Single domain wall effect on parametric processes via Cherenkov-type phase matching

We report on important influence of single domain wall (DW) of electrically poled ferroelectric crystal on parametric processes via Cherenkov-type phase matching. It shows that the effective nonlinear polarization is confined in DW and its phase velocity can be modulated when incident light is off domain wall's direction. These effects lead to novel Cherenkov second harmonic generation (CSHG) which has no analogue in bulk ferroelectrics. Complex DW-modulated parametric process via Cherenkov-type phase matching, such as Cherenkov sum frequency generation (CSFG), is also demonstrated in DW. We propose that nonlinear coefficient in DW is significantly enhanced.