共查询到20条相似文献,搜索用时 31 毫秒
1.
Dani KM Tignon J Breit M Chemla DS Kavousanaki EG Perakis IE 《Physical review letters》2006,97(5):057401
Using three-pulse four-wave-mixing optical spectroscopy, we study the ultrafast dynamics of the quantum Hall system. We observe striking differences as compared to an undoped system, where the 2D electron gas is absent. In particular, we observe a large off-resonant signal with strong oscillations. Using a microscopic theory, we show that these are due to many-particle coherences created by interactions between photoexcited carriers and collective excitations of the 2D electron gas. We extract quantitative information about the dephasing and interference of these coherences. 相似文献
2.
We review recent investigations of the femtosecond non-linear optical response of the two-dimensional electron gas (2DEG) in the quantum Hall effect regime. We find that the time and frequency profile of the four-wave-mixing non-linear optical spectrum is strongly influenced by Coulomb correlations between the photoexcited electron-hole pairs and the 2DEG collective excitations. We discuss experimental and theoretical results showing non-Markovian memory effects in the polarization dephasing, and an optically induced time-dependent coupling between the two lowest Landau level magnetoexcitons. 相似文献
3.
We propose a simple and powerful protocol to map an arbitrary atomic coherence between two quantum states into a population distribution of three metastable states, and later to retrieve the atomic coherence from the population distribution. The protocol applies simple sequences of radiation pulses with arbitrary temporal profile, either as coincident or as consecutive pulses. Mapping of rather short-lived atomic coherences into very long-lived atomic populations permits the prolongation of storage times (e.g. of optical information encoded in atomic coherences) by many orders of magnitude — without the need for complicated techniques to reduce homogeneous broadenings. 相似文献
4.
Ultrafast third-order optical nonlinearities of the as-deposited and annealed Au:Bi2O3 nanocomposite films deposited by magnetron cosputtering are investigated by using femtosecond time-resolved optical Kerr effect (OKE) and pump probe techniques. The third-order optical nonlinear susceptibility is estimated to be 2.6Ф×10^- 10 esu and 1.8 × 10.9 esu at wavelength of 800nm, for the as-deposited and the annealed film, respectively. The OKE signal of the as-deposited film is nearly temporally symmetrical with a peak centred at zero delay time, which indicates the dominant contribution from intraband transition of conduction electrons. For the annealed film, the existence of a decay process in OKE signal implies the important contribution of hot electrons. These characteristics are in agreement with the hot electron dynamics observed in pump probe measurement. 相似文献
5.
Optical Absorption Spectra and Intraband Dynamics in Terahertz-Driven Semiconductor Superlattice 下载免费PDF全文
We have theoretically investigated the optical absorption spectrum and intraband dynamics by subjecting a superlattice to both a terahertz (THz)-frequency driving field and an optical pulse by using an excitonic basis.In the presence of a THz dc field, the satellite structures in the absorption spectra are presented. The satellite structure is a result from the THz nonlinear dynamics of Wannier-Stark ladder excitons. On the other hand, the coherent intraband polarization is investigated. We find that the excitonic Bloch oscillation is driven by the THz field and yields an intraband polarization that continues to oscillate at times much longer than the intraband dephasing time. The temporal evolution of the slowly varying components of the intraband polarization is dependent on the THz frequency. 相似文献
6.
Resonant optical excitation of a direct bandgap semiconductor below the band edge induces excitonic coherences. Experiments
based on transient four-wave mixing or cw spectral-hole burning provide an excellent approach to eliminate inhomogeneous broadening
and enable determination of the time scale and origin of the decay of the optically induced quantum coherence. Such measurements
are of interest in basic physics since they reflect fundamental interactions between the exciton and the surrounding environment
including, for example, lattice vibrations and interface fluctuations. They also relate to potential applications of these
excitations such as in coherent control or quantum information processing.
Received: 30 March 2000 / Accepted: 2 September 2000 / Published online: 12 October 2000 相似文献
7.
This study highlights the theoretical investigation of quantum coherence in mechanical oscillators and its transfer between the cavity and mechanical modes of an optomechanical system comprising an optical cavity and two mechanical oscillators that,in this study, were simultaneously coupled to the optical cavity at different optomechanical coupling strengths. The quantum coherence transfer between the optical and mechanical modes is found to depend strongly on the relative magnitude of the two optomechanical couplings. The laser power, decay rates of the cavity and mechanical oscillators, environmental temperature, and frequency of the mechanical oscillator are observed to significantly influence the investigated quantum coherences. Moreover,quantum coherence generation in the optomechanical system is restricted by the system's stability condition, which helps sustain high and stable quantum coherence in the optomechanical system. 相似文献
8.
