Photon generation in an electromagnetic cavity with a time-dependent boundary

We report the observation of photon generation in a microwave cavity with a time-dependent boundary condition. Our system is a microfabricated quarter-wave coplanar waveguide cavity. The electrical length of the cavity is varied by using the tunable inductance of a superconducting quantum interference device. It is measured at a temperature significantly less than the resonance frequency. When the length is modulated at approximately twice the static resonance frequency, spontaneous parametric oscillations of the cavity field are observed. Time-resolved measurements of the dynamical state of the cavity show multiple stable states. The behavior is well described by theory. Our results may be considered a preliminary step towards demonstrating the dynamical Casimir effect.     

Stable operation of a cw optical parametric oscillator near the signal-idler degeneracy

The frequency stability of a cw optical parametric oscillator (cw OPO) near the signal-idler degeneracy has been studied. The strong tendency of a near-degenerate OPO to mode hop has been suppressed by using a bulk Bragg grating as a spectral filter in the OPO cavity. An experimental demonstration of stable parametric oscillation in a single longitudinal mode of the OPO cavity is reported, together with the capability of tuning the signal-idler difference frequency from 1 to 4 THz. The OPO has potential use in cw terahertz generation.     

利用原子与SU(2)相干态腔场的Raman相互作用制备原子纠缠态

利用一个参量频率转换过程,在腔中制备双模SU(2)相干态,然后注入一系列全同的Λ型三能级原子,这些原子与腔场的一个模发生拉曼相互作用,通过系列原子-腔场相互作用生成腔场-原子纠缠态,通过对腔场进行选择性测量,可获得多种形式多原子纠缠态.     

Generation of narrow-band correlated photon pairs by spontaneous down conversion in a cavity

The problem of generating a narrow-band biphoton field during spontaneous parametric down conversion of light in a quadratic nonlinear medium in a cavity is discussed. It is shown that, in the case of double resonance (for signal and idle fields), the form of the single-photon wave packet is biexponential and has a half-width determined by the photon life time in the cavity. An experiment is carried out on the generation of narrow-band biphotons in a crystal of lithium iodine with I-type matching in a frequency degenerate collinear regime. The second-order correlation function of the cavity-enhanced biphotons is measured using the electric nanosecond time delay line.     

Modification of pattern formation in doubly resonant second-harmonic generation by competing parametric oscillation

We analyze pattern formation in doubly resonant intracavity second-harmonic generation in the presence of competing nondegenerate parametric downconversion. We show that for positive cavity detuning of the fundamental frequency the threshold for parametric oscillation is lower than that of transverse, pattern forming instabilities. The parametric oscillation strongly modifies the pattern dynamics found previously in a simplified analysis that neglects parametric instability [Phys. Rev. E 56, 4803 (1997)]. Stationary and dynamic patterns in the presence of parametric oscillation are found numerically.     

Experimental evidence of spontaneous symmetry breaking in intracavity type II second-harmonic generation with triple resonance

We describe a spontaneous symmetry-breaking phenomenon between the intensities of the ordinary and extraordinary components of the fundamental field in intracavity type II harmonic generation. It is based on a triply resonant cavity containing a type II chi(2) crystal pumped at fundamental frequency omega0. The pump beam generates a second-harmonic mode at frequency 2omega0 that acts as a pump for frequency-degenerate type II parametric downconversion. Under operating conditions symmetric with respect to the ordinary and extraordinary components of the fundamental wave, we show a breaking of the symmetry of the intensities of these two waves.     

非线性光学腔中的相位调制光机械动力学

研究了Fabry-Perot光学腔中包含一个光学参量放大器来增强腔场与机械振子之间的耦合的光机械动力学行为.在解析边带机制下用量子郞之万方程具体研究了振子的涨落光谱、光学多稳态行为、机械阻尼与修正共振频移和基态冷却.通过数值解讨论了辐射压力诱导机械振子和腔场的稳态振幅所展现的光学多稳态行为,同时也分析了辐射压力引起的修正共振频移和机械阻尼与参量增益、输入激光功率和参量相位这三个因素的关系.此外,随着调节泵浦场的参量相位,振子的涨落光谱呈现简正模式分裂.通过精确求解最终有效声子数论证了基态冷却.结果表明,机械振子的冷却由初始浴温度、机械品质因数和参量相位这个三个因素控制.参量相提供一个新的方法来操控非线性光机械动力学.     

利用原子-腔场的拉曼相互作用制备双模SU(2)薛定谔猫态

利用一个参量频率转换过程,在腔中制备双模ＳＵ（２）相干态,然后注入一个与腔场的一个个模发生拉曼相互作用的Ａ型三能级原子,通过原子－腔场相互作用生成腔场－原子纠缠,通过对原子进行选择性测量,腔场－原子纠缠态将塌缩到纯态,即双模ＳＵ（２）薛定谔猫态。     

Nonlinear frequency mixing in a resonant cavity: Numerical simulations in a bubbly liquid

The study of nonlinear frequency mixing for acoustic standing waves in a resonator cavity is presented. Two high frequencies are mixed in a highly nonlinear bubbly liquid filled cavity that is resonant at the difference frequency. The analysis is carried out through numerical experiments, and both linear and nonlinear regimes are compared. The results show highly efficient generation of the difference frequency at high excitation amplitude. The large acoustic nonlinearity of the bubbly liquid that is responsible for the strong difference-frequency resonance also induces significant enhancement of the parametric frequency mixing effect to generate second harmonic of the difference frequency.     

