Search Results (5)

Tunable circular devices made of liquid crystals or other materials, like lenses, axicons, or phase plates, are often constrained by limitations in size, tunability, power, and other parameters. These constraints restrict their use and limit their applicability. In this review, a thorough study of the use of light’s orbital angular momentum in the manufacturing of liquid crystal (LC) devices is presented. Twisted light fosters the simultaneous optimization of most critical parameters. Experimental demonstrations of the unmatched performance of tunable LC lenses, axicons, and other elements in parameters such as lens diameter (>1″), power and tunability (>±6 diopters), fill factor (>98%), and time response have been achieved by reversible vortex generation created by azimuthal phase delay. This phase delay can eventually be removed within the optical system so that lens performance is not affected. Full article

Optofluidics is a constantly developing research area that combines known technologies from chemistry and photonics. Various systems have been created, which are used in biology and chemistry as well as in other subjects. The combination of materials such as polydimethylsiloxane (PDMS) and liquid crystal (LC) provides a number of possibilities to create functional structures. The properties of LC allow systems to be developed in PDMS, e.g., lenses with different focal lengths depending on the polarization of light or multiplexers have been proposed. Appropriately controlling LC molecule orientation is a crucial element in creating tunable systems. The motivation of this research is to determine the proper arrangement of an electrode array to control the orientation of liquid crystal molecules and thus the refractive index. The performed tests allowed the initial parameters to be determined to produce LC:PDMS structures with a periodic orientation of LC molecules. As the channel sizes have to be micrometer-scale, a proper electrode arrangement has to be developed. The materials from which electrodes can be created are also limited due to PDMS properties as well as the size of the channels. The plan is to create a tunable LC:PDMS structure with LC molecules in a periodic reorientation, which would allow the system to function as a tunable Bragg grating. It would be the first achievement of this kind, and it would open up new possibilities for the combination of liquid crystal and PDMS in photonic systems. Full article

Active lenses with focal tunable properties are highly desired in the modern imaging systems from the visible to the microwaves. In this paper, we demonstrate a terahertz (THz) lens with electrically switchable focal length. It is composed of a large-birefringence liquid crystal (LC) layer infiltrating a dielectric metasurface. When the birefringence of LC is tuned with an external bias, the phase shift of a single meta-unit will change. With parameter sweep using the finite-different time-domain (FDTD) simulation method, meta-units with varying geometries are optimized to achieve a focal length switchable metalens. The numerical results show that the focal length can be switched between 8.3 mm and 10.5 mm at bias OFF and ON states, respectively, which is consistent with the design. A feasible fabrication procedure of the lens is further discussed. Such a device can be designed beyond the THz band to the visible or the microwaves, and may be widely applied in integrated imaging systems. Full article

Emerging applications requiring light beam manipulation, such as high-efficiency sunlight concentrators for solar cells, switchable micro-lens arrays for autostereoscopic displays, tunable lenses for augmented reality goggles, auto-focusing spectacles, and smart contact lenses, mostly depend on one or more active optical components with the desired and controllable beam modifying functionalities, preferably manufactured at relatively low cost. Recent progress in research on components based on the combination of liquid crystals (LCs) and various polymer micro-structures is reviewed in this paper. It is found that such components can address the demands appropriately and have the potential of paving the way for large-scale applications of active optical beam shaping components. Full article

We demonstrate a physical model of photoalignment and photopatterning based on rotational diffusion in solid azo-dye nanolayers. We also highlight the new applications of photoalignment and photopatterning in display and photonics such as: (i) liquid crystal (LC) E-paper devices, including optically rewritable LC E-paper on flexible substrates as 3D E-paper, as well as optically rewritable technology for photonics devices; (ii) photonics LC devices, such as LC Switches, polarization controllers and polarization rotators, variable optical attenuators, LC filled photonic crystal fiber, switchable diffraction grating; (iii) patterned micro-polarizer array using photo-alignment technology for image sensor; (iv) electrically tunable liquid crystal q-plates; (v) electrically switchable liquid crystal Fresnel lens; (vi) liquid crystal optical elements with integrated Pancharatnam-Berry phases. We are sure, that in the field of (LC), the main point is no longer display research, but new photonic applications of LC are emerging in telecommunication, fiber optical communication systems, sensors, switchable lenses, LC light converters and other LC photonics devices. Full article