The Effect of Incoherent Population Pumping on Squeezing in Resonance Fluorescence

The effect of incoherent population pumping on the steady-state population inversion and the quadrature squeezing spectra produced in the resonance fluorescence of a two-level atom is investigated. In the presence of incoherent population pumping, the steady-state population inversion is increased for small frequency detuning but is not changed for large frequency detuning. For resonant excitation at low intensities, the weak incoherent pumping degrades the degree of the squeezing and shifts the position of the maximum squeezing; for off-resonant excitation at strong intensities, the weak incoherent pumping hardly changes the squeezing spectra. But when the incoherent pumping is strong the squeezing may be completely destroyed for both cases.     

Lasing without inversion in a four-level diamond system

<正>We study the lasing without inversion in a four-level diamond configuration in the case of incoherent pumping field within the framework of the bare-state basis.With the strong fields limit,we obtain the approximate steady-state solution,and discuss the dependence of population distribution and system gain on probe detuning and auxiliary field Rabi frequency.     

Narrow spectral lines of modulation harmonics of gamma radiation in unordered magnetic materials

The spectra of gamma-resonance lines excited using the amplitude modulation of the pumping field of the Mössbauer effect were studied in unordered magnetic materials with a strong spread of magnetic hyperfine fields at nuclei of Mössbauer isotopes. The analysis demonstrates that the spectra of modulation harmonics consist of narrow lines, and their form and intensity are determined by the contribution of magnetic local hyperfine fields, which are excited at a pumping frequency. The inversion of intensities for odd harmonics with the change in sign of detuning of the pumping frequency relative to the average Larmor frequency of the Mössbauer nucleus was noted. The application of this method to the spectral analysis of inhomogeneous magnetic materials is discussed.     

Cavity-Induced Enhancement of Squeezing in Resonance Fluorescence of a V-Type Three-Level Atom

The quadrature squeezing spectra in the resonance fluorescence of a V-type three-level atom driven by a coherent field and coupled to a single-mode cavity is investigated. For weak excitation, the fluorescence field exhibit squeezing in the out-of-phase quadrature. The coupling between the atom and the cavity mode can greatly enhance the squeezing centred at the laser frequency. More importantly, for strong excitation, under the effect of the cavity-atom coupling, the in-phase quadrature of fluorescence can exhibit two-mode squeezing at the two inner sideband frequencies. By working in the dressed-state representation and hiring secular approximation, we give an analytical explanation for the effect. The result shows, under appropriate conditions, the squeezing can be greatly enhanced by appropriately tuning the cavity resonant frequency.     

光泵三能级原子体系产生光子数压缩态

本文证明光泵三能级原子体系可以产生光子数压缩态。分别计算非相干泵浦、弱相干泵浦和强相于泵浦几种情形下的Fano因数。结果表明,弱相干泵浦时可获得最佳压缩效应,相应的Fano因数为0.16。这种产生光子数压缩态的方法在实验上是简便可行的。 关键词：     

Quantum correlations and optical effects in a quantum-well cavity with a second-order nonlinearity

In this paper, we investigate the photon correlations and the statistical properties of light produced by an optical cavity with an embedded quantum well interacting with squeezed light. We show that the squeezed source substantially improves the intensity of the emitted light and generates a narrowing and a duplication of the spectrum peaks. With a strong dependence on frequency detuning, the cavity produces considerably squeezed radiation, and perfect squeezing is predicted for weak light–matter interactions. Furthermore, the system under consideration presents a bunching effect of the transmitted radiation resulting from weak pumping of the coherent field. The results obtained may have potential applications in the fields of very accurate measurement and quantum computing.     

Probe gain with population inversion in a four-level atomic system with vacuum-induced coherence

For a four-level atomic system with a doublet of closely spaced levels, we find that, owing to the coherence that results from the vacuum of the radiation field, population trapping at excited levels and probe gain with population inversion can be achieved with weak incoherent pumping. This gain is different from both the conventional lasing gain and gain without inversion in that there exists population inversion on probe transitions but the inversion is achieved by the vacuum-induced coherence.     

