Generation and Shaping of Liquid Light
Our group explores how strongly interacting photons can be stabilized into highly coherent, incompressible states, and how we can leverage synthetic dimensions to achieve control over optical frequency combs.
The Liquid Nature of Light
In a vacuum, light propagates linearly and inherently does not interact with itself. When light passes through materials, electrons mediate photon-photon interactions. Typically, these interactions cause photons to form a gaseous bosonic state, which is highly susceptible to turbulent behavior that severely reduces the system's coherence.To overcome this turbulence, our research focuses on forcing light into a state that mimics a liquid. In fluid dynamics, liquids are incompressible and tend to produce laminar flow, which mitigates chaotic behavior and maintains high coherence.We utilize ring-cavity semiconductor lasers characterized by extremely fast gain recovery times. Because the gain recovers so quickly, it suppresses light intensity fluctuations faster than any other timescale in the system. This suppression keeps the photon density uniform throughout the entire cavity. As a result, the light becomes incompressible, allowing us to imprint coherent, arbitrary flows into its phase dynamics.
Spectral Shaping with Synthetic Lattices
To shape the liquid light, we rely on a concept known as a synthetic frequency lattice. Rather than manipulating the light in physical space, we treat the evenly spaced frequency modes of our laser cavity as discrete sites within an artificial crystal lattice.We control this artificial crystal by applying radio-frequency modulation to the laser. This modulation acts as the connective bridges between the frequency sites, coupling the modes together. By actively tuning this modulation using multiple frequencies and adjusting their relative phases, we can dictate how the light flows through this synthetic space.
Future Directions: The Hydrodynamic Picture
Our next major milestone is to achieve arbitrary shaping and absolute control over the properties of light by levereging the fluid dynamics picture. By mapping our optical systems directly onto hydrodynamic equations, we derive analytic relationships between the external modulation inputs and the resulting light properties. Viewing the optical comb not just as discrete modes, but as a continuous fluid governed by hydrodynamic laws, will allow us to predictably design and engineer arbitrary optical waveforms.
References
- I. Heckelmann et al., ``Quantum walk comb in a fast gain laser,'' Science, vol. 382, pp. 434-438 (2023).
- Dikopoltsev, A. et al. “Collective quench dynamics of active photonic lattices in synthetic dimensions”. Nat. Phys. 21, 1134–1140 (2025).
- D. Piciocchi, A. Dikopoltsev et al., ``Spectral shaping of fast-gain frequency combs through phases in synthetic dimensions,'' Optica 13, 621-627 (2026).