Rabi oscillations revival induced by time reversal: a test of mesoscopic quantum coherence

Using an echo technique proposed by Morigi et al., we have time-reversed the atom-field interaction in a cavity quantum electrodynamics experiment. The collapse of the atomic Rabi oscillation in a coherent field is reversed, resulting in an induced revival signal. The amplitude of this "echo" is sensitive to nonunitary decoherence processes. Its observation demonstrates the existence of a mesoscopic quantum superposition of field states in the cavity between the collapse and the revival times.     

Specific architectures for optical parametric oscillators

Optical parametric oscillators are coherent light sources showing properties that are not encountered with usual laser sources. This article deals with optical architectures that take advantage of the specific properties of the three-wave mixing parametric interaction. We show that optical cavities can be specifically designed to increase either the optical conversion of the parametric process or to reduce dramatically the emitted line width. To cite this article: A. Berrou et al., C. R. Physique 8 (2007).     

Second order parametric processes in nonlinear silica microspheres

We analyze second order parametric processes in a silica microsphere coated with radially aligned nonlinear optical molecules. In a high-Q nonlinear microsphere, we discover that it is possible to achieve ultralow threshold parametric oscillation that obeys the rule of angular momentum conservation. Based on symmetry considerations, one can also implement parametric processes that naturally generate quantum entangled photon pairs. Practical issues regarding implementation of the nonlinear microsphere are also discussed.     

Second-order nonlinear optical materials for efficient generation and amplification of temporally-coherent and narrow-linewidth terahertz waves

We have considered forward and backward optical parametric oscillation and amplification, and difference-frequency generation for efficiently generating and amplifying terahertz waves in several second-order nonlinear optical materials. We have used a single crystal of CdSe as an example. We have also investigated GaSe, periodically-poled LiNbO₃ and LiTaO₃, and diffusion-bonded-stacked GaAs and GaP plates. The advantage of using birefringence in CdSe and GaSe is tunability of the output terahertz frequency. Furthermore, both CdSe and GaSe can be used to achieve the backward parametric oscillation without any cavity. On the other hand, in periodically-poled LiNbO₃ and LiTaO₃, one can take advantage of large diagonal elements of second-order nonlinear susceptibility tensor. In the diffusion-bonded-stacked GaAs and GaP plates, quasi-phase matching can be achieved by alternatively rotating the plates. We have shown that it is feasible to achieve forward optical parametric oscillation in the THz domain using these plates. The advantage of using coherent parametric processes is possibility of efficiently generating and amplifying temporally-coherent and narrow-linewidth terahertz waves. Compared with a noncollinear configuration, by using the parallel wave propagation configurations, the conversion efficiency can be higher because of longer effective interaction length among all the waves.     

An optical scheme for conditional generation of W state and photon-added coherent state

We propose a simple scheme to generate an arbitrary photon-added coherent state of a travelling optical field by combining an array of degenerate parametric amplifiers and corresponding single-photon detectors. Particularly, when the single-photon-added coherent state is observed by developing the novel technique of Zavatta et al （2004 Science 306 660）, we can simultar/eously obtain the generalized N-qubit W state.     

A FULL QUANTUM THEORY OF THE THREE-MODE INTERACTIONS INSIDE AN OPO CAVITY

A full quantum treatment about the process of parametric down-conversion with frequency degenerate but polarization pon-degenerate in an optical parametric oscillator (OPO) cavity is presented. Using the linearized Langevin equations and spectral matrix, we calculated the squeezing spectra of the coupled mode in the output field. The squeezing as a function of driving field and detection frequency is obtained. The resuits obtained, which are compared with those found semiclassically by Reynaud et al., indicate that it is possible to generate a two-mode coherent squeezed state with large amplitude. The quantum correlation between the signal and the idler modes is also discussed. It is shown that there is an inseparable relationship between the two-mode squeezing and the intermode quantum correlation.     

Strong coupling regime in semiconductor microcavities

We introduce to the physics of semiconductor microcavities in the strong coupling regime, also known as cavity-polariton. We discuss the optical response, cavity-polariton dispersion curve, inhomogeneous broadening due to disorder effect and homogeneous broadening due to acoustic phonon scattering. We present novel effects on high quality samples on elastic scattering and parametric oscillation effects in the non-linear response under resonant excitation. To cite this article: R. Houdré et al., C. R. Physique 3 (2002) 15–27     

Enhancement of Available Conversion Efficiency of Optical Parametric Amplifier in a Cascaded Photonic Crystal Structure

Using the cascaded structure of a linear and a second-order nonlinear photonic crystals, we realize a high-efficiency optical parametric amplifier in the case of exact phase matching. This proposal is verified using the slow-envelope nonlinear finite difference time domain numerical method. Compared with the case of the individual nonlinear photonic crystal structure, the oscillation threshold is decreased obviously; and the peak power amplification factor of the transmitted signal is enhanced more than 20 times.     

