Reflectats

Reflectats are a class of emergent excitations described in speculative and experimental optics literature as quasi-particles that mediate an enhanced reflective response in engineered media. In this usage they are distinct from photons or phonons and are viewed as bound states arising from strong light–matter coupling within nanostructured metamaterials and photonic crystals.

The concept arose from theoretical models of coupled resonator systems and boundary modes that can, under certain geometries and dispersion conditions, accumulate energy near an interface and reflect incident light with a controllable phase. Reflectats are typically described by an effective mass and a dispersion relation that allows a narrow range of incident angles and frequencies to produce high reflectivity.

Key properties include polarization-sensitive response, tunable phase shifts upon reflection, and finite lifetimes limited by material loss and dephasing. Their existence is generally validated through indirect measurements of reflectivity spectra and phase profiles, often using ultrafast optical pump–probe techniques or near-field imaging.

Experimental status is active but unsettled; some reports interpret observed signals as evidence of reflective bound states tied to metasurfaces, while others caution that conventional surface plasmons or guided resonances can produce similar results. Replications and independent verifications are ongoing.

Applications proposed for reflectats include adaptive optics, beam steering, compact holographic elements, and cloaking-related devices. Practical deployment faces challenges such as material losses, fabrication tolerances, and integration with existing photonic platforms.

See also metasurfaces, metamaterials, photonic crystals, bound states in the continuum.