Self-focusing effect via Kerr nonlinearity is observed in periodically poled lithium niobate （PPLN） waveguide arrays formed by electro-optic effect. Voltage-control method is demonstrated to control the focusing and diffraction of light. Theoretical simulation results show good agreement with experimental results.
An optical alignment-free and highly accurate method is employed to measure the magnetic field-dependent refractive index of magnetic fluid （MF） in bulk. The measured refractive index decreases significantly with the increasing magnetic strength and then tends to saturate in the high intensity range. By applying a tunable magnetic field ranging between 0 and 1661 Oe, the maximum shift of the refractive index of MF in bulk is found to be 0.0231.
We propose that domain inversion can be directly induced by femtosecond laser both theoretically and experimentally, which opens a path to achieve three-dimensional （3D） nonlinear crystal with a period in sub-micron-scale. A simulation of domain inversion is modeled by considering the temporal distribution of femtosecond pulses. The calculation results clarify that the domain inversions can happen within or after the interaction with the laser pulse, and the response time of domain inversion is in the picosecond level depending on the intensity and the materials. The domain reversal windows of lithium niobate by femtosecond laser are observed which agrees with theoretical predictions qualitatively.
The response time and transmittivity of the magnetic fluid （MF） for different concentrations at room temperature were investigated in this letter. The volume fraction of the investigated sample ranged from 0.44% to 6.47%. It was found that the transmittivity decreased with increasing concentration under a given magnetic field, and the evolution time was changed with different concentrations. Moreover the light intensity decreased rapidly at the beginning and then became stable when the magnetic field was applied.
