Transient two-wave mixing in a linear configuration of an adaptive interferometer based on Er-doped fiber with saturable absorption

We report results of transient two-wave mixing (TWM) in Er-doped fibers with saturable absorption in a linear configuration of an adaptive interferometric vibrometer with essentially different powers of recording waves. The TWM signal modulation depth detected in the weak (reflected) wave was shown to be twice as strong as in the symmetric configuration with equal recording powers. In accordance with theoretical predictions, the experimentally observed TWM signal amplitude grew continuously with the fiber optical density in the whole investigated range of alpha(0)L approximately 0.2-4. At the recording wavelength 1492 nm it proved to be quite close to the theoretical limit of approximately alpha(0)L/2 for weakly absorbing fibers, and in 1-m-long fiber of high optical density reached maximal value of approximately 0.8. The TWM response time went down with the recording light power and for P(0) approximately 10 mW was in the submillisecond region.     

Diffusion-induced deflection and the effect of two-wave mixing gain on dissipative photovoltaic solitons

In an open-circuit dissipative photovoltaic (PV) crystal, by considering the diffusion effect, the deflection of bright dissipative photovoltaic (DPV) solitons has been investigated by employing numerical technique and perturbational procedure. The relevant results show that the centre of the optical beam moves along a parabolic trajectory, while the central spatial-frequency component shifts linearly with the propagation distance; furthermore, both the spatial deflection and the angular derivation are associated with the photovoltaic field. Such DPV solitons have a fixed deflection degree completely determined by the parameters of the dissipative system. The small bending cannot affect the formation of the DPV soliton via two-wave mixing.     

All-fiber erbium-doped dissipative soliton laser with multimode interference based on saturable-reserve saturable hybrid optical switch

Reverse saturable absorption is essential for the realization of dissipative solitons. In this paper, we introduce reverse saturable absorption by using nonlinear multimode interference (NL-MMI), for the first time, to the best of our knowledge, and obtain a stable dissipative soliton operation. By adjusting the coupling efficiency from multimode fiber to single mode fiber, the absorption properties of NL-MMI can be switched between saturation and reverse saturation. The dissipative soliton can be obtained with pulse width of 975 fs in the experiment, the 3-dB bandwidth at 1555 nm is 16 nm, and the maximum output power is 11.48 mW. The nonlinear absorption optical modulation and high damage threshold characteristics of the NL-MMI based ultrafast optical switch provide a new idea for realizing dissipative solitons.     

On the two-wave mixing in BaTiO3 with a self-bent pump beam

Received: 25 February 1997/Revised version: 20 June 1997     

Motion of dissipative soliton complexes in a nonlinear interferometer with driving radiation

A numerical analysis has been made of the motion of spatial dissipative soliton complexes in a wide-aperture interferometer with the Kerr nonlinearity, which is excited by continuous coherent driving radiation. It has been demonstrated that, depending on the symmetry of the radiation intensity distribution, the complex can exhibit four variants of dynamics, including the curvilinear motion of its center. The results obtained have been compared with the case of laser soliton complexes (without coherent driving radiation) and with the predictions made from the phenomenological model of the motion of soliton complexes.     

Fe：KTN晶体的二波耦合特性研究

首次报道四方相FeiKTN晶体的二波耦合性质.测得晶体的二波耦合增益系数和衍射效率分别为7.3cm~(-1)和42％,响应时间为2.8sec.文中还分析了主要载流子的符号并计算了其它参数.     

Experimental observation of transient mode-locking in the build-up stage of a soliton fiber laser

In this paper, we demonstrated a series of short-living mode-locking(ML) states(each lasting a few to a hundred microseconds) that happened before a fiber laser reached a steady ML state. With time-stretched dispersion Fourier transform spectroscopy, a rich diversity of transient multi-pulse dynamics were revealed spectrally and temporally. As a result, we found that the formation of the short-living ML states was related to abundant pump power, and their decaying evolution dynamics were possibly governed by gain depletion and recovery. Our results revealed unexpected transient lasing behaviors of a soliton laser and thus might be useful to understand the complex dynamics of mode-locked lasers.     

Symmetry of the mixing Hamiltonian in lattices with a basis

To determine substitutional and injection superstructures in alloys having a complex lattice with a basis by the method of concentration waves it is necessary to know the eigenvectors of the Fourier transform matrices V_pq() of the mixing potential of a homogeneous solid solution. A technique has been developed, investigating the variations of the matrix elements V_pq() for symmetry transformations of the spatial lattice group, to solve this problem. The symmetry elements belonging to the wave vector group determine the internal structure of the matrices V_pq() for lattices with a basis. Symmetry elements not appearing in the wave vector group determine the relation between matrices belonging to different rays of the star wave vector. Restrictions on the matrix elements V_pq(), following from symmetry, are found for an h.c.p. lattice. The eigenvectors are calculated for the matrices V_pq(), whose vectors terminate in high-symmetry points, lines, and planes of the Brillouin zone. This made it possible to separate the problem of thermodynamic competition of intermediate phases in an alloy with a hexagonal lattice into symmetric and potential parts, similarly to the way this occurs in Bravais lattices.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 13–25, August, 1993.     

