Reflective coils were an integral part of Doctor Nel Apgar's Krieger wave converter.

In 2366 Dr. Apgar requested additional deliveries of dicosilium, which he needed for his wave converter. Geordi La Forge suspected that he was building larger reflective coils and therefore needed more dicosilium, possibly to further develop the converter into a weapon and sell it to the Ferengi or Romulans. (TNG: "A Matter of Perspective")