DFT study on the clamped linear electro-optic effect in KH2PO4

摘要

The clamped linear electro-optic (E-O) effect in KH2PO4 (KDP) is studied employing the electronic density-functional theory. It is found that proton atoms in the hydrogen bonds that connect the PO4 units are much more flexible than the other atoms in KDP when an external electric field is applied. However, our results show that the main contribution to the clamped linear E-O effect in KDP crystals is from the relative displacements of the anions and cations in the phosphate group induced by a low frequency applied electric field, instead of the contribution of vibration of proton atoms. The ration Δni/Δlk indicating the relationship between the atoms displacement and the refractive index are found to be well consistent with experimental results.