Expanding momentum bandgaps in photonic time crystals through resonances

TL;DR

This paper demonstrates that introducing resonances in materials significantly expands momentum bandgaps in photonic time crystals, making their experimental realization more feasible with existing materials and laser powers.

Contribution

The study shows that resonances can drastically enhance momentum bandgaps in photonic time crystals, overcoming previous modulation strength limitations.

Findings

Resonant materials enable larger momentum bandgaps at lower modulation strengths.

Both bulk media and metasurfaces can support this resonance-based enhancement.

The approach is compatible with low-loss materials and realistic laser powers.

Abstract

The realization of photonic time crystals is a major opportunity but also comes with significant challenges. The most pressing one, potentially, is the requirement for a substantial modulation strength in the material properties to create a noticeable momentum bandgap. Reaching that noticeable bandgap in optics is highly demanding with current, and possibly also future, material platforms since their modulation strength is small by tendency. Here, we demonstrate that by introducing temporal variations in a resonant material, the momentum bandgap can be drastically expanded with modulation strengths in reach with known low-loss materials and realistic laser pump powers. The resonance can emerge from an intrinsic material resonance or a suitably spatially structured material supporting a structural resonance. Our concept is validated for resonant bulk media and optical metasurfaces and paves the way toward the first experimental realizations of photonic time crystals.