Optical Multi-wave Mixing Process Based on Electromagnetically Induced Transparency

In this paper, we propose and analyze an optical multi-wave mixing scheme for the generation of coherent light in a five-level atomic system in the context of electromagnetically induced transparency. A detailed semiclassical study of the propagation of generated mixing and probe fields is demonstrated. The analytical dependence of the generated mixing field on the probe field and the respective detuning is predicted. Such a nonlinear optical process can be used for generating short-wavelength radiation at low pump intensities.     

Continuous-wave four-wave mixing with linear growth based on electromagnetically dual induced transparency

Using Schrodinger-Maxwell formalism, we propose and analyze a continuous-wave four-wave mixing (FWM) scheme for the generation of coherent light in a six-level atomic system based on electromagnetically dual induced transparency. We derive the corresponding explicit analytical expressions for the generated mixing field. We find that the scheme greatly enhances FWM production efficiency and is also capable of inhibiting and delaying the onset of the detrimental three-photon destructive interference by choosing the proper decay rate in the second electromagnetically induced transparency (EIT) process.In addition, such an optical process also provides possibilities for producing short-wave-length coherent radiation at low pump intensities.     

Coherent optical detection of highly excited Rydberg states using electromagnetically induced transparency

We demonstrate coherent optical detection of highly excited Rydberg states (up to n=124) using electromagnetically induced transparency (EIT), providing a direct nondestructive probe of Rydberg energy levels. We show that the EIT spectra allow direct optical detection of electric field transients in the gas phase, and we extend measurements of the fine structure splitting of the nd series up to n=96. Coherent coupling of Rydberg states via EIT could also be used for cross-phase modulation and photon entanglement.     

Observations of Autler-Townes spatial splitting of four-wave mixing image

We report the self- and external-dressed Autler-Townes (A-T) splittings of the images of the generated four-wave mixing signal (FWM) and electromagnetically induced transparency (EIT) of probe images in cascade three-level atomic system. Such spatial properties of probe and FWM signals are induced by the enhanced cross-Kerr nonlinearity. We demonstrate the controlled electromagnetically induced spatial dispersion (EISD), splitting and focusing of probe and FWM signals images by adjusting self- and external-dressing fields. Studies on such controllable A-T spatial splitting and spatial EIT effect can be very useful in applications of spatial signal processing and optical communication.     

Steady-state linear optical properties and Kerr nonlinear optical response of a four-level quantum dot with phonon-assisted transition

The linear optical properties and Kerr nonlinear optical response in a four-level loop configuration Ga As/Al Ga As semiconductor quantum dot are analytically studied with the phonon-assisted transition(PAT). It is shown that the changes among a single electromagnetically induced transparency(EIT) window, a double EIT window and the amplification of the probe field in the absorption curves can be controlled by varying the strength of PAT κ. Meanwhile, double switching from the anomalous dispersion regime to the normal dispersion regime can likely be achieved by increasing the Rabi energy of the external optical control field. Furthermore, we demonstrate that the group velocity of the probe field can be practically regulated by varying the PAT and the intensity of the optical control field. In the nonlinear case, it is shown that the large SPM and XPM can be achieved as linear absorption vanishes simultaneously, and the PAT can suppress both third-order self-Kerr and the cross-Kerr nonlinear effect of the QD. Our study is much more practical than its atomic counterpart due to its flexible design and the controllable interference strength, and may provide some new possibilities for technological applications.     

Controlled parametric generation in a double-ladder system via all-resonant four-wave mixing

We demonstrate parametric generation of a new coherent field with a polarization orthogonal to the signal field via an all-resonant four-wave mixing process in a double-ladder system. We show that the generation of the coherent field is an efficient resonantly enhanced process that can be realized with a fairly dilute medium and relatively weak drive fields. The large parameter domain that exists in this system provides good control for both the weak probe and the generated field. Potential applications in optical communication are outlined.     

Resonantly enhanced continuous-wave four-wave mixing with spontaneously generated coherence in a five-state cold atomic medium

Using Schroedinger-Maxwell formalism, we propose and analyse a continuous-wave four-wave mixing (FWM) scheme for the generation of coherent light in a five-state double-A atomic system with or without spontaneously generated coherence (SGC) based on electromagnetically induced transparency (EIT). We derive the corresponding explicit analytical expressions for the generated FWM field under the steady-state condition. The influence of hyperfine sublevel and SGC effect on the amplitude of the generated FWM field is predicted in detail via the derived analytical expressions. We also give a brief discussion on the experimental realization of the proposed scheme.     

