Method and system for measuring number of topological charges of partially coherent vortex beam and whether topological charges are positive or negative

Abstract

The invention discloses a method and a system for measuring the number of the topological charges of a partially coherent vortex beam and whether the topological charges are positive or negative. Themethod includes the following steps: recording the light intensity of a to-be-measured partially coherent vortex beam; introducing three disturbances of different phase assignments to the to-be-measured partially coherent vortex beam; carrying out Fourier transformation on the to-be-measured partially coherent vortex beam after disturbance, and recording the light intensity of the Fourier plane after the three different phase assignments; getting a cross spectrum density function of the to-be-measured partially coherent vortex beam through inverse Fourier transformation according to the threedifferent phase assignments and the light intensity of the Fourier plane under the three different phase assignments; getting the complex coherent degree of the to-be-measured partially coherent vortex beam according to the cross spectrum density function and the light intensity of the to-be-measured partially coherent vortex beam; and drawing a phase distribution map of the complex coherent degree, wherein the number of coherent singular points in the phase distribution map is the number of topological charges, whether the topological charges are positive or negative is determined according to the rotation direction of phase change around the coherent singular points, the topological charges are positive if the rotation direction is anticlockwise, and the topological charges are negativeif the rotation direction is clockwise.

Description

technical field [0001] The invention relates to the field of optical measurement, in particular to a method and system for measuring the magnitude and sign of the topological charge of a partially coherent vortex beam. Background technique [0002] As an important branch of modern optics, singularity optics has attracted the attention of a large number of researchers at home and abroad. The so-called singularity refers to the point where certain parameters in the light field cannot be defined, such as the phase singularity proposed and defined by Nye and Berry. The most typical phase singularity is the vortex beam. Under the condition of complete coherence, the light intensity at the center of the vortex beam is zero, and the phase presents a spiral structure gradual change, and the phase of the crossing midpoint is uncertain, which is the phase singularity. [0003] Vortex beams have great application prospects in laser particle capture, micromanipulation, information enco...

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Problems solved by technology

At present, there is a lack of a method that can effectively measure the topological

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