Microsecond optical switching of five channels by KTN electro‐optic deflector

Abstract

A 1 × 5 optical switch with a switching speed of microseconds is demonstrated. Switching between different channels in a planar lightwave circuit waveguide array was controlled using an electro-optic beam deflector. A single crystal of potassium tantalate niobate (KTa 1−x Nb x O 3 , KTN) was used as a deflector to realise this operation. A switching speed of 8.1 μs was demonstrated for the switching of two adjacent channels.Introduction: Optical switching using electro-optic (EO) deflectors has received a lot of attention because of their fast switching speed. An EO deflector deflects a launched optical beam to switch between spatially arranged output channels using an applied voltage. (Pb, La)(Zr, Ti)O 3 (PLZT), LiNbO 3 (LN) and LiTaO 3 (LT) with prism structures are commonly used to realise multi-channel and high-speed EO switches [1-3]. A potassium tantalate niobate (KTa 1-x Nb x O 3 , KTN) single crystal is also a promising material for an EO deflector because of its huge second-order EO (Kerr) effect. In addition to a KTN single crystal having superior material properties, a novel deflection technique has been proposed [4] based on the refractive index distribution inside the KTN crystal. With an EO crystal, the gradient of the refractive index cumulatively adds a phase delay as the optical beam propagates through it. Thus, it is possible to obtain a deflection angle of more than several degrees, which is much larger than those of the conventional prism-shaped EO deflectors. Therefore, we can expect a large number of switching channels when KTN is used as an EO switch. In this Letter, we describe a 1 × 5 optical switch with a switching speed of microseconds consisting of a KTN deflector and a planar lightwave circuit (PLC) waveguide array. The highest switching speed when switching two adjacent channels was 8.1 μs.

Improving the Electro-Optical Deflection Performance of KTN Crystals Based on the Temperature Compensation Effect

“…Both types of deflectors offer advantages such as a large deflection angle, low energy consumption, and nanosecond deflection speed. In recent years, KTN crystals have been used to make dynamic optical waveguides, electro-optical modulators, high-speed scanners, and other optoelectronic functional devices. − However, there are still some problems to be solved in the practical application of KTN crystals, and researchers have conducted in-depth studies on them. For example, Yin et al solved the problem that the charge injection depth is limited by the bound charge and used the physical mechanism of excitation of bound electrons by blue-light photons to increase the charge injection depth and increase the deflection angle.…”