Spectral dependence of light-induced change in dye solution refractive index

HE GUANG-SHENG, ZHOU FU-XIN, LIU SONG-HAU +1 more

Using intense pulsed laser beam of 5320 ? to excite the BDN dye solution inside the F-P interferometer, we have found the transient and intrinsic optical bistability effect. The various possible mechanisms to induce the refractive-index change of the sample medium and their relative contributions have been estimated; finally it is confirmed that in the duration of input laser pulse the refractive-index variation increases with time approximately in the form of semi-cubic parabola, and the main mechanism to cause this variation is the opto-thermal effect of the sample medium.

L. G. S. Brooker

Vladimir Pavlovoch Torchigin

Sylvain Mailhot, Pierre Galarneau, Roger A. Lessard +1 more

Degenerate four-wave mixing (DFWM) is a simple method to achieve phase conjugation. It uses the third-order nonlinearity of the electric susceptibility to produce changes in the optical properties of materials. A dynamic grating is then induced. Such gratings might be used as fast optical memories in optical computing. Our aim is to find media with large nonlinear susceptibilities and fast response time. We report phase conjugation of 532-nm laser radiation by DFWM in dye solutions. The time dependence of the conjugated wave is investigated experimentally and compared to theoretical predictions. We have also studied the influence of the solvents, dye concentration, and pump intensity on the phase conjugated signal. The results are compared with those predicted by three nonlinear mechanisms. Thermally induced refractive-index changes, Kerr effect, and saturable absorption are considered.

Ragini Saxena, Pochi Yeh

Light-induced change in the index of refraction of a Kerr medium is well known.1 Illumination with a spatially periodic light intensity leads to the formation of an index grating in the Kerr medium. We make a comparative study of the response time and power requirement for index grating formation in photorefractive and Kerr media. We examine the conditions in which the index grating in the Kerr medium will be spatially shifted from the light intensity that induces it. Two-beam coupling via Bragg diffraction from the nonlocal index grating is studied.2 The coupling constant is found to depend on the relaxation mechanism of the atoms in the Kerr media and the frequency detunings of the two beams from the line center.

L. V. L�vshin, Irina A. Struganova, Bulat N. Toleutaev