Leveraging optical anisotropy of van der Waals magnets for novel device applications

Semiconducting van der Waals materials with a direct band gap that emit light and exhibit magnetic order have a range of potential applications, such as making spintronic devices, magneto-optical devices, transmon qubits etc. CrSBr stands out in this regard due to its many startling properties such as large refractive index, high degree of transport and optical anisotropy, linearly polarized photoluminescence (PL), magnetic field and thickness-dependent magnetic order, strong light-matter coupling, magnetic field tunable exciton energy to name a few. In this study, we focus on the optical anisotropy of this material using polarization-resolved PL and momentum direction dependence in Fourier spectroscopy. We show that the optical anisotropy depends on the flake thickness, excitation wavelength, and cavity detuning. Ultimately, we exploit the large optical anisotropy to spatially confine the polaritons selectively along the b-crystal axis while having a propagating polariton along a axis. Our study shows that CrSBr is an excellent platform for developing next-generation novel photonic devices.