M-type Atomic System Research Articles

One- and two-dimensional electromagnetically induced gratings in a microwave-driven M-type atomic system

In this paper, we theoretically investigate a scheme for both 1D and 2D electromagnetically induced gratings (EIGs) in M-type atomic systems in which two ground states are coupled by a microwave field. It is observed that the presence of a microwave field enhances the probe diffraction efficiency to higher orders, thus leading to the construction of phase gratings in 1D and 2D cases. The study shows that changing the system parameters numerically, such as the strength of the applied microwave field, standing wave field, and the length of the atomic medium, leads to modulation of diffraction efficiency into higher orders. The application of microwave fields is a more convenient parameter for attaining increased first-order diffraction. We believe that the proposed system with a microwave field can be used for designing novel microwave sensing devices for optical networking and communication.

Tunable Optical Rotation with an <i>M</i>-Type Atomic System Using Vortex Beam

We consider the optical rotation of the polarization of a linearly polarized probe field passing through an M-type atomic system by using the interaction between two vortex control fields and optical transitions. We investigate theoretically to generate the spatially dependent structured light with the atoms acting as a spatially varying circular birefringent medium. We show that the polarization and intensity distributions of the vector beam spatially vary by changing the orbital angular momentum (OAM) of the vortex control field.

Doppler narrowing of EIT linewidth in closed-loop systems

We theoretically investigate a five-level closed-loop M-type atomic system and a three-level closed-loop $$\Lambda $$ -system in hot atomic vapour. In contrast to closed-loop $$\Lambda $$ -system, two unpopulated ground states of the M-system are coupled by a microwave field. We find that thermal averaging in the M-system causes many interesting modification of probe absorption lineshape including narrowing, splitting and absorption enhancement. In M-system, the linewidth of probe absorption after thermal averaging becomes remarkably narrow (100 times smaller) with respect to the linewidth of stationary atoms. On the contrary, the closed-loop $$\Lambda $$ -system generates only 1.6 times smaller linewidth in thermal vapour. The absence of population transfer through the microwave field leads to this significant narrowing effect in the M-system which is unachievable in closed-loop $$\Lambda $$ -systems. Hence, M-system has potential application in high-resolution spectroscopy, generation of ultra slow light, phase-dependent optical switching, and in microwave electro- and magnetometry.

High-precision two- and three-dimensional atom localization via spatial dependent probe absorption in a closed-loop M-type atomic system

We propose a scheme for high-precision two- and three-dimensional atom localization in a coherently driven closed-loop five-level M-type atomic system by using a density matrix formalism. Our system consists of not only strong and probe fields but also a microwave field to form a closed loop in the atomic system. Due to position-dependent interaction of the atom in the standing-wave field, the absorption spectra of the probe field provide the precise information about atom localization in a subspace of one wavelength. While numerically solving the density matrix equations, various kinds of localization patterns are obtained, such as parallel wave-, crater-, valley-, and bell-shape-like, in the case of two-dimensional atom localization. Further, the three-dimensional atom localization case is also discussed under different parametric conditions. High precession and high resolution of atom localization are observed for our case and the localization can be tuned to the desired subspace by properly adjusting external parameters. Moreover, maximum conditional probability distribution of the atom is also achieved, i.e., 1 in both two- and three-dimensional localization cases under appropriate conditions.

Two-dimensional atom localization based on coherent field controlling in a five-level M-type atomic system.

We study two-dimensional sub-wavelength atom localization based on the microwave coupling field controlling and spontaneously generated coherence (SGC) effect. For a five-level M-type atom, introducing a microwave coupling field between two upper levels and considering the quantum interference between two transitions from two upper levels to lower levels, the analytical expression of conditional position probability (CPP) distribution is obtained using the iterative method. The influence of the detuning of a spontaneously emitted photon, Rabi frequency of the microwave field, and the SGC effect on the CPP are discussed. The two-dimensional sub-half-wavelength atom localization with high-precision and high spatial resolution is achieved by adjusting the detuning and the Rabi frequency, where the atom can be localized in a region smaller thanλ/10×λ/10. The spatial resolution is improved significantly compared with the case without the microwave field.

Effect of Phase Modulation on Electromagnetically Induced Grating in a Five-Level M-Type Atomic System**Supported by the National Natural Science Foundation of China under Grant Nos 11274112 and 11474092, the Key Project of Shanghai Municipal Education Commission under Grant No 14ZZ056, the Shanghai Natural Science Fund Project under Grant No 14ZR1410300, and the Key Research Project of Henan Province Education Department

We theoretically investigate the phenomena of electromagnetically induced grating in an M-type five-level atomic system. It is found that a weak field can be effectively diffracted into high-order directions using a standing wave coupling field, and different depths of the phase modulation can disperse the diffraction light into different orders. When the phase modulation depth is approximated to the orders of , and , the first-, second- and third-order diffraction intensity reach the maximum, respectively. Thus we can take advantage of the phase modulation to control the probe light dispersing into the required high orders.

