The negative index of refraction of nonlinear chemical waves has become a recent focus in nonlinear dynamics researches. Theoretical analysis and computer simulations have predicted that the negative index of refraction can occur on the interface between antiwaves and normalwaves in a reaction-diffusion (RD) system. However, no experimental evidence has been found so far. In a recent study, Pro. Qi Ouyang and PhD candidate Xujin Yuan in School of Physics, PKU, successfully observed the negative refraction at the interface of normal wave (outwardly rotating spiral) and antiwave (inwardly rotating spiral) parameter region in the CIMA Reaction-Diffusion system experiment; and successful explanation has been made according to the competition mechanism of nonlinear wave.

In order to have wave refraction on the interface, chemical waves on one side of reaction medium should pass the interface and become the wave source in the other side of reaction medium. And antiwave with a lower frequency succeeds in competition. So only normal wave with a lower frequency can generate negative refraction at the interface. Both the experiment and numerical simulation are consistent with the theoretical analysis. The relevant results has published on recent (Xujin Yuan, Hongli Wang, and Qi Ouyang, Phys. Rev. Lett. 106, 188303 (2011)).