Negative refraction at the interface of uniaxial anisotropic media

In this paper, negative refraction at the interface of uniaxial crystal is discussed in detail. It is pointed out that dispersion relation is more useful to narrate the extraordinary light refraction in uniaxial crystal, especially in the case of negative refraction. Generally, the negative refraction only exists within a small incident angle around 10°. The negative refraction here is very different from that in left-handed material where wave vector and energy flux are anti-parallel.