title: Design, fabrication, and evaluation of a multilevel spiral-phase Fresnel zone plate for optical trapping.
abstract: A compact optics configuration for the generation of donut beams for trapping atoms at the micrometer scale using a multilevel spiral-phase Fresnel zone plate (FZP) and a semiconductor laser is proposed. A FZP is designed and a multilevel spiral phase is integrated into it. A spiral-phase FZP with a radius of 1 mm and with more than 1300 half-period zones is designed with multiple angular levels for integer and fractional topological charges, and the device is fabricated using electron-beam lithography direct writing. The performance of the device is evaluated, and the generation of symmetric and asymmetric donut beams is successfully demonstrated.
authors.affiliation: Department of Electrical Engineering, Indian Institute of Technology Madras, Chennai 600036, India.
authors.forename: A
authors.initials: A
authors.lastname: Vijayakumar
authors.forename: Shanti
authors.initials: S
authors.lastname: Bhattacharya