Liquid light in synthetic lattices for frequency comb generation

The study of light dynamics in the frequency domain has been pivotal for applications in metrology and communications. One of the most impactful states is the optical frequency comb—a broadband light state where frequencies are equally spaced. To generate these combs, we rely on two key processes: nonlinear frequency proliferation and stabilization. When frequency proliferation occurs inside multimode lasers, the gain recovery time emerges as a critical factor for stabilization. Over 40 years ago, the stabilization process was described by slow and selective dissipation, like gain curvature in frequency or gain modulation in time [1]. However, recent advances in semiconductor-based frequency-comb sources have shown that when the gain recovery time becomes very short [2], the dynamics of light in the frequency domain becomes radically different [3-6].

In my talk, I will present the exploration of light dynamics in a discrete frequency space, when gain recovery times are fast [7,8]. I will show that light traveling through a medium with fast gain saturation transforms it into a type of liquid, which forces coherent dynamics despite destabilization processes, for example quenching or dephasing. This liquid state of light allows to explore fully the synthetic lattice in the frequency space, reaching its maximal limit given by the linear system. Such a platform not only advances our understanding of quench dynamics in non-equilibrium systems, but can also lead to innovative quantum inspired devices, like the recently discovered quantum walk comb source [7].

References

[1] H. Haus, “A theory of forced mode locking” IEEE J. Quantum Electron. 11, 323–330 (1975).

[2] U. Senica, A. Dikopoltsev, et al., “Frequency-Modulated Combs via Field-Enhancing Tapered Waveguides”, Laser Photonics Rev, 2300472 (2023).

[3] J. B. Khurgin, et al. "Coherent frequency combs produced by self frequency modulation in quantum cascade lasers." APL 104.8 (2014).

[4] N. Opačak, et al., “Theory of frequency-modulated combs in lasers with spatial hole burning, dispersion, and Kerr nonlinearity” Phys. Rev. Lett. 123, 243902 (2019).

[5] D. Burghoff, "Unravelling the origin of frequency modulated combs using active cavity mean-field theory." Optica 7.12 (2020): 1781-1787.

[6] M. Piccardo, et al. "Frequency combs induced by phase turbulence." Nature 582.7812 (2020): 360-364.

[7] I. Heckelmann*, M. Bertrand*, A. Dikopoltsev*, et al., “Quantum walk comb in a fast gain laser”, Science 382, 434-438 (2023).

[8] A. Dikopoltsev, et al. "Quench dynamics of Wannier-Stark states in an active synthetic photonic lattice." arXiv:2405.04774 (2024).