More recently, the generalized multiple-prism dispersion theory has been extended to include positive and negative refraction.

The researchers believe this produced a negative refraction of 0.6.

In addition, acoustic metamaterials have realized negative refraction for sound waves.

Using metamaterials Berkeley researchers been able achieve negative refraction; effectively creating a cloaking device.

In 2005, the first near field superlens was demonstrated by N.Fang et al., but the lens did not rely on negative refraction.

They are produced as metamaterials for research on building antennas with negative refraction.

This gives rise to the desired results of negative refraction.

A negative refraction could someday lead to an optical microscope that could make out tiny biological structures like individual viruses.

However, negative refraction is not the effect that creates invisibility-cloaking.

But, negative refraction does not occur in these systems, and not yet realistically in Photonic crystals.