As a longitudinal automaticphase-matching process, nonlinear Cherenkov radiation (NCR) has been thoroughlydiscussed inultrashort pulse-shaping, efficientfrequency conversion and nondestructive domain-wall detection and imaging. Generally, efficient NCR occurs in ferroelectric doman walls and the boundary of nonlinear crystal.

We analyzed the coupled wave equation at the nonlinear interface and demonstrate the enhancement of NCR can be attribute to the sharp charge of nonlinear coefficient . If the absolute value of the difference of  , the NCR intensity is enhanced. We fabricated a structure where BBO and LN are tightly abutted upon each otherto achieve a sharper modulation of  than the boundary of BBO crystal. This method demonstratedthat NCR in a bulk medium can be enhanced by the presence of another medium. As the radiation angle is determined by the dispersion relationship of the medium, the added crystal does not change the NCR properties.

See also:Optics Express, 24(12), 12825-12830(2016).