NSF CAREER Award to Develop Next Generation Optical Frequency Combs
ECE Assistant Professor Sunil Mittal was awarded a $560K NSF CAREER award for “On-Chip Coupled Resonator Arrays for Generating Unconventional Classical and Quantum Optical Frequency Combs (CRAYONS).”
Abstract Source: NSF
Non-Technical Description:
An optical frequency comb is a light source whose frequency spectrum comprises many evenly spaced frequencies that form a comb-like structure. These sources underpin a wide range of technologies, including precision time and frequency measurements, global positioning systems (GPS), terabit-scale transmitters for optical communications, light detection and ranging (LiDAR) for autonomous vehicles, and energy-efficient all-optical computing. While recent progress in generating combs using on-chip integrated photonic resonators has enabled compact and scalable platforms, existing devices remain limited in efficiency, tunability, and flexibility for emerging applications. This project will leverage large arrays of coupled resonators to create a new class of optical frequency combs that enable application-specific comb engineering with substantially improved efficiency and agile tunability. The research is tightly integrated with STEM education, outreach, and workforce development activities that provide experiential learning opportunities for K-12, undergraduate, and community college students.
Technical Description:
The use of chip-integrated photonic resonators with Kerr nonlinearity has enabled a compact, scalable route for generating broadband optical frequency combs. However, most existing on-chip Kerr comb sources rely on single resonators, which severely limit their efficiency, agile tunability, minimum achievable line spacing, and the ability to engineer comb spectra for application-specific needs. This project overcomes these limitations by leveraging large arrays of on-chip coupled nonlinear resonators to realize unconventional comb states that are inaccessible in conventional single-resonator platforms. Guided by condensed-matter-physics-inspired design principles, including topological, Floquet, and non-Hermitian engineering, the project will demonstrate new comb paradigms, including (1) incommensurate combs that, unlike conventional combs, are not uniformly spaced yet remain mode-locked; (2) mode-locked nested combs that form a comb within a comb structure, enabling high spectral resolution for spectroscopy; and (3) quantum combs that provide enhanced quantum resources. Collectively, these architectures will enable tunable comb line spacing, reconfigurable spectral structure, and significantly improved conversion efficiency, while allowing the comb spectrum to be tailored to specific target applications. The project will train a workforce with interdisciplinary expertise spanning optical, electrical, and quantum engineering, and support the advancement of next-generation photonic technologies for classical and quantum applications.