Efficient and Tunable Reflection of Phonon Polaritons at Built-In Intercalation Interfaces

Area of Science:

• Condensed Matter Physics
• Nanophotonics
• Materials Science

Background:

• Phonon polaritons, arising from light coupling to lattice vibrations in polar materials, exhibit unique anisotropic and low-loss propagation.
• Controlling phonon polaritons, analogous to plasmon polaritons, via reflection at interfaces has remained a significant challenge.

Purpose of the Study:

• To investigate the effective and tunable reflection of phonon polaritons at embedded interfaces within van der Waals crystals.
• To explore the potential of these interfaces as nanoscale optical components.

Main Methods:

• Fabrication of hydrogen-intercalated α-MoO3 flakes to create embedded interfaces.
• Experimental characterization of phonon polariton reflection and phase shifts at these interfaces.

Main Results:

• Demonstrated effective reflection of phonon polaritons at embedded interfaces without breaking geometrical continuity.
• Achieved low-loss reflection with high efficiency (50%) and distinct phase changes (-0.8π and -0.3π).
• Showcased potential for electrical tunability of polariton reflection.

Conclusions:

• Embedded interfaces in van der Waals crystals can serve as efficient and tunable phonon polariton reflectors.
• These findings pave the way for constructing on-demand polariton reflectors, phase modulators, and retarders.
• The results offer a new pathway for developing future polaritonic circuits using van der Waals materials.