Soliton pulses in two-mode periodic fibers

The conditions of the formation and the propagation of soliton pulses in a periodic two-mode non-linear fiber are studied. The analysis takes into account the dispersion of a fiber material and the intermode dispersion of the interacting modes subject to the conditions of their phase matching.     

双模双光子激光的半经典理论

在本文中,拉姆(Lamb)的半径典激光理论被用来讨论双模双光子激光运转,将文献[7]的单模结果推广到两模频率相差甚大的双模双光子激光情况。     

Preparation and control of entangled states in the two-mode coherent fields interacting with a moving atom via two-photon process

We investigate the preparation and the control of entangled states in a system with the two-mode coherent fields interacting with a moving two-level atom via the two-photon transition. We discuss entanglement properties between the two-mode coherent fields and a moving two-level atom by using the quantum reduced entropy, and those between the two-mode coherent fields by using the quantum relative entropy. In addition, we examine the influences of the atomic motion and field-mode structure parameter $p$ on the quantum entanglement of the system. Our results show that the period and the duration of the prepared maximal atom-field entangled states and the frequency of maximal two-mode field entangled states can be controlled, and that a sustained entangled state of the two-mode field, which is independent of atomic motion and the evolution time, can be obtained, by choosing appropriately the parameters of atomic motion, field-mode structure, initial state and interaction time of the system.     

Distributed entanglement in the two-photon two-mode non-linear process

In this paper we consider a quantum optics model where two-mode quantum light cavity with Kerr-like medium is coupled to an atom via two-photon process. The dynamical evolution of the system is studied in terms of entanglement measured by quantum relative entropy. The entanglements for the different bipartite partitions of the system, i.e., atom-two modes, mode-mode, mode-(atom+mode), are calculated explicitly and interesting trade-off relations between the different kinds of entanglement can be observed in different cases. The results show the entanglement between mode-mode is generally out of phase with that between atom and two modes, even though the two modes do not interact directly, and the Kerr-like medium prevents the atom and two modes from entangling.     

Soliton splitting in a dispersion-oscillating fiber

A single-mode fiber with a sinusoidal variation of the core diameter was fabricated. The soliton splitting due to the longitudinal oscillation of the fiber dispersion is demonstrated experimentally. The experimental observations are confirmed through numerical simulations. The periodical modulation of the fiber dispersion can be used for controlling the soliton splitting even under the strong effect of the Raman scattering.     

Stabilization of an active harmonically mode-locked fiber laser using two-photon absorption

Two-photon absorption provided by a semiconductor mirror structure is shown to reduce amplitude fluctuations significantly in a harmonically mo e-locked fiber ring laser. Pulse dropouts are eliminated in a laser that produces picosecond pulses at a repetition rate of 2 GHz.     

Squeezing in two-photon absorption

The conditions for homodyne detection of squeezing are related to the density matrix of the squeezed light. It is shown that coherent light subjected to two-photon absorption for an appropriate length of time develops a small amount of squeezing.     

Polarization and phase control of two-photon absorption in an isotropic molecular system

<正>We theoretically and experimentally study the polarization and phase control of two-photon absorption in an isotropic molecular system.We theoretically show that the two-photon transition probability decreases when the laser polarization changes from linear through elliptical to circular,and the laser polarization does not affect the control efficiency of two-photon transition probability by shaping the spectral phase.These theoretical results are experimentally confirmed in coumarin 480.Furthermore,we propose that the combination of the laser polarization with the spectral phase modulation can further increase the control efficiency of the two-photon absorption.     

Soliton molecule in fiber laser

The soliton molecule is achieved in nonlinear polarization rotation fiber laser. The structure of soliton molecule is heterogeneous diatomic molecule. The soliton molecule originates from the splitting of the high energy soliton. The dips of the soliton molecule spectra show that there is the interaction between the constituents of the soliton molecule, resulting in that the constituents are in the bound state as a unit. The laser bias can change the fine structure of the soliton molecule, which can be observed in the autocorrelator and oscilloscope.     

Soliton squeezing in microstructure fiber

We demonstrate, for the first time to our knowledge, the generation of squeezed light by means of soliton self-phase modulation in microstructure fiber. We observe and characterize the formation of solitons in the microstructure fiber at 1550 nm. A maximum squeezing of 2.7 dB is observed, corresponding to 4.0 dB after correcting for detection losses. The dependence of this quantum-noise reduction on various system parameters is studied in detail. Features of the microstructure fiber can be exploited for generation of low-energy continuous-variable entangled pulses for use in all-fiber teleportation experiments.     

