Shutter, electrooptic

Modulators are needed to convert electrical signals into optical amplitudes or phase modulations. Polymeric waveguides may be more compatible with integrated optics owing to processing considerations, and will be much cheaper to manufacture. Routing switches, electrooptic shutters, and amplitude modulators are imponant components for optical communications networks. Directional couplers, mode sorters, and Mach-Zender interferometers (Figure 2) are representative of the specific device mechanisms. These devices can op-... 

The answer to this question has become even more important with the advent of modern liquid crystal display technologies, that are based on reliable and technologically controllable surface alignment of liquid crystals, used in a variety of electrooptic devices, such as liquid crystal displays, light modulators, optical shutters, switches, holographic systems, etc. 

A special class of materials that is also ferroelectric are electrooptic ceramics. Materials such as lanthanum-modified lead zirconate titanate (PLZT) produce excellent electrooptic devices. These polycrystalline ceramics exhibit voltage-variable behavior—that is, they can be switched from optically transparent to opaque by the application of voltage. Most of these devices, which are used for shutters, modulators, and displays, are processed by hot pressing to full density. Experiments in many laboratories are being carried out to tape-cast these materials into thin sheets. The main problem encountered to date has been the ability to sinter to full density. The use of nanosized powders has helped in this regard. The ability to tape-cast large sheets could open a wide variety of applications for these materials. 

Tremendous activity [33] has characterized the field of research on polymer-dispersed liquid crystals (PDLCs) which are potentially useful for a variety of electrooptical applications including light shutters and switchable windows, displays, and other devices. These materials consist of micrometer-size nematic droplets dispersed in a polymer matrix and their optical response is based on the electrically controlled light-scattering properties of the droplets. 

Optical shutters utilize the properties of quadratic electrooptic materials as shown in Fig. 3.53. Switching from zero field to the field required for half-wave retardation results in a light shutter. If the electrooptic material is placed between crossed polarizers, polarized... 

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