Study of radiofrequency radiation by means of optical effect of electromagnetically induced transparency

We propose a method of all-optical investigation of radiofrequency (RF) radiation based on the coherent effect of electromagnetically induced transparency (EIT). It is shown that if the atomic coherence is perturbed by an RF field, the shape of probe pulse propagating in a three-level ??-type atomic medium under EIT conditions is modified correspondingly to the temporal structure of the RF pulse. The effect is sensitive to the parameters of the pulse which enables measuring the intensity and the spectrum of the RF pulse. The method can be used for storage and lossless transfer of RF information over long distances using optical pulses.     

Electromagnetically induced transparency and electromagnetically induced absorption in Y-type system

The propagation of a probe field through a four-level Y-type atomic system is described in the presence of two additional coherent radiation fields, namely, the control field and the coupling field. An expression for the probe response is derived analytically from the optical Bloch equations under steady state condition to study the absorptive properties of the system under probe field propagation through an ensemble of stationary atoms as well as in a Doppler broadened atomic vapor medium. The most striking result is the conversion of electromagnetically induced transparency(EIT) into electromagnetically induced absorption(EIA) as we start switching from weak probe regime to strong probe regime. The dependence of this conversion on residual Doppler averaging due to wavelength mismatch is also shown by choosing the coupling transition as a Rydberg transition.     

Frequency‐sensitive switching control effect induced by two‐photon resonance in an EIT‐based layered medium

The optical response of an atomic vapor can be coherently manipulated by tunable quantum interference occurring in atomic transition processes. A periodic layered medium whose unit cells consist of a dielectric and an EIT (electromagnetically induced transparency) atomic vapor is designed for light propagation manipulation. Such an EIT‐based periodic layered medium exhibits a flexible frequency‐sensitive optical response, where a very small change in probe frequency can lead to a drastic variation of reflectance and transmittance. As the destructive quantum interference relevant to two‐photon resonance arises in EIT atoms interacting with both control and probe fields, the controllable optical processes that depend sensitively on the external control field will take place in this EIT‐based periodic layered medium. Such a frequency‐sensitive and field‐controlled optical behavior of reflection and transmission in the EIT photonic crystal can be applicable to designs of new devices such as photonic switches, photonic logic gates and photonic transistors, where one laser field can be controlled by the other one, and would have potential applications in the areas of integrated optical circuits and other related techniques (e.g., all‐optical instrumentations).     

Linear Growth of Continuous-Wave Four-Wave Mixing with Dual Induced Transparency

Using Schrödinger-Maxwell formalism, we propose and analyze an optical four-wave mixing (FWM) scheme for the generation of coherent light in a coherent six-level atomic medium based on dual electromagnetically induced transparency (EIT). We show that the significantly enhanced conversion efficiency enabled by ultraslow propagation of pump waves has no direct relationship with the single-photon detuning, which is different from the FWM with a single EIT. The most important feature is that our scheme is also capable of inhibiting and delaying the onset of the detrimental three-photon destructive interference that looks like a recent scheme [Phys. Rev. Lett. 91 (2003) 243902] and may be used for generating short-wave-length coherent radiation.     

Group velocity in a nuclear EIT-like Λ scheme and comparison with optical EIT

The group velocity of gamma radiation scattered in the forward direction by a nuclear lambda scheme experiencing level mixing induced transparency, which shows some similarity to optical EIT, has been investigated. The equations for the nuclear coherences governing the group velocity have been solved. The group velocity decreases with the density of the resonant nuclei and with a decrease in the intensity of the mixing interaction. A comparison between the group velocity of the gamma radiation and the probe radiation in “classical” optical EIT conditions has been made.     

里德伯电磁感应透明中的相位

本文在典型的里德伯电磁感应透明系统中研究弱探测场在相互作用原子系统中的传播特性,重点关注基于偶极阻塞效应的探测场相位的合作光学非线性行为.通过与探测场透射率和光子关联作对比,发现相位的光学响应具有新特性:共振和Autler-Townes劈裂条件下相位对入射场强和初始光子关联不敏感,而在两者之间的频率范围内相位响应具有非线性特征,尤其在经典光频率处最显著.此外,提高主量子数和原子密度都会促进相位的非线性效应.综上,与探测场透射率和光子关联一样,相位可以作为合作光学非线性的另一个标识来刻画非线性现象,对里德伯电磁感应透明研究是一个有力的补充.     

