Low-voltage optical phase modulation by electric-field-induced phase transition of KTN bulk crystal

We report a low-voltage optical phase modulation that employs the electric-field-induced paraelectric-ferroelectric phase transition of KTN crystal. A large refractive-index change occurs within a narrow applied-voltage range as a result of structural changes in the crystal. We reduced the half-wave voltage to 2.1 V
_p-p
, which is very small for a 1-mm-thick bulk crystal.