Twin laser - Y-waveguide - fiber-coupled system

Abstract

We considered a model in which two equal sources are symmetrically and vertically separated with respect to a central longitudinal axis, in which a Y-waveguide is placed to couple the two output signals to one fiber. Our aim was to establish the optimum considerations of coherently adding the Gaussian fundamental mode of this twin laser/s system transmitted in the junction waveguide. The coupling efficiency between each laser/s Gaussian output and each waveguide branch, and between the output waveguide and the fiber was calculated, avoiding waveguide rotations or vertical translations. For simplicity, equal minimum Gaussian waist width for each laser/s output and each waveguide branch was assumed. In addition, the fractional power transmission coupling (normalization) was numerically simulated. To estimate the intensity transmitted by the entire twin laser - Y waveguide - fiber compound system, we used the coupling coefficient of an output laser beam and one branch of the waveguide (assumed equal for both signals in the twin laser/s array) as a weight factor for the field transmitted by the waveguide branch. An ideal Y-waveguide for coupling to a fiber was designed to diminish coupling losses between the two output signals for a laterally coupled semiconductor twin laser.