Communications Materials (Feb 2024)

Deeply subwavelength mid-infrared phase retardation with α-MoO3 flakes

  • Michael T. Enders,
  • Mitradeep Sarkar,
  • Maxime Giteau,
  • Aleksandra Deeva,
  • Hanan Herzig Sheinfux,
  • Mehrdad Shokooh-Saremi,
  • Frank H. L. Koppens,
  • Georgia T. Papadakis

DOI
https://doi.org/10.1038/s43246-024-00453-z
Journal volume & issue
Vol. 5, no. 1
pp. 1 – 7

Abstract

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Abstract Phase retardation is a cornerstone of modern optics, yet, at mid-infrared (mid-IR) frequencies, it remains a major challenge due to the scarcity of simultaneously transparent and birefringent crystals. Most materials resonantly absorb due to lattice vibrations occurring at mid-IR frequencies, and natural birefringence is weak, calling for hundreds of microns to millimeters-thick phase retarders for sufficient polarization rotation. Here, we demonstrate mid-IR phase retardation with flakes of α-MoO3 that are more than ten times thinner than the operational wavelength, achieving 90 degrees polarization rotation within one micrometer of material. We report conversion ratios above 50% in reflection or transmission mode, and wavelength tunability by several micrometers. Our results showcase that exfoliated flakes of low-dimensional crystals can serve as a platform for mid-IR miniaturized integrated low-loss polarization control.