Characterization of Multicore Integrated Active Waveguides Written in an Er3+/Yb3+ Codoped Phosphate Glass

Abstract

A new methodology to completely characterize active multicore waveguides is proposed. The method is applied to two-core waveguides written in an Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> /Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> co-doped phosphate glass by femtosecond laser inscription. Determination of the core diameter and refractive index variation is based on asymmetric excitation of the dual core waveguide and measurements of the intensity output distribution. Moreover, a single core waveguide has also been written for characterization purposes and signal enhancement measurements carried out on it have allowed the determination of the glass active properties. Finally, enhancement measurements on the two-core waveguides for different pump powers and core-to-core separations have been performed, together with simulations of the experiments using the parameters determined in the characterization procedure. The good agreement between measurements and simulations supports the validity of the characterization method presented. The proposed characterization technique is suitable for any multicore symmetric structure regardless the fabrication method and the number of cores, allowing the benefits of multi-core fibre designs to be transferred to integrated active structures.