observation of stable new bound soliton pairs at the 10 GHz repetition rate in a hybrid FM harmonic mode-locked Er-fiber laser (1177 soliton pairs simultaneously in the laser cavity). The two solitons in the soliton pair have the identical pulse shape and are with the antiphase (pi phase difference). Their time separation is about three times the FWHM soliton width and varies with the phase modulation strength. The corresponding mechanism for explaining the formation as well as the superior stability of these closely bound soliton pairs is also given.     

Vibrating and shaking soliton pairs in dissipative systems

We show that two-soliton solutions in nonlinear dissipative systems can exist in various forms. As with single solitons, they can be stationary, periodic or chaotic. In particular, we find new types of vibrating and shaking soliton pairs. Each type of pair is stable in the sense that the bound state exists in the same form indefinitely.     

Enhanced quantum correlations in bound higher-order solitons

Quantum effects in N-bound solitons can be drastically enhanced compared to the fundamental soliton. In particular, the spectral photon-number correlations are much stronger. The formation of spectral domains of almost perfect positive and negative correlations is predicted. Criteria that are based on the Cauchy-Schwarz inequality are used for studying nonclassical correlations. Interferences between different soliton components of the N-bound solution being responsible for the strong changes in the coherent amplitude may also be a mechanism for the strong correlations. The results offer novel possibilities of producing light with highly nonclassical properties.     

Linearized quantum-fluctuation theory of spectrally filtered optical solitons

We study the quantum fluctuations of an optical nonlinear Schr?dinger soliton after spectral filtering. The photon-number-bandwidth correlation of the emerging soliton produces squeezing in the photon number of the filtered soliton. Bandwidth oscillations caused by the interference of the soliton with the quantum-noise continuum, however, give oscillations of the photon-number squeezing and, in addition, prevent achievement of arbitrarily high values of squeezing through spectral filtering.     

Bright-dark incoherently coupled soliton pairs composed of spatially incoherent solitons

It is shown that bright-dark incoherently coupled soliton pairs can exist in photorefractive (PR) crystals under steady-state conditions, each soliton constituent of which is spatially incoherent. The characteristics of bright-dark incoherently coupled soliton pairs are studied by the coherent density approach and the intensity expressions of soliton pairs are obtained. The propagation properties of coherent components of each constituent in a soliton pair are also discussed in detail.     

Incoherently coupled soliton pairs in nonlocal nonlinear media

We show that incoherently coupled soliton pairs can exist in nonlocal Kerr-type nonlinear media. Such solitons can propagate in bright--bright, dark--dark, and gray--gray configurations. When the nonlocal nonlinearity is absent, these bright--bright and dark--dark soliton pairs are those observed previously in local Kerr-type nonlinear media. Our analysis indicates that for a self-focusing nonlinearity the intensity full width half maximum (FWHM) of the bright--bright pair components increases with the degree of nonlocality of the nonlinear response, whereas for a self-defocusing nonlinearity the intensity FWHM of the dark--dark and gray--gray pair components decreases with the increase in the degree of nonlocality of the nonlinear response. The stability of these soliton pairs has been investigated numerically and it has been found that they are stable.     

Asymmetric W-shaped and M-shaped soliton pulse generated from a weak modulation in an exponential dispersion decreasing fiber

We study localized waves on continuous wave background in an exponential dispersion decreasing fiber with two orthogonal polarization states. We demonstrate that asymmetric W-shaped and M-shaped soliton pulse can be generated from a weak modulation on continuous wave background. The numerical simulation results indicate that the generated asymmetric soliton pulses are robust against small noise or perturbation. In particular, the asymmetric degree of the asymmetric soliton pulse can be effectively controlled by changing the relative frequency of the two components. This character can be used to generate other nonlinear localized waves, such as dark–antidark and antidark–dark soliton pulse pair, symmetric W-shaped and M-shaped soliton pulse. Furthermore, we find that the asymmetric soliton pulse possesses an asymmetric discontinuous spectrum.     

Separate spatial soliton pairs in a biased series centrosymmetric photorefractive crystal circuit

It is shown theoretically that three types of separate soliton pairs: bright-bright, bright-dark, and dark-dark, can be established in a biased series circuit consisting of two centrosymmetric photorefractive crystals and the two solitons in a separate soliton pair can affect each other by the light-induced current. The effects of the intensities of soliton beams and background lights on the normalized profiles of solitons are discussed.     

有外加电源的串联光折变晶体回路中的独立空间全息-哈密顿屏蔽孤子对

在由两块垂直于光轴两端面镀上电极的光折变晶体和一个外加电源组成的串联光折变晶体回路中, 在适当的条件下可以形成独立空间全息-哈密顿屏蔽孤子对. 这种孤子对共有四种类型:明-明、暗-暗、明-暗以及暗-明. 当入射光束的空间展宽尺寸远小于晶体宽度时, 孤子对中的哈密顿暗孤子可以通过光感应电流影响另一个孤子, 而哈密顿明孤子和全息孤子则不能影响另一孤子.     

有外加电源的串联光折变晶体回路中的独立空间全息-哈密顿屏蔽孤子对

在由两块垂直于光轴两端面镀上电极的光折变晶体和一个外加电源组成的串联光折变晶体回路中, 在适当的条件下可以形成独立空间全息-哈密顿屏蔽孤子对. 这种孤子对共有四种类型:明-明、暗-暗、明-暗以及暗-明. 当入射光束的空间展宽尺寸远小于晶体宽度时, 孤子对中的哈密顿暗孤子可以通过光感应电流影响另一个孤子, 而哈密顿明孤子和全息孤子则不能影响另一孤子.     

