Design and modeling of GaAs/AlGaAs nonlinear waveguides by Hertzian potential formulation

Abstract

We present in this work the design of second harmonic generation process in χ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(2)</sup> nonlinear waveguides by a new time domain simulator. The presented Hertzian potential formulation (HPF) is applied to quasi-phase-matched GaAs/AlGaAs nonlinear waveguide with dielectric discontinuities. With the introduction of the presented rigorous time domain method it is possible to represent the physical phenomena such as light propagation and second harmonic generation (SHG) process inside a nonlinear optical device with a good convergent solution and low computational cost. We first check the convergence of the HPF approach by comparing the numerical results with experimental ones for a GaAs/AlGaAs nonlinear waveguide with a fundamental mode at λ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FU</inf> =1.955 μm coupled to a coprapagating second-harmonic SH mode (λ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SH</inf> =9.775 μm) through an appropriate nonlinear susceptibility coefficient. Then we apply the modelling to a GaAs/AlGaAs ridge waveguide with λ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FU</inf> =1.55 μm and λ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SH</inf> =0.775 μm by evaluating the second harmonic conversion efficiency versus the waveguide length. The model is generic and can be applied also to periodic microwave waveguides.