Transient four-wave mixing and real time holography in atomic systems

The problem of transient four-wave mixing with noncoincident optical pulses is analyzed using the formalism of the time evolution and the density matrix operators. The results are relevant to problems involving real time holography and wave conjugation. The treatment establishes a bridge between the conventional formalisms of nonlinear optics and of photon echoes

Spontaneous and stimulated Raman scattering in long low loss fibers

This paper considers the problem of forward Raman scattering process in a single transverse mode fiber. Both pump wave depletion and spontaneous scattering are considered in the analysis. Analytic solutions of the governing differential equations are obtained. We examine the conditions under which a nondepleted pump approximation is valid. Expressions are derived for the maximum fiber loss and the minimum fiber length which allow significant pump to Stokes wave conversion. It is shown that for a given fiber length there is an optimal pumping power, or at a given pump power there is an optimal fiber length that yields maximum first-order Stokes power output. Good agreement with published experimental results in the threshold power prediction is obtained

Theory of cw Raman oscillation in optical fibers

A theory for Raman fiber laser oscillators is presented. The Stokes output and the residual pump power are shown to be calculable from a knowledge of the input pump power and the fiber characteristics. The evolution of the pump and the Stokes waves along the fiber are also obtained. The threshold pump power and the oscillation condition are considered. Pump depletion is incorporated in the analysis and is shown to be the dominant saturation effect present in a Raman fiber laser

Tunable graded rod laser assembly

A tunable laser assembly including a pair of radially graded indexed optical segments aligned to focus the laser to form an external resonant cavity with an optical axis, the respective optical segments are retativity moveable along the optical axis and provide a variable et aion gap sufficient to permit variable tuning of the laser wavelength without altering the effective length of the resonant cavity. The gap also include a saturable absorbing material providing a passive mode-locking of the laser

Image phase compensation and real-time holography by four-wave mixing in optical fibers

It is proposed that real-time holography can be performed inside multimode fibers (or optical waveguides) using four-wave optical mixing. Of particular interest is the generation of complex-conjugate replicas of input fields for image transmission and compensation of propagation distortion. A theoretical analysis and a numerical estimate are presented

Spatial convolution and correlation of optical fields via degenerate four-wave mixing

A nonlinear optical technique is described that performs, essentially instantaneously, the functions of spatial correlation and convolution of spatially encoded waves. These real-time operations are accomplished by mixing spatially dependent optical fields in the Fourier-transform plane of a lens system. The use of a degenerate four-wave mixing scheme eliminates (in the Fresnel approximation) phase-matching restrictions and (optical) frequency-scaling factors. Spatial bandwidth-gain considerations and numerical examples, as well as applications to nonlinear microscopy, are presented

A theoretical and experimental investigation of the modes of optical resonators with phase-conjugate mirrors

We present an analysis of resonator properties for a cavity bounded by a phase conjugate mirror, which is generated by a degenerate four-wave nonlinear optical interaction. Using a ray matrix formalism to describe the conjugate mirror, resonator stability conditions are derived. Longitudinal and transverse mode characteristics are discussed. Results are compared with an experiment where laser oscillation was observed at 6943 Å using carbon disulfide as the nonlinear interacting medium comprising the phase conjugate mirror

Continuous backward-wave generation by degenerate four-wave mixing in optical fibers

We report on the observation of cw backward-wave generation using degenerate four-wave mixing in a nonresonant medium. The interaction took place inside a 3-m-long CS2-filled 4-µm i.d. optical fiber. With a pump power of only 6 mW inside the fiber, a backward-wave conversion efficiency of 0.45% has been observed, which is in reasonable agreement with theoretical predictions