Young's Diagnostics of Phase Singularities into Polychromatic Light Fields

摘要

Two original approaches for the diagnostics of phase singularities (such as optical vortices or screw dislocations of a wave front) based on the Young-Rubinowicz model of diffraction phenomena are represented. Both techniques are implemented without using a separate reference wave, as in common interferometric techniques. That is whytheyare veryconvenient for analysis of spatially coherent polychromatic fields. The first technique is based on the use of an opaque strip as the diffraction device. Bending Young's interference fringes produced bythe edge diffraction waves from two rims of the strip within the geometrical shadow region reflect helicityof a wave front, so that the direction and magnitude of bending correspond directlyto the sign and the modulus of topological charge of the optical vortex, respectively. This technique is practicable for diagnostics of isolated polychromatic vortices, such as "rainbow" Laguerre-Gaussian modes, where the condition of mutual spectral purityis satisfied automatically. Another technique is based on the use of a half-plane diffraction. A knife-edge serves as the source of a virtual reference wave, which interferes with the tested field within the directlyilluminated region. One observes typical interference forklets near the geometrical shadow boundary, which detect optical vortices. This technique is more applicable to diagnostics of phase singularities in polychromatic speckle fields.