Simulation of Laser Beam in Focal Region of High-NA Asphere

In high-NA focusing situations, the vectorial nature of light plays a non-negligible role. To demonstrate such effects, a high-NA aspherical lens is employed to focus a collimated linearly polarized Gaussian beam, and the asymmetry of the focal spot is investigated. By examining the electromagnetic field components in the focal plane, it can be found that the asymmetry is caused by a relatively strong Ez component.