Circular Airy beam with an arbitrary conical angle beyond the paraxial approximation

Abstract

An arbitrary conical angle is introduced to the circular Airy beam (CAB) beyond the paraxial approximation, with the possibility to demonstrate its obvious tunability for the propagation properties of the CAB. The expressions are worked out to describe the electric field based on the angular spectrum representation, where a closed-form approximation of the angular spectrum is derived by using the stationary phase method. It is found that the nonparaxiality becomes obvious for large conical angles. In particular, the field intensity at the focal point can be enhanced about 10 times with respect to the conventional CAB by simply tailoring the conical angle. Meanwhile, the longitudinal component of the field is enhanced and gradually plays a leading role as the conical angle is increased. Moreover, the longitudinal gradient of the field intensity is also enlarged for large conical angles, suggesting a stable optical trapping for microparticles, which may find many applications in optical manipulations.