Twisted Bilayer Photonic Crystals

Problem

Photonic crystals are periodic and well-studied. Twisted bilayer photonic crystals are quasi-periodic and show disorder-like properties, even though the structure is highly ordered. For long, people cannot exactly compute the properties of this system and treated it like disorder. Exact solutions only exist for special cases of certain twist angles.

Our work

Theory and algorithm: We came up with an algorithm to compute such systems exactly for all cases in general and effective theories for the phenomenon (Lou et al., 2021; Lou & Fan, 2025).
Experimental verification: We verify our theory and numerical results with experiment (Lou et al., 2022; Tang* et al., 2023).
Applications enabled: We work out all the details to use it for device applications (Lou & Fan, 2022; Lou et al., 2024; Tang* et al., 2025).

Check out the related publications below for more details.

References

2025

Comp. Phys. Comm.

RCWA4D: Electromagnetic solver for layered structures with incommensurate periodicities

Beicheng Lou and Shanhui Fan

Computer Physics Communications, 2025

Abs

We describe RCWA4D, an electromagnetic solver for layered structures with incommensurate periodicities. Our method is based on an extension of the rigorous coupled wave analysis. We illustrate our method on the example of twisted bilayer photonic crystal and show that various properties of such structures can be reliably simulated. The method can be generalized to multi-layer structures in general in which each layer is periodic or quasi-periodic.
Nat. Photon.

An adaptive moiré sensor for spectro-polarimetric hyperimaging

Haoning Tang^*, Beicheng Lou^*, Fan Du, and 8 more authors

Nature Photonics, May 2025

2024

ACS Photon.

Free-Space Beam Steering with Twisted Bilayer Photonic Crystal Slabs

Beicheng Lou, Haoning Tang, Fan Du, and 3 more authors

ACS Photonics, May 2024

2023

Sci. Adv.

Experimental probe of twist angle–dependent band structure of on-chip optical bilayer photonic crystal

Haoning Tang^*, Beicheng Lou^*, Fan Du, and 6 more authors

Science Advances, May 2023

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Recently, twisted bilayer photonic materials have been extensively used for creating and studying photonic tunability through interlayer couplings...

2022

Sci. Adv.

Tunable guided resonance in twisted bilayer photonic crystal

Beicheng Lou, Benjamin Wang, Jesse A Rodríguez, and 2 more authors

Science Advances, May 2022

Abs

We experimentally demonstrate tunable guided resonance in twisted bilayer photonic crystals. Both the transmission spectra feature resonances with frequencies strongly dependent on the twist angle...
ACS Photon.

Tunable Frequency Filter Based on Twisted Bilayer Photonic Crystal Slabs

Beicheng Lou and Shanhui Fan

ACS Photonics, May 2022

2021

PRL

Theory for Twisted Bilayer Photonic Crystal Slabs

Beicheng Lou, Nathan Zhao, Momchil Minkov, and 3 more authors

Phys. Rev. Lett., May 2021

Abs HTML

We analyze scattering properties of twisted bilayer photonic crystal slabs through a high-dimensional plane wave expansion method. The method is applicable for arbitrary twist angles and does not suffer from the limitations of the commonly used supercell approximation. We show strongly tunable resonance properties of this system which can be accounted for semianalytically from a correspondence relation to a simpler structure. We also observe strongly tunable resonant chiral behavior in this system. Our work provides the theoretical foundation for predicting and understanding the rich optical physics of twisted multilayer photonic crystal systems.