Parametric generation of twin photons in vertical triple microcavities

We report the realization of a monolithic vertical-cavity, surface emitting micro-optical parametric conversion nanostructure, triply resonant with the parametric frequencies, allowing parametric oscillation with ultra-low pump power threshold. The photonic phase-space naturally provides triple resonance for the parametric frequencies, together with built-in cavity phase-matching for the pump wave at normal incidence. Parametric oscillation is observed in both the strong and weak exciton–photon coupling regime, allowing a high operating temperature. Signal and idler beams can be collected at 0° or at finite angles. The OPO threshold is low enough to envisage the realization of an all-semiconductor electrically-pumped micro-parametric oscillator. To cite this article: C. Diederichs et al., C. R. Physique 8 (2007).     

Time-reversed sound beams of finite amplitude.

Numerical simulations based on the nonlinear parabolic wave equation are used to investigate time reversal of sound beams radiated by unfocused and focused sources. Emphasis is placed on nonlinear propagation distortion in the time-reversed beam, and specifically its effect on field reconstruction. Distortion of this kind, due to amplification during time reversal, has been observed in recent experiments [A. P. Brysev et al., Acoust. Phys. 44, 641-650 (1998)]. Effects of diffraction introduced by time-reversal mirrors with finite apertures are also considered. It is shown that even in the presence of shock formation, the ability of time reversal to retarget most of the energy on the source or focal region of the incident beam is quite robust.     

准位相匹配材料研究新进展及应用

准位相匹配材料（光学超晶格）是一种人工非线性光学材料，目前已被广泛应用于倍频，三倍频，光参量振荡等激光变频领域，这种材料可以通过提供倒格矢来满足非线性光学过程中的位相失配，从而提高非线性光学过程转换效率，文章简要回顾了准位相匹配理论的发展过程，对其基本原理及主要应用做了较为详细的描述，并对近年来该领域的一些新进展做了介绍。     

Perfect photon absorption based on the optical parametric process

The perfect photon absorption is studied in a cavity quantum electrodynamics(CQED) system, in which an optical parameter amplifier(OPA) is coupled to the cavity mode. This makes it possible to control the optical phase to realize the perfect photon absorption. It is found that in the presence of one and two injected fields, the perfect photon absorption is present in these two cases and can be controlled by adjusting the parametric phase. Moreover, different from the previous predictions of perfect photon absorption in atomic CQED systems, the perfect photon absorption can be changed significantly by the relative phase. Our work provides a new platform to use the parametric processes to make an available way to control the behaviors of photons and to take advantage of the optical phase to achieve the perfect photon absorption.     

Theory of nonlinear dispersive waves and selection of the ground state

A theory of time-dependent nonlinear dispersive equations of the Schr?dinger or Gross-Pitaevskii and Hartree type is developed. The short, intermediate and large time behavior is found, by deriving nonlinear master equations (NLME), governing the evolution of the mode powers, and by a novel multitime scale analysis of these equations. The scattering theory is developed and coherent resonance phenomena and associated lifetimes are derived. Applications include Bose-Einstein condensate large time dynamics and nonlinear optical systems. The theory reveals a nonlinear transition phenomenon, "selection of the ground state," and NLME predicts the decay of excited state, with half its energy transferred to the ground state and half to radiation modes. Our results predict the recent experimental observations of Mandelik et al. in nonlinear optical waveguides.     

Three-colour entanglement generated by an injection-seeded nondegenerate optical parametric oscillator

Three-colour continuous-variable (CV) entanglement can be directly generated by an injection-seeded nondegenerate optical parametric oscillator (INOPO). The quantum correlations among the pump, signal, and idler beams are calculated and discussed by applying sufficient inseparability criteria for CV entanglement. The results clearly show that strong three-colour CV entanglement can be produced by operating the pump above the oscillation threshold. The INOPO is easier to realize experimentally and more steady in comparison to that without an injected signal since the injected signal can increase the nonlinear conversion efficiency and the stability, as well as allow a large degree of tunability. This scheme can be very useful for the applications in quantum communication and computation networks.     

