Coherent Population Trapping Effect Research Articles

Effect of coherent population trapping in a compact microfabricated Cs gas cell pumped by intra-cavity contacted VCSELs with rhomboidal oxide current aperture

Miniature laser source based on intracavity-contacted vertical-cavity surface-emitting laser with rhomboidal oxide current aperture was investigated for coherent population trapping (CPT) resonance excitation in microfabricated 133Cs gas cell filled with Ne buffer gas under the pressure of 300 torr. The cell operation temperature was 90°C. The laser output power was 550 μW at bias current of 3.2 mA and 65°C. The short-term stability of ∼2.5·10-11 at the measurement time of 1 sec was estimated from CPT resonance signal measurements.

Influence of coherent population trapping on Raman scattering

We have considered the Raman scattering in molecular media. Applying two laser fields in a two-photon resonance with vibrational transition, we have studied the role of rotational levels for excitation of vibrational coherence. It is shown that the molecular vibrational coherence strongly depends on the effect of coherent population trapping for rotational levels. The obtained results are important for applications of Raman spectroscopy to molecular detection in engineering, chemical, and biological applications.

Observation of Coherent Population Trapping in Ensembles of Diamond NV-Centers under Ground-State Level Anticrossing Conditions

The coherent population trapping effect in ensembles of diamond NV-centers under ground-state level anticrossing conditions was implemented with the application of a strong external magnetic field oriented along the [111] crystal axis.

Наблюдение когерентного пленения населенности в ансамблях NV-центров в алмазе в условиях антипересечения уровней основного состояния

We realize the coherent population trapping effect in ensembles of diamond NV-centers in the ground state level anticrossing regime when the sample is placed into a strong external magnetic field along the [111] crystal axis.

Spectral-Modulation Characteristics of Vertical-Cavity Surface-Emitting Lasers

The requirements imposed on vertical-cavity surface-emitting lasers in a number of metrological problems in which optical pumping of alkali atoms is used are considered. For lasers produced by different manufacturers, these requirements are compared with the experimentally observed spectral characteristics at a constant pump current and in the microwave modulation mode. It is shown that a comparatively small number of lasers in the microwave modulation mode make it possible to obtain the spectrum required for atomic clocks based on the coherent population-trapping effect.

Спектрально-модуляционные характеристики лазеров с вертикальным резонатором

AbstractThe requirements imposed on vertical-cavity surface-emitting lasers in a number of metrological problems in which optical pumping of alkali atoms is used are considered. For lasers produced by different manufacturers, these requirements are compared with the experimentally observed spectral characteristics at a constant pump current and in the microwave modulation mode. It is shown that a comparatively small number of lasers in the microwave modulation mode make it possible to obtain the spectrum required for atomic clocks based on the coherent population-trapping effect.

Quantum treatment of laser cooling on weak transitions: multipeaks and bimodal momentum distributions

The work is devoted to the study of the features and parameters of the momentum distributions of atoms laser cooled on weak optical transitions. It was shown that atoms distributions are described by a bimodal momentum distribution whose characteristics depends on the parameters of the light field. In a strong field a velocity selective coherent population trapping effect is observed.

Light shift of the Ramsey resonance of coherent population trapping in optically dense medium

In this work we calculate the Ramsey resonances of coherent population trapping effect in cold atomic ensembles. The main goal is to investigate the light shift of the resonance on the different parameters in optically dense medium, because such medium can to distort and absorb the interrogating laser pulses.

Controlling the light shift of the CPT resonance by modulation technique

Motivated by recent developments in atomic frequency standards employing the effect of coherent population trapping (CPT), we propose a theoretical framework for the frequency modulation spectroscopy of the CPT resonances. Under realistic assumptions we provide simple yet non-trivial analytical formulae for the major spectroscopic signals such as the CPT resonance line and the in-phase/quadrature responses. We discuss the influence of the light shift and, in particular, derive a simple expression for the displacement of the resonance as a function of modulation index. The performance of the model is checked against numerical simulations, the agreement is good to perfect. The obtained results can be used in more general models accounting for light absorption in the thick optical medium.

