Orthogonal Standing-wave Fields Research Articles

Microwave assisted Fraunhofer diffraction pattern in a four-level light–matter coupling scheme

The experimental realization of two-dimensional (2D) electromagnetically induced grating is explored by monitoring the Fraunhofer diffraction pattern in a microwave-driven four-level Y-type atomic medium under the action of two orthogonal standing-wave (SW) fields. Due to the position-dependent atom–field interaction, the information about the high diffraction order of the probe light can be obtained via the Fraunhofer diffraction pattern of the probe light. It is found that the diffraction behavior is significantly improved due to the joint quantum interference induced by the SW and microwave-driven cycling fields. Most importantly, the amplitude and phase diagram of the transmission function of the probe light can be modulated at a particular position and the probe energy may transfer to the high orders of the diffraction by properly adjusting the system parameters. The proposed scheme may provide a promising way to achieve highly sensitive diffraction patterns with applications in quantum information processing.

Two-dimensional electromagnetically induced grating via phase regulation in a closed-loop four-level atomic system

We proposed a theoretical scheme for two-dimensional (2D) electromagnetically induced grating (EIG) in a closed-loop four-level atomic system driven by a weak probe field, a traveling-wave control field, two orthogonal standing-wave fields and a microwave field. Due to low amplitude modulation accompanied with large phase modulation, EIG can be obtained and the probe energy can be diffracted into first-order and even high-order directions with high efficiency. The results show that the diffraction pattern and efficiency of the EIG could be adjusted effectively by the probe field detuning, the coherent field intensity, the interaction length. Meanwhile, the quantum interference between the amplitude modulation and phase modulation can be manipulated by the relative phase, which can be used to regulate the diffraction pattern and efficiency of the 2D EIG. Our scheme of 2D EIG may be useful in beam splitting and all-optical switching.

Acoustic radiation torque on an interface reflecting acoustic vortex beams

Torque exerted by acoustic waves to rotate objects can result from asymmetry such as the case of an averaged torque on a Rayleigh disk exerted by an ordinary acoustic field. In the absence of asymmetry, acoustic torque can occur by viscous absorption either in the object or in the adjacent boundary layer of the object when using specific types of acoustic fields such as acoustic vortex beams carrying twisted wave fronts [Zhang and Marston, Phys. Rev. E 84, 065601 (2011)] or two orthogonal standing wave fields [Zhang and Marston, J. Acoust. Soc. Am. 136, 2917 (2014)]. Recent study suggested a torque on a flat water-air interface exerted by an ultrasonic vortex beam obliquely incident and reflecting off the interface [Zou, Lirette, and Zhang, Phys. Rev. Lett. 125, 074301 (2020)]. This torque is not associated with viscous absorption and instead results from variation of orbital angular momentum carried by the vortex beam during the reflection. The torque would otherwise disappear in normal incidence or using ordinary beams. The investigations advance understanding of radiation torque physics and approaches for non-contact manipulations using acoustic waves.

Two-dimensional electromagnetically induced grating via spontaneously generated coherence and incoherent pump

A new scheme for two-dimensional (2D) electromagnetically induced grating is proposed based on spontaneously generated coherence in a Λ-type atomic system, in which the atom interacts with two orthogonal standing-wave fields and an incoherent pumping field. Due to spatial periodical modulation, the zero absorption or even gain accompanied with large dispersion is obtained in atomic medium, and electromagnetically induced grating is formed. Thus the weak probe field could be diffracted into first-order or high-order directions with high efficiency. The diffraction feature and efficiency of the gratings could be adjusted by the probe field detuning, the interaction length, the incoherent pumping field intensity, and the relative phase as well. The scheme of 2D grating we presented may have some potential application in beam splitting and all-optical switching.

Tunable optical vortex array in a two-dimensional electromagnetically induced atomic lattice.

Optical vortex arrays (OVAs) containing multiple vortices have been in demand for multi-channel optical communications and multiple-particle trapping. In this Letter, an OVA with tunable intensity and spatial distribution was implemented all-optically in a two-dimensional (2D) electromagnetically induced atomic lattice (EIL). Such a square lattice is constructed by two orthogonal standing-wave fields in 85Rb vapor, resulting in the periodically modulated susceptibility of the probe beam based on electromagnetically induced transparency (EIT). An OVA with dark-hollow intensity distribution based on 2D EIL was observed in the experiment first. This work thus studied the nonlinear 2D EIL process both theoretically and experimentally, presenting, to the best of our knowledge, a novel method of dynamically obtaining and controlling an OVA and further promoting the construction of all-optical networks with atomic ensembles.

Spatial-dependent probe transmission based high-precision two-dimensional atomic localization

Herein, we propose a scheme for the realization of two-dimensional atomic localization in a λ-type three-level atomic medium such that the atom interacts with the two orthogonal standing-wave fields and a probe field. Because of the spatially dependent atom-field interaction, the information about the position of the atom can be obtained by monitoring the probe transmission spectra of the weak probe field for the first time. A single and double sharp localized peaks are observed in the one-wavelength domain. We have theoretically archived high-resolution and high-precision atomic localization within a region smaller than λ/25 × λ/25. The results may have potential applications in the field of nano-lithography and advance laser cooling technology.

