Journal of the Optical Society of America B

Nondegenerate resonant multiwave mixing, and frequency-doubled phase conjugation

S. Le Boiteux, J. W. R. Tabosa, Pierre Simoneau, Daniel Bloch, M. Ducloy

Published Jan 1, 1987• 0 citations

Abstract

Nondegenerate four-wave mixing (FWM) has been used for wavelength conversion of optical information.1 In such experiments, two beams F-P (frequency ω1) intersect in a nonlinear medium with a small crossing angle θ (≈ 10 mrad), while a third beam B {frequency ω2) is nearly counterpro- pagating to F [Fig. 1(a)]. This can be viewed as real-time holography with frequency conversion.1 However, the physics differ considerably when the medium is transparent at frequency ω1, as there is no optically induced grating. This occurs when FWM is based on resonant two-photon, ω1 + ω2, absorption (frequencies ω1 and ω2 being resonant with a cascade three-level system and ω1 coupling unpopulated excited states). One interesting feature is that the two-photon coherence is nearly Doppler-free and does not depend much on the θ angle.

Related papers

Optical phase conjugation with frequency up-conversion via high-order, nondegenerate multiwave mixing

M. Ducloy

One proposes a new way of getting optical phase conjugation, associated to frequency conversion (namely, frequency doubling, frequency multiplication or mixing), within a broad angular field of view. This technique is based on nondegenerate, higher order multiwave mixing in a phase-matched backward configuration. Applications to wave front reversal, spatial or temporal information processing with frequency up-conversion are outlined.

Applied Physics LettersJun 1, 198527 citations

Theory of degenerate four-wave mixing in resonant Doppler-broadened media. - II. Doppler-free heterodyne spectroscopy via collinear four-wave mixing in two- and three-level systems

M. Ducloy, Daniel Bloch

In this article, we analyse a new sensitive spectroscopic technique in which a sample cell is irradiated by a two-frequency pump beam (ω + Δ ± δ/2) and a counter-propagating probe beam (ω). The phase-conjugate fields re-emitted at frequencies ω ± δ, via four-wave mixing processes, are detected through their heterodyne beating with the probe field. The properties of the heterodyne beat signal are studied by means of a perturbation calculation of the nonlinear response of the medium, carried out to the third order in the incident fields. In resonant gas media, the emission lineshape exhibits a Doppler-free doublet structure [frequency splitting 3 δ/2 for single-photon resonances, and δ/2 for two-photon transitions]. By using a phase-sensitive detection of the beat signal, one can separately analyse real (dispersion) or imaginary parts (absorption) of the nonlinear susceptibility. For single-photon transitions, the signal phase shift is related to the atomic levels lifetime and allows one to study the relaxation dynamics in gas phase (like quenching collisions, velocity diffusion, etc...). This is particularly interesting for cross-over resonances, in which only the common level contributes. In three-level systems, one also predicts a selective resonant enhancement of the phase-conjugate emission through Raman-type two-photon processes. Most of these predictions have been experimentally verified.

Journal de physiqueJan 1, 198248 citations

Nondegenerate two-photon phase conjugation

Barbara A. Capron, Murray Sargent

Our semiclassical theory of two-photon multiwave mixing1 is a generalization of the degenerate four-wave mixing case2 to treat nondegenerate pump/signal/conjugate frequencies. We apply that theory to four-wave mixing in two-photon media. We present explicit formulas for the nondegenerate signal/conjugate absorption and coupling coefficients for cases for which the two-photon Stark shifts are sufficiently small compared to the homogeneous linewidths. More general cases require that the spatial hole burning averages be performed numerically. We find intricate dependencies of the transmission and reflection spectra on the pump intensity and on dynamic Stark shifts. In particular, the reflection coefficients do not necessarily bleach to zero as the pump intensity is increased indefinitely, and interferences occur between pure index and mixed absorption/index contributions

Annual Meeting Optical Society of AmericaJan 1, 19871 citation

Theory of degenerate four-wave mixing in resonant Doppler-broadened systems - I. Angular dependence of intensity and lineshape of phase-conjugate emission

M. Ducloy, Daniel Bloch

We present in this paper a theoretical study of the angular dependence of phase-conjugate emission via resonant degenerate four-wave mixing (FWM) in Doppler-broadened gas media. The nonlinear optical polarization is calculated through an expansion of the atomic density matrix up to the third order in the incident fields. One finds that, when the incident frequency is resonant for a single-photon transition, both strength and lineshape of the phase-conjugate emission strongly depend on the angle 0 between standing pump wave and probe wave. The emission intensity, maximum at grazing incidences, decreases rapidly by several orders of magnitude when 0 increases. Simultaneously the emission linewidth increases from homogeneous to Doppler width. Similar effects are predicted for nearly-degenerate FWM (different pump and probe frequencies). In particular, one shows that the bandwidth of the equivalent optical reflection filter undergoes a Doppler-broadening linearly increasing with sin θ. On the opposite, none of the above effects is predicted in two-photon-resonant FWM which does not exhibit any angular dependence.

Journal de physiqueJan 1, 198174 citations

New developments in phase conjugation in resonant vapors: Nondegenerate four-wave mixing and self-oscillating PC cavity

Pierre Simoneau, S. Le Boiteux, Daniel Bloch +2 more

One knows that in three-level saturation spectroscopy the signal is generally related both to a population change process, induced by the saturating beam, and to a coherent process—two-photon or Raman coherence—induced by the simultaneous interaction of the saturating and probe fields. If the saturating beam couples two unpopulated states (transparent transition), a signal is still observable which originates solely from the coherent process.

Jun 9, 19860 citations

Wave-mixing and Phase Conjugation in Laser Active Media

Kazuo Kuroda

Nonlinear optics normally involves the change in the susceptibility of a material due to the presence of optical radiation. In many cases, the light-matter interaction produces a change in the refractive index of the medium, as occurs in photorefractive media, as well as in Kerr-like media, Brillouin-active media and absorbing media with thermallyinduced refractive index changes. Such nonlinear refractive index variation corresponds to a change in the real part of the optical susceptibility %. In resonant materials, the optical radiation induces stimulated emission (or absorption) causing transfer of population between different energy states of the medium. This can lead to saturation of the amplification (or absorption) corresponding to changes in the imaginary part of the susceptibility x= i2odk where the amplitude gain coefficient a(I) is a saturable function of the intensity /, and k is the magnitude of the wavevector of the optical radiation. The interference of two (or more) coherent beams I(x) in the laser amplifier can cause a modulation of the population inversion N(x). This modulation of the inversion is commonly known as spatial hole burning in lasers and leads to formation of a gain-grating a(x) = 1/2GN(X) where G is the stimulated emission cross-section. The gain grating can act as a very efficient diffractive optical element exhibiting high diffraction efficiency that may be even greater than unity [16] and also very high phase conjugate reflectivity using four-wave mixing (FWM) geometries [5-7].

CRC Press eBooksMar 14, 20020 citations