Characterization of Inverse Design Gallium Arsenide Couplers

• Edgar Rubio Hernandez, Physics, University of St. Thomas

• Matthew Doty, Materials Science and Engineering, University of Delaware

This research investigates the performance of inverse design Gallium Arsenide photonic couplers with an aim to compare the efficiency of different structures to further minimize optical power loss. Inverse-design couplers are devices that have been computationally optimized to transfer the most amount of light between free space and integrated photonic structures, such as waveguides, and is a growing area of research in regard to developing scalable hardware for quantum applications. Devices designed for 60 nm and 100 nm operating bandwidths, with 25 µm and 50 µm waveguides, were measured by performing a wavelength sweep from 1525 nm to 1625 nm in 1nm increments. The transmitted signal was first normalized to the reference signal to account for fluctuations in the incident optical power, then normalized to the gold-mirror response to determine total efficiency of the device. The 25 µm waveguide devices demonstrated superior performance compared to the 50µm devices. The shorter devices achieved comparatively higher peak and average efficiencies, while the longer 50 µm waveguides exhibited lower average efficiency. This trend is consistent with increased optical loss over longer propagation distances, although variations in fabrication quality may also have influenced the measured performance. This study establishes a baseline for the next generation of devices to be fabricated, as devices that have shown to be capable can be improved by optimizing for room-temperature operation.