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Université de Fribourg

A Bell-Bloom experiment with polarization-modulated light of arbitrary duty cycle

Fescenko, Ilja ; Knowles, Paul E. ; Weis, Antoine ; Breschi, Evelina

In: Optics Express, 2013, vol. 21, no. 13, p. 15121–15130

We report on a study of polarization-modulation experiments on the 4 → 3 hyperfine component of the D₁ transition in Cs vapor contained in a paraffin-coated cell. The laser beam’s polarization was switched between left- and right-circular polarization at a rate of 200 Hz. Variations of the transmitted light power were recorded while varying the amplitude of a transverse magnetic...

Université de Fribourg

Atomic magnetic resonance induced by amplitude-, frequency-, or polarization-modulated light

Grujić, Zoran D. ; Weis, Antoine

In: Physical Review A, 2013, vol. 88, no. 1, p. 012508

In recent years diode laser sources have become widespread and reliable tools in magneto-optical spectroscopy. In particular, laser-driven atomic magnetometers have found a wide range of practical applications. More recently, so-called magnetically silent variants of atomic magnetometers have been developed. While in conventional magnetometers the magnetic resonance transitions between atomic...

Université de Fribourg

Spectroscopy of alkali-metal atoms in dense supercritical ⁴He at low temperatures

Moroshkin, Peter ; Lebedev, Victor ; Weis, Antoine

In: Physical Review A, 2013, vol. 87, no. 2, p. 022513

We present an experimental study of laser-induced fluorescence spectra of Cs atoms embedded in superfluid and solid ⁴He, as well as in dense supercritical fluid He. The studied temperature range is increased with respect to earlier studies by the use of intense laser pulses for the transient local heating of the helium sample. The analysis of the experimental spectra is based on two different...

Université de Fribourg

Ground-state Hanle effect based on atomic alignment

Breschi, Evelina ; Weis, Antoine

In: Physical Review A - Atomic, Molecular and Optical Physics, 2012, vol. 86, no. 5, p. 053427

We have studied the ground-state Hanle effect (GSHE) excited by linearly polarized laser light on the D₁ line of cesium atoms. We have solved algebraically the Liouville equation using the irreducible tensor formalism, and derive an analytical expression for the resonance line shapes in a magnetic field of arbitrary direction. The model predictions are in excellent agreement with experimental...

Université de Fribourg

Acoustic and visual display of photons: a handheld demonstration device

Dimitrova, L. ; Lechkov, A. ; Grigorova, T. ; Weis, Antoine

In: Physica Scripta, 2012, vol. 2012, no. T149, p. 014010

A handheld device for rendering the signals produced by individual photons is presented in this paper. Electric pulses produced by individual photons in a photomultiplier are made audible by a small loudspeaker built into the housing. Output connectors allow the pulse signals to be displayed by an external amplifier/loudspeaker system, an oscilloscope, or to be further processed by pulse counting...

Université de Fribourg

A portable double-slit quantum eraser with individual photons

Dimitrova, Todorka Lulcheva ; Weis, Antoine

In: European Journal of Physics, 2011, vol. 32, no. 6, p. 1535

The double-slit experiment has played an important role in physics, from supporting the wave theory of light, via the discussions of the wave–particle duality of light (and matter) to the foundations of modern quantum optics. Today it keeps playing an active role in the context of quantum optics experiments involving single photons. In this paper, we present a truly portable double-slit...

Université de Fribourg

Measurement of longitudinal and transverse spin relaxation rates using the ground-state Hanle effect

Castagna, Natascia ; Weis, Antoine

In: Physical Review A - Atomic, Molecular and Opical Physics, 2011, vol. 84, no. 5, p. 053421

We present a theoretical and experimental study of the resonant circularly-polarized-light-induced Hanle effect in the ground state of Cs vapor atoms in a paraffin-coated cell. The effect manifests itself as a narrow resonance (centered at B=0) in the dependence of the optical transmission coefficient of the vapor on the magnitude of an external magnetic field B⃗. We develop a theoretical model...

Université de Fribourg

Laser ablation and spectroscopy of copper in liquid and solid ⁴He

Moroshkin, Peter ; Lebedev, Victor ; Weis, Antoine

In: Physical Review A - Atomic, Molecular and Optical Physics, 2011, vol. 84, no. 5, p. 052519

We present an experimental study of the laser-induced fluorescence spectra of Cu atoms in bulk liquid and solid helium matrices as well as in the dense plasma created by the laser ablation of copper in liquid helium. We observe transitions of the valence electron and of inner-shell electrons. The former produce structureless line shapes, a large broadening, and a blueshift. The latter practically...

Université de Fribourg

Phonon generation in condensed ⁴He by laser-excited atomic bubbles

Moroshkin, Peter ; Lebedev, Victor ; Weis, Antoine

In: Europhysics Letters, 2011, vol. 96, no. 2, p. 26002

We discuss the interaction between nanometer-sized defects (atomic bubbles) and elementary excitations (phonons) in quantum fluids and solids. We observe that optical excitations in embedded metal atoms induce bubble expansions/contractions that create strongly localized phonon wave packets in the quantum matrix. We derive the structure and dynamics of these vibronic excitations from the...

Université de Fribourg

Formation of metallic nanowires by laser ablation in liquid Helium

Lebedev, Victor ; Moroshkin, Peter ; Grobéty, Bernard ; Gordon, Eugene ; Weis, Antoine

In: Journal of Low Temperature Physics, 2011, vol. 165, no. 3-4, p. 166-176

Laser ablation of metals in liquid helium results in the formation of metal filaments with diameters on the order of 2–10 nanometres and of spherical nanoparticles. In superfluid helium these nanowires aggregate into centimeter-sized networks. We study the morphology and the electric conductivity of these large aggregates, as well as extinction spectra and the crystalline structure of the...