Controllable two- and three-dimensional atom localization via spontaneously generated coherence

A scheme for two-dimensional (2D) and three-dimensional (3D) atom localization in a four-level N-type atomic system is proposed. The scheme is based on the probe absorption measurement when the atom passes through the orthogonal standing-wave fields. Using the electromagnetically induced transparency, we prove that the probe field absorption is spatially localized in sub-wavelength domain. We also show that the spatial resolution of 2D and 3D atom localization strongly depends on the probe field detuning, the quantum interference parameters induced by spontaneous emission, and the relative phase between the driving fields.

High-precision three dimensional atom localization via multiphoton quantum destructive interference.

We propose an effective scheme for high-precision three dimensional(3D) atom localization via measuring the population of excited state in a four-level atomic system driven by a probe field and three orthogonal standing-wave fields. In this scheme, the position-dependent multiphoton quantum destructive interference leads to multiphoton excitation of the excited state and enhances the fluorescence emission. We show that adjusting the frequency detuning and phase shifts associated with the standing-wave fields can modify the multiphoton quantum destructive interference and lead to a redistribution of the atoms. The maximal probability of finding the atom at the certain position in one period of the standing-wave fields can be 100% and the highest spatial precision is about 0.02λ.

Precision in two-and three-dimensional atom localization via detuning and phase shifts using four-level tripod atomic system

The high-precision position measurement scheme of a single atom in two-dimensions and three-dimensions is investigated in a four-level tripod-type system. The atom interacts with the two orthogonal standing wave fields (OSWFs) and three OSWFs for two- and three-dimensional (2D, 3D) atom localization. The high-precision position of the atom is observed by adjusting the suitable system parameters. We achieve a high-precision single localized peak in the 2D plane and a single localized sphere smaller than the cubic optical wavelength in 3D volume space. We also see the impact of the Doppler shift on atom localization in 2D and 3D. We show that the Doppler shift dramatically deteriorates the precision of spatial information. The proposed high-precision atom localization scheme has applications in laser cooling and Bose–Einstein condensation phenomena.

Two-dimensional atom localization via a combination of the standing-wave and Gaussian fields

The localization of atom is studied in two-dimensional (2D) in a four-level V-type atomic system by using the Gaussian field. The atom localization is investigated through the absorption spectrum of the weak probe field inside two orthogonal standing-wave fields. We consider three hypotheses for the interaction between the atom and fields (standing-wave and Gaussian fields), each hypothesis is considered individually. We obtain the expression for the first-order approximation of the absorption of the probe field mathematically for the hypothesis (I). The Gaussian field parameter plays an important role in the precision of the atom localization. The 2D atom localization can be dependent on the detuning of the probe field (resonance and off-resonance), the Rabi frequencies and the phase shifts.

Observation of diffraction pattern in two-dimensional optically induced atomic lattice.

The diffraction pattern of a two-dimensional optically induced atomic lattice is reported experimentally in a three-level atomic system. Such a two-dimensional optical lattice is established by two orthogonal standing-wave fields induced by the interference of two pairs of coupling laser beams. When the probe beam is launched into it, a spatially modulated discrete diffraction pattern can be obtained at the output plane of the vapor cell under the electromagnetically induced transparency condition. We investigate the diffraction pattern under different experimental parameters and find that it can be effectively controlled by tuning the coupling laser power and two-photon detuning. Our work may potentially pave the way for studying the control of light and other intriguing physical phenomena based on such a periodically modulated atomic lattice.

A large time delay of light via two dimensional atom localization in a coupled cavity waveguide

We investigate the time delay behavior of light through a Λ-type atomic system interacting with two orthogonal standing-wave fields in a modified reservoir. Results show that transmission spectra splitting occurs in a coupled cavity waveguide (CCW) and the time delay of light relies remarkably on the strong coupling effect between a localized atom and a CCW. The atom localization can even be larger than λ∕100 in two orthogonal directions, which arises from field-induced interference effect in a modified reservoir. The proposed scheme not only provides a high-precision atom localization but also achieves a large time delay of the probe light.

Efficient two-dimensional sub-wavelength atom localisation via probe absorption in a four-level Λ-shaped atomic system

Two-dimensional (2D) atom localisation of a four-level Λ-shaped atomic system with a nearly hyper-fine doublet interacting with two orthogonal standing-wave fields is investigated. The spatial information of a moving atom in xy plane is obtained by measuring the probe field absorption. The effect of quantum interference on two-dimensional atom localisation is described. The intensity of standing-waves and the detuning of the probe and standing-wave fields are found to strongly affect the two-dimensional atom localisation that lead to different spatial distribution patterns.