Resonant two-photon absorption in a tetragonal CdP2

Kinetic, spectral, intensity, angular, and polarization of resonant two-photon absorption (TPA) in β-CdP₂ has been investigated. Resonant TPA was observed for which the total energy of the two photons was 2.60 eV. It is shown that resonant TPA takes place via a real intermediate level d ₃ in the band gap at the depth E _c-0.86 eV. The electron transverse relaxation time for resonant TPA, the cross section for absorption of laser photons in d ₃→C transitions, the equilibrium population of d ₃ centers in a doped n-type sample, and the resonant TPA constant were determined as 4.3×10⁻¹⁴ s, 1.25×10⁻¹⁷ cm², 0.95, and 0.028 cm/MW, respectively. Fiz. Tverd. Tela (St. Petersburg) 40, 1252–1256 (July 1998)     

Z-scan analytical theory for material with saturable absorption and two-photon absorption

By using the Adomian decomposition method, we present the transmitted optical intensity of a nonlinear medium with the concurrence of saturable absorption (SA) and two-photon absorption (TPA) processes. We obtain the analytical expression of the open-aperture Z-scan and investigate the interplay between SA and TPA in the Z-scan trace. Through Z-scan measurements at different levels of laser intensities, both the saturable intensity and TPA coefficient could be obtained quickly yet unambiguously.     

Application of two-mode fiber in voltage sensor

A new mode patter's demodulation technique is put forward. Researches of experiment and theory showthat the coupling efficiency of two kinds of different fibers depends on the relative offset between the twofibers when the core diameter of the information pick-up fiber is a little smaller than the major semi-axesof the elliptical-core two-mode fiber. Especially, when the relative offset δ≈ 1, fusing splice coupling efficiency reaches peak value. Furthermore, based on the new demodulation scheme, the sine voltagesignal applied on the piezoelectric lead zirconate titanate (PZT) is obtained and the detection precision of the system is within +0.2% when the voltage changes between 0.1 and 20 V.     

Biexciton two-photon absorption in CuBr

The biexciton states in CuBr have been studied at K ? 0 by two-photon absorption, using two different laser sources. The energy and the symmetry of these states have been unambiguously assigned: E_B(Γ₁) = 5.9061 eV, E_B(Γ₅) = 5.9103 eV, E_B(Γ₃) = 5.9128 eV.     

双光子吸收的Franz-Keldysh效应

从实验上证实Hg_0.695Cd_0.305Te 光电二极管空间电荷区中存在双光子吸收的Franz-Keldysh效应.利用一个皮秒Nd:YAG激光器抽运的光学参量产生器和差频产生器作为激发光源,测量了入射波长为λ₀=7.92μm的脉冲激光所激发的光响应随入射光强的变化关系.脉冲光响应峰值强度随入射光强的增大呈现二次幂函数增强趋势.采用等效RC电路模型将脉冲光伏信号峰值与入射光强相关联,得到空间电荷区中强电场下单光束 关键词： Franz-Keldysh效应 碲镉汞 双光子吸收 脉冲光伏信号     

Apodization of elliptical-core two-mode fiber acousto-optic filter based on acoustic polarization control

We propose and demonstrate a novel apodization technique for an elliptical-core two-mode fiber acousto-optic filter by twisting the fiber and adjusting the acoustic polarization. The sidelobe suppression in the filter spectrum was improved from -9.7 to -15.5 dB. A theoretical analysis that includes acoustic birefringence explains the experimental results with good agreement.     

双光子吸收的Franz-Keldysh效应

从实验上证实Hg_0.695Cd_0.305Te 光电二极管空间电荷区中存在双光子吸收的Franz-Keldysh效应.利用一个皮秒Nd:YAG激光器抽运的光学参量产生器和差频产生器作为激发光源，测量了入射波长为λ₀=7.92μm的脉冲激光所激发的光响应随入射光强的变化关系.脉冲光响应峰值强度随入射光强的增大呈现二次幂函数增强趋势.采用等效RC电路模型将脉冲光伏信号峰值与入射光强相关联，得到空间电荷区中强电场下单光束     

Optical bistability due to a two-photon absorption resonance with fluctuations

Using the intensity-dependent complex dielectric function for a two-photon absorption resonance we derive the Langevin equation for the fluctuating light-field in the non-linear resonator. The corresponding Fokker-Planck equation is solved by expanding the distribution function in terms of products of trigonometric functions and generalized Laguerre polynomials. The expansion coefficients are calculated using the method of matrix continued fractions. Numerical results for the stationary case are given.     

Soliton coupling in birefringent optical fiber with third-order dispersion

Nonlinear coupling of polarized solitons in birefringent optical fiber in the presence of third-order dispersion is considered in the framework of the coupled nonlinear Schrödinger equations. The influence of third-order dispersion on the interaction between solitons is investigated. For sufficiently strong third-order dispersion the interaction may even become repulsive. The stable conditions for solitons of partial pulses are analyzed and amplitude threshold, which decreases with third-order dispersion coefficient decreasing, for the capture of solitons of partial pulses into a coupled two-component pulse is obtained.     

Soliton compression in Brillouin fiber lasers

Pulse propagation in optical fibers may electrostrictively excite acoustic waves as a result of cladding Brillouin scattering, transversally propagating with respect to the fiber axis in the fiber's cladding, and mechanical coating. We show, for the first time to our knowledge, experimentally and theoretically that these transverse resonances within finite frequency ranges may cooperatively couple with the acoustic longitudinal modes of a fiber resonator, giving rise to stable trains of either spread or compressed three-wave Brillouin solitons and propose a first stability map for the rich four-wave dissipative dynamics.