skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Four-Wave Mixing and Biphoton Generation in a Two-Level System

Abstract

We find that in a two-level system there are two kinds of four-wave mixing processes which destructively contribute to the third-order nonlinear susceptibility. In a paired-photon generation scheme by using a single retroreflected pump beam, these two processes occur with definite time orders. The biphoton temporal correlation, which is measured with a back-to-back geometry in a laser-cooled two-level atomic ensemble, shows a damped Rabi oscillation and photon antibunching. Without suppressing the background of Rayleigh scattering, the upper limit of Cauchy criteria is estimated.

Authors:
;  [1]; ;  [2]
  1. Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States)
  2. Physics Department, University of Maryland, Baltimore County, Baltimore, Maryland 21250 (United States)
Publication Date:
OSTI Identifier:
20955424
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevLett.98.053601; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; FREQUENCY MIXING; GEOMETRY; LASERS; NONLINEAR PROBLEMS; OSCILLATIONS; PHOTONS; RAYLEIGH SCATTERING

Citation Formats

Du Shengwang, Yin, G. Y., Wen Jianming, and Rubin, Morton H.. Four-Wave Mixing and Biphoton Generation in a Two-Level System. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.053601.
Du Shengwang, Yin, G. Y., Wen Jianming, & Rubin, Morton H.. Four-Wave Mixing and Biphoton Generation in a Two-Level System. United States. doi:10.1103/PHYSREVLETT.98.053601.
Du Shengwang, Yin, G. Y., Wen Jianming, and Rubin, Morton H.. Fri . "Four-Wave Mixing and Biphoton Generation in a Two-Level System". United States. doi:10.1103/PHYSREVLETT.98.053601.
@article{osti_20955424,
title = {Four-Wave Mixing and Biphoton Generation in a Two-Level System},
author = {Du Shengwang and Yin, G. Y. and Wen Jianming and Rubin, Morton H.},
abstractNote = {We find that in a two-level system there are two kinds of four-wave mixing processes which destructively contribute to the third-order nonlinear susceptibility. In a paired-photon generation scheme by using a single retroreflected pump beam, these two processes occur with definite time orders. The biphoton temporal correlation, which is measured with a back-to-back geometry in a laser-cooled two-level atomic ensemble, shows a damped Rabi oscillation and photon antibunching. Without suppressing the background of Rayleigh scattering, the upper limit of Cauchy criteria is estimated.},
doi = {10.1103/PHYSREVLETT.98.053601},
journal = {Physical Review Letters},
number = 5,
volume = 98,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}
  • We study phase-conjugate degenerate four-wave mixing in an optically pumped, two-level atomic system (the 3s{sup 2}S{sub 1/2}, F=2, m{sub F}=2{yields}3p{sup 2}P{sub 3/2}, F=3, m{sub F}=3 transition in a diffuse, collision-free, thermal beam of sodium). In this investigation, we study the detailed line shape and strength of the four-wave mixing signal as a function of the intensity of the cw pump waves, and of the velocity of the atoms. Our technique allows us to examine the four-wave mixing interaction under conditions in which the Doppler shift, the natural linewidth of the transition, and the Rabi frequency for the interaction are eachmore » comparable with one another. From our experimental measurements and computational results, we show that the line shapes are very complex in this regime, and that they depend sensitively upon the atomic velocity, especially in the case when the intensity of the forward and backward pump beams exceeds the saturation intensity for the transition.« less
  • We study phase-conjugate degenerate four-wave mixing (DFWM) in an optically pumped, two-level atomic system (the 3s {sup 2}S{sub 1/2}, F=2, m{sub F}=2{yields}3p {sup 2}P{sub 3/2}, F=3, m{sub F}=3 transition in a diffuse, collision-free, thermal beam of sodium) using phase-modulated laser beams. In this investigation, we study the detailed line shape of the four-wave mixing signal as a function of the temporal delay between the probe field and the pump fields at different intensities of the cw pump waves and modulation frequencies. We show that phase modulation of the pump and probe beams leads to strong amplitude modulation of the phase-conjugatemore » beam and report excellent agreement between our experimental observations of the DFWM spectra and the results of numerical calculations. Our numerical results suggest an enhancement of the 'local' DFWM signal when the sidebands of the phase-modulated laser are resonant with dressed-state transitions, but that this resonance is less obvious in the total signal generated. We also show that the complex line shapes depend sensitively upon the delay of the probe beam, with the peak DFWM signal occurring when the probe beam is advanced compared to the pump beam.« less
  • Quasi-degenerate four-wave mixing (FWM) of low-intensity radiation (with an intensity less than 1 mW cm{sup -2}) was observed for the 5S{sub 1/2}(F=2)-5P{sub 3/2} (F'=3) transition in an optically transparent {sup 87}Rb vapour under conditions of electromagnetically induced absorption. The efficiency of frequency conversion was no less than 1% with respect to the intensity of pump waves. Nonlinear FWM is highly selective relative to the frequency detuning of pump waves (the FWM full width at half maximum was less than 50 kHz). (letters to the editor)
  • We have theoretically studied the space-time entangled biphoton state generated from a two-level atomic system. In the photon counting measurement, the two-photon coincidence counting rate is a damped oscillation. The oscillation period is determined by the effective Rabi frequency and the damping rate is determined by the linewidth of the inhomogeneous-broadened ground state and the dipole dephasing rate. In an optical-pathway-balanced configuration, the two-photon temporal correlation shows an antibunching effect which corresponds to the interference between two types of nonlinear four-wave mixing processes occurring in such a two-level system. The visibility of the normalized second-order quantum coherence function g{sup (2)}({tau})more » increases along with the increase of the effective Rabi frequency, but has an upper limit at 45%. We find agreement between the theory and the experiments [P. Kolchin et al., Phys. Rev. Lett. 97, 113602 (2006); S. Du, J.-M. Wen, M. H. Rubin, and G. Y. Yin, ibid 98, 053601 (2007)].« less
  • The generation of tunable coherent VUV rediation from 120.8nm to 125.Onm by nonresonant four-wave sum-mixing, W{sub yw}=W{sub L}+W{sub uv} with W{sub L} and W{sub uv} as the fundamental and the second harmonic of the dye laser, in the low-energy-side of the first resonance level of nonlinear media has been demonstrated for the first time. The small dimension of gas jet provided by PZT valve eliminated the negative dispersion requirement of the four-wave sum-mixing process, thus we observed the tunable coherent VUV radiation with the comparable efficiency in the positive regeon. The intensity dependence of the VUV radiation on the densitymore » of medium shows a oscillation behavior, which indicates that constructive and destructive interference occurs as the nonlinear polarization and generated radiation go in and out off phase.« less