FOCUSING PROPERTIES OF AN AXICON PAIR

The focusing properties of a so-called reflaxicon (a combination of a diverging and a converging axicon) are studied both theoretically and experimentally. Calculations of intensity distributions produced by th is system are made by evaluating the Kirchhoff-Fresnel diffraction int egral, first by means of an approximate technique, the stationary phas e method, then by a more exact numerical method. The calculations are presented for various planes along the axis of the axicons. The effect s of the presence of the supporting mount of the axicons and of some i mportant misalignments of the system on the distributions is also inve stigated. Experimental results of actual intensity distributions produ ced by focusing a near-fundamental Gaussian beam by such a system are also presented and are seen to be in fair agreement with numerical cal culations. Such calculations would be valuable in many applications fo r predicting important characteristics (e.g., peak intensity, length o f the focal line, degree of asymmetry) of the intensity distributions formed by optical systems containing an axicon pair as the focusing co mponent.