共查询到20条相似文献,搜索用时 46 毫秒
1.
In this paper, the probe absorption spectra of a V-type atom embedded in photonic band gap (PBG) reservoir have been investigated under conditions that quantum interference among decay channels is important. The effect of the probe polarization on the absorption amplitude and spectral structure is investigated in detail. Comparing with similar models located in vacuum reservoir studied earlier, the study here shows that the probe polarization has some different effects on the absorption spectra in PBG reservoir. 相似文献
2.
The probe absorption-dispersion spectra of a radio-frequency (RF)-driven five-level atom embedded in a photonic crystal are investigated by considering the isotropic double-band photonic-band-gap (PBG) reservoir. In the model used, the two transitions are, respectively, coupled by the upper and lower bandsin such a PBG material, thus leading to some curious phenomena. Numerical simulations are performed for the optical spectra. It is found that when one transition frequency is inside the band gap and the other is outside the gap, there emerge three peaks in the absorption spectra. However, for the case that two transition frequencies lie inside or outside the band gap, the spectra display four absorption profiles. Especially, there appear two sharp peaksin the spectra when both transition frequencies exist inside the band gap. The influences of the intensity and frequency of the RF-driven field on the absorptive and dispersive response are analyzed under different band-edge positions. It is found that a transparency window appears in the absorption spectra and is accompanied by a very steep variation of the dispersion profile by adjusting system parameters. These results show that the absorption-dispersion properties of the system depend strongly on the RF-induced quantum interference and the density of states (DOS) of the PBG reservoir. 相似文献
3.
We have theoretically studied the effects of quantum coherence in a driven quasi-degenerate two-level atomic system. We have shown that the quantum interference, which can be destructive or constructive, can be controlled by an externally applied magnetic field allowing one to implement both electromagnetically induced transparency and electromagnetically induced absorption in the same atomic system. Determined by frequency dispersion of the index of refraction of the system, the group velocity of light pulses ranges from ultra-slow to superluminal with changing of the magnitude of the magnetic field. 相似文献
4.
The control of spontaneous emission from an radio-frequency (RF)-driven five-level atom embedded in a three-dimensional photonic
crystal is investigated by considering the anisotropic double-band photonic-band-gap (PBG) reservoir. It is shown that, due
to the coexistence of the PBG and the quantum interference effect induced by the RF-driven field, some interesting features,
such as the spectral-line narrowing, the spectral-line enhancement, the spectral-line suppression and the occurrence of a
dark line in spontaneous emission, can be realized by adjusting system parameters under the experimentally available parameter
conditions. The proposed scheme can be achieved by use of an RF-driven field into hyperfine levels in rubidium atom confined
in a photonic crystal. These theoretical investigations may provide more degrees of freedom to vary the spontaneous emission. 相似文献
5.
We study the effects of quantum interference in the spontaneous emission spectrum of a four-level driven atomic system. We use three strong laser fields to drive the atom and a weak laser field to prepare the initial state of the atom. The atomic system exhibits Autler-Townes triplet in the spectrum. The single Lorentzian peak splits into triplet and their widths are controlled by the relative strengths of the laser fields. 相似文献
6.
The two models of three-level (one upper level and two lower levels, or two upper levels and one lower level) atom embedded in a double-band photonic crystal are adopted. The atomic transitions from the upper levels to the lower levels are assumed to be coupled by the same reservoir which are respectively the isotropic photonic band gap (PBG) modes, the anisotropic PBG modes and the free vacuum modes. The effects of the fine structure of the atomic ground state levels in the model with one upper level and two lower levels, and the quantum interferences in the model with two upper levels and one lower level on the spontaneous emission spectrum of an atom are investigated in detail. Most interestingly, it is shown that new spontaneous emission lines are produced from the fine splitting of atomic ground state levels in the isotropic PBG case. The quantum interferences induce additional narrow spontaneous lines near the transition from the empty upper level to the lower level. 相似文献
7.
With the Schrödinger equations, we investigate the low-intensity light pulse propagation through a semiconductor quantum wells. Through studying the dispersion and absorption properties of the weak probe field, it is shown that slow light propagation is observed in this system. From the view point of practical purpose, it is more advantageous than its corresponding atomic system. Such investigation of slow light propagation may lead to important practical applications in semiconductor quantum information. 相似文献
8.
Quantum interference in the probe absorption spectrum of a four-level atom embedded in a double-band photonic crystal has been investigated. The double V-type transitions from the two upper levels to the two lower levels interact with the free vacuum modes and the PBG modes synchronously. We study the additional transparency and the elimination of the probe absorption line in this paper. The new features of two transparencies resulting from the singularity of the state density of PBG modes are also predicted. 相似文献
9.
We study the coherent control of spontaneous emission of a double-driven four-level atom embedded in photonic crystals. Combined effect of different relative locations between the upper band edge and the two upper levels and the phase of microwave coupling field is discussed. It is shown that quantum interference effect such as laser-induced dark line depends strongly on the phase of microwave field. 相似文献
10.
S. Roshan Entezar 《Optics Communications》2009,282(6):1171-1174
In this paper, the effect of quantum interference on the entanglement of a driven V-type three-level atom and its spontaneous emission field was investigated by using the quantum entropy. The results indicate that, in the absence of quantum interference the atom and its spontaneous emission field are always entangled at the steady-state. But, in the presence of full quantum interference their steady-state entanglement depends on the atomic parameters. Specifically, with appropriate atomic parameters they can be entangled or disentangled at the steady-state. We realized that the steady-state entanglement is due to completely destructive nature of quantum interference. On the contrary, the steady-state disentanglement is due to instructive nature of quantum interference. 相似文献
11.
