Broadband optical vortex generation from patterned cholesteric liquid crystals

Abstract

Singular optics is an emerging field, in which an optical wave with a helical wavefront is handled for optical manipulation and nanofabrication. We present a method to generate optical vortices via reflection from cholesteric liquid crystals with planar alignment. Numerical and experimental results show that the device is operable at multiple wavelengths with theoretically high conversion efficiency (lossless) without requiring fine-control of retardation. Although the operational wavelength range is limited by the birefringence and helix pitch of the material, broadband operation is possible by expanding the reflection band width by either introducing a pitch distribution or stacking multiple devices.C0NTACT Hiroyuki Yoshida

Ultrabroadband gradient-pitch Bragg-Berry mirrors

“…Also, in contrast to Ref. [39], we notice that present study provides with behavior of the polychromatic beam shaping versus the incidence angle and in the far field, thus bringing a thorough overview of the optical properties of gradient-pitch Bragg-Berry optical elements. ACKNOWLEDGMENT This study has been carried out with financial support from the French National Research Agency (project ANR-15-CE30-0018).…”

Spin-to-Orbital Angular Momentum Mapping of Polychromatic Light

“…[18,19]. In particular, polychromatic optical vortex beam generation using "Bragg-Berry" mirrors [20][21][22][23][24] unveiled a promising option. However, as previously noticed in Ref.…”

Circularly-polarized, large-angle reflective deflectors based on periodically patterned cholesteric liquid crystals

“…Polarization holography enables easy control over the patterning period, and devices with periods as small as 0.84, 1.24, and 2.51 µm were fabricated, resulting in a maximum de ection angle of 48.9°at a wavelength of 640 nm. Because the operation wavelength of the device is determined by the pitch of the device, broadband devices can be fabricated by stacking several lms or by creating a pitch gradient [19]. Also, the helical structure leads to strong CP selectivity, with experimental contrast ratios of >300:1 being achieved.…”