700 kHz beam scanning using electro-optic KTN planar optical deflector

For high-speed optical beam scanning, we developed a novel planar optical deflector using KTa1-xNbxO3 (KTN) crystals. When a KTN deflector is operated at high frequencies, heat generated by KTN causes a decrease in its relative dielectric constant, which limits the deflection angle at frequencies above 200 kHz. To overcome this problem, we decreased the thickness of KTN to reduce its capacitance because the heat it generates is proportional to its capacitance. We arranged the two electrodes on the same surface, whereas previously reported structures have each electrode on opposite surfaces. We successfully reduced KTN’s capacitance to 1/30 of that previously reported. The deflection angle of this novel structure at 700 kHz is 16.89 mrad, which is more than half of that at 100 kHz, while the deflection angle of previously reported thick KTN rapidly decreases at more than 200 kHz. The experimental results indicate that our proposed planar optical deflector is effective for suppressing heat generation in KTN and improving the scanning speed of deflectors.