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Title: Coherent population trapping with polarization modulation

Abstract

Coherent population trapping (CPT) is extensively studied for future vapor cell clocks of high frequency stability. In the constructive polarization modulation CPT scheme, a bichromatic laser field with polarization and phase synchronously modulated is applied on an atomic medium. A high contrast CPT signal is observed in this so-called double-modulation configuration, due to the fact that the atomic population does not leak to the extreme Zeeman states, and that the two CPT dark states, which are produced successively by the alternate polarizations, add constructively. Here, we experimentally investigate CPT signal dynamics first in the usual configuration, a single circular polarization. The double-modulation scheme is then addressed in both cases: one pulse Rabi interaction and two pulses Ramsey interaction. The impact and the optimization of the experimental parameters involved in the time sequence are reviewed. We show that a simple seven-level model explains the experimental observations. The double-modulation scheme yields a high contrast similar to the one of other high contrast configurations like push-pull optical pumping or crossed linear polarization scheme, with a setup allowing a higher compactness. The constructive polarization modulation is attractive for atomic clock, atomic magnetometer, and high precision spectroscopy applications.

Authors:
; ;  [1]
  1. LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, 61 avenue de l'Observatoire, 75014 Paris (France)
Publication Date:
OSTI Identifier:
22596669
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 119; Journal Issue: 24; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMIC CLOCKS; CONFIGURATION; LASER RADIATION; LASERS; MAGNETOMETERS; MODULATION; OPTICAL PUMPING; OPTIMIZATION; POLARIZATION; PULSES; SIGNALS; TRAPPING; VAPORS; ZEEMAN EFFECT

Citation Formats

Yun, Peter, E-mail: enxue.yun@obspm.fr, Guérandel, Stéphane, and Clercq, Emeric de. Coherent population trapping with polarization modulation. United States: N. p., 2016. Web. doi:10.1063/1.4954690.
Yun, Peter, E-mail: enxue.yun@obspm.fr, Guérandel, Stéphane, & Clercq, Emeric de. Coherent population trapping with polarization modulation. United States. doi:10.1063/1.4954690.
Yun, Peter, E-mail: enxue.yun@obspm.fr, Guérandel, Stéphane, and Clercq, Emeric de. Tue . "Coherent population trapping with polarization modulation". United States. doi:10.1063/1.4954690.
@article{osti_22596669,
title = {Coherent population trapping with polarization modulation},
author = {Yun, Peter, E-mail: enxue.yun@obspm.fr and Guérandel, Stéphane and Clercq, Emeric de},
abstractNote = {Coherent population trapping (CPT) is extensively studied for future vapor cell clocks of high frequency stability. In the constructive polarization modulation CPT scheme, a bichromatic laser field with polarization and phase synchronously modulated is applied on an atomic medium. A high contrast CPT signal is observed in this so-called double-modulation configuration, due to the fact that the atomic population does not leak to the extreme Zeeman states, and that the two CPT dark states, which are produced successively by the alternate polarizations, add constructively. Here, we experimentally investigate CPT signal dynamics first in the usual configuration, a single circular polarization. The double-modulation scheme is then addressed in both cases: one pulse Rabi interaction and two pulses Ramsey interaction. The impact and the optimization of the experimental parameters involved in the time sequence are reviewed. We show that a simple seven-level model explains the experimental observations. The double-modulation scheme yields a high contrast similar to the one of other high contrast configurations like push-pull optical pumping or crossed linear polarization scheme, with a setup allowing a higher compactness. The constructive polarization modulation is attractive for atomic clock, atomic magnetometer, and high precision spectroscopy applications.},
doi = {10.1063/1.4954690},
journal = {Journal of Applied Physics},
number = 24,
volume = 119,
place = {United States},
year = {Tue Jun 28 00:00:00 EDT 2016},
month = {Tue Jun 28 00:00:00 EDT 2016}
}
  • We propose a constructive polarization modulation scheme for atomic clocks based on coherent population trapping (CPT). In this scheme, the polarization of a bichromatic laser beam is modulated between two opposite circular polarizations to avoid trapping the atomic populations in the extreme Zeeman sublevels. We show that if an appropriate phase modulation between the two optical components of the bichromatic laser is applied synchronously, the two CPT dark states which are produced successively by the alternate polarizations add constructively. Measured CPT resonance contrasts up to 20% in one-pulse CPT and 12% in two-pulse Ramsey-CPT experiments are reported, demonstrating the potentialmore » of this scheme for applications to high performance atomic clocks.« less
  • Coherent-population-trapping resonances within the degenerate two-level system of the F=2{yields}F{sup '}=1 transition of the {sup 87}Rb D{sub 1} line were investigated in an uncoated Rb vapor cell by means of level-crossing-type experiments. Tuning over the two-photon resonance is achieved sweeping a magnetic field around zero value. The influence of transverse magnetic fields on the amplitude and the width of the resonances, recorded in fluorescence and absorption, were investigated in the cases of excitation with linear, circular, and elliptical laser light polarization. A theoretical analysis was performed for the case of linearly polarized excitation, the results of which are in goodmore » agreement with the experiment.« less
  • The shape of the coherent-population-trapping (CPT) resonances was investigated theoretically and experimentally at different laser powers. The CPT resonances were observed in fluorescence on the degenerate two-level system of the (F{sub {phi}}=2{yields}F{sub f}=1) transition of the {sup 87}Rb D{sub 1} line by means of a Hanle effect configuration in an uncoated vacuum cell. Numerical simulations based on the density matrix formalism, which take into account the high-rank polarization moment (HRPMs) influence and the velocity distribution of the atoms, were used to calculate the shape of the nonlinear magnetic resonances. The comparison of the theoretical and experimental shapes of the CPTmore » resonances demonstrated that the HRPMs influence the shape at all laser excitation powers, and this influence can be used to explain some peculiarities at the center of the CPT resonance shape.« less
  • We study how coherent Stokes and anti-Stokes Raman scattering influence coherent population trapping. In an experiment using an atomic sodium vapor cell we observe induced transparency, induced absorption, and gain features, all of subnatural linewidth. The electromagnetically induced resonance is a peak or a dip depending on which side of the optical transition the fields are tuned to, and thus whether coherent anti-Stokes Raman scattering or coherent Stokes Raman scattering is the dominant process.
  • We present a new laser-cooling scheme based on velocity-selective optical pumping of atoms into a nonabsorbing coherent superposition of states. This method has allowed us to achieve transverse cooling of metastable /sup 4/He atoms to a temperature of 2 ..mu..K, lower than both the usual Doppler cooling limit (23 ..mu..K) and the one-photon recoil (4 ..mu..K). The corresponding de Broglie wavelength (1.4 ..mu..m) is larger than the atomic transition optical wavelength.