Vibrational Strong Light-Matter Coupling in an Open Microcavity Based on Reflective Germanium Coatings.

Area of Science:

• Optics and Photonics
• Materials Science
• Spectroscopy

Background:

• Open microcavities (OMCs) are crucial for tuning optical resonances and studying light-matter interactions.
• Vibrational strong coupling (VSC) in the mid-infrared (MIR) typically uses dielectric Bragg reflectors (DBRs) or gold (Au) mirrors.

Purpose of the Study:

• To demonstrate VSC in the MIR using germanium (Ge) thin-film mirrors in OMCs.
• To compare the performance of Ge mirrors against traditional DBR and Au mirrors for VSC.

Main Methods:

• Fabrication of OMCs with Ge thin-film mirrors.
• Deposition of poly(methyl methacrylate) (PMMA) on an inner OMC mirror surface.
• Tuning the cavity to the PMMA carbonyl stretch mode resonance (~1731 cm⁻¹).
• Measurement and comparison of VSC properties, including optical transmission and Rabi splitting.

Main Results:

• Achieved VSC in the MIR using Ge mirrors.
• Observed enhanced optical transmission through polaritonic resonances with Ge mirrors.
• Reported a Rabi splitting of 8.8 meV for Ge OMC, compared to 7.0 meV (DBR) and 7.4 meV (Au).

Conclusions:

• Ge mirrors provide a simplified and effective alternative for MIR semiconductor mirrors in OMCs.
• The enhanced performance makes Ge-based OMCs promising for applications like polariton chemistry.