Wavelength Swept Light Source Based on KTa_1-xNb_xO₃ High-Speed Optical Beam Electro-optic Deflector Crystal and its Application to the Optical Coherence Tomography

Abstract

This article describes the development of an electro-optic (EO) optical beam deflector using KTa_1-xNb_xO₃ (KTN) crystal. The combination of the substantial second-order EO (Kerr) effect of the KTN crystal and control of the electron injection into the crystal makes the deflection angle appreciable. The operation principle of this fast and significant deflection is described. Wavelength-swept light sources for optical coherence tomography (OCT) have been built equipped with a KTN deflector. An external cavity laser diode (ECLD) configuration that incorporates such a KTN deflector was used. In this ECLD, the output wavelength was swept by the deflection angle of the KTN deflector. A 200-kHz scan rate was obtained with a 20 mW average output power at a scan range of over 100 nm. The measured coherence length was 7 mm. Tomographic images of some biological tissue were successfully obtained using the swept-light-source OCT system.