P. J. Delfyett A. Dienes J. P. Heritage M. Y. Hong Y. H. Chang 《Applied physics. B, Lasers and optics》1994,58(3):183-195
We describe the generation of femtosecond high power optical pulses using hybrid passive-active mode-locking techniques. Angle stripe geometry GaAs/AlGaAs semiconductor laser amplifiers are employed in an external cavity including prisms and a stagger-tuned quantum-well saturable absorber. An identical amplifier also serves as an optical power amplifier in a stretched pulse amplification and recompression sequence. After amplification and pulse compression this laser system produces 200 fs, 160 W peak power pulses. We discuss and extend our theory, and supporting phenomenological models, of picosecond and subpicosecond optical pulse amplification in semiconductor laser amplifiers which has been successful in calculating measured spectra and time-resolved dynamics in our amplifiers. We have refined the theory to include a phenomenological model of spectral hole-burning for finite intraband thermalization time. Our calculations are consistent with an intra-band time of approximately 60 fs. This theory of large signal subpicosecond pulse amplification will be an essential tool for understanding the mode-locking dynamics of semiconductor lasers and for analysis of high speed multiple wave-length optical signal processing and transmission devices and systems based on semiconductor laser amplifiers. 相似文献
9.
We consider the dynamics of a quantum coherence of two chosen spins in systems of dipolar coupled nuclear spins s=1/2 in solid. With the purpose to study this coherence we suggest two different methods. One of them uses the partial trace technique and reduced density matrix. The second method is based on the calculation the intensity of multiple quantum coherences using two-spin operator and the density matrix of the whole spin system. Results of calculations of the multiple-quantum dynamics in spin clusters of various dimensionalities are presented. It is shown that the whole density matrix method is more informative than the method based on the reduced density matrix. 相似文献
10.
Xin Du Xing He Yunfei Song Yang Wang Yuqiang Liu Lilin Jiang Mingfu Zhang Yanqiang Yang 《Optics & Laser Technology》2012,44(5):1324-1327
We have studied the quantum beats of vibrational modes in different phase samples by employing femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) technique. The temporal chirped white-light continuum (WLC) is used for the Stokes pulse, we have achieved the selective excitation of vibrational modes in both the low and high wavenumber regions without complicated laser system, and observed quantum coherence between vibrational modes. This work is of special significance to enhance our understanding of quantum coherence and develop the applications of quantum technologies. 相似文献
11.
The transformation laws governing the statistical properties of the quantum noise of an optical amplifier when its gain factor and spectral line profile are varied are considered. The correlation functions of quantum noise both at the amplifier output and after nonlinear transformation normalized to the correlation time of quantum noise at the amplifier output were found to be independent of the amplifier gain provided that it exceeds 10 for the Gaussian spectral line profile and 103 for the Lorentzian profile. The spectral density of quantum noise transformed in a nonlinear system was shown to possess the same similarity property. It was found that the statistical characteristics possess a similarity property even in the case of variation of the spectral line profile from Gaussian to Lorentzian. It was concluded that such a characteristic of quantum noise of an optical amplifier as the correlation time bears virtually all information on the above-mentioned statistical properties at a reasonably large amplifier gain. The similarity property revealed has an important application. It allows finding the matching condition between the optical signal spectrum and the gain profile of the optical quantum amplifier to achieve the highest sensitivity of signal detection by the amplifier. 相似文献
12.
对基于新型非线性晶体BiB3O6(BIBO)的飞秒光参量变换过程的参量特性进行了研究. 计算了BIBO晶体三个光学主平面内的相位匹配条件和有效非线性系数,确定了克尔透镜锁模钛宝石激光器的基频光与倍频光抽运时最佳的光学主平面和相位匹配方式,并分析了三波的时间走离和空间走离,以及信号光的参量增益和带宽. 为利用基于BIBO晶体的飞秒光参量技术获得高能量、宽调谐、窄脉宽的光源提供理论依据和实验指导.
关键词:
3O6')" href="#">BiB3O6
光参量变换
共线相位匹配
光学主平面 相似文献
13.
Kuhr S Alt W Schrader D Dotsenko I Miroshnychenko Y Rosenfeld W Khudaverdyan M Gomer V Rauschenbeutel A Meschede D 《Physical review letters》2003,91(21):213002
We have prepared and detected quantum coherences of trapped cesium atoms with long dephasing times. Controlled transport by an "optical conveyor belt" over macroscopic distances preserves the atomic coherence with slight reduction of coherence time. The limiting dephasing effects are experimentally identified, and we present an analytical model of the reversible and irreversible dephasing mechanisms. Our experimental methods are applicable at the single-atom level. Coherent quantum bit operations along with quantum state transport open the route towards a "quantum shift register" of individual neutral atoms. 相似文献
14.
Yi-Ming Duan 《中国物理 B》2023,32(1):17303-017303
We investigate the nonlinear optical rectification (NOR) of spherical quantum dots (QDs) under Hulthén plus Hellmann confining potential with the external tuning elements. Energy and wavefunction are determined by using the Nikiforov-Uvarov method. Expression for the NOR coefficient is derived by the density matrix theory. The results show that the applied external elements and internal parameters of this system have a strong influence on intraband nonlinear optical properties. It is hopeful that this tuning of the nonlinear optical properties of GaAs/Ga1-xAlxAs QDs can make a greater contribution to preparation of new functional optical devices. 相似文献
15.
