Giant Broadband Refraction in the Visible in a Disordered Ferroelectric Perovskite

In this work we report broadband refraction and diffraction experiments in a ferroelectric perovskite, a solid-solution K
_0.997
Ta
_0.64
Nb
_0.36
:Li
_0.003
(KTN:Li), that demonstrate an index of refraction of across the entire visible spectrum. The sample has a natural-occurring room temperature phase that propagates visible light along its normal axis without significant diffraction or chromatic dispersion, irrespective of beam size, intensity, and angle of incidence.