Comparative simulation of spiral zone plates with a relief from silica glass and silver

Abstract

Comparative simulation of optical vortices generation by spiral zone plates with a relief from silver and silica glass using a frequency depended finite difference time domain method. The right circularly polarized Gaussian pulse was used as incident light. An analysis of the Umov-Poynting vector, amplitude and phase distributions in the focal plane shows was the presence of complex optical vortices with an inverse energy flow in its’ centre. Influence of the amplitude spiral zone plate relief height on energy backflow is studied. Comparison of simulation results for two types of spiral zone plate confirms the possibility of using the amplitude analogue instead of the phase zone plate since it is simpler to manufacture.