Broadband Multichannel Optical Vortex Generators via Patterned Double-Layer Reverse-Twist Liquid Crystal Polymer

• Published in: Crystals (Basel) Vol. 10; no. 10; p. 882
• Main Authors: Zhang, Hanqing, Duan, Wei, Wei, Ting, Xu, Chunting, Hu, Wei
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-10-2020
• Subjects: Angular momentum; Arrays; beam shaping; Broadband; Communications systems; Design; Efficiency; geometric phase; Glass substrates; Light; Liquid crystal polymers; Liquid crystals; Optical communication; orbital angular momentum; Phase transitions; Signal transmission; Vortex generators; Wavelength division multiplexing
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst10100882

The capacity of an optical communication system can be greatly increased by using separate orbital angular momentum (OAM) modes as independent channels for signal transmission and encryption. At present, a transmissive OAM mode generator compatible with wavelength division multiplexing is being highly pursued. Here, we introduce a specific double-layer reverse-twist configuration into liquid crystal polymer (LCP) to overcome wavelength dependency. With this design, broadband-applicable OAM array generators are proposed and demonstrated. A Damman vortex grating and a Damman q-plate were encoded via photopatterning two subsequent LCP layers adopted with oppositely handed chiral dopants. Rectangular and hexagonal OAM arrays with mode conversion efficiencies exceeding 40.1% and 51.0% in the ranges of 530 to 930 nm, respectively, are presented. This provides a simple and broadband efficient strategy for beam shaping.