Variation in linear susceptibility tensor at crystal surface probed by linear Cherenkov radiation

Abstract

At the surfaces of crystals, linear susceptibility tensors would differ from their counterparts in the interior of the bulk crystal. However, this phenomenon has not been shown in a visible way yet. In previous researches, numerous types of nonlinear Cherenkov radiation based on different materials have been studied, while linear Cherenkov radiation is barely reported. We experimentally prove the generation of linear Cherenkov radiation on the potassium dihydrogen phosphate (KDP) crystal surface and theoretically analyze its phase-matching scheme. In our study, o-polarized light and e-polarized light can mutually convert through the linear Cherenkov process. According to this result, we figure out new nonzero elements at off-diagonal positions in the linear susceptibility tensor matrix at crystal surfaces, compared with the normal form of a bulk KDP.