A consistent quantum theory of a two-pulse pump-probe experiment in the femto-and picosecond spectroscopy of diatomic molecules is developed. The theory aims at the use of weak quantum femtosecond light pulses to excite molecular coherence. It is suggested that the experiment be realized using a double-frequency excitation scheme that is feasible for Na2 molecules. On the basis of the theory developed, the luminescence signals are calculated at different temperatures and different optical densities of the medium for the time range from 100 fs to ~ 100 ps. The results obtained show the presence of a strong dependence of the time and frequency spectra of a luminescence signal on the optical density of the medium at temperatures from 50 to 300 K. The proposed approach makes it possible to use the quantum coherence properties of optically dense media for more detailed study of the vibronic dynamics of diatomic molecules, in particular, detection of weak optical transitions. 相似文献
16.
超宽光谱的飞秒脉冲测量一直是超快激光领域的重要研究方向之一.常规的飞秒脉冲自相关方法是通过测量自相关倍频信号来获得,而倍频信号具有波长选择性,不同中心波长的飞秒脉冲测量需要更换不同的倍频晶体,十分不方便.因此,提出了一种改进型的瞬态光栅频率分辨光学开关(TG-FROG)方法用于测量飞秒脉冲.该方法结合四波混频和频率分辨光学开关方法,其基本过程是将待测脉冲分为三束,其中两束脉冲经过精密的延时控制并聚焦在光学介质上达到时空重合,利用三阶非线性效应产生稳定的瞬态光栅作为开关光;另一束脉冲作为探测光与产生的瞬态光栅进行相互作用产生一个信号光,使用光谱仪对该信号光的光谱与延迟时间进行测量,并通过反演迭代算法处理而获取待测飞秒脉冲的光谱与电场信息.该方法只需要待测光的功率密度达到三阶非线性效应就可以实现测量,因此可以应用于任意中心波长的飞秒脉冲测量.利用该方法对中心波长分别为800 nm, 400 nm的飞秒脉冲,以及超连续亚10 fs的周期量级超宽光谱飞秒脉冲进行了测量,并与常规的干涉自相关仪器测量结果进行了比较,所得测量结果基本一致.实验结果表明,建立的基于TG-FROG方法对不同中心波长,不同脉冲宽度的飞秒脉冲测量是十分有效的. 相似文献
17.
《Superlattices and Microstructures》1999,25(1-2):295-300
A back-gated undoped heterostructure, in which a two-dimensional electron gas (2DEG) is formed at the inverted undoped heterointerface through the back-side field effect, offers the possibility of high mobility and the feasibility of fabricating several kinds of back-gated structures. We used such a 2DEG system to fabricate a Corbino-disk structure. The results for the back-gated Corbino-disk structure show that the density of the 2DEG is well controlled by the back-gate bias and the fine structures corresponding to the integer and fractional quantized Hall effects are clearly observed, reflecting the high quality of the 2DEG formed in the undoped heterostructure. The characteristics in a low magnetic field region confirm the homogeneous back-gate control of the 2DEG down to a density of less than 1010cm−2. 相似文献
18.
We investigate the ultrafast control of coherent population transfer in a Λ-type three-level system with a train of pump-Stokes femtosecond pulse pairs, where the pulse sequences can be produced either by optical delay line or by pulse shaping with sinusoidal phase modulation. It is shown that when the pump and Stokes pulses in each pair are applied in the counterintuitive order, similar to that in the stimulated Raman adiabatic passage technique, due to temporal quantum interference (besides optical interference in the case of overlapped subpulses), ultrafast control of coherent population transfer can be achieved by scanning the inter-pair time delay or by changing the sinusoidal phase modulation parameters. This method has potential applications in ultrafast control of chemical reactions and quantum information processing. 相似文献
19.
We analyze both the spatial as well as the temporal coherence of an electron-hole condensate and the radiation emitted from it. These coherences evolve from being full for the low density Bose-Einstein condensate to a chaotic behavior for a high density Bardeen-Cooper-Schrieffer-like state. Time coherence is transferred, to the emitted radiation in the ultrafast regime, in a damped oscillatory way. 相似文献
20.
Zhuan Li Li-Ping Deng Li-Sen Xu Kaige Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):147-156
We study a four-level double-Λ atomic ensemble interacting with two
time-dependent signal fields and two stationary control fields. Though, in
each Λ channel, a pair of signal and control fields couple
resonantly with the two lower levels of atoms, the occurrences of
electromagnetically induced transparency (EIT) is affected by the coherence
of the four fields. In the discussion of atomic susceptibilities, we show
that the quantum coherence between the two lower levels can be either formed
or released according to the phase matching of the four fields. We analyze
the propagation equation of the two signal fields, and find two
characteristic solutions: the stationary transmission wave and the transient
decay wave. The former corresponds to a correlated EIT effect in which two
signal pulses are shape-matched. The latter is an opposite effect to the
correlated EIT in which two pulses quench simultaneously, thus named as the
correlated two-signal absorption (CTSA). We propose the CTSA condition in
correspondence with the EIT condition. The numerical simulation shows that
the double-Λ configuration is capable of manipulating synchronous
optical signals and thus provides multiplicity and versatility in quantum
information process. 相似文献