S.-y. Xie Y.-p. Yang X. Wu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(1):129-143
We study the spontaneous emission properties of a V-type three-level atom embedded in a photonic crystal with the anisotropic
dispersion relation. We show that the localized field can disappear and the diffusion field can become intense in some regions.
This originates from no singularity of the density of states. The quantum interference leads to oscillatory, quasi-oscillatory
or complete decay behavior of population. The complete decay can also be realized in certain condition without depending on
the initial state.
Received 9 April 2000 and Received in final form 1st August 2000 相似文献
12.
Z. Ficek J. Seke A.V. Soldatov G. Adam N.N. Bogolubov Jr 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):411-419
We investigate the absorption and dispersion properties of a two-level atom driven by a polychromatic field. The driving field
is composed of a strong resonant (carrier) frequency component and a large number of symmetrically detuned sideband fields
(modulators). A rapid increase in the absorption at the central frequency and the collapse of the response of the system from
multiple frequencies to a single frequency are predicted to occur when the Rabi frequency of the modulating fields is equal
to the Rabi frequency of the carrier field. These are manifestations of the undressing or a disentanglement of the atomic
and driving field states, that leads to a collapse of the atom to its ground state. Our calculation permits consideration
of the question of the undressing of the driven atom by a multiple-modulated field and the predicted spectra offer a method
of observing undressing. Moreover, we find that the absorption and dispersion spectra split into multiplets whose structures
depend on the Rabi frequency of the modulating fields. The spectral features can jump between different resonance frequencies
by changing the Rabi frequency of the modulating fields or their initial phases, which can have potential applications as
a quantum frequency filter.
Received 23 October 2001 and Received in final form 31 January 2002 相似文献
13.
We consider a degenerate parametric oscillator whose cavity contains a two-level atom. Applying the Heisenberg and quantum Langevin equations, we calculate in the bad-cavity limit the mean photon number, the quadrature variance, and the power spectrum for the cavity mode in general and for the signal light and fluorescent light in particular. We also obtain the normalized second-order correlation function for the fluorescent light. We find that the presence of the two-level atom leads to a decrease in the degree of squeezing of the signal light. It so turns out that the fluorescent light is in a squeezed state and the power spectrum consists of a single peak only. 相似文献
14.
A Λ-type three-level atomic system in the electromagnetically induced transparency (EIT) configuration interacting with a broadband squeezed vacuum (SV) bath is studied with quantum interference (QI) between decay channels taken into account. We formulate two sufficient critical conditions for the medium to be dispersionless or absorptionless. Computational results for the dispersion and absorption spectra show that presence of both QI and SV offers more avenues to manipulate the group velocity of probe pulse for its variation from sub-luminal to super-luminal regimes. The relative phase between the two external fields is found to act as a control knob of the atomic medium. 相似文献
15.
We propose a new method to form a novel controfiable photonic crystal with cold atoms and study the photonic band gap (PBG) of an infinite 1D CO2-laser optical lattice of SSRb atoms under the condition of quantum coherence. A significant gap generated near the resonant frequency of the atom is founded and its dependence on physical parameters is also discussed. Using the eigenquation of defect mode, we calculate the defect mode when a defect is introduced into such a lattice. Our study shows that the proposed new method can be used to optically probe optical lattice in situ and to design some novel and controllable photonic crystals. 相似文献
16.
We examine the effects of driving field linewidth on a one-atom dressed state laser. Unexpectedly, the linewidth leads to anomalous effects on the cavity field. The mean photon number of the cavity field is raised or the normalized variance is reduced to a certain degree as the linewidth increases for an appropriate range of parameters. The responsible mechanism is attributed to the fluctuation-induced modification of the electromagnetic reservoir where the atom stays. 相似文献
17.
The spontaneous emission spectra of a five-level double tripod-type atom embedded in photonic crystals (PCs) are investigated by means of two external fields driving different atomic transitions. We find that due to the quantum interference effects caused by two driving fields, the spontaneous emission spectra exhibit different features from the case of only one driving field. The influences of the parameters of two external driving fields, photonic band-gap (PBG), as well as the atomic initial states on the spectra are analyzed in detail. It is shown that some interesting phenomena such as spectral-line enhancement, spectral-line suppression, spectral-line narrowing, the appearance of dark lines, and multi-peak structures can be observed in the spectra by appropriately modulating the available system parameters. These investigations may find applications in high-precision spectroscopy. 相似文献
18.
The master equation for a two-level atom driven by a strong classical field and damped into a tailored reservoir with nonflat density of modes is derived under the Born-Markov approximation. To derive the master equation, the dressing transformation on the atomic operators is performed first, and, next, the dressed operators are coupled to the reservoir and the corresponding damping rates are calculated. The effects of a strong field and/or structured reservoir are seen as nonstandard terms in the master equation, some of which are reminiscent of terms known for squeezed vacuum reservoirs. The master equation leads to the generalized optical Bloch equations that can easily be solved for the steady state and, together with the quantum regression theorem, allow for analytical expressions for the fluorescence, as well as absorption spectra. 相似文献
19.
20.
The spontaneous emission behavior of a double Λ-type four-level atom embedded in a photonic crystal (PC) with anisotropic dispersion relations is investigated. It is shown that some interesting phenomena such as the spectral-line enhancement, the spectral-line narrowing, the spectral-line suppression and the spontaneous emission cancellation can be observed by adjusting the density of states of the photonic-band-gap (PBG) reservoir and the combination of two pump intensities. The proposed scheme can be achieved by use of coherent pump fields into the transitions from the upper levels to the ground level in rubidium atom confined in a PC. These theoretical investigations may provide more degrees of freedom to manipulate the atomic spontaneous emission. 相似文献