Efficient three-dimensional atom localization using probe absorption in a diamond-configuration atomic system

A new scheme for three-dimensional (3D) atom localization is proposed based on measuring the probe absorption spectra in a four-level diamond-configuration atomic system, in which the atom interacts with three orthogonal standing-wave laser fields. Due to spatial-dependent interaction between atom and fields, position information of the atom can be obtained by measuring the absorption spectra of the weak probe field. The results show that atom localization properties can be significantly improved and some interesting spatial localization structures such as double-layer lantern-like, single-layer lantern-like, gourd-like, cylinder-like, and ellipsoid-like patterns can be achieved when we adjust system parameters properly. Most importantly, we can find the atom at a particular position in 3D space with 100% probability under appropriate conditions.

High-precision three-dimensional atom localization in a three-level pump–probe atomic system

We propose a new scheme for three-dimensional (3D) atom localization controlled by incoherent pump in a three-level Λ-type atomic system. The spatial position information of an atom in 3D space can be achieved via measuring probe gain and absorption when the atom passes through three mutually perpendicular standing-wave fields. It is found that high-detecting-probability and high-precision 3D atom localization can be obtained via properly adjusting the relevant parameters in the presence of the combination of a traveling-wave field and three orthogonal standing-wave fields. Furthermore, it is also shown that the incoherent pumping field can switch the localization patterns from the probe-gain sphere to the probe-absorption sphere and enhance 3D atom-localization precision.

Two-dimensional electromagnetically induced gain-phase grating with an incoherent pump field

We propose a scheme of two-dimensional electromagnetically induced grating in a three-level Ladder-type atomic system, which is driven by a weak probe field, two orthogonal standing-wave fields, and an incoherent pump field. Due to the position-dependent atom-field interaction, the periodical susceptibility of the probe field can be obtained. By using an incoherent pump field, one can control the absorption (gain) and dispersion of the probe field. By choosing proper parameters, a electromagnetically induced gain-phase grating can be formed in the present system, and the probe energy can be diffracted from zeroth-order into high-order directions. Our scheme may be useful to design new photonic devices in optical information processing.

Efficient atom localization via probe absorption in an inverted-Y atomic system

The behaviour of atom localization in an inverted-Y atomic system is theoretically investigated. For the atoms interacting with a weak probe field and several orthogonal standing-wave fields, their position information can be obtained by measuring the probe absorption. Compared with the traditional scheme, we couple the probe field to the transition between the middle and top levels. It is found that the probe absorption sensitively depends on the detuning and strength of the relevant light fields. Remarkably, the atom can be localized at a particular position in the standing-wave fields by coupling a microwave field to the transition between the two ground levels.

3D atom microscopy in the presence of Doppler shift

The interaction of hot atoms with laser fields produces a Doppler shift, which can severely affect the precise spatial measurement of an atom. We suggest an experimentally realizable scheme to address this issue in the three-dimensional position measurement of a single atom in vapors of rubidium atoms. A three-level Λ-type atom–field configuration is considered where a moving atom interacts with three orthogonal standing-wave laser fields and spatial information of the atom in 3D space is obtained via an upper-level population using a weak probe laser field. The atom moves with velocity v along the probe laser field, and due to the Doppler broadening the precision of the spatial information deteriorates significantly. It is found that via a microwave field, precision in the position measurement of a single hot rubidium atom can be attained, overcoming the limitation posed by the Doppler shift.

Resonance fluorescence microscopy via three-dimensional atom localization

A scheme is proposed to realize three-dimensional (3D) atom localization in a driven two-level atomic system via resonance fluorescence. The field arrangement for the atom localization involves the application of three mutually orthogonal standing-wave fields and an additional traveling-wave coupling field. We have shown the efficacy of such field arrangement in tuning the spatially modulated resonance in all directions. Under different parametric conditions, the 3D localization patterns originate with various shapes such as sphere, sheets, disk, bowling pin, snake flute, flower vase. High-precision localization is achieved when the radiation field detuning equals twice the combined Rabi frequencies of the standing-wave fields. Application of a traveling-wave field of suitable amplitude at optimum radiation field detuning under symmetric standing-wave configuration leads to 100% detection probability even in sub-wavelength domain. Asymmetric field configuration is also taken into consideration to exhibit atom localization with appreciable precision compared to that of the symmetric case. The momentum distribution of the localized atoms is found to follow the Heisenberg uncertainty principle under the validity of Raman–Nath approximation. The proposed field configuration is suitable for application in the study of atom localization in an optical lattice arrangement.

Two-dimensional electromagnetically induced grating via nonlinear modulation in a five-level atomic system

We theoretically propose a scheme for two-dimensional electromagnetically induced grating in a five-level atomic system interacting with two orthogonal standing-wave fields. In such atomic system, nonlinear absorption or refractivity can be significantly enhanced with nearly vanishing linear absorption under different resonant conditions. When applying two coupling fields with standing-wave pattern, absorption grating or phase grating, which efficiently diffracts a probe beam into high-order directions, can be formed in the media. The diffraction efficiencies of the gratings depend strongly on the interaction length, the intensities and detunings of the coupling fields. By investigating the third-order nonlinearity of the system, it is found that the spatial variations of amplitude and phase arise from the nonlinear modulation. The proposed gratings can be used as multi-channel beam splitter and have potential applications in optical information processing and optical networking.