低维半导体异质结中的量子相干红外发射机理理论研究

给出了一种在非粒子反转条件下量子阱和量子点激光器的红外发射机理.此种红外发射是基于在同一作用区产生并作为红外场相干源的两种带间跃迁激光场的共振非线性混合.这种频率下转换机理并不依赖于在半导体激活媒质中的长时相干假定条件,在室温和泵注入电流条件下仍然有效.频率下转换的固有效率可以达到相当于每个可见光子产生一个红外光子的量子极限值.根据红外发射的可参变特性,这种非粒子反转的方法尤其适用于长波红外工作范围.     

非线性光学腔中的相位调制光机械动力学

研究了Fabry-Perot光学腔中包含一个光学参量放大器来增强腔场与机械振子之间的耦合的光机械动力学行为.在解析边带机制下用量子郎之万方程具体研究了振子的涨落光谱、光学多稳态行为、机械阻尼与修正共振频移和基态冷却,通过数值解讨论了辐射压力诱导机械振子和腔场的稳态振幅所展现的光学多稳态行为,同时也分析了辐射压力引起的修...     

Negative-index metamaterials: second-harmonic generation, Manley–Rowe relations and parametric amplification

Second harmonic generation and optical parametric amplification in negative-index metamaterials (NIMs) are studied. The opposite directions of the wave vector and the Poynting vector in NIMs results in a “backward” phase-matching condition, causing significant changes in the Manley–Rowe relations and spatial distributions of the coupled field intensities. It is shown that absorption in NIMs can be compensated by backward optical parametric amplification. The possibility of distributed-feedback parametric oscillation with no cavity has been demonstrated. The feasibility of the generation of entangled pairs of left- and right-handed counter-propagating photons is discussed. PACS 78.67.-n; 42.65.Ky; 42.65.Lm     

Quantization and generation of squeezed states of electromagnetic field in a cavity with variable parameters

Quantization of an electromagnetic field in a cavity filled with a uniform medium having a time-varying dielectric constant and in a cavity with a moving wall is considered. It is shown that squeezed and correlated states of the field can be generated. The possible limits of the squeezing and correlation coefficients are indicated. Two methods of parametric buildup of field modes, by variation of the dielectric constant and by vibrating the cavity wall at double the frequency, are compared.Presented at the International Workshop on Squeezed and Correlated States in Quantum Optics, Moscow, December 3–7, 1990.     

Quadripartite entanglement from cascaded χ nonlinear interactions

We theoretically analyze the generation of quadripartite continuous-variable entanglement, with different frequency, by cascaded nonlinear process in a quadruply resonant optical cavity. This process is realized by one optical parametric down-conversion operated below threshold cascaded by two sum-frequency generations in a quasiperiodic optical supperlattice. It shows that the signal, idler and two sum frequency modes are entangled according to the sufficient inseparability criterion proposed by van Loock and Furusawa. The quantum correlation spectra among these four modes versus normalized analysis frequency and nonlinear coupling coefficients are discussed as well in detail.     

Compensating losses in negative-index metamaterials by optical parametric amplification

Optical parametric amplification controlled by the auxiliary electromagnetic field enables transparency, amplification, and oscillation with no cavity in strongly absorbing negative-index metamaterials. The opposite directions of the wave vector and the Poynting vector in such materials result in extraordinary optical properties, including "backward" phase matching and the generation of entangled pairs of left- and right-handed counterpropagating photons.     

Entanglement of movable mirror and cavity field enhanced by an optical parametric amplifier

A scheme to generate entanglement in a cavity optomechanical system filled with an optical parametric amplifier is proposed. With the help of the optical parametric amplifier, the stationary macroscopic entanglement between the movable mirror and the cavity field can be notably enhanced, and the entanglement increases when the parametric gain increases.Moreover, for a given parametric gain, the degree of entanglement of the cavity optomechanical system increases with increasing input laser power.     

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.     

Optical parametric oscillator for flow diagnostics

Cluster hopping effects and frequency instabilities prevent a wide use of doubly-resonant optical parametric oscillators (DROPOs) in the field of optical diagnostics, especially in the nanosecond regime. By using a two-cavity device, we demonstrate here that stable single-mode output can be obtained, provided that the length of each cavity is carefully chosen.     

Quantum light from a whispering-gallery-mode disk resonator

Optical parametric down-conversion has proven to be a valuable source of nonclassical light. The process is inherently able to produce twin-beam correlations along with individual intensity squeezing of either parametric beam, when pumped far above threshold. Here, we present for the first time the direct observation of intensity squeezing of -1.2 dB of each of the individual parametric beams in parametric down-conversion by use of a high quality whispering-gallery-mode disk resonator. In addition, we observed twin-beam quantum correlations of -2.7 dB with this cavity. Such resonators feature strong optical confinement and offer tunable coupling to an external optical field. This work exemplifies the potential of crystalline whispering-gallery-mode resonators for the generation of quantum light. The simplicity of this device makes the application of quantum light in various fields highly feasible.     

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。