Abstract
Three-dimensional diffraction patterns of monochromatic electromagnetic waves contain moving line singularities where the magnitude of the transverse field is zero, and its direction is therefore indeterminate. They are called disclinations, by analogy with the corresponding linear features in liquid crystals. A disclination in a vector wave is a natural generalization of a dislocation in a scalar wave. Where the scalar wave approximation in optics predicts a dislocation, or interference null, the full vector theory reveals a double helix structure: a disclination line in the electric field and another in the magnetic field winding around each other with a spacing of order (wavelength/2π). A perturbing plane wave causes this composite structure itself to become coiled. When there is a ‘polarization effect’ in the diffraction pattern a disclination in the electric field becomes a moving helix or, more generally, a coiled coil. As it moves it sweeps out a surface on which the polarization is everywhere linear. In optical experiments this observable surface is the most significant effect of disclinations. In general, however, the disclinations constitute elements of structure of the electromagnetic field, and their arrangement thus provides an effective way of describing the three-dimensional geometry of even very complicated diffraction fields, for example of microwaves.
Reference17 articles.
1. x <0. I t will be noted th at provided th a t kx = 0 the
2. a.
3. Berry M. V. 1978 J .Phys. A 11 27-37.
4. Berry M. V. 1981 In Physics of defects Les Houches Session X X X V 28 July-29 August 1980 (ed. R. Balian M. Kleman &J.-P. Poirier) pp. 453-543. Amsterdam New York Oxford: North Holland.
5. The elliptic umbilic diffraction catastrophe
Cited by
164 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献