Thermal and Optical Characterization of Photonic Integrated Circuits by Thermoreflectance Microscopy

We report high resolution, non-invasive, thermal and optical characterization of semiconductor optical amplifiers (SOAs) and SOA-based photonic integrated circuits (PICs) using thermoreflectance microscopy. Chip-scale temperature imaging of SOAs and PICs, along with an energy balance model, are used to calculate the optical power distribution within and between SOAs to determine optical gain, fiber coupling loss, and passive component loss under normal device operating conditions. This technique is demonstrated to map optical power in SOA-based Mach-Zehnder interferometer (SOA-MZI) PICs, with close agreement with photocurrent and fiber-coupled measurements. The use of amplified spontaneous emission (ASE) for fiber-free characterization of the PICs is also shown, enabling non-invasive, wafer-scale testing prior to packaging.