Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Collisionally triggered generation of a coherent signal

M. Dagenais

Published Sep 1, 1981• 18 citations
Publisher

Abstract

We demonstrate the generation of a coherent signal by an incoherent process. In a first step, population is transferred from the ground state to two excited states by a collisional redistribution process. Then, in a second step, a coherent Raman signal is generated from these two populated excited states. At high pressure, it is predicted that a Raman-type resonance between two equally populated levels should be observed. Information about inelastic-collision cross sections and dephasing coefficients in the excited states is obtained.

DOI
10.1103/physreva.24.1404

Related papers

Collisionally induced coherent signals and collisional redistribution

M. Dagenais

It is demonstrated that, in the presence of collisions and for nonresonant lasers, it is energetically possible to access resonantly excited states and induce a coherence between the states. This situation cannot arise in the absence of collisions if the starting state does not decay. This explains why, when collisions are introduced, a new signal can be generated in a wave-mixing type of experiment. The collisionally induced generation of a coherent signal is intimately related to the process of collisional redistribution. It is shown that all the collisionally induced coherent signals that have been reported up to now involve putting real populations in the excited states. This fact has not always been fully appreciated. No resonance between unpopulated states can exist. The time dependence of these new coherent signals is briefly discussed. In the case of a Raman resonance between equally populated states, it is pointed out that new coherent pathways of equal importance should be considered for explaining the experimental results. A new pressure-induced signal in four-wave mixing is also discussed. It is called "collisionally triggered two-photon quasiresonant coherent signal."

Physical Review A•Aug 1, 1982•23 citations

Collision-Induced Coherence Effect on Coherent Population Transfer

Xihua Yang, Zhang Jun, Zhang Hui-Fang +1 more

We investigate the effect of collision-induced coherence on coherent population transfer with the stimulated Raman adiabatic passage technique in a double A-type four-level system with a widely separated excited doublet. It is shown that when the two pulsed lasers with Rabi frequencies nearly comparable to the energy separation of the doublet are tuned to the particular frequency where the condition for quantum interference is satisfied, the very low transfer efficiency due to the nonadiabatic coupling between the two degenerate adiabatic states could be enhanced significantly with the increase of the collisional decay rates in a moderate range. The enhanced transfer efficiency results from the weakening of the nonadiabatic coupling between the two degenerate adiabatic states realized through collision-induced destructive quantum interference.

Chinese Physics Letters•Jul 1, 2009•4 citations

Temporal and spatial evolution of collision-induced stimulated effects in alkali atoms

Z. Konefał, Zygmunt Trumpakaj

A computational study of the optical propagation of Stokes light in a collisionally broadened three-level V-system Raman amplifier is presented. The Stokes light consists of two distinct spectral components: off-resonance stimulated Raman scattering and on-resonance stimulated fluorescence. These two signals are induced by collisional transfer of population from the excited state to the state. The intensity dependence of these effects on the buffer gas and intensity and detuning of the exciting radiations is calculated. In the calculations the probe signals and spontaneous scatterings were used to induce the stimulated signals. We have carried out the calculations over physically realistic propagation distances. The theory was compared with our experimental work and the results of the numerical analysis are used to explain some events observed in the experiments in which the physical mechanism has not yet been understood.

Journal of Physics B Atomic Molecular and Optical Physics•Jul 28, 1998•3 citations

Extra resonances in degenerate four-wave mixing triggered by pressure-induced decay of the lower state

A. D. Wilson‐Gordon, Harry Friedmann

By using the Schenzle-Brewer model, in which the ground state of a two-level system also has a finite lifetime, it is shown that two pressure-induced extraresonant degenerate four-wave mixing signals are obtained. The first extra resonance is similar to that predicted and observed by Bogdan et al. [Opt. Lett. 6, 82, 348 (1981)]. It is characterized by a linewidth equal to the inverse lifetime of the upper state and appears only in the presence of collisional redistribution. The second extra resonance is characterized by a linewidth equal to the inverse lifetime of the ground state and does not depend on collisional redistribution for its appearance.

Optics Letters•Dec 1, 1983•20 citations

Coherent Raman scattering in a low pressure gas

Jacques Moret‐Bailly

Incoherent emissions of light by a gas require collisions of molecules, while coherent emissions, at low pressure, are amplifications of pre-existing rays. At very low pressure, very accidental collisions of atoms of an excited gas initiate flare-ups, and Raman pumping of the gas by a temporally incoherent ray of light absorbs molecular quanta without other energy diffusion.