Bound soliton pulses in passively mode-locked fiber laser

A passively mode-locked soliton fiber ring laser was successfully demonstrated, and bound soliton pulses with an FWHM pulsewidth of 326 fs and fixed separation of 938 fs were first observed. The number of bound soliton pairs in the cavity can be controlled under lower pump power. The transmission effects were investigated by injecting bound soliton pulses into a single mode fiber.     

非对称光折变全息空间光孤子的存在曲线

证明了在加外电场的光折变晶体中存在非对称全息空间光孤子对，其特征是孤子对中的两个 孤子具有相同的宽度、不同的振幅.给出了这种孤子对的存在曲线，其中存在三个具有不同 特征的区域：对于给定的外加电场来说，当孤子对中两个孤子的入射峰值强度之和与背景光 强度之比足够大或者足够小时，孤子宽度强烈依赖于这个比值，而在此中间的一段区域，孤 子宽度几乎不随这个比值而变化.非对称情况下这个中间区域的范围比对称情况的窄. 关键词： 空间光孤子 光折变非线性光学 全息光栅     

Practical scheme for non-postselection entanglement concentration using linear optical elements

We report a practical non-postselection entanglement concentration scheme in which a maximally entangled Bell-state photon pair is produced from two pairs of partially (or non-maximally) entangled photons. Since this scheme is built only upon linear optical elements and does not require photon-number resolving detectors, it has immediate applications in experimental implementations of various quantum information protocols which require two-photon Bell-states.     

Grey–grey separate spatial soliton pairs in a biased series photorefractive polymer circuit

Grey–grey separate spatial soliton pairs are predicted in a biased series circuit consisting of two guest-host photorefractive polymers. The numerical results show that two grey solitons in a soliton pair can affect each other by the light-induced current.     

Effects of dark soliton crystal temperature on the self-deflection of bright soliton in a biased serial photovoltaic photorefractive crystal circuit

Based on the theory of one-dimensional separate soliton pairs formed in a serial photovoltaic photorefractive crystal circuit, the effects of the dark soliton crystal temperature on the self-deflection of the bright one in a bright-dark soliton pair are investigated. The numerical results indicate that the spatial shift of the bright soliton can experience obvious increase in their self-deflection with the increase of the temperature of the dark soliton. The self-bending process is further studied using perturbation techniques and the results are found to be good agreement with that obtained by numerical method.     

Separate Holographic-Hamiltonian screening soliton pairs in a biased series photorefractive crystal circuit

Separate Holographic-Hamiltonian screening soliton pairs are predicted in a biased series photorefractive crystal circuit consisting of two photorefractive crystals connected electronically by electrode leads in a chain with a voltage source. The existence of four types of the separate soliton pairs: dark–dark, bright–dark, dark–bright and bright–bright in such a circuit is proved. Under the limit in which the spatial extent of the optical wave is much less than the width of the crystal, the Hamiltonian dark soliton can affect the other soliton by the light-induced current whereas the Hamiltonian bright soliton and holographic soliton cannot affect the other soliton in the soliton pair.     

Peregrine solitons and algebraic soliton pairs in Kerr media considering space–time correction

Exact unified rational solutions describing a family of Peregrine solitons as well as related algebraic soliton pairs in either self-focusing or self-defocusing Kerr media are presented, with distinct defining regimes and an explicit relationship for those of opposite nonlinearity. The active role of the space–time correction effect that plays in these soliton species is highlighted, leading to unique dynamics such as the persistence of Peregrine solitons in a defocusing Kerr medium, the availability of giant peak amplitude for the bright–bright soliton pair, and the existence of so-called bright–dark soliton pair. The evolution dynamics of the algebraic two-soliton state toward a spliced single soliton is also discussed.     

Incoherently coupled Hermite-Gaussian breather and soliton pairs in strongly nonlocal nonlinear media

We theoretically investigate the propagation of incoherently coupled Hermite-Gaussian breather and soliton pairs in strongly nonlocal nonlinear media. It is found that multipole-mode soliton pairs with arbitrary different orders of Hermite-Gaussian shape can exist when the total power of two beams equals the critical power and the ratio of the beam widths for the Gaussian part is inversely proportional to the square root of the ratio of the wave numbers. When the total power does not equal the critical power, the Hermite-Gaussian breather pair exists and their beam widths evolve analogously. For general cases where the ratio of the beam widths is arbitrary, soliton-breather pairs or breather-breather pairs can be formed and their beam widths evolve synchronously in-phase or out-of-phase. Numerical simulations directly based on the nonlocal nonlinear Schrödinger equation are conducted for comparison with our theoretical predictions. The numerical stability analysis shows the higher-order Hermite-Gaussian solitons can not be stable for small nonlocality or for some media like liquid crystals.     

Observation of antisymmetric dispersion-managed solitons in a mode-locked laser

We report experimental evidence of antisymmetric solitons in a mode-locked fiber laser with a strong dispersion map. A dispersion-managed soliton breathes as it traverses the dispersion map, and the antisymmetric dispersion-managed soliton can be considered a tightly bound soliton pair with pi phase difference between the component solitons. The antisymmetric soliton is observed only at particular values of the net cavity dispersion.