Reconfigurable mode converters based on low-loss phase change materials for integrated optical computing

Reconfigurable integrated photonics leveraging phase-change materials (PCMs) is a rapidly evolving field with diverse applications, including optical computing and programmable optics. Its development is driven by the high optical contrast and nonvolatility enabled by reversible phase switching in PCMs. Consequently, the design and modeling of such devices are critical for enabling their practical applications. In this work, we compare multiple inverse design algorithms for integrated optical structures, using a mode converter based on the low-loss PCM Sb₂Se₃ as a representative example. To bridge the gap between idealized designs and the realistic performance of integrated devices, the resulting mode converters are numerically assessed for key metrics such as mode contrast, insertion loss, and robustness against fabrication variations. To further investigate their applicability, we develop a photonic tensor core incorporating these mode converters as weight elements. We then analyze the operational range of output optical power and the image convolution quality achieved by the photonic core, highlighting the impact of the choice of weight elements on its overall performance.