Phase Conjugation Properties Research Articles

Effects of atomic motion on the polarization properties of phase conjugation by two-photon-resonant degenerate four-wave mixing.

We have studied the polarization properties of phase conjugation by degenerate four-wave mixing utilizing the 3S\ensuremath{\rightarrow}4S two-photon-allowed transition of sodium. We have observed high-fidelity vector phase conjugation (simultaneous conjugation of the optical wave front and the state of polarization) at a reflectivity of \ensuremath{\sim}1% for the case where the states of polarization of the two counterpropagating pump waves were circular and counterrotating. High-fidelity polarization conjugation with high reflectivity was obtained only when the forward pump wave was much stronger than the backward pump wave. To explain these results, it is necessary to include the effects of grating washout due to atomic motion in the theoretical analysis.

Polarization properties of optical phase conjugation by two-photon resonant degenerate four-wave mixing.

We develop a semiclassical theory of the polarization properties of phase conjugation by two-photon resonant degenerate four-wave mixing. The theory includes the effects of saturation by the pump waves. We solve the density-matrix equations of motion in steady state for a nonlinear medium consisting of stationary atoms with a ground and excited state connected by two-photon transitions. As an illustration of the general results, we consider an ${S}_{0}$\ensuremath{\rightarrow}${S}_{0}$ two-photon transition, which is known to lead to perfect polarization conjugation in the limit of third-order theory. We show that the fidelity of the polarization-conjugation process is degraded for excessively large pump intensities. The degradation can occur both due to transfer of population to the excited state and due to nonresonant Stark shifts. Theoretical results are compared to those of a recent experiment [Malcuit, Gauthier, and Boyd, Opt. Lett. 13, 663 (1988)].

Polarization properties of phase conjugation by degenerate four-wave mixing in a medium of rigidly held dye molecules

The saturation properties of dye molecules that are rigidly held in a solid host are qualitatively different from those of molecules that are free to rotate. We have found that these unique saturation characteristics can be exploited to achieve nearly perfect vector phase conjugation for field strengths near the saturation intensity. We have studied these properties experimentally by using fluorescein-doped boric acid glass as the nonlinear-optical material.

Vector phase conjugation by two-photon-resonant degenerate four-wave mixing

We have studied the polarization properties of phase conjugation by degenerate four-wave mixing resonantly enhanced by the sodium 3S1/2 → 6S1/2 two-photon-allowed transition. As predicted by third-order theories, this interaction leads to simultaneous conjugation of the optical wave front and state of polarization (vector phase conjugation) when the pump intensities are sufficiently weak. However, qualitatively different polarization behavior is observed for pump intensities near or above the two-photon saturation intensity.

Polarization properties of four-wave optical phase conjugation under continuous conditions

Experimental and theoretical investigations were made of the polarization characteristics of a four-wave phase-conjugate mirror utilizing the 3S1/2–3P3/2 transition in sodium atoms and different combinations of linearly and circularly polarized external waves. A good agreement was established between the experimental results and a theory developed allowing for the optical transfer of atoms between magnetic sublevels and for a residual Doppler broadening due to the noncollinearity of the wave vectors of the interacting waves.

Doppler-Free Spectroscopy Based on Phase Conjugation by Degenerate Four-Wave Mixing in Hollow Cathode Discharge

Optical phase conjugation in the hollow cathode lamp by degnerate four-wave mixing is a novel analytical laser spectroscopic method in which a laser beam is generated as the signal beam. With the use of a demountable hollow cathode discharge cell and a continuous-wave dye laser, the signal beam is clearly visible to the naked eye when 1 µg of sodium is placed inside the cathode cavity. Since the signal beam is a time-reversed replica of the probe laser beam, highly efficient optical signal detection can be performed with minimum optical background noise. Since the signal is Doppler-free with negligible Lorentzian broadening (30 Torr discharge pressure), it provides excellent spectral resolution. Sodium D2 hyperfine lines of 3s 2S1/2 ( F' = 2) → 3p 2P3/2 ( F = 3) and 3s 2S1/2 ( F' = 1) → 3p 2P3/2 ( F = 0) were resolved. In addition to excellent spectral resolution and ease of signal detection, the technique also offers unique properties of optical phase conjugation.

Large-| t| elastic pp, p̄p elastic scattering and the triple-scattering mechanism

Although the differential cross section for large-| t| pp and p̄p elastic scattering at high energies behaves roughly like t −8 independent of s, there are difficulties in ascribing this to the triple scattering mechanism, which has the wrong phase and charge conjugation properties, and does not reproduce the slow shrinkage apparent in the data. Instead we find that a model including the pomeron (P) and a P ⊗ P cut, presented some years ago, gives a simple and natural description of all features of the data.

Self-imaging and unitarity

The unitary, group, and phase-conjugation properties of the diffraction operator, in the absence of evanescent waves, are used to prove a new translation invariance for amplitude self-imaging, to obtain solutions for intensity self-imaging, and to give a simple description of imaging by a phase-conjugate mirror.

High-power single-mode laser operation using stimulated Rayleigh scattering

We report single-mode high-power Nd:YAG laser operation by stimulated thermal Rayleigh Q switching. We also analyze the phase-conjugation properties of collinear four-wave mixing that is due to low-frequency excitations in absorbing liquids.