•Jan 26, 2020•0 citations

Theoretical study of atom collision by two-nondegenerate four-wave mixing

孙江 Sun Jiang, Xiaoyang Chang, Su-Heng Zhang +1 more

In recent years, the collisional redistribution of radiation and collision-induced broadening of Rydberg atomic spectral lines by buffer gas perturbation have aroused the renewed interest. Rydberg atoms having a large dipole moment and long lifetime can interact with each other coherently for relatively long time, which makes them a potential candidate for quantum information processing. Besides, collisional redistribution has an important potential application in laser cooling and trapping. Based on previous experimental data, in this paper, two-nondegenerate four-wave mixing (NFWM) for studying atom collision, composed of two-photon resonant NFWM and collisional redistribution NFWM, is reported. The spectrum variation of the two-NFWM affected by the pressure, temperature, detuning and collision-broadening rate coefficient is analyzed. The principle of two-NFWM involving three incident beams is explained as follows. Consider two-NFWM in a |0-|1-|2 cascade three-level system, where states between |0 and |1 and between |1 and |2 ightangle are coupled by resonant frequencies 1 and 2 , respectively. Beam 1 with frequency 1 propagates along the direction opposite to the direction of beam 2, beams 2 and 2' have the same frequency 2, and between their directions there exists a small angle. Assuming that 1 1 and 2 2 so that 1 drives the transition from |0 to |1 while 2 drives the transition from |1 to |2, the simultaneous interactions of atoms with beams 1 and 2 will induce atomic coherence between |0 and |2 through two-photon excitation. This coherence is probed by beam 2', and as a result a two-photon resonant NFWM signal of frequency 1 is generated in the direction almost opposite to the direction of beam 2'. To avoid strong absorption at the resonant frequency of transition from |0 to |1, here the wavelength of beam1 is detuned from the exact resonance. An atom population of level |1 caused by collisional redistribution can be induced when a certain buffer gas pressure is imposed. The collisional redistribution NFWM process also exists in this case. Beam 2 drives the transition from |1 to |2 to induce an atomic coherence which is probed by beam 2' for giving rise to an atomic population grating. A collisional redistribution NFWM signal propagating along the same direction as the two-photon resonant NFWM signal is generated when beam 1 is scattered by the grating. Much information about atomic collisions can be obtained by analyzing the two NFWM signals. In a cascade three-level system composed of ground state, intermediate state and Rydberg state, and the two-NFWM can be used to investigate not only the broadening and shifting of the Rydberg level but also the collisional redistribution of the intermediate state. Unlike other experiments studying the pressure dependence of the longitudinal relaxation rate of atom states, this technique is a purely optical coherent means, and can measure the transverse relaxation rate 20 between Rydberg state and ground state as well as the pressure dependence of the transverse relaxation rate 21 between Rydberg state and intermediate state.