Optimization of stabilization regimes in atomic clocks, based on the effect of coherent population trapping

Using the atomic density matrix formalism, we investigate the dynamic regime of formation of the error signal for resonances of coherent population trapping excited in a three-level Λ-system by a bichromatic field. The optimal parameters of harmonic modulation used in the frequency locked loop are determined with allowance for low-frequency noise.

Optical-density-enhanced squeezed-light generation without optical cavities

To achieve high degree of quantum noise squeezing, an optical cavity is often employed to enhance the interaction time between light and matter. Here, we propose to utilize the effect of coherent population trapping (CPT) to directly generate squeezed light without any optical cavity. Combined with the slow propagation speed of light in a CPT medium, a coherent state passing through an atomic ensemble with a high optical density (OD) can evolve into a highly squeezed state even in a single passage. Our study reveals that noise squeezing of more than $10$ dB can be achieved with an OD of 1,000, which is currently available in experiments. A larger OD can further increase the degree of squeezing. As the light intensity and two-photon detuning are key factors in the CPT interaction, we also demonstrate that the minimum variance at a given OD can be reached for a wide range of these two factors, showing the proposed scheme is flexible and robust. Furthermore, there is no need to consider the phase-matching condition in the CPT scheme. Our introduction of high OD in atomic media not only brings a long light-matter interaction time comparable to optical cavities, but also opens new avenue in the generation of squeezed light for quantum interface.

Image transfer through coherent population trapping based on an atomic ensemble

We report on an experiment on transferring an image through coherent population trapping (CPT) effect in a hot rubidium vapor. We demonstrate experimentally that an image can be transferred from a control light to a probe light. Moreover, we describe the demonstration that the image can be transferred from a control light to two different probes showing a feasibility of transferring an image onto multiple probes. We believe that this effect definitely has important applications in image metrology, high dimensional information transfer in quantum information field, etc.

Doppler-free spectroscopy on the Cs D1 line with a dual-frequency laser.

We report on Doppler-free laser spectroscopy in a Cs vapor cell using a dual-frequency laser system tuned on the Cs D1 line. Using counter-propagating beams with crossed linear polarizations, an original sign reversal of the usual saturated absorption dip and large increase in Doppler-free atomic absorption is observed. This phenomenon is explained by coherent population trapping (CPT) effects. The impact of laser intensity and light polarization on absorption profiles is reported in both single-frequency and dual-frequency regimes. In the latter, frequency stabilization of two diode lasers was performed, yielding a beat note fractional frequency stability at the level of 3×10-12 at 1 s averaging time. These performances are about an order of magnitude better than those obtained using a conventional single-frequency saturated absorption scheme.

Coherent population trapping in a Raman atom interferometer

We investigate the effect of coherent population trapping (CPT) in an atom inter-ferometer gravimeter based on the use of stimulated Raman transitions. We find that CPT leads to significant phase shifts, of order of a few mrad, which may compromise the accuracy of inertial measurements. We show that this effect is rejected by the k-reversal technique, which consists in averaging inertial measurements performed with two opposite orientations of the Raman wavevector k, provided that internal states at the input of the interferometer are kept identical for both configurations.

Suppression of coherent scattering by coherent population trapping on molecular vibrational levels

AbstractRaman scattering has been studied in molecular media. The role of rotational levels has been investigated. It is shown that the molecular vibrational coherence strongly depends on the effect of coherent population trapping for rotational levels. The obtained results are important for application of Raman spectroscopy to molecular detection for engineering, chemical, and biological applications.

Coherent population effect in a Λ-configuration atom driven by two trains of ultrashort pulses

In this paper, we investigate the evolutional dynamics of a Λ-type atomic system of which two branches of transitions are driven by two trains of ultrashort pulse respectively. The accumulating of atomic populations and coherences due to excitations of successive pulses are demonstrated by the numerical simulations. The realization of the coherent population trapping (CPT) effect is verified. When the spontaneous generated coherence (SGC) is considered, the system will evolve to the dark state even when the initial state is not the dark state if the degree of the SGC is not maximal and the degree of the SGC will influence the time needed to reach the atomic steady state. With the maximal degree of SGC, whether the system will evolve into the dark state depends on the initial state. This fact means that the maximal SGC spoils the dark state geometry, which a Λ-type atom driven by light field satisfies. Additionally, we found that the involvement of the phase of the driving field can counteract the destruction stem from the maximal degree of the SGC on the dark state geometry, i.e. the system can be trapped in the dark state even when the initial state is not the dark state. Meanwhile, it is found that the phase can adjust the time needed by the system to reach the steady state in a quite wide range.

