Low-Loss Isotopic MoO3 Phonons

This study explores high-purity isotope-enriched α-MoO3 (92Mo and 100Mo isotopes), synthesized via refined physical vapor deposition to mitigate the high optical loss in natural α-MoO3. Isotope enrichment effectively reduces phonon scattering, enhancing phonon coherence and enabling longer propagation lengths of phonon polaritons (PhPs). Raman spectroscopy identified isotopic materials through narrower Ag2 peaks, confirming improved coherence, while s-SNOM revealed extended PhP propagation lengths, increasing from 2.79 μm in natural α-MoO3 to 6.76 μm in α-100MoO3 and over 12 μm in α-92MoO3.

The correlation of s-SNOM imaging with Raman spectroscopy was key to linking enhanced phonon lifetime and reduced optical loss to isotope enrichment, paving the way for advancements in low-loss nanophotonic devices.

This measurement was realized with the IR-neaSCOPE+TERs.