Low-Symmetry α-MoO_3 Heterostructures for Wave Plate Applications in Visible Frequencies

摘要

Low-symmetry van der Waals materials are promising candidates for thenext generation of polarization-sensitive on-chip photonics since they donot require lattice matching for growth and integration. Due to their lowsymmetrycrystal behavior, such materials exhibit anisotropic and polarization-dependent optical properties for a wide range of optical frequencies.Here, depolarization characteristics of orthorhombic α-MoO_3 is studied inthe visible range. Using polarizers and analyzers, it is demonstrated thatα-MoO_3 has negligible loss and that birefringence values as high as 0.15 and0.12 at 532 nm and 633 nm, respectively, are achievable. With such a highbirefringence, quarter- and half-wave plate actions are demonstrated for a1400 nm α-MoO_3 flake at green (532 nm) and red (633 nm) wavelengths,and polarizability as high as 90 is reported. Furthermore, a system ofdouble α-MoO_3 heterostructure layer is investigated that provides thepossibility of tuning polarization as a function of rotation angle betweenthe α-MoO_3 layers. These findings pave the way to the promising futureof on-chip photonic heterostructures and twist-optics that can dictate thepolarization state of light.