Achieving momentum bandgaps via large‑amplitude temporal modulation in plasmonic time crystals

Develop and implement temporal modulation schemes with amplitudes sufficient to open observable momentum bandgaps in time‑modulated plasmonic systems, including platforms supporting surface plasmon‑polaritons and graphene surface plasmon‑polaritons, in order to realize the momentum‑bandgap regime predicted for plasmonic time crystals.

Background

Temporal modulation of spatially homogeneous photonic systems creates photonic time crystals in which frequency is not conserved and bandgaps arise in momentum space rather than in frequency. Analogous concepts have been explored for surface, bulk, and graphene plasmon‑polaritons, where breaking time‑translation symmetry leads to new regimes, including momentum bandgaps and associated gain states.

To observe these momentum bandgaps in plasmonic systems, one must achieve sufficiently large temporal modulation amplitudes. Despite several proposed approaches, realizing modulation strengths adequate for clear observation remains unresolved and is identified as an open challenge by the authors.