Two-wave Mixing Process Research Articles

PHOTOREFRACTIVE MEDIA FOR OPTICAL INTERCONNECTIONS

The photorefractive effect and its applications in optical interconnections are described. The fundamental limit, the dynamics of grating formation, and the two-wave mixing (TWM) process are discussed. Reconfigurable interconnections for parallel optical computing is demonstrated using photorefractive holograms. Neural network interconnections with photorefractive media are also presented.

Nearly degenerate two-wave mixing in saturable absorbers

We present a theory to describe nondegenerate two-wave mixing in saturable absorbers. The theory takes into account the saturation of the travelling grating produced by the intersection of two light beams and the two-wave mixing process is regarded as the zero-order self-diffraction of the incident waves in this grating. The results are in agreement with experimental data obtained for ruby.

Theory of amplitude and phase effects in 2-D-two-wave mixing

The two-wave mixing process in a photorefractive medium is investigated including nonuniform amplitude distributions of the pump and signal waves, plane-aberrated phase fronts, absorption, and arbitrary grating phase shift phi . The resulting system of two-dimensional coupled-wave equations is solved numerically with the aid of a two-dimensional Runge-Kutta method. Numerical data are shown to explain the gain distributions and image distortion properties in photorefractive amplifiers of the crossed beam, transmission and reflection grating type. A simple relation is presented describing the amplitude-phase crosstalk in two-wave mixing. One example is illustrated showing the possibility for compensating for aberrations using special pump and/or signal beam profiles with a grating phase shift different from 90 degrees . >

Mutually pumped phase conjugation in Kerr media and the effects of external seeding

Mutually pumped phase conjugation, a process by which two incident laser beams can mutually pump each other to generate the phase-conjugate replica of the other beam, is studied in a transparent Kerr medium with an electrostrictive nonlinearity. The nonlinear medium acts as a phase-conjugating mirror to both of the incident beams and generates their Stokes-shifted phase-conjugated outputs by the nearly degenerate four-wave mixing process. Our results show that this process will occur only if the coupling strength, defined by the product of the Kerr amplitude gain coefficient, the total input intensity, and the interaction length, is above the threshold value of 2. If the intensity of one of the input beams exceeds the threshold value and the second input beam is weaker than the first, then the weak beam is phase conjugated with a large reflectivity that has a maximum value of the intensity ratio of the strong to the weak input beam. For negligible absorption in the medium, a complete transfer of energy of both the incident beams into the phase-conjugate beams can occur for finite interaction lengths that are only slightly larger than the threshold value. Seeding the oscillation beams tends to lower the phase-conjugate power reflectivities, probably because of increased contribution from the competing two-wave mixing process.

Laser-beam cleanup using photorefractive two-wave mixing and optical phase conjugation

Using photorefractive two-wave mixing in a strontium barium niobate (Sr(x)Ba(1-x)Nb(2)O(6)) crystal in conjunction with a self-pumped barium titanate (BaTiO(3)) phase conjugator, we have demonstrated the cleanup of a phase-distorted laser beam. A clean seed beam is amplified by the phase-aberrated pump beam through the photorefractive two-wave mixing process. The optical phase conjugation is used to eliminate the phase aberration introduced by the photorefractive gain medium.