KTN単結晶を用いた光デバイスとその応用

抄録

A solid solution of KTaO₃ and KNbO₃ is well known as KTa_1-xNb_xO₃ (KTN). KTN single crystals have attractive optical properties including the photo-refractive and electro-optic effects. We have been studying and developing optical devices using KTN, which exhibits a large relative permittivity around the cubic-tetragonal phase-transition. A large Kerr effect, where the refractive index changes in proportion to the square of an applied electric field, is also available based on this large permittivity. A waveguide optical modulator, a spectrometer, a beam deflector and a varifocal lens using the Kerr effect of KTN single crystals were investigated by using a fast kHz or MHz response without any mechanical systems. In this paper, first we introduce the operating principle of the beam deflector and its applications, and then we describe the operating principle of a varifocal lens and its performance.