循环跃迁的Δ 型三能级系统中的无反转激光

研究了在引入非相干抽运的情况下,循环跃迁的Δ型共振三能级系统中产生的无反转激光.利用主方程的方法, 导出了缀饰态中强相干场极限下布居数项和相干项的稳态近似解析解以及产生无反转激光所需要满足的条件;并利用数值模拟的方法讨论了布居数分布、 系统增益对探测场和相干场拉比频率的依赖性以及随时间的演化规律. 结果表明:无论各个参量取何值,共振Δ型三能级系统总是处于无粒子数反转的状态; 只要探测场或相干场之中有一个为强场,便可产生无反转激光; 当其中任意一个场远强于另一个场时,系统的无反转增益将不再依赖于任何一个场的拉比频率.     

电子俘获材料的红外最小可激发阈值

A study is made of the steady-state populations of a three-level ladder atom in a squeezed vacuum, driven by a superposition of a monochromatic laser wave with incoherent population pumping. Using the density matrix equations for the system, the steady-state populations are calculated numerically and shown graphically as functions of two-photon detuning for various cases of the squeezed vacuum and different incoherent pump rates. It is shown that the incoherent population pumping tends to greatly decrease the two-photon absorption from the squeezed vacuum.     

Steady state Behaviour of a Three level Ladder Atomic System with Incoherent Population Pumping in a Squeezed Vacuum

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双模压缩真空场与Λ型三能级原子非共振作用

研究了双模压缩真空场与Λ型三能级原子非共振相互作用系统中,场模失谐量对原子布居概率和光场的双模互关联函数、二阶相干度的影响.结果表明：失谐量使原子Rabi振荡呈现周期性崩塌与复苏现象；当光场初始压缩因子r较小时,失谐量将削弱光子的反聚束效应；当r较大时,失谐量又将增强光场两模相关的稳定性.     

Sub-Poissonian radiation of a one-atom two-level laser with incoherent pumping

The quantum statistical properties of the radiation of a one-atom two-level laser with incoherent pumping are analyzed. Solution of the Liouville equation for the density operator in the basis of Fock states shows that stationary radiation from a single-mode laser with incoherent pumping can be in a squeezed (sub-Poissonian) stationary state if the rate of spontaneous decay is lower than the rate of cavity losses and the pump rate. Inside the cavity the Fano factor reaches F=0.85 (15% squeezing). Multiple squeezing (F=0.19) is possible in the transient lasing regime. Significant squeezing obtains at the cavity output; the spectral Fano factor at zero frequency is 0.36 under optimal conditions. Zh. éksp. Teor. Fiz. 115, 1210–1220 (April 1999)     

驱动场相位扩散对三能级梯型系统无反转激光的影响

在旋波、慢变振幅近似下,求解考虑了驱动场相位扩散后的系统密度矩阵运动方程,并给出了这个三能级梯型系统稳态线性解析解.利用得到的稳态线性解析解分析驱动场相位扩散是如何影响该系统输出无反转激光的.对稳态线性解析解数值计算的结果显示:由于驱动场相位扩散会导致无反转激光增益减小;即使由于驱动场相位扩散引起的线宽足够大,在该系统中仍能够获得无反转激光;线宽往往是破坏无反转激光产生和折射率的提高;因驱动场相位扩散导致无反转激光增益的减小,并不是总能够通过增大驱动场的Rabi频率得到补偿.     

