The nonlinear optical limiting and relative nonlinear refractive index in far-field of acid
blue29 dye are investigated using radiation of 35mW CW He-Ne laser. It is found that both
nonlinear refraction and nonlinear absorption change with decreasing of solvents polarity and
varying the input powers.
The optical limiting action of C<sub>60</sub>Ph<sub>5</sub>Cl and C<sub>60</sub>Cl<sub>6</sub> in solid host has been investigated at 532 nm with nanosecond pulses. The limiting thresholds for C<sub>60</sub>Ph<sub>5</sub>Cl and C<sub>60</sub>Cl<sub>6</sub>, were 8 J/cm<sup>2</sup> and 7 J/cm<sup>2</sup>, and the linear transmittances were 22 % and 50 %, respectively. These results were compared with previous work, which was carried out on C<sub>60</sub>Ph<sub>5</sub>Cl and C<sub>60</sub>Cl<sub>6</sub> molecules in toluene solutions. It was found a fair agreement between the two cases (solution and solid). This behavior can be understood on the basis of the reverse saturable absorption mechanism which determines the optical limiting properties of the C<sub>60</sub>Ph<sub>5</sub>Cl and C<sub>60</sub>Cl<sub>6</sub> molecules. Such lower limiting thresholds make these compounds good candidates for optical limiting materials.
We present preliminary results on the SHG properties of a number of organic materials in powder form using a Q-switched Nd-YAG laser (7 ns, λ=1064 nm) as the fundamental input. The organic powder was packed into sealed cells, which is set at an angle of 45<sup>0</sup> to the input beam. The intensity of reflected S.H. light (λ= 532 nm) was measured at an angle of 90° to the input beam. The urea was subjected to the same treatment, and used as a reference. Beside that we have calculated second-order hyperpolarizibilities (β) of the studied materials using PC-GAMESS package.