The field of chiral photonics continues to form on the premise that traditional photonics can be enhanced by making use of the spin degree of freedom of light. Unlike standard photonic platforms, chiral photonics aims to make use of the handedness of circularly polarized photons to retain and propagate additional information in a photonic circuit. Though past work in the field of chiral photonics has required lab scale optical tables, recent advances in materials and topological crystal research has made the directional propagation and routing of circularly polarized light achievable on a single chip. What remains a key challenge to this field is the efficient and active manipulation and modulation of circularly polarized photons at these single chip scales. While photons are beneficial for their ability to travel quickly and propagate long distances through a photonic circuit [1], their degrees of freedom remain difficult to control due to their lack of response to external fields. One promising avenue is to make use of exciton-polaritons [2]. These half-light, half-exciton hybrid quasiparticles can retain their photon like properties while also inheriting the tunable nonlinearities of the matter excitation. This phenomenon has been demonstrated in TMD materials, where it was shown that exciton-polaritons can inherit and retain valley information [3], [4]. Extending the ideas of hybrid light-matter interactions in traditional semiconductors to magnetic systems can offer opportunities to study new magneto-optical physics and could pave the way to faster more efficient modulation of circularly polarized photons for chiral photonic devices.
In particular, 2D magnetic semiconductors, such as the transition metal trihalides, can form magnetization dependent bandgaps that support excitons mediated by circularly polarized photons [5]. Placing these 2D magnetic materials in microcavities can enhance the interactions between these excitons and circularly polarized photons, creating magneto-exciton-polaritons with modified properties. These hybrid quasiparticles can then be tuned via the material’s sensitivity to external magnetic fields, applied voltage, and mechanical force.
Exciton-polaritons in 2D magnetic semiconductors provide a unique opportunity to study many-body physics within a quantum regime where photons, electrons, and spins are all strongly coupled. By studying the hybrid dynamics of magneto-exciton-polaritons, we aim to develop and expand a new platform for chiral photonics, where the spin degree of freedom of light is controlled via the optical properties of magnetic nanomaterials. By understanding the fundamentals of these spin correlated light-matter interactions we open up the possibility for new and interesting chiral photonic devices.
[1] P. Liu, H. Zeng, D. A. Czaplewski, and N. P. Stern, “Low Index Contrast Valley Hall Topological Photonics for Robust Transport in the Visible Spectrum,” ACS Photonics, vol. 9, no. 3, pp. 922–928, Mar. 2022, doi: 10.1021/acsphotonics.1c01741.
[2] W. Liu et al., “Generation of helical topological exciton-polaritons,” Science, vol. 370, no. 6516, pp. 600–604, Oct. 2020, doi: 10.1126/science.abc4975.
[3] Y.-J. Chen, J. D. Cain, T. K. Stanev, V. P. Dravid, and N. P. Stern, “Valley-polarized exciton–polaritons in a monolayer semiconductor,” Nat. Photonics, vol. 11, no. 7, pp. 431–435, Jul. 2017, doi: 10.1038/nphoton.2017.86.
[4] T. LaMountain et al., “Valley-selective optical Stark effect of exciton-polaritons in a monolayer semiconductor,” Nat. Commun., vol. 12, no. 1, Art. no. 1, Jul. 2021, doi: 10.1038/s41467-021-24764-8.
[5] K. L. Seyler et al., “Ligand-field helical luminescence in a 2D ferromagnetic insulator,” Nat. Phys., vol. 14, no. 3, pp. 277–281, Mar. 2018, doi: 10.1038/s41567-017-0006-7.