JQI Seminar: Mahoud Mehrabad
Description
Title:Â More is different: new frontiers of ultrabroadband multimodal nonlinear optics with integrated multi-timescale systems
Abstract: In condensed matter physics, new collective phenomena emerge when many simple elements interact: more is different. In this talk I will show how the same idea opens new regimes of nonlinear optics on a chip. Our platform is a two-dimensional lattice of hundreds of coupled silicon nitride ring resonators, an integrated system with two nested timescales: a fast single-ring timescale near one terahertz and a slow super-ring timescale of a few gigahertz set by the lattice. I will describe how this multi-timescale structure gives rise to topological frequency combs [1], nested mode-locked states [2], and frequency-phase matching that delivers ultrabroadband harmonic generation from the telecom band to the visible, without tuning and across wafer-scale fabrication variation [3]. I will then present our latest results, in which a single lattice realizes more than 100 artificial gauge fields hosting over 10,000 photonic modes across nearly an optical octave [4], and close with where multi-timescale systems are heading, including programmable, scale-dependent topology [5].
References:
[1] C. J. Flower, M. Jalali Mehrabad, L. Xu, et al., "Observation of topological frequency combs," Science 384, 1356 (2024).
[2] L. Xu, M. Jalali Mehrabad, C. J. Flower, et al., "On-chip multi-timescale spatiotemporal optical synchronization," Science Advances 11, eadw7696 (2025).
[3] M. Jalali Mehrabad, L. Xu, et al., "Multi-timescale frequency-phase matching for high-yield nonlinear photonics," Science 390, 612 (2025).
[4] L. Xu, A. Padhye, ..., M. Hafezi, and M. Jalali Mehrabad, "Single-shot realization of 10000-mode octave-spanning artificial gauge fields," arXiv:2606.23960 (2026).
[5] M. Jalali Mehrabad, A. Parhizkar, L. Xu, et al., "Quantum metamorphosis: programmable emergence and the breakdown of bulk-edge dichotomy in multiscale systems," arXiv:2511.13831 (2025).
*You will need to bring your cell phone, so you can sign in using the QR code outside of ATL 2400. You will need to submit your first and last name, email, and affiliation on the form by 11:15am to be able to get lunch after the seminar. Lunch is first come, first served.*
Abstract: In condensed matter physics, new collective phenomena emerge when many simple elements interact: more is different. In this talk I will show how the same idea opens new regimes of nonlinear optics on a chip. Our platform is a two-dimensional lattice of hundreds of coupled silicon nitride ring resonators, an integrated system with two nested timescales: a fast single-ring timescale near one terahertz and a slow super-ring timescale of a few gigahertz set by the lattice. I will describe how this multi-timescale structure gives rise to topological frequency combs [1], nested mode-locked states [2], and frequency-phase matching that delivers ultrabroadband harmonic generation from the telecom band to the visible, without tuning and across wafer-scale fabrication variation [3]. I will then present our latest results, in which a single lattice realizes more than 100 artificial gauge fields hosting over 10,000 photonic modes across nearly an optical octave [4], and close with where multi-timescale systems are heading, including programmable, scale-dependent topology [5].
References:
[1] C. J. Flower, M. Jalali Mehrabad, L. Xu, et al., "Observation of topological frequency combs," Science 384, 1356 (2024).
[2] L. Xu, M. Jalali Mehrabad, C. J. Flower, et al., "On-chip multi-timescale spatiotemporal optical synchronization," Science Advances 11, eadw7696 (2025).
[3] M. Jalali Mehrabad, L. Xu, et al., "Multi-timescale frequency-phase matching for high-yield nonlinear photonics," Science 390, 612 (2025).
[4] L. Xu, A. Padhye, ..., M. Hafezi, and M. Jalali Mehrabad, "Single-shot realization of 10000-mode octave-spanning artificial gauge fields," arXiv:2606.23960 (2026).
[5] M. Jalali Mehrabad, A. Parhizkar, L. Xu, et al., "Quantum metamorphosis: programmable emergence and the breakdown of bulk-edge dichotomy in multiscale systems," arXiv:2511.13831 (2025).
*You will need to bring your cell phone, so you can sign in using the QR code outside of ATL 2400. You will need to submit your first and last name, email, and affiliation on the form by 11:15am to be able to get lunch after the seminar. Lunch is first come, first served.*