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Optical Engineering • Open Access

Eight-connected contour method for accurate position detection of optical vortices using Shack–Hartmann wavefront sensor
Author(s): Hongxin Huang; Jia Luo; Yoshinori Matsui; Haruyoshi Toyoda; Takashi Inoue

Paper Abstract

We propose a simple method of realizing an accurate position detection of phase singularities in an optical vortex (OV) beam using a Shack–Hartmann wavefront sensor (SH-WFS). The method calculates circulations which are the discrete contour integrals of phase slope vectors measured by the SH-WFS and then determines the accurate positions of the singular points by calculating the centers-of-gravity with a fixed window size around the local peak of the circulation distribution. We use closed paths that connect the centers of eight-connected, instead of 2×2-neighboring lenslet apertures for calculating the circulations. Both the numerical analysis and proof-of-principle experiment were performed to confirm the measurement accuracy. In experiments, the positions of singular points in OV beams generated by a liquid-crystal-on-silicon spatial light modulator were measured. The root-mean-square error of the position measurement was approximately 0.09 in units of the lens size of the lenslet array used in the SH-WFS. We also estimated the topological charges of the singular points being detected based on the peak circulations, and the results agreed well with theoretical ones. The method achieves both rapid implementation and sublens-size spatial resolution detection and is suitable for applications that require real-time control of OV beams.

Paper Details

Date Published: 25 June 2015
PDF: 8 pages
Opt. Eng. 54(11) 111302 doi: 10.1117/1.OE.54.11.111302
Published in: Optical Engineering Volume 54, Issue 11
Show Author Affiliations
Hongxin Huang, Hamamatsu Photonics K.K. (Japan)
Jia Luo, Zhejiang Univ. (China)
Yoshinori Matsui, Hamamatsu Photonics K.K. (Japan)
Haruyoshi Toyoda, Hamamatsu Photonics K.K. (Japan)
Takashi Inoue, Hamamatsu Photonics K.K. (Japan)

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