Focusing characteristics of chirped phase-modulated Lorentz-Gaussian vortex beams.

This work presents a thorough investigation of the focusing characteristic of chirped phase modulated Lorentz-Gaussian (LG) vortex beams based on the vector diffraction theory. The results show that changing the first-order chirp parameter can effectively adjust the size of the focusing spot, and the distance between focusing spots can also be controlled. The second-order chirp parameter can control the up-and-down movement of the optical chain in the focusing region. Simultaneously, the length of the focusing spots can be accurately changed by modulating the waist width . In addition, the influence of integer topological charge number on controlling the size of an optical dark trap is discussed in detail. And fractional topological charge number can control the rotation of focus peak and the number of optical dark traps. Potential applications of these findings include optical shape and capture, optical particle transmission, and contemporary medical care.