Modulation of four-wave mixing via photonic band gap

The dressed four-wave mixing （FWM） in a four-level S5Rb atomic system, experimentally demon- strated in this paper, is comprised by two coexisting processes. One is emission signal due to enhanced nonlinear via electromagnetically induced transparency （EIT）. The other is the Bragg reflection of probe beam because of the created photonic band gap （PBG）, which is affected by both linear and third-order nonlinear susceptibility. Moreover, we have demonstrated that different experimental parameters can significantly influence the measured signal with flexibly controlled PBG. These studies are found useful for understanding the fundamental mechanisms in generated FWM processing.     

电磁诱导透明窗口中温度、功率及偏振特性对四波混频信号的影响

电磁诱导透明(EIT)效应改变了介质的吸收特性,导致了线性极化率的抑制和非线性极化率的提高,从而可以实现高效率四波混频的产生.实现了基于EIT的高效四波混频,且研究了样品温度、入射光功率和入射光偏振状态对四波混频信号的影响特性.研究发现,温度对样品铷的两个同位素87Rb和85Rb的影响有所差别,它们分别存在一个最佳工作...     

调谐耦合场作用下的无反转光放大

 讨论了调谐耦合场作用下的Λ型三能级系统中的无反转光放大（AWI）现象,调谐耦合场同时激励两个基态精细结构能级与激发态能级之间的跃迁,使系统同时呈现电磁诱导透明（EIT）和自发诱导相干凹陷两种特性,而且当调节这个耦合场的频率失谐量在某一特定范围时,系统会在EIT信号上叠加出现AWI现象。研究结果表明：该系统中EIT和自发诱导相干凹陷之间存在能量转移现象,当EIT上出现AWI现象时,虽然激发态能级与基态能级之间没有出现粒子数反转,但是两个基态精细结构能级之间出现了粒子数反转。     

Investigation of KTiOPO4 nanocrystals by means of second-harmonic light emission

The finding of nonlinear nanometric-sized probes is of key importance for the development of nonlinear microscopy in physical as well as biological sciences. We isolate nonlinear KTiOPO4 nanocrystals and study them by second-harmonic generation microscopy （SHGM） and atomic force microscopy （AFM） independently. With both polarization analysis and defocused imaging of the emitted second harmonic field, we extract the Euler angles of the crystalline axes of a single nanocrystal. A balanced coherent optical homodyne detection shows the coherent nature of the nanocrystal nonlinear emission and allows a phase measurement of the emitted second-harmonic field. These features make the KTiOPO4 nanocrystal a good candidate for a vectorial probe of electromagnetic near fields.     

调谐耦合场作用下的电磁诱导透明和增益

在通常的A型三能级系统中,耦合场和探测场分别与一对光学跃迁能级发生相互作用,使探测吸收曲线上出现线宽极窄的电磁诱导透明(Electromagnetically Induced Transparency,EIT)特性.本文采用调谐耦合场同时激励两个基态精细结构能级与激发态能级之间的跃迁,使系统同时呈现EIT和自发诱导相干...     

Mid-infrared efficient generation by resonant four-wave mixing in a three-coupled-quantum-well nanostructure

We present a cascade configuration for the realization of highly efficient four-wave mixing (FWM) process in an asymmetric semiconductor three-coupled-quantum-well (TCQW) structure based on intersubband transitions (ISBTs). In the proposed TCQW scheme, the efficiency of the generated FWM mid-infrared (MIR) signal is significantly enhanced and the obtained maximum efficiency is greater than 50%. The corresponding explicit analytical expressions for the input probe and generated FWM pulsed fields are derived by use of the coupled Schrödinger-Maxwell approach and the FWM efficiency versus several variables is also discussed in details. Such a semiconductor system is much more practical than its atomic counterpart because of its flexible design and the wide adjustable parameters. This nonlinear optical process in the TCQW solid-state material can be used for efficiently generating coherent short-wavelength radiation.     

Enhancing and suppressing four‐wave mixing in electromagnetically induced transparency window

We demonstrate the enhancement and suppression of four‐wave mixing (FWM) in an electromagnetically induced transparency (EIT) window in Y‐type ⁸⁵Rb atomic system. The generated two‐photon FWM signal can be selectively enhanced and suppressed via an EIT window. The EIT of probe as well as the enhancement and suppression of FWM signals can be modified by the sequential‐cascade double dressing. The influence of different probe polarization configurations is also studied. Different polarization states of the probe laser can select different transitions among Zeeman sublevels and different dressing strengths. Copyright © 2010 John Wiley & Sons, Ltd.