Multi-twist retarders: broadband retardation control using self-aligning reactive liquid crystal layers

Abstract

We report on a family of complex birefringent elements, called Multi-Twist Retarders (MTRs), which offer remarkably effective control of broadband polarization transformation. MTRs consist of two or more twisted liquid crystal (LC) layers on a single substrate and with a single alignment layer. Importantly, subsequent LC layers are aligned directly by prior layers, allowing simple fabrication, achieving automatic layer registration, and resulting in a monolithic film with a continuously varying optic axis. In this work, we employ a numerical design method and focus on achromatic quarter- and half-wave MTRs. In just two or three layers, these have bandwidths and general behavior that matches or exceeds all traditional approaches using multiple homogenous retarders. We validate the concept by fabricating several quarter-wave retarders using a commercial polymerizeable LC, and show excellent achromaticity across bandwidths of 450-650 nm and 400-800 nm. Due to their simple fabrication and many degrees of freedom, MTRs are especially well suited for patterned achromatic retarders, and can easily achieve large bandwidth and/or low-variation of retardation within visible through infrared wavelengths.

ON-SKY PERFORMANCE ANALYSIS OF THE VECTOR APODIZING PHASE PLATE CORONAGRAPH ON MagAO/Clio2

“…, where d i stands for layer thickness, f i for the twist of a layer, and i for the layer number (see Komanduri et al 2013). This recipe is used to build our coronagraph with our custom fast-axis pattern and also a test article with the same parameters but a fixed fast axis.…”

Lyot-plane phase masks for improved high-contrast imaging with a vortex coronagraph

“…For example, with a bandwidth of 20%, the inner and outer boundaries of the dark hole are expanded and contracted by about 10%, respectively. Achromatic phase masks may be fabricated by direct writing of multilayer liquid crystals ( Komanduri et al 2013;Otten et al 2014). The width and shape of the off-axis PSF are very important for imaging applications.…”

Broadband 1×2 liquid crystal router with low thermal dependence for polymer optical fiber networks

“…Each LC cell of the proposed router has its own electrodes (6 electrodes in total). Therefore, it would be necessary to use electrodes optimized over the range from 400-700 nm or compact structures in order to reduce the losses [27].…”

“…from being x-polarized to be y-polarized. The most common PR scheme consists of a single TN cell, while achromatic or broadband designs include TN cells, retardation plates and/or homogenous nematic (HN) LC cells [24][25][26][27][28].…”

“…Some designs are based on multiple TN cells, as the one reported in [26] with experimental T y Z92% in the VIS using two TN cells of 20 μm thickness. Other designs are based on a TN between HN cells [25,28] or fixed retardation plates [24,27]. There have also been reported PRs based on ferro-electric LCs with a bistable operation and an almost achromatic response [18].…”