Lithography-free IR polarization converters via orthogonal in-plane phonons in α-MoO3 flakes

• DOI: 10.1038/s41467-020-19499-x
• Publication Date: 2020-11-13T11:03:48Z
• Authors: Sina Abedini Dere...; Thomas G. Folland; Akshay A. Murthy; Xianglian Song; Ibrahim Tanriover; Vinayak P. Dravid; Joshua D. Caldwell; Koray Aydin
• Keywords: 0301 basic medicine; 0303 health sciences; 03 medical and health sciences; Science; Q; FOS: Physical sciences; Article; Physics - Optics; Optics (physics.optics)

AbstractExploiting polaritons in natural vdW materials has been successful in achieving extreme light confinement and low-loss optical devices and enabling simplified device integration. Recently, α-MoO3 has been reported as a semiconducting biaxial vdW material capable of sustaining naturally orthogonal in-plane phonon polariton modes in IR. In this study, we investigate the polarization-dependent optical characteristics of cavities formed using α-MoO3 to extend the degrees of freedom in the design of IR photonic components exploiting the in-plane anisotropy of this material. Polarization-dependent absorption over 80% in a multilayer Fabry-Perot structure with α-MoO3 is reported without the need for nanoscale fabrication on the α-MoO3. We observe coupling between the α-MoO3 optical phonons and the Fabry-Perot cavity resonances. Using cross-polarized reflectance spectroscopy we show that the strong birefringence results in 15% of the total power converted into the orthogonal polarization with respect to incident wave. These findings can open new avenues in the quest for polarization filters and low-loss, integrated planar IR photonics and in dictating polarization control.