Producing true-color rainbows with patterned multi-layer liquid-crystal polarization gratings

Instrumentatio

Vector-apodizing phase plate coronagraph: design, current performance, and future development [Invited]

Instrumentatio

On the History of Reactive Mesogens: Interview with Dirk J. Broer

Prof. Dirk Broer is among the pioneers and most active researchers in the field of stimuli-responsive liquid crystal (LC) networks. He is the inventor of reactive mesogens, a class of materials with far-reaching implications in liquid-crystal photonics and in the triumph of LC-based shape-shifting polymers. Together with his team, Prof. Broer continuously produces innovative solutions for controlling and programming new functions into soft responsive materials. Through this Interview, it is our great pleasure to gain insights into his personal views on both the past and the future, and to learn about the historical turns that led to the development of reactive mesogens as well as his vision on where the field is heading

An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram

An anisotropic hologram is combined with an edge-lit planar waveguide to produce an improved liquid crystal display (LCD) backlight. A holographic-polymer dispersed liquid crystal material is exposed to a slanted one-dimensional interference pattern to produce an anisotropic Bragg transmission grating with strong diffraction for P-polarized light and very low diffraction for S-polarized light. While the hologram is recorded at a UV wavelength (351 nm), light at visible wavelengths propagating from the waveguide edge is redirected toward the normal direction. The emission is collimated, polarized, and unidirectional, effectively integrating several functions that are typically embodied in separate optical films in a conventional LCD

Polarization Gratings: A Novel Polarimetric Component For Astronomical Instruments

Polarization gratings (PGs) have been recently been developed for ultraefficient liquid crystal displays, nonmechanical optical beam steering, and telecommunication devices at optical and near-infrared wavelengths (0.4-2.0 μm). A PG simultaneously acts as both a spectroscopic and polarimetric disperser for circularly polarized light. With the use of a quarter-wave retarder (or analog) to convert linearly to circularly polarized light, these devices can be used as linear polarimetric analyzers. PGs offer high throughput and high levels of birefringence and can currently be constructed inexpensively to diameters of 150 mm, and development projects are in progress to double that size. In this article we report on the characterization of a PG sample at mid-infrared wavelengths (2-40 μm), including the birefringence, throughput, spectral response, and cold cycling survivability. We discuss these devices in the context of astronomical polarimetry, especially as the polarimetric components for a conceptual study of a SOFIA-based polarimeter. © 2010. The Astronomical Society of the Pacific

The Single-mode Complex Amplitude Refinement (SCAR) coronagraph

We present the monochromatic lab verification of the newly developed SCAR coronagraph that combines a phase plate (PP) in the pupil with a microlens-fed single-mode fiber array in the focal plane. The two SCAR designs that have been measured, create respectively a 360 degree and 180 degree dark region from 0.8–2.4λ∕D around the star. The 360 SCAR has been designed for a clear aperture and the 180 SCAR has been designed for a realistic aperture with central obscuration and spiders. The 360 SCAR creates a measured stellar null of 2–3 × 10−4, and the 180 SCAR reaches a null of 1 × 10−4. Their monochromatic contrast is maintained within a range of ±0.16λ∕D peak-to-valley tip-tilt, which shows the robustness against tip-tilt errors. The small inner working angle and tip-tilt stability makes the SCAR coronagraph a very promising technique for an upgrade of current high-contrast instruments to characterize and detect exoplanets in the solar neighborhood