Negative Refraction in Photonic Crystal Prisms
An intriguing property of the left-handed material is negative refraction. The optical properties of materials that are transparent to electromagnetic (EM) waves can be characterized by an index of refraction. Given the direction of the incident beam at the interface of vacuum and the material, the direction of the outgoing beam can be determined using Snell�s formula. All naturally available materials possess a positive refractive index. In lefthanded materials EM waves bend negatively and consequently a negative index of refractive index can be assigned to such materials without violating Maxwell�s equations. This negative bending allows considerable control over light propagation and opens the door for new approaches to a variety of applications from microwave to optical frequencies. We have demonstrated neagative refraction by a metallic photonic crystal.