Abstract
The axis tilt of light beam in optical system would introduce the dispersion of orbital angular momentum (OAM) spectrum. To deal with it, a two-step method is proposed and demonstrated. First, the tilt angle of optical axis is identified with a deduced relation between the tilt angle and the variation of OAM topological charges with different reference axes, which is obtained with the help of a charge coupled device (CCD) camera. In our experiments, the precision of measured tilt angle is about 10−4rad with topological charges of −3~3. With the measured angle value, the additional phase delay due to axis tilt can be calculated so that the dispersion of OAM spectrum can be corrected with a simple formula while the optical axis is not aligned. The experimental results indicate that the original OAM spectrum has been successfully extracted for not only the pure state but also the superposed OAM states.
Highlights
Since orbital angular momentum (OAM) was characterized as a new freedom of lightwave by Allen, et al in ref. 1, it has been attracted much research interest and shown its potential on various applications
For real applications, there may be misalignment between the optical axis of incident light beam and that of optical system so that the pure OAM state would transform to the superposition of some OAM states, which is known as the dispersion of OAM spectrum[11, 12]
Our method to deal with inclined optical axis of light beam carrying OAM has been demonstrated
Summary
Since OAM was characterized as a new freedom of lightwave by Allen, et al in ref. 1, it has been attracted much research interest and shown its potential on various applications. Et al have deduced the relationship of the dispersed OAM spectrum versus the tilt angle and lateral displacement Based on such analytical formulation, the misalignment can be extracted from the OAM spectrum, which can be obtained from several coefficients one by one with the help of an optical correlator. The original OAM spectrum of a pure OAM state and a superposition of several OAM states can be well extracted according to our experimental results At last, since both calculating the tilt angle and correcting the OAM spectrum are based on analytical formulae, these procedures can be automatically and fast done with a computer while there is no iteration required
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