Acta Physica Sinica•Jan 1, 2016•0 citations
We demonstrate the generation of a coherent signal by an incoherent process. In a first step, population is transferred from the ground state to two excited states by a collisional redistribution process. Then, in a second step, a coherent Raman signal is generated from these two populated excited states. At high pressure, it is predicted that a Raman-type resonance between two equally populated levels should be observed. Information about inelastic-collision cross sections and dephasing coefficients in the excited states is obtained.
It is demonstrated that, in the presence of collisions and for nonresonant lasers, it is energetically possible to access resonantly excited states and induce a coherence between the states. This situation cannot arise in the absence of collisions if the starting state does not decay. This explains why, when collisions are introduced, a new signal can be generated in a wave-mixing type of experiment. The collisionally induced generation of a coherent signal is intimately related to the process of collisional redistribution. It is shown that all the collisionally induced coherent signals that have been reported up to now involve putting real populations in the excited states. This fact has not always been fully appreciated. No resonance between unpopulated states can exist. The time dependence of these new coherent signals is briefly discussed. In the case of a Raman resonance between equally populated states, it is pointed out that new coherent pathways of equal importance should be considered for explaining the experimental results. A new pressure-induced signal in four-wave mixing is also discussed. It is called "collisionally triggered two-photon quasiresonant coherent signal."
We investigate the effect of collision-induced coherence on coherent population transfer with the stimulated Raman adiabatic passage technique in a double A-type four-level system with a widely separated excited doublet. It is shown that when the two pulsed lasers with Rabi frequencies nearly comparable to the energy separation of the doublet are tuned to the particular frequency where the condition for quantum interference is satisfied, the very low transfer efficiency due to the nonadiabatic coupling between the two degenerate adiabatic states could be enhanced significantly with the increase of the collisional decay rates in a moderate range. The enhanced transfer efficiency results from the weakening of the nonadiabatic coupling between the two degenerate adiabatic states realized through collision-induced destructive quantum interference.
A computational study of the optical propagation of Stokes light in a collisionally broadened three-level V-system Raman amplifier is presented. The Stokes light consists of two distinct spectral components: off-resonance stimulated Raman scattering and on-resonance stimulated fluorescence. These two signals are induced by collisional transfer of population from the excited state to the state. The intensity dependence of these effects on the buffer gas and intensity and detuning of the exciting radiations is calculated. In the calculations the probe signals and spontaneous scatterings were used to induce the stimulated signals. We have carried out the calculations over physically realistic propagation distances. The theory was compared with our experimental work and the results of the numerical analysis are used to explain some events observed in the experiments in which the physical mechanism has not yet been understood.
By using the Schenzle-Brewer model, in which the ground state of a two-level system also has a finite lifetime, it is shown that two pressure-induced extraresonant degenerate four-wave mixing signals are obtained. The first extra resonance is similar to that predicted and observed by Bogdan et al. [Opt. Lett. 6, 82, 348 (1981)]. It is characterized by a linewidth equal to the inverse lifetime of the upper state and appears only in the presence of collisional redistribution. The second extra resonance is characterized by a linewidth equal to the inverse lifetime of the ground state and does not depend on collisional redistribution for its appearance.
In recent years, the collisional redistribution of radiation and collision-induced broadening of Rydberg atomic spectral lines by buffer gas perturbation have aroused the renewed interest. Rydberg atoms having a large dipole moment and long lifetime can interact with each other coherently for relatively long time, which makes them a potential candidate for quantum information processing. Besides, collisional redistribution has an important potential application in laser cooling and trapping. Based on previous experimental data, in this paper, two-nondegenerate four-wave mixing (NFWM) for studying atom collision, composed of two-photon resonant NFWM and collisional redistribution NFWM, is reported. The spectrum variation of the two-NFWM affected by the pressure, temperature, detuning and collision-broadening rate coefficient is analyzed. The principle of two-NFWM involving three incident beams is explained as follows. Consider two-NFWM in a |0-|1-|2 cascade three-level system, where states between |0 and |1 and between |1 and |2 ightangle are coupled by resonant frequencies 1 and 2 , respectively. Beam 1 with frequency 1 propagates along the direction opposite to the direction of beam 2, beams 2 and 2' have the same frequency 2, and between their directions there exists a small angle. Assuming that 1 1 and 2 2 so that 1 drives the transition from |0 to |1 while 2 drives the transition from |1 to |2, the simultaneous interactions of atoms with beams 1 and 2 will induce atomic coherence between |0 and |2 through two-photon excitation. This coherence is probed by beam 2', and as a result a two-photon resonant NFWM signal of frequency 1 is generated in the direction almost opposite to the direction of beam 2'. To avoid strong absorption at the resonant frequency of transition from |0 to |1, here the wavelength of beam1 is detuned from the exact resonance. An atom population of level |1 caused by collisional redistribution can be induced when a certain buffer gas pressure is imposed. The collisional redistribution NFWM process also exists in this case. Beam 2 drives the transition from |1 to |2 to induce an atomic coherence which is probed by beam 2' for giving rise to an atomic population grating. A collisional redistribution NFWM signal propagating along the same direction as the two-photon resonant NFWM signal is generated when beam 1 is scattered by the grating. Much information about atomic collisions can be obtained by analyzing the two NFWM signals. In a cascade three-level system composed of ground state, intermediate state and Rydberg state, and the two-NFWM can be used to investigate not only the broadening and shifting of the Rydberg level but also the collisional redistribution of the intermediate state. Unlike other experiments studying the pressure dependence of the longitudinal relaxation rate of atom states, this technique is a purely optical coherent means, and can measure the transverse relaxation rate 20 between Rydberg state and ground state as well as the pressure dependence of the transverse relaxation rate 21 between Rydberg state and intermediate state.