Refractive multi-conical elements for cylindrical vector beam generation

Abstract

In this paper, it is proposed to use Brewster angle refraction on a conical surface to form an azimuthally polarized beam. After reflection from the conical interface of the two media, the azimuthally polarized beam is conically divergent. An azimuthally polarized beam has a vortical phase dependence. In order to collimate the output beam and make it plane-parallel, it is proposed to use one, two or three conical surfaces combined in one element. The outer surface is used to collimate the converted beam, which significantly distinguishes the proposed element from previously proposed approaches. We have named the refractive optical elements Volcone, Tetracone, and Tricone. The Volcone produces ring shape beam and the Tricone and Tetracone produce round shape beam. The polarization states of the rays when passing through the interface of the media, as well as polarization transformations using the proposed elements using our own developed ray tracing program taking into account polarization, are investigated. The description of the polarization state was carried out using Jones notation. The Volcone is fabricated by diamond turning, in which an internal conical cavity is made. The paper describes a method for calculating the path of beams through refractive conical elements, taking into account phase and polarization conversions. The Volcone is experimentally made of polymethyl methacrylate on a computer numerical control milling machine. The experiment with the Volcone demonstrates the effectiveness of the proposed element. We present Tricone geometry calculation for the following manufacturing.