Third-order nonlinearity enhancement in an artificial Kerr medium through bulk intrinsic birefringence

Local field effects on reorientation in suspensions of anisotropic particles

The field-induced reorientation of microellipsoids in suspension depends on particle parameters, e.g., intrinsic dielectric anisotropy, shape, and size, as well as on the concentration of the particles. We study this process and the resulting orientational order parameter of the suspension in fields of arbitrary strength. The mean-field approach presented here provides an explicit link between the particle properties and their orientation distribution, taking into account the electrostatic interaction among the particles at moderate concentrations. It reproduces published experimental observations in the steady state and should be useful for studying reorientation phenomena as well as electro-optical properties in these systems.

Dielectric response and electro-optical effects in suspensions of anisotropic particles

The dielectric properties of suspensions of microellipsoids may be controlled by reorientation of the particles in an applied electric field. We study this process and the resulting electro-optical effects for fields of arbitrary strength. The magnitude of these effects is determined by the concentration of the particles, their intrinsic dielectric anisotropy and their shape. The approach presented here provides an explicit link between the particle properties, their orientation distribution and the field-induced birefringence and electro-optical phase shift of the suspensions, taking into account the electrostatic interaction among the particles at moderate concentrations. It reproduces well published experimental observations and should therefore be useful for studying electro-optical properties as well as reorientation phenomena in these systems.

Electro-optic modulation in an anisotropic artificial Kerr medium

We describe the performance of intensity and phase modulators that use an aqueous suspension of polytetrafluoroethylene (PTFE) microparticles. In this medium, the electro-optic effect is caused by the reorientation of anisotropic microparticles in an applied electric field. The intensity modulator was constructed in the Kerr geometry by the use of a sample path length of 20 µm. The response time of the modulator is less than 25 ms, and the depth of modulation was measured to be 28 dB for a switching voltage of 134 V(rms). The switching voltage necessary to achieve a π-phase shift with the phase modulator is less than 30 (Vrms).

Polarization-resolved optical phase conjugation in an artificial anisotropic Kerr medium

Optical phase conjugation by degenerate four-wave mixing has been achieved in a liquid suspension of polymer microellipsoids as a result of light-induced rotational effects. Different polarization configurations of the pump and probe beams have been used, and the resulting conjugate polarization states have been discriminated. The results are discussed in terms of different kinds of particle orientational gratings.