Focusing properties of power order space-variant phase modulate Bessel-Gaussian vortex beam

Abstract

The purpose of this paper is to study the focusing properties of power order space-variant phase modulate the Bessel-Gaussian (BG) vortex beam, which is based on vector diffraction theory. Results show that under different power order of space-variant phase, the modulation of topological charge number and phase parameter have different evolution rules. Specifically, when power order n = 1, the position of the focal pattern will be arbitrarily adjusted on the X-axis by modulating the phase parameter C. Under the condition of n = 2, the focal spot will be expanded along y = -x with the increase of topological charge l. Meanwhile, by modulating C, two opposite phenomena of focal spot separation will be obtained. When n = 3, the increase of l will make the focal spot expand along the positive and negative directions of the Y-axis. Besides, increasing the value of C, the original focal spot intensity will converge to the X-axis, and a new intensity peak will be formed on the X-axis. A series of focal properties have been obtained as the power order space-variant phase introduced. These novel properties have potential applications in many fields such as particle trapping, particle movement and optical modulation related fields.