Generating optical vortex with large topological charges by spiral phase plates in cascaded and double-pass configuration

Spiral phase plate (SPP), as a kind of optical component for generating optical vortex (OV), has the ability to convert the traditional non-singular beams into OV with spiral phase distribution. However, due to the demanding of machining accuracy, the production of high quality SPPs with large topological charges (TCs) is usually complicated and expensive. An approach to generate OV with large TCs based on low-order SPPs is presented. In the proposed scheme, the addition of TCs is realized by cascading multiple SPPs, and the double-pass configuration is employed to implement doubling of TCs. Based on the combination of cascaded and double-pass configuration, an OV with TCs as high as 28 is generated, using two SPPs of TCs 6 and 8, respectively. The method of alignment and the alignment deviation is discussed.