%0 Journal Article
%T Interferometry with Vortices
%A P. Senthilkumaran
%A Jan Masajada
%A Shunichi Sato
%J International Journal of Optics
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/517591
%X Interference of optical beams with optical vortices is often encountered in singular optics. Since interferometry makes the phase observable by intensity measurement, it brings out a host of applications and helps to understand the optical vortex. In this article we present an optical vortex interferometer that can be used in optical testing and has the potential to increase the accuracy of measurements. In an optical vortex interferometer (OVI), a lattice of vortices is formed, and the movement of the cores of these vortices is tracked when one of the interfering beams is deformed. Instead of multiple vortices in an OVI, an isolated single vortex also finds applications in optical testing. Finally, singularity in scalar and vector fields is presented, and the relation between them is illustrated by the superposition of these beams. 1. Introduction Phase singularities in light waves appear at points or lines in a beam cross section, where the phase of the wave changes abruptly [1¨C6]. When this abrupt phase change occurs along a line, it is called edge dislocation, and when it occurs at a point, it is called a screw dislocation. Screw dislocation type phase singularity is also called an optical vortex. The singular point with undefined phase and zero amplitude forms the vortex core. A wavefront with optical vortex (OV) has a characteristic helical geometry. As the vortex beam propagates, this zero amplitude point draws a curve in space. The helical wavefront winds about this dark thread of amplitude. The helix may be left- or right- handed, and accordingly the vortex is considered to possess positive or negative topological charge. Optical vortices possess a number of interesting features. On the flip side, they can cause stagnation problems in phase retrieval where wavefront geometry is reconstructed [7, 8] and in diffractive optics [9, 10]. On the positive side, since the seminal work published by Nye and Berry [1], hundreds of papers have been published on various aspects of the OVs. Large number of papers is devoted to optical vortex applications. In a vortex coronagraph an optical vortex lens is used as a filter that enables detection of a feeble star in bright background [11¨C13]. Optical vortices are useful in optical tweezers with dark traps [14¨C17]. They are useful in fluorescence microscopy where the STED (stimulated emission depletion) pulse is used for dumping the fluorescence response of the molecule located outside the dark core of the optical vortex [18¨C20]. Vortices are useful in collimation testing and in the detection of elevation and
%U http://www.hindawi.com/journals/ijo/2012/517591/