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1.
Phys Rev Lett ; 122(11): 113401, 2019 Mar 22.
Article in English | MEDLINE | ID: mdl-30951353

ABSTRACT

By measuring the transmission of near-resonant light through an atomic vapor confined in a nanocell we demonstrate a mesoscopic optical response arising from the nonlocality induced by the motion of atoms with a phase coherence length larger than the cell thickness. Whereas conventional dispersion theory-where the local atomic response is simply convolved by the Maxwell-Boltzmann velocity distribution-is unable to reproduce the measured spectra, a model including a nonlocal, size-dependent susceptibility is found to be in excellent agreement with the measurements. This result improves our understanding of light-matter interaction in the mesoscopic regime and has implications for applications where mesoscopic effects may degrade or enhance the performance of miniaturized atomic sensors.

2.
Phys Rev Lett ; 120(24): 243401, 2018 Jun 15.
Article in English | MEDLINE | ID: mdl-29956978

ABSTRACT

We measure the near-resonant transmission of light through a dense medium of potassium vapor confined in a cell with nanometer thickness in order to investigate the origin and validity of the collective Lamb shift. A complete model including the multiple reflections in the nanocell reproduces accurately the observed line shape. It allows the extraction of a density-dependent shift and width of the bulk atomic medium resonance, deconvolved from the cavity effect. We observe an additional, unexpected dependence of the shift with the thickness of the medium. This extra dependence demands further experimental and theoretical investigations.

3.
Phys Rev Lett ; 120(16): 163903, 2018 Apr 20.
Article in English | MEDLINE | ID: mdl-29756941

ABSTRACT

In this Letter, we show that it is possible to structure the longitudinal polarization component of light. We illustrate our approach by demonstrating linked and knotted longitudinal vortex lines acquired upon nonparaxially propagating a tightly focused subwavelength beam. The remaining degrees of freedom in the transverse polarization components can be exploited to generate customized topological vector beams.

4.
Phys Rev Lett ; 118(25): 253601, 2017 Jun 23.
Article in English | MEDLINE | ID: mdl-28696754

ABSTRACT

We experimentally demonstrate the heralded generation of bichromatic single photons from an atomic collective spin excitation (CSE). The photon arrival times display collective quantum beats, a novel interference effect resulting from the relative motion of atoms in the CSE. A combination of velocity-selective excitation with strong laser dressing and the addition of a magnetic field allows for exquisite control of this collective beat phenomenon. The present experiment uses a diamond scheme with near-IR photons that can be extended to include telecommunications wavelengths or modified to allow storage and retrieval in an inverted-Y scheme.

5.
Phys Rev Lett ; 112(25): 253201, 2014 Jun 27.
Article in English | MEDLINE | ID: mdl-25014812

ABSTRACT

We present experimental observations of atom-light interactions within tens of nanometers (down to 11 nm) of a sapphire surface. Using photon counting we detect the fluorescence from of order one thousand Rb or Cs atoms, confined in a vapor with thickness much less than the optical excitation wavelength. The asymmetry in the spectral line shape provides a direct readout of the atom-surface potential. A numerical fit indicates a power law -C(α)/r(α) with α = 3.02 ± 0.06 confirming that the van der Waals interaction dominates over other effects. The extreme sensitivity of our photon-counting technique may allow the search for atom-surface bound states.

6.
Phys Rev Lett ; 108(17): 173601, 2012 Apr 27.
Article in English | MEDLINE | ID: mdl-22680863

ABSTRACT

We present an experimental measurement of the cooperative Lamb shift and the Lorentz shift using a nanothickness atomic vapor layer with tunable thickness and atomic density. The cooperative Lamb shift arises due to the exchange of virtual photons between identical atoms. The interference between the forward and backward propagating virtual fields is confirmed by the thickness dependence of the shift, which has a spatial frequency equal to twice that of the optical field. The demonstration of cooperative interactions in an easily scalable system opens the door to a new domain for nonlinear optics.

7.
Opt Lett ; 37(16): 3405-7, 2012 Aug 15.
Article in English | MEDLINE | ID: mdl-23381272

ABSTRACT

A light, compact optical isolator using an atomic vapor in the hyperfine Paschen-Back regime is presented. Absolute transmission spectra for experiment and theory through an isotopically pure 87Rb vapor cell show excellent agreement for fields of 0.6 T. We show π/4 rotation for a linearly polarized beam in the vicinity of the D2 line and achieve an isolation of 30 dB with a transmission >95%.

8.
Phys Rev Lett ; 109(23): 233001, 2012 Dec 07.
Article in English | MEDLINE | ID: mdl-23368190

ABSTRACT

We present an experimental measurement of the refractive index of high density Rb vapor in a gaseous atomic nanolayer. We use heterodyne interferometry to measure the relative phase shift between two copropagating laser beams as a function of the laser detuning and infer a peak index n=1.26±0.02, close to the theoretical maximum of 1.31. The large index has a concomitant large index gradient creating a region with steep anomalous dispersion where a subnanosecond optical pulse is advanced by >100 ps over a propagation distance of 390 nm, corresponding to a group index n(g)=-(1.0±0.1)×10(5), the largest negative group index measured to date.

9.
Int Rehabil Med ; 8(1): 34-8, 1986.
Article in English | MEDLINE | ID: mdl-2942511

ABSTRACT

This study was designed to assess whether physiotherapy exercises administered for low back pain have the physiological effects that they purport to have (increase spinal mobility and muscle strength) and whether these effects are of clinical relevance (related to changes in pain and function). Thirty-six patients were allocated to three treatment conditions, mobilizing exercises, isometric exercises or an attention-placebo control procedure. The results did not support the hypotheses concerning the effects of physiotherapy exercises, and hence challenge widely held views concerning the mechanism by which some patients suffering from low back pain improve whilst undergoing physiotherapy exercises.


Subject(s)
Back Pain/rehabilitation , Exercise Therapy/methods , Adult , Back Pain/physiopathology , Clinical Trials as Topic , Double-Blind Method , Female , Humans , Isometric Contraction , Male , Middle Aged , Movement , Muscles/physiopathology , Pain , Spine/physiopathology
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