12noon – 1pm February 21st 2025

LISE 303

Abstract: The cascaded-mode conversion mechanism represents a transformative advancement in integrated photonics, enabling precise engineering of light’s spectral, temporal, and spatial properties within optical waveguide systems. In this work, we introduce a method for remote, near-arbitrary three-dimensional near-field shaping via cascaded mode conversion and interference of counterpropagating guided waves with distinct propagation constants. Building on this framework, we propose a novel class of optical resonators—cascaded mode resonators—that exploit transverse mode coupling in a cascaded process mediated by mode-converting mirrors. Unlike conventional Fabry-Perot resonators, these devices exhibit a generalized round-trip phase condition, enabling tailored resonance characteristics across a broad operational range. Further, we demonstrate cascaded-mode interferometers, a new interferometric architecture that leverages interference among multiple transverse modes in a single multimode waveguide. This approach achieves arbitrary spectral responses in a compact footprint, circumventing the need for complex multi-component systems. These advancements address critical challenges in integrated photonics, offering enhanced efficiency, versatility, and miniaturization for next-generation optical devices. By redefining control over light at the chip scale, this work paves the way for transformative applications in telecommunications, sensing, quantum technologies, and beyond, meeting the escalating demand for compact and adaptable integrated optical systems.

About the speaker: Jinsheng Lu is a Postdoctoral Researcher at Harvard SEAS in Federico Capasso’s
group. He earned both his Bachelor’s (2016) and Ph.D. (2021) in Optical Engineering from Zhejiang University. His Ph.D. research focused on Optical Forces and Manipulations. In 2019, he joined the Capasso group as a joint Ph.D. student, working on On-Chip Optical Tweezers. Since 2021, as a postdoc, his research has focused on Mode Converters Integrated Photonics.