Abstract
As one of the diffractive optical elements, circular Dammann grating has shown its excellent versatility in practical applications. The electrically switchable Dammann grating has been extensively investigated; however, the research on the optically tunable circular Dammann grating has received less attention and reports on this subject have been insufficient in the past decade. In this paper, three-order and eight-order binary-phase liquid crystal circular Dammann gratings with two mutually orthogonal photo-induced alignments in every two adjacent alignment domains, fabricated by a micro-patterned liquid crystal polymer phase mask, are proposed to generate annular uniform-intensity patterns in the far field. A simple maskless optical tuning of an eight-order liquid crystal circular Dammann grating is demonstrated by controlling the polarization of an ultraviolet light as well as the energy dose. The proposed liquid crystal circular Dammann gratings with high efficiencies and desirable uniformities exhibit outstanding optical as well as electrical tunabilities, enabling the widespread prospective applications in adaptive photonic chips stimulated flexibly by only light or by the combination of light and electric field.
Highlights
Liquid crystal (LC) diffractive optical elements (DOEs) [1,2,3,4,5] (e.g., liquid crystal (LC) gratings, LC lenses, LC airy beam generators, etc.) with attractive features such as excellent electro-optical properties and compact size have inspired the launch of substantive explorations and efficient endeavors in both academia and industry
Ge et al proposed a blue-phase (BP) LC Dammann grating [15] based on two alternating domains with isotropic refractive index and electric-field-induced extraordinary refractive index, which manifested the properties of fast response and polarization independence, but exhibited a crucial flaw of a high driving voltage of ~180 V
We present optically and electrically tunable binary-phase LC circular Dammann grating (CDG) based on a two-step photoalignment technique, which can experimentally generate equal-intensity rings with a uniformity of up to 0.0765 and an diffraction efficiency approaching 80%
Summary
Liquid crystal (LC) diffractive optical elements (DOEs) [1,2,3,4,5] (e.g., LC gratings, LC lenses, LC airy beam generators, etc.) with attractive features such as excellent electro-optical properties and compact size have inspired the launch of substantive explorations and efficient endeavors in both academia and industry. LC arrangements was fabricated through a multi-exposure photoalignment process, whose maximum zeroth and first/second diffraction orders could be separately achieved by adjusting the analyzer Such an LC CDG was characterized by a slow response time, polarization dependence, and optical instability due to the azo dye material employed in their experiment. Once the proposed LC CDG is fabricated by a liquid crystal polymer (LCP)-based amplitude photomask, no mask at all is needed in the dynamic optical tuning process, and the angle between the easy axes of the LC molecules in odd zones and even zones is merely controlled by the polarization of the ultraviolet (UV) light as well as the energy dose. Based on these abovementioned features, the proposed light-driven LC CDG could exploit extensive prospective applications [20,21,22,23,26,27], such as optical data storage, optical coding, communication, etc
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