Abstract
Active planar optical devices that can dynamically manipulate light are highly sought after in modern optics and nanophotonics. The geometric phase derived from the photonic spin-orbit interaction provides an integrated strategy. Corresponding elements usually suffer from static functions. Here, we introduce an inhomogeneously self-organized anisotropic medium featured by photo-invertible chiral superstructure to realize geometric phase elements with continuously tunable working spectrum and light-flipped phase profile. Via preprograming the alignment of a cholesteric liquid crystal mixed with a photo-responsive chiral dopant, we demonstrate light-activated deflector, lens, Airy beam and optical vortex generators. Their polychromatic working bands are reversibly tuned in an ultra-broadband over 1000 nm covering green to telecomm region. The chirality inversion triggers facile switching of functionalities, such as beam steering, focusing/defocusing and spin-to-orbital angular momentum conversion. This work offers a platform for advanced adaptive and multifunctional flat optics with merits of high compactness, low loss and broad bandwidth.
Highlights
Active planar optical devices that can dynamically manipulate light are highly sought after in modern optics and nanophotonics
Cholesteric liquid crystal (CLC) is a liquid crystalline phase where the rod-like molecules self-assemble into a helical superstructure with periodic modulation of refractive index, forming a one-dimensional soft photonic crystal
The lightdriven CLC is fabricated by doping a nematic host with a righthanded compound R5011 and a left-handed azobenzene chiral molecular switch ChAD-3C-S, which exhibits excellent chemical stability and good solubility
Summary
Active planar optical devices that can dynamically manipulate light are highly sought after in modern optics and nanophotonics. We introduce an inhomogeneously self-organized anisotropic medium featured by photo-invertible chiral superstructure to realize geometric phase elements with continuously tunable working spectrum and light-flipped phase profile. Via preprograming the alignment of a cholesteric liquid crystal mixed with a photo-responsive chiral dopant, we demonstrate light-activated deflector, lens, Airy beam and optical vortex generators Their polychromatic working bands are reversibly tuned in an ultra-broadband over 1000 nm covering green to telecomm region. Namely Pancharatnam-Berry phase[1], derived from the photonic spinorbit interaction[2], provides an integrated candidate for functional planar apparatuses[3,4,5] It accompanies a space-variant conversion of polarization states and is usually achieved in inhomogeneous anisotropic media[6,7]. This work moves a steady step on the prospective way towards active multifunctional planar optics
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