Mode-selective coupler for wavelength multiplexingusing LiNBO_3:Ti optical waveguides

摘要

A mode-selective directional coupler based on titanium in-diffused channel waveguides in lithium niobateis investigated. This coupler may be utilized as a key part of an add-drop multiplexer for dense wavelengthdivision multiplexing in optical network nodes. The proposed coupler is based on evanescent coupling ofthe fundamental mode of a single-mode channel to the first higher mode of a parallel bi-modal waveguide.Our experimental results show that a compact directional coupler with coupling efficiencies larger than90%, large bandwidth around 1550 nm, and with negligible polarization dependence can be realized usingelectro-optic lithium niobate substrates.