| Summary: | Analytically discussed is the evolution properties of optical vortices superimposed by Gaussian backgrounds. A kind of Tornado-like pattern is obtained after linear propagations, when the Gaussian background is wide enough compared with optical vortices. The same structures are exhibited by the intensity and the phase for the Tornado-like pattern, and the latter can be regarded as a clockwise rotation of the former. The gradient force exerted by the Tornado-like pattern upon micro-particles is investigated from the application point of view in optical tweezers. Compared to conventional optical vortices, the Tornado-like pattern shows the superior performance on the trapping ability for microparticles.
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