Coupled cw dye lasers using intracavity four-wave mixing.

An experimental investigation of laser-oscillator frequency locking by a four-wave interaction was conducted. An experiment was performed that successfully demonstrated the locking of two cw dye lasers using this concept with Na vapor serving as the nonlinear (coupling) medium.

On the equality of stimulated Brillouin scattering reflectivity to conjugate reflectivity of a weak probe beam.

If a strong pump wave, with energy that is above threshold for stimulated Brillouin scattering, and a weak probe wave are incident into a nonlinear medium, then it has been shown by others that the reflectivity of the weak probe is equal to the reflectivity of the strong pump and that the probe is phase conjugated provided that the pump is phase conjugated. We present an analysis that predicts an exact equality of the reflectivities and identifies the parametric limitations.

Correction of phase aberrations via stimulated Brillouin scattering.

We have obtained quantitative measurements on the correction of severely aberrated laser beams using stimulated Brillouin scattering (SBS) at 0.69 microm. We have shown that under certain conditions SBS can be used to restore an aberrated optical beam to its original unaberrated condition. When an optical beam double passes an aberrating region after reflecting from an "ordinary" mirror (i.e., a plane mirror) the aberration is twice that obtained from a single pass. However, when the aberrated beam enters a medium that allows SBS to occur, it emerges from its second pass through the aberrating medium in the same condition as that in which it originally entered. Quantitative experiments are described in which a single-mode ruby laser beam is intentionally aberrated by passing it through an etched plate. When the beam is allowed to double-pass the plate using an ordinary reflector (i.e., plane mirror), the beam divergence is more than 10 times the diffraction-limited divergence. However, when we replace the ordinary reflector with a cell in which SBS can take place, the SBS reflected beam is restored to diffraction-limited divergence when it is allowed to pass back through the aberrating medium. Applications of this time-reversal or phase-reversal technique for correcting aberrations in optical trains and atmospheric turbulence are discussed.