The modulation to Cerenkov second-harmonic in a LiTaO₃ waveguide with annular poling domain

We report the modulated Cerenkov up-conversion in a LiTaO₃ waveguide with an annular domain structure. As a result of the continuous rotational symmetry of such a structure, the phase velocity of the nonlinear polarization wave has a wide modulation tolerance. The reciprocal vectors which could be involved in the interaction had a threshold range associated with the waveguide parameters. The experimental results and simulations demonstrated that the radiation intensity had a close relationship with the overlap between the pump and the radiated wave, which could be decreased by non-collinear reciprocal vectors. Our detailed discussions on the Cerenkov frequency-doubling process using such an annular-poling crystal may lay the groundwork for the further study of the modulation of other nonlinear Cerenkov processes. (paper)