Impact of Liquid Crystals in Active and Adaptive Optics

Abstract

Active and dynamic modulation of light has been one of major contributions of liquid crystals to Optics. The spectrum of application range from signposting panels to high resolution imaging. The development of new materials is the key to continued progress in this field. To promote this we will present in this paper recent uses of liquid crystals as active or adaptive modulators of light. Besides, we will reflect on their current limitations. We expect with this to contribute to the progress in the field of liquid crystals and thus the development of new useful tools for Active and Adaptive Optics.

An overview of LC polyazomethines with aliphatic–aromatic moieties: Thermal, optical, electrical and photovoltaic properties

“…Conversely, one of the main disadvantages of LC polymers is the fact that they do not exhibit obvious and easily detected mesophases as in the case of small organic LC compounds. Presently, LC polymers are mainly tested as (i) NLO materials, (ii) membranes with penetrability created by an electrical field, (iii) temperature detectors or (iv) materials for nanoelectronics [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Among the various types of LC polymers, two main groups of thermotropic polymers are indicated: 1) polymers with mesogenic groups in the main chain, e.g., polyesters or polyamides (Kevlar) and 2) polymers with mesogenic groups in the side chain, e.g., polyolefins or polysiloxanes.…”

Electro-Optical Switching of Dual-Frequency Nematic Liquid Crystals: Regimes of Thin and Thick Cells

“…Liquid crystal (LC) materials have become cornerstones of modern devices, with applications ranging from displays [1] to adaptive optics [2] to, more recently, radio-frequency (RF) and microwave and millimeter wave frequencies (MMW) electronics [3]. Their ability to change the orientation of molecules under the action of a biasing electric field along with an anisotropy of their properties not only revolutionized the display industry but opened a new frontier in the development of tunable and reconfigurable devices for non-display applications.…”

“…Thick liquid crystal cells are characterized by a higher phase shift according to Equation (1). At the same time, their time response is very slow because it is a quadratic function of the cell gap [1][2][3]. To simultaneously achieve both thick and fast switching liquid crystal cells, several methods have been proposed: One is a polymer-liquid crystal composite [8,9], which allows for obtainment a rapid switching of thicker liquid crystal layers, but with the loss of phase retardation.…”

“…where V-is a driving voltage, V th is a threshold voltage, γ is a rotational viscosity, K is an elastic constant (with single elastic constant approximation), and d is a cell gap. Equations (2) and 3do not capture all electro-optical features, such as grayscale transitions [16]. However, they are useful for the analysis of experimental results.…”

Innovative technology for optical and infrared astronomy

“…In themselves, they show great promise for improving the direct detection and characterization of exoplanets, but they also demonstrate a new paradigm for the development of customized optical devices. Liquid crystal spatial light modulators (SLMs) have been used for low performance wavefront correction (Love 30 ) and it is also possible to generate micro-lens arrays using liquid crystals, to enable both wavefront sensing and correction to be done with the same device (Arines 31 ). Liquid crystal SLMs have the disadvantage of exhibiting chromatic phase correction, but a whole new class of devices that could be applied in astronomy is likely to emerge from the very active field of metamaterial research.…”