arXiv subjects

B. Dubetsky

Publications and source records attributed to B. Dubetsky.

26 records · Page 2Linked to original sources

arXiv2001

Spectrum of light scattering from an extended atomic wave packet

The spectrum of the light scattered from an extended atomic wave packet is calculated. For a wave packet consisting of two spatially separated peaks moving on parallel trajectories, the spectrum contains Ramsey-like fringes that are sensitive to the phase difference between the two components of the wave packet. Using this technique, one can establish the mutual coherence of the two components of the wave packet without recombining them.

physics.atom-ph↗

arXiv2000

Atom Interference using microfabricated structures

Atom density profile arising in the atomic beam after passing through the one or two microfabricated structures (MS) is considered. Two limiting cases the beam with large and small angular divergence are considered. An equivalence of the considerations based on the Fresnel-Kirchhoff theory of diffraction and on the atomic recoil-effect is established. Higher order gratings' profiles produced in the collinear beam owing to the atomic Talbot effect are calculated. For an atomic beam with large angular divergence, two regimes of atoms' scattering off the MS, classical and quantum, are analyzed. For classical scattering from two MSs, the atomic density periodic modulation focusses at the echo points owing to the shadow effect. Elaborated simple geometric interpretation of the echo-effect. Dephasing-rephasing processes induced by two MSs having rational ratio of their periods are fully classified. Positions and profiles of the higher order gratings are calculated. Gratings' deformations caused by the quantum scattering are included. In this case, corresponding to the atomic Talbot-Lau effect, for a distance between fields equal to 1/n part of the Talbot distance, one compresses n times the grating caused by the shadow effect.

physics.atom-ph↗

arXiv2000

Nonlinear, ground-state, pump-probe spectroscopy

A theory of pump-probe spectroscopy is developed in which optical fields drive two-quantum, Raman-like transitions between ground state sublevels. Three fields are incident on an ensemble of atoms. Two of the fields act as the pump field for the two-quantum transitions. The absorption or gain of an additional probe field is monitored as a function of its detuning from one of the fields which constitutes the pump field. Although the probe absorption spectrum displays features common to those found in pump-probe spectroscopy of single-quantum transitions, new interference effects are found to modify the spectrum. Many of these features can be explained within the context of a dressed atom picture.

physics.atom-ph↗

arXiv1999

Filtered Talbot lens: Producing $λ/2n$-periodic atomic patterns with standing wave fields having period $λ$

We propose a scheme to create high-contrast, periodic atom density distributions having period $λ/2n$ using the Talbot effect, where $% λ$ is the wave length of the optical fields that scatter the atoms and $n$ is a positive integer. This {\em filtered Talbot lens} is comprised of two standing-wave optical fields. An atomic beam propagates perpendicular to the fields. The first field, which is far-detuned from the atomic transition frequency, acts as an array of lenses that focuses the atoms. The second field, positioned at the atom optical focus of the first, is resonant with the atomic transition frequency and acts as an amplitude mask, leaving unperturbed only those atoms that pass through its nodes. At distances following the interaction with the second field that are equal to an integral fraction of the Talbot length, atomic density gratings having period $λ/2n$ are formed.

physics.atom-ph↗

arXiv1999

Atom focusing by far-detuned and resonant standing wave fields: Thin lens regime

The focusing of atoms interacting with both far-detuned and resonant standing wave fields in the thin lens regime is considered. The thin lens approximation is discussed quantitatively from a quantum perspective. Exact quantum expressions for the Fourier components of the density (that include all spherical aberration) are used to study the focusing numerically. The following lens parameters and density profiles are calculated as functions of the pulsed field area $θ$: the position of the focal plane, peak atomic density, atomic density pattern at the focus, focal spot size, depth of focus, and background density. The lens parameters are compared to asymptotic, analytical results derived from a scalar diffraction theory for which spherical aberration is small but non-negligible ($θ\gg 1$). Within the diffraction theory analytical expressions show that the focused atoms in the far detuned case have an approximately constant background density $0.5(1-0.635θ^{- 1/2})$ while the peak density behaves as $% 3.83θ^{1/2}$, the focal distance or time as $θ^{-1}(1+1.27θ^{- 1/2})$, the focal spot size as $0.744θ^{-3/4}$, and the depth of focus as $1.91θ^{- 3/2}$. Focusing by the resonant standing wave field leads to a new effect, a Rabi- like oscillation of the atom density. For the far-detuned lens, chromatic aberration is studied with the exact Fourier results. Similarly, the degradation of the focus that results from angular divergence in beams or thermal velocity distributions in traps is studied quantitatively with the exact Fourier method and understood analytically using the asymptotic results. Overall, we show that strong thin lens focusing is possible with modest laser powers and with currently achievable atomic beam characteristics.

physics.atom-ph↗

arXiv1998

Quasiperiodic Atom Optics, Focusing, and Wave packet Rephasing

We propose a laser field configuration which acts as a quasiperiodic atom optical diffraction grating. Analytical and computational results for the atomic center-of-mass wavefunction after the grating reveal a quasiperiodic density pattern, a semiclassical focusing effect, and a quasiperiodic self-imaging of the atomic wavefunction analogous to a Talbot effect.

physics.atom-ph↗

arXiv1998

Matter wave interference using two-level atoms and resonant optical fields

A theory of matter wave interference is developed in which resonant optical fields interact with two-level atoms. When recoil effects are included, spatial modulation of the atomic density can occur for times that are greater than or comparable with the inverse recoil frequency. In this regime, the atoms exhibit matter-wave interference. Two specific atom field geometries are considered. In the first, atoms characterized by a homogeneous velocity distribution are subjected to a single radiation pulse. The pulse excites the atoms which then decay back to the lower state. The spatial modulation of the total atomic density is calculated as a function of $t$, where $t$ is the time following the pulse. In contrast to the normal Talbot effect, the spatially modulated density is not a periodic function of $ t,$ owing to spontaneous emission; however, after a sufficiently long time, the contribution from spontaneous processes no longer plays a role and the Talbot periodicity is restored. In the second atom-field geometry, there are two pulses separated by an interval $T$. The atomic velocity distribution in this case is assumed to be inhomogeneously broadened. In contrast to the normal Talbot-Lau effect, the spatially modulated density is not a periodic function of $T$, owing to spontaneous emission; however, for sufficiently long time, the contribution from spontaneous processes no longer plays a role and the Talbot periodicity is restored. The structure of the spatially modulated density is studied, and is found to mirror the atomic density following the first pulse. The spatially modulated atomic density serves as an indirect probe of the distribution of spontaneously emitted radiation.

physics.atom-ph↗

arXiv1998

High resolution amplitude and phase gratings in atom optics

An atom-field geometry is chosen in which an atomic beam traverses a field interaction zone consisting of three fields, one having frequency $Ω=c/λ$ propagating in the $\hat{z}$ direction and the other two having frequencies $Ω+δ_{1}$ and $Ω+δ_{2}$ propagating in the -$\hat{z}$ direction. For $n_{1}δ_{1}+n_{2}δ_{2}=0$ and $|δ_{1}| T,|δ_{2}| T\gg 1$, where $n_{1}$ and $n_{2}$ are positive integers and $T$ is the pulse duration in the atomic rest frame, the atom-field interaction results in the creation of atom amplitude and phase gratings having period $% λ/[2(n_{1}+n_{2})]$. In this manner, one can use optical fields having wavelength $λ$ to produce atom gratings having periodicity much less than $λ$.

physics.atom-ph↗