双光子吸收效应对孤子和孤子对传输的影响

用分步傅立叶变换法求解含双光子吸收效应的光孤子NLS方程,研究了双光子吸收效应对一阶孤子和孤子对传输的影响,发现双光子吸收效应除对孤子产生等效损耗外,还影响了孤子对在传输中的相互作用。在特定的双光子吸收系数条件下双光子吸收效应可以使孤子对平行地向前传输。     

Resonant two-wave mixing in photorefractive materials with the aid of dc and ac fields

A recently predicted resonant effect for the enhancement of two-wave mixing in photorefractive materials is investigated. The resonance occurs when the frequency of the applied ac field agrees with the eigenfrequency of the excited space-charge wave. Experimentally a clear resonance is found, as predicted by the theory, for high dc electric fields, but the resonance is smeared out for lower fields. A modified theory, taking into account the second temporal harmonic of the space-charge wave, shows good agreement with the experimental results.     

Reverse saturable absorption of a novel rhodamine-B cation fulleride salt at 532 nm

A novel rhodamine-B cation fulleride salt was synthesized by metathetical reaction. Its tetrahydrofuran solution was prepared and the fluence-dependent transmission was measured with 10-ns 532-nm laser pulses in a collimated optical setup. With increases in the input fluence, its transmittance decreased significantly, which indicated reverse saturable absorption behavior. For comparison, the input fluence-dependent transmittance of fullerene C₆₀ and rhodamine-B solution were also measured. The nonlinear optical limiting effect of the fulleride salt in tetrahydrofuran is slightly lower than that of C₆₀ in toluene and the explanations are provided. Received: 25 August 2000 / Accepted: 6 November 2000 / Published online: 3 April 2001     

Spatial frequency dependence of the energy transfer in two-wave mixing experiments with BSO crystals

Energy transfer between two beams interfering in an electrooptic Bi₁₂SiO₂₀ crystal is analyzed as a function of the spatial frequency of the recorded hologram. We report high coefficients in a wide range of low spatial frequencies $\text{(Λ}{}^{-1}\text{?44 mm}{}^{-1}\text{)}$, when the drift length of the photocarriers becomes comparable to the fringe spacing. Exponential gain coefficients of Γ = 7 cm^-1 have been reached for high intensity beams ratio (β > 10⁴) and an optimized fringe displacement speed (moving grating recording). Application to coherent image amplification (×20) is shown.     

Experimental observation of the elliptically polarized fundamental vector soliton of isotropic Kerr media

We report the experimental observation of the elliptically polarized fundamental vector soliton of isotropic Kerr media and its unique polarization evolution. This was achieved in the spatial domain in a nonbirefringent CS2 planar waveguide.     

基于运动光栅光折变双光束耦合的刚性全息明孤子的动态演化

研究基于运动光栅双光束耦合的耗散光折变系统中的空间光孤子的动态演化问题.数值计算 表明，系统参数同这种孤子的稳定性密切相关.在某组系统参数下，孤子可以在晶体内稳定 传播足够远的距离.双光束耦合的相位与强度耦合系数之比越大，孤子的稳定性越好.讨论了 将这种系统应用于光学开关、中继及分路器件的可能性. 关键词： 空间光孤子 光折变非线性光学 耗散系统 全息光栅     

Pulsating solitons in a laser with relaxation of gain and saturable absorption

Results of numerical simulation of the formation of pulsating solitons in a laser with relaxation of gain and saturable absorption are presented. The regions of relaxation parameters are found in which stationary pulsating solitons and solitons with strong modulation of the pulsation amplitude are observed. Examples of multiple subsequent doubling of the oscillation period, caused by changing relaxation parameters, are presented.     

Interaction of solitons in a medium with relaxation of gain and saturable absorption

Results of numerical simulation of soliton interaction in a laser with relaxation of gain and saturable saturation are presented. Interactions of co-and counterpropagating fast and slow solitons are analyzed. Typical scenarios of collisions and new resulting soliton-like structures are found.     

Numerical simulations and experimental investigations on transverse effects of two-wave mixing in a photovoltaic photorefractive crystal

The transverse effects of two Gauss waves mixing in a photovoltaic photorefractive crystal,i.e.,the dynamical evolutions of signal beam with different parameters,are traced numerically and experimentally.Both the one-dimensional numerical simulations and two-dimensional experimental investigations show that the self-focusing effect of signal beam becomes more obvious as the intensity of pump beam and the angle between the signal and pump beams increase.In accordance with these results,the state of two Gauss...