AlGaAs-OI waveguides for nonlinear applications (Conference Presentation)

Abstract

Aluminium Gallium Arsenide (AlGaAs) is regarded as a very promising material for non-linear optical applications thanks to its strong second and third order non-linear coefficients. Moreover, its bandgap can be easily increased to values above 1.3 eV by varying the percentage of Aluminium, which mitigates the two photon absorption at telecom wavelengths that typically hinders the use of silicon based devices for these applications. However, the major drawback of GaAs/AlGaAs waveguides lies in the relatively low modal confinement in the vertical direction that translates into high propagation losses. The integration of an AlGaAs core on a silica cladding layer (i.e. AlGaAs on Insulator or AlGaAs-OI) is a very new and promising material platform for non-linear photonics as it combines the superior non-linear properties of AlGaAs with the very strong modal confinement offered by the low refractive index of the silica cladding. To date the most challenging aspect of AlGaAs-OI has been in the fabrication of the platform itself. In this talk key aspects regarding the design, fabrication and testing of AlGaAs-OI waveguides for nonlinear applications shall be explored, focussing on the fabrication challenges and how they were overcome. In particular, we will review AlGaAs epilayer designs with stop-etch layers that allow effective removal of the GaAs substrate and dry etching chemistries for smooth and vertical waveguide sidewalls. We will also discuss how these different designs and fabrication techniques impact on the waveguide propagation losses and on the performance of micro-ring resonators for non-linear applications.