Applications laser addressed devices

Mixtures of mesogens often exhibit spread transition temperatures which manifest themselves as biphasic regions for some applications, such as laser-addressed devices, this feature is undesirable. To overcome this problem, several mixtures have been specifically developed [11] to have narrow temperature range transitions from Sm to N and from N to isotropic, i. e., S6 in Table 2. 

Optically bistable devices are of considerable interest for information storage and processing applications. Bistable Fa-bry-Perot resonators [104] may be useful as dynamic optical memories as well as elements for information processing. Optically sensitive alignment layers [62], as well as a wide variety of laser addressable materials [105-107] promise the use of liquid crystals as materials for optical information storage. 

Finally, we will describe the properties of phosphors needed for devices in which the electron excitation is generated by electric fields. This includes LED s, Laser LEDs and electroluminescence (EL). We will first address the CRTs used for specialty applications. 

This article addresses key aspects of diffractive optics. Common analytical models are described and their main results summarized. Exact numerical methods are applied when precise characterization of the periodic component is required, whereas approximate models provide analytical results that are valuable for preliminary design and improved physical insight. Numerous examples of the applications of diffractive optical components are presented. These are optical interconnects, diffractive lenses, and subwavelength elements including antireflection surfaces, polarization devices, distributed-index components, and resonant filters. Finally, recording of gratings by laser interference is presented and an example fabrication process summarized. 

Both CdS and a-Si have been successfully used as the photocondoctor 45°-twisted nematic layers and, on an experimental basis, ferroelectric layers have been used for the liquid crystal. CCD structures and silicon vidicon microdiode arrays have been used in place of the photocon-ductive layer. The device is useful both when the write beam is coherent (for example, a scanned laser) and when it is incoherent (for example, a CRT). In the latter case, the SLM can be used as an incoherent-to-coherent converter. The CRT-written device has also found application as a projection display. There exists a very large potential market for optically addressed SLMs in a variety of optical processing applications and for projection displays. 

Dyes that dissolve in the liquid crystal and have high extinction coefficients at the laser emission wavelength are required. If the device is for projection applications, the dye should not absorb at the wavelengths that may be used to project the final image-infrared dyes and lasers are well suited for this. The dye will experienee very high temperatures for very short time periods when addressed by the laser and should therefore be stable to heat and light. Dichroic dyes appear to give smaller spot widths than isotropic dyes, and so dyes with a modest order parameter (5=0.5-0.6) are desirable [23]. 

An improvement of this device has been described in which the nematic-cholesteric mixture is replaced by a smectic material. Thermal writing induces the change of the smectic from the perpendicular to a scattering texture. Unlike the nematic-cholesteric materials, selective erasure is possible with the smectic device. The thermal writing is too slow for television-rate applications because of the thermal inertia of the glass-liquid-crystal system. With a laser-beam power of 20 mW, addressing speed is approximately 10 elements/sec for the smectic device. In the projection mode, the resolution is 50 lines/mm at a contrast ratio of approximately 10 1. 

Although this article addresses general aspects of microworld control, the primary emphasis is towards molecular or chemical control. It was pointed out in the introduction that the field of microworld control has broadened out to encompass a variety of other applications of equal significance. This list includes the creation of quantum computers, controlled solid-state electronics, atom lasers, novel quantum electronic devices and optical materials, as well as possibly other applications. Each of these subjects has its own community of scientists, and unfortunately, there has been little interaction between the groups involved. Some of these communities are actually larger than those involved in chemical reaction control efforts. For example, a quantum... 

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