Electrically Tunable Spin-Orbit Coupled Photonic Structures in Liquid Crystal Microcavities

Electrically Tunable Spin-Orbit Coupled Photonic Structures in Liquid Crystal Microcavities

Speaker: Jacek Szczytko

Affiliation: University of California, Irvine

Abstract:

¹Faculty of Physics, University of Warsaw, Poland; ² Université Clermont Auvergne, CNRS, Institut Pascal, Clermont-Ferrand, France; ³Military University of Technology, Warsaw, Poland; ⁵Institut Universitaire de France, Paris, France

We demonstrate electrically tunable photonic structures with strong polarization-dependent band engineering in liquid-crystal (LC) optical microcavities using two complementary approaches. The first employs lithographically patterned nematic LC microcavities, where mesas etched into the ITO electrode beneath the distributed Bragg reflector (DBR) create tunable photonic potentials and enable electrical control of spin-orbit coupling (SOC). The second exploits the self-organization of cholesteric liquid crystals to form either a one-dimensional uniform lying helix (ULH), in which the helix axis is aligned along a single direction, or zero-dimensional torons, where the helical structure wraps around a topological liquid-crystal defect. In these self-organized structures, electrically controlled molecular reorientation modifies the photonic potential and band structure while inducing interband SOC, which can be interpreted as a synthetic non-Abelian gauge potential. Furthermore, doping the liquid crystal with laser dyes enables electrically tunable polarized lasing, including emission carrying orbital angular momentum.

Unlike spin-orbit coupling in solid-state materials, which is largely fixed by material properties, liquid-crystal microcavities offer dynamic and reversible control of photonic band structures. The polarized cavity modes are described by an effective two-mode Hamiltonian for massive spin-½ particles, derived using Green’s function techniques and k⋅p perturbation theory. This framework naturally captures effective photonic SOC and non-Hermitian effects in birefringent cavities [1].

The one-dimensional ULH acts as a polarization-dependent periodic potential whose strength is controlled by an external electric field, enabling reversible opening and closing of photonic band gaps. Furthermore, the molecular tilt induces coupling between lattice bands of opposite parity, giving rise to electrically tunable interband SOC. Under optical pumping, the dye-doped microcavity exhibits lasing that inherits these electrically tunable properties [2], including dual-beam and circularly polarized emission [3]. In toron-based microcavities, the applied electric field controls the toron size and, consequently, the optical angular momentum of the confined photonic modes, allowing the ground state to switch between zero and non-zero orbital angular momentum [4].

These two complementary strategies: top-down lithographic patterning and bottom-up liquid-crystal self- organization, establish a versatile platform for engineering reconfigurable photonic potentials and band structures, enabling synthetic gauge fields, topological photonic phases, and electrically programmable coherent light sources carrying tailored polarization and orbital angular momentum..

References

[1] P. Oliwa et al,  Phys. Rev. Research 6, 013324 (2024). https://doi.org/10.1103/PhysRevResearch.6.013324

[2] D. Dovzhenko et al. Nature Commun. 17, 5335 (2026) https://doi.org/10.1038/s41467-026-71733-0

[3] M. Muszynski, et al., Laser Photonics Rev. 2025, 19, 2400794 (2025) https://doi.org/10.1002/lpor.202400794

[4] M. Muszynski, et al., Science Advances 12, aeb6167 (2026) https://doi.org/10.1126/sciadv.aeb6167

This work was supported by the National Science Centre Poland 2023/51/B/ST3/03025 and Horizon2020 FET Open research and innovation action under the grant agreements No. 964770 (TopoLight).