Transfer of populations in the multi-level system by partly overlapping of the laser pulses

The M-type atomic system, which interacts with four laser pulses is considered. The complete transfer of populations in various sequences of the laser pulses switching on and off is calculated. It is shown that even in the absence of the overlapping of pulses acting in the inner transitions it is possible to transfer the all atomic populations regardless of the sequence of switching of pulses.

Superluminal optical vector solitons in a five-level M-type atomic system

We investigate generation of superluminal vector optical solitons in a five-level M-type atomic system within active-Raman-gain regime. By analyzing the linear and nonlinear optical properties of the system, we demonstrate that the dispersion effects of the probe fields can be well balanced by self-phase and cross-phase modulation of the Kerr nonlinearity and various types of optical vector solitons with superluminal group velocity can be formed in the system. Moreover, by choosing proper parameters Manakov temporal vector solitons can also be realized in this atomic system.

Absorption and dispersion control in a five-level M-type atomic system

We investigate the steady optical response of a coherently driven five-level M-type atomic system in three different situations. When all three coupling fields have the same zero detuning, we just find one deep transparency window accompanied by a steep normal dispersion in the probe absorption and dispersion spectra. When two coupling fields are detuned from the relevant transitions to the same extent, however, a second deep transparency window may be observed in the presence of a narrow absorption line of linewidth ∼ 50 kHz. In this case, two single-photon far-detuned transitions can be replaced by a two-photon resonant transition, so the five-level M system in fact reduces into a four-level quasi-Λ system. Finally, we note that no deep transparency windows and no narrow absorption lines can be found when all three coupling fields have unequal detunings.

Three-dimensional atom localization in a five-level M-type atomic system

By using three mutually perpendicular standing-wave fields, we propose a scheme for three-dimensional (3D) subwavelength atom localization in a five-level M-type atomic system. Based on the electromagnetically induced transparency, position probability distribution of the atom in 3D space could be determined via measuring the probe absorption which is proportional to the filter function. It is shown that patterns of 3D atom localization depends sensitively on the coupling schemes of the standing-wave fields. When the standing-wave fields couple three different transitions, the same atom localization patterns are formed in the eight subspaces of the 3D space. While all the standing-wave fields are applied on one transition, we can realize different atom localization patterns in the eight subspaces. From the view of the xy plane, various symmetric or asymmetric atom localization patterns could be formed at different z positions by adjusting the parameters of the laser fields.

Two-dimensional atom localization via spontaneous emission in a coherently driven five-level M-type atomic system

A scheme is proposed for two-dimensional atom localization in the subwavelength domain via controlled spontaneous emission. We consider a five-level M-type atomic system interacting with two orthogonal standing-wave laser fields and the vacuum of the radiation field. The interaction of the atom with space-dependent standing-wave fields can provide information about the position of the atom passing through, thus leading to atom localization. It is found that the localization is significantly improved due to the interference effect between the spontaneous decay channels and the dynamically induced quantum interference generated by the two standing-wave fields. By properly varying the system parameters, we can achieve high-precision and high-resolution atom localization.

Quantum interference effect on spontaneous emission spectrum in a doubly driven M-type atom

An M-type atomic system with two closely spaced upper levels interacting with the same modes of the vacuum radiation field exhibits the interference effect between the spontaneous decay channels. The phenomenon of this decay-interference along with the dynamically induced quantum interference created in the system by two coherent fields can change significantly the spontaneous emission spectrum. Our results highlight large enhancement of ultranarrow spectral components within the spontaneous emission line shape in various conditions. We have shown the occurrence of two contradistinctive phenomena: compression of two spectral lines towards their mid-position and the spreading of two lines away from each other under different dynamic conditions. The phenomenon of suppression of spectral line and the quenching of spontaneous emission have also been focused.

Zeeman Coherences Narrowing due to Ramsey Effects Induced by Thermal Motion of Rubidium Atoms

We investigated effects of spatially separated laser fields on amplitudes and widths of electromagnetically induced transparency in M-type atomic system. We have shown narrowing of the electromagnetically induced transmission resonance and therefore enhancement of medium non-linearities that can be explained by diffusion-induced Ramsey narrowing. Depending on the polarization of two laser beams, narrow probe Hanle transmission resonance changes its sign in respect of the profile obtained when the pump laser beam is off.