Abstract
Abstract Optical vortices carrying orbital angular momentum (OAM) have recently attracted increasing interest for providing an additional degree of freedom for capacity scaling in optical communications. The optical vortex generator is an essential component to facilitate OAM-enabled optical communications. Traditional devices face challenges of limited compactness, narrow bandwidth, and first-order OAM modes. Here, using the direct-binary search (DBS) optimization algorithm, we design, fabricate, and demonstrate a digitized subwavelength surface structure on silicon platform for the generation of wavelength-/polarization-/charge-diverse optical vortices. It features an ultra-compact footprint (∼3.6 × 3.6 μm2) and ultra-wide bandwidth (1480–1630 nm), supporting two polarizations (x-pol., y-pol.) and high-order OAM modes (OAM+1, OAM−1, OAM+2, OAM−2) with high purity of larger than 84%. The mode crosstalk matrix is measured in the experiment with favorable performance. When generating x-pol. OAM+1, x-pol. OAM−1, y-pol. OAM+1, and y-pol. OAM−1 mode, the crosstalk of the worst case is less than −14 dB. When generating OAM+1, OAM−1, OAM+2, and OAM−2 mode, the crosstalk between any two OAM modes is less than −10 dB, and the lowest crosstalk is about −17 dB. In addition, we also show the possibility for generating much higher-order OAM modes (e.g. OAM+3, OAM−3, OAM+4, and OAM−4) with the digitized subwavelength surface structure. The wavelength-/polarization-/charge-diverse optical vortex generator enables the full access of multiple physical dimensions (wavelength, polarization, space) of lightwaves. The demonstrations may open up new perspectives for chip-scale solutions to multi-dimensional multiplexing optical communications.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: 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.