Two-dimensional numerical simulation of acoustic wave phase conjugation in magnetostrictive elastic media

The effect of parametric wave phase conjugation (WPC) in application to ultrasound or acoustic waves in magnetostrictive solids has been addressed numerically by Ben Khelil et al. [J. Acoust. Soc. Am. 109, 75-83 (2001)] using 1-D unsteady formulation. Here the numerical method presented by Voinovich et al. [Shock waves 13(3), 221-230 (2003)] extends the analysis to the 2-D effects. The employed model describes universally elastic solids and liquids. A source term similar to Ben Khelil et al.'s accounts for the coupling between deformation and magnetostriction due to external periodic magnetic field. The compatibility between the isotropic constitutive law of the medium and the model of magnetostriction has been considered. Supplementary to the 1-D simulations, the present model involves longitudinal/transversal mode conversion at the sample boundaries and separate magnetic field coupling with dilatation and shear stress. The influence of those factors in a 2-D geometry on the potential output of a magneto-elastic wave phase conjugator is analyzed in this paper. The process under study includes propagation of a wave burst of a given frequency from a point source in a liquid into the active solid, amplification of the waves due to parametric resonance, and formation of time-reversed waves, their radiation into liquid, and focusing. The considered subject is particularly important for ultrasonic applications in acoustic imaging, nondestructive testing, or medical diagnostics and therapy.     

用W态实现量子隐形传态的腔QED方案

本文提出一个用类W态作为纠缠通道,采用不同于文献[19]的测量基来实现量子隐形传态的腔QED方案.在这个方案里,只需要利用原子和腔场通过J-C哈密顿量发生共振相互作用,一步就可制备纠缠通道.另外,通过原子与腔场的失谐作用,利用Bell态测量,可实现概率为100%的量子隐形传态.在目前的腔QED技术条件下,该方案是可以实现的.     

Amplitude reduction of parametric resonance by dynamic vibration absorber based on quadratic nonlinear coupling

The paper proposes an amplitude reduction method for parametric resonance with a new type of dynamic vibration absorber utilizing quadratic nonlinear coupling. A main system with asymmetric nonlinear restoring force and harmonic excitation causes parametric resonance in the system. In contrast with autoparametric vibration absorber, the natural frequency of the vibration absorber is tuned to be in the neighborhood of twice that of the main system. For such a vibration absorber, we investigate the effect on the amplitude reduction for a parametrically excited main system. Analytical results using the method of multiple scales show that the amplitude of parametric resonance is reduced by the effect of the vibration absorber. The experimental results by a simple apparatus indicate that the parametric resonance is stabilized by the effects of both vibration absorber and Coulomb friction of the main system. Moreover, numerical results considering the Coulomb friction of the main system show that the amplitude of parametric resonance becomes close to zero by the proposed vibration absorber.     

On the efficacy of an active absorber with internal state feedback for controlling self-excited oscillations

An active absorber, utilizing the state feedback of the absorber mass, is proposed for controlling the self-excited vibration of a single degree-of-freedom extended Rayleigh oscillator. The control strategy renders the design standalone. The process of optimizing the control gains is discussed. The analysis reveals that by selecting a suitably high value of the absorber frequency, the overall damping of the system can be made as high as the critical damping irrespective of the amount of negative linear damping present in the primary self-excited system. It is shown that a higher value of the absorber frequency is profitable in almost all respects related to the performance as well as the robustness of the system under parametric uncertainty. The nonlinear analysis of the system reveals that the proposed absorber can control the amplitude of oscillation even in case detuning (up to some limit) of the absorber frequency from its nominal value. The region of global stability increases with the increase in the value of the absorber frequency. However some aspects, like higher absorber deflection, reduced lower bound of the admissible detuning and the lower range of the tolerance on the mass ratio limit using a very high value of absorber frequency. The results of numerical simulations confirm the analytical results.     

Spontaneous parametric down-conversion

Spontaneous parametric down-conversion (SPDC) in media with no inversion center and the use of this phenomenon in the spectroscopy of natural oscillation states of a crystal lattice (i.e., optical phonons) are retrospectively described. We think that the SPDC spectroscopy method is estimated inappropriately and hope to again attract the attention of readers to one of the most interesting quantum phenomena of nonlinear optics that has no classical analog. The capabilities of SPDC spectroscopy will certainly be used in both fundamental science and technology of new materials.