Phase control of probe response in an open ladder type system with spontaneously generated coherence

The control role of the relative phase between the probe and driving fields on the gain and dispersion in an open three-level ladder atomic system with incoherent pumping and spontaneously generated coherence is investigated. It is shown that by adjusting the value of the relative phase, the switching from lasing with inversion to lasing without inversion (LWI) can be realized; high index of the refraction with zero absorption can be achieved. It is also found that when the driving field is on resonance, the dispersion curve versus the probe detuning is very similar to the gain curve if the relative phase corresponding to the dispersion advances π/2 than that corresponding to the gain. LWI gain from the open system is obviously larger than that from corresponding closed system. When the incoherent pumping is absent, the open system can get LWI gain, moreover the gain is larger than that when the incoherent pumping presents for suitable value of the relative phase, but the corresponding closed system exhibits only absorption. In addition, manipulation effects of atomic exit and ratio of the injection rates on phase dependent gain are also analyzed.     

Optimal sideband-squeezing in the resonance fluorescence of a two-level atom

The quantum fluctuation spectra of phase quadratures of the fluorescent light from a coherently driven two-level atom damping in a common vacuum is investigated. We find that by optimally choosing the Rabi frequency of the driving field, detuning between the atom and the driving field, and phase of the local oscillator the strong sideband squeezing in the spectrum of the optimal phase quadrature can be created and the degree of squeezing in the sidebands can reach about 56%.     

Role of incoherent pumping field on absorption–dispersion properties of probe pulse in a graphene nanostructure under external magnetic field

The optical properties of weak probe light based on quantum coherence and interference in Landau-quantized graphene nanostructure driven by two coherent fields and incoherent pumping field is investigated. The linear dynamical properties of the graphene by means of density matrix method and perturbation theory are discussed. It is found that under certain condition and for appropriate choosing the parameters of the medium, the absorption, dispersion, group index of the weak probe light can be controlled. Moreover, it is shown that by means of incoherent pumping field the superluminal light propagation in the system is accompanied by amplification to make sure that the probe field is amplified as it passes through the system. Moreover, it is observed that the probe amplification can be obtained in the presence or absence of population inversion by properly choosing of system’s parameters. We hope that these results may have useful in the future quantum communicational system and networks.     

克尔介质中压缩真空场与耦合双原子依赖强度耦合系统光场的压缩特性

研究了存在克尔介质时依赖强度耦合单模压缩真空场与耦合双原子非共振相互作用系统光场的压缩性质,运用数值方法讨论了系统参量对光场压缩性质的影响。结果表明:克尔介质、失谐量、原子间相互作用、光场初始压缩因子对光场的压缩性质有较大的影响。随原子间偶极偶极相互作用的增大,光场的压缩随时间逐渐变浅,压缩的次数减少;随克尔效应或失谐量的增大,光场的压缩程度先逐渐变浅后增强、压缩次数先减少后增多;当光场初始压缩因子较小时,光场压缩程度较小,当光场初始压缩因子较大时,光场压缩程度增大;而原子的初始状态对光场的压缩程度没有明显的影响。     

量子干涉效应对原子共振荧光非经典特性的影响

研究了两个自发辐射路径之间的量子干涉效应对V型三能级原子压缩谱和光子反聚束效应的影响 .结果表明 ,量子干涉可以加强压缩效应和展宽出现压缩的相位角分量的范围 ,但却会减弱反聚束效应.Phase-dependent squeezing spectrum and photon antibunching of resonance fluorescence from a three-level V-type atom driven by a coherent field are investigated. We show that for weak excitation intensities quantum interference can greatly enhance squeezing and change the phase quadrature at which the maximum squeezing occurs. We also notice that the maximum squeezing can appear not only in either the in-phase or the out-of-phase quadrature but also in any phase quadrature, and at which phase quadrature...     

Entanglement of the <Emphasis Type="Italic">su</Emphasis>(1; 1) Quantum System Interacting with a Single Two-Level Atom in the Presence of Damping Terms

We consider the effect of damping on a quantum system described by the su(1; 1) Lie algebra and interacting with a two-level atom. We obtain the numerical solution of the associated differential equations and discuss in detail some statistical aspects, atomic population inversion, squeezing phenomena, and negativity. In addition, we analyze the effect of the decay parameter on the population inversion and purity. Finally, we examine entropy squeezing and the degree of entanglement for some values of the damping and detuning parameters.