An optical tool to optimize the output of a photonic integrated chip architecture

Photonic Integrated Chips (PICs) are an up-and-coming solution for base building blocks of quantum computers. The ready accessibility of photonics integrated systems and the fact that they allow for direct monolithic integration with electronics in a compact architecture have pushed the academic community to inspect their capabilities further. Still, at this stage, their characterization, control, and fine-tuning is an open issue for which this work aims to provide a viable solution. In this paper we present a method for an easy setup and an efficient architecture to simultaneously optimize multiple outputs of a PIC. The proposed solution can be embedded in an automation tool for tuning and verifying output on- and off-chip detectors. We fabricated a Silicon Oxynitride (SiON)-based PIC featuring a network of Mach-Zehnder interferometers (MZI) arranged in Clements architecture driven by Titanium-Titanium Nitride (TiTiN) thermistors. We interfaced the chip electronically through commercial driver modules and optically through optical guides and controlled it through a Python optimization algorithm. Finally, we retrieved the feedback of the control both by sensing it through integrated silicon photodetectors and by an image processing algorithm capable of inspecting the light intensity scattered by the waveguides in a custom region.