Doppler amplification of motion of a trapped three-level ion

The system of a trapped ion translationally excited by a blue-detuned near-resonant laser, sometimes described as an instance of a phonon laser, has recently received attention as interesting in its own right and for its application to non-destructive readout of internal states of non-fluorescing ions. Previous theoretical work has been limited to cases of two-level ions. Here, we perform simulations to study the dynamics of a phonon laser involving the Λ-type ion, in which coherent population trapping (CPT) effects lead to different behavior than in the previously studied cases. We explore optimization of the laser parameters to maximize amplification gain for initially seeded motion and consider the related signal-to-noise ratios for internal state readout. We find that good Doppler amplification and state readout performance can be obtained even when operating quite near the CPT dip.

Tunneling Control of Optical Properties of a Quantum Well from Adjacent Quantum Well by Coherent Population Trapping Effect

Now the coherent population trapping (CPT) effect attracts a big researcher’s interest. The essence of this effect is the appearing of specific superposition of long-lived states in multilevel quantum system interacting with two-frequency coherent (usually laser) field. This superposition state (dark state) is not interacts with the field. The dark resonances were investigated theoretically [1, 2] as well as experimentally in semiconductor quantum wells in the basis of InGaAs/AlInAs and GaAs [3]. The dark resonances are of particular interest for the development of devices for recording and storing of quantum information and also for quantum logic elements. So the methods of recording and reading of qubits with a high degree of fidelity were realized on the basis of the EIT resonance in the atoms inside an optical lattice. In this work we investigate the CPT effect in the double tunnel-coupled quantum wells interacting with laser radiation 1,2,3  (Fig.1). The microwave field V closes the contour of excitation (-system). We found that it is possible to create the specific collapse of population (dark resonance), which takes place for the excited level of simple -system, for the ground level 3 of additional excitation canal. Moreover, destruction and restoration of CPT by variation of the total phase Ф (Fig.1) of exciting fields in the -system gives us the possibility to control population of the ground level 3 . We investigate the cases of constant and pulsed optical radiation. In the case of pulsed radiation we found that only edges of signal pulse are absorbed. Middle of the pulse does not interact with the quantum wells due to dark state of the level 3 . It can be useful for reducing of the pulse duration and generation of the higher harmonics. This work is supported by Russian President grant for young candidates of sciences (project МК-384.2013.2), non-profit foundation Dynasty, Russian Foundation for Basic Research (project 14-02-31422), Regional Public Science Support Foundation, British Petroleum company, State Assignment for universities 2014/184.

Image cloning beyond diffraction based on coherent population trapping in a hot rubidium vapor

Following recent theoretical predictions, we report on an experimental realization of image cloning beyond usual diffraction, through the coherent population trapping (CPT) effect in a hot rubidium vapor. In our experiment, an alphabet letter image was transferred from a coupling field to a probe field, based on the CPT effect. Furthermore, we demonstrate that the cloned probe field carrying the image is transmitted without the usual diffraction. To our best knowledge, this is the first experimental report about image cloning beyond diffraction. We believe this mechanism, based on CPT, has definite and important applications in image metrology, image processing, and biomedical imaging.

Ramsey effect of coherent population trapping in anti-relaxation-coated Rb vapor cells

We examine experimentally and theoretically the Ramsey effects on the coherent population trapping (CPT) resonance in a paraffin-coated Rb vapor cell. The observed CPT spectrum in the Hanle configuration of the 5S1/2(F = 2)−5P1/2(F′ = 1) transition of 87Rb atoms consists of a narrow structure with a spectral width of 0.10 mG due to the wall-induced Ramsey effect and a broad structure with a spectral width of 23 mG due to the transit effect. Considering the velocity distribution of atoms and the number of wall-atom collisions, we numerically calculated the transmittance of the laser beam as a function of the longitudinal magnetic field. The experimental results of the CPT Ramsey interference were in good agreement with the theoretical results, and the dependences of the CPT Ramsey effects on the atom-laser interaction time were investigated in detail.