The speed of light can be intentionally reduced in various media. Various techniques have been developed over the years to slow down light, including electromagnetically induced transparency (EIT), Bose-Einstein condensate (BEC), photonic crystals, and stimulated Brillouin scattering (SBS).
Notably, researchers from Harvard, led by Lene Vestergaard Hau, reduced light speed to 17 m/s in an ultracold atomic gas using EIT, which sparked the interest in exploring EIT analogs in metasurfaces, a transformative platform in optics and photonics.
Despite the benefits, slow-light structures face a significant challenge: Loss, which limits storage time and interaction length. This issue is particularly severe for metasurface analogs of EIT due to scattering loss of nanoparticles and sometimes absorption loss of materials.