An ‘electromagnetic wiggler’ originating from refraction of waves at the side edge of a Bragg reflector

Abstract

Calculations are reported which predict that light incident on the side edge of a Bragg reflector can show varied and unusual refraction behaviour, including a rapid transition from positive to negative refraction. Although under certain conditions negative refraction can occur, it is concluded that perfect lensing based on it is unlikely to be realised in practice. However, it is shown that light incident obliquely on the structure can be made to propagate normal to the interface after refraction while exhibiting lateral oscillations of its Poynting vector, an effect that could possibly find application in an ‘electromagnetic wiggler’. It is also shown that negative group velocity rather than negative effective mass is required for the observation of the negative refraction, and in the case of low refractive index contrast, negative refraction occurs only when the size of the illumination spot exceeds a critical value, which is inversely proportional to the contrast of the refractive indices.