Thin film switch, optical

PLZT in thin and thick film form can be exploited for a variety of applications including optical signal switching and modulation. An attraction of PLZT is its high electro-optic coefficient and in consequence low drive voltages to perform a particular function (c.f Table 8.1). The PLZT thin film switch described below is included to illustrate principles rather than because of very significant commercial importance. 

The fabrication process of vanadium oxide (VO2) has also been studied using RBS/C. Since optieal and electrical properties of VO2 are dramatically changed at 68°C due to phase transition, VO2 is regarded as one of the candidates for thermally activated electronic or optical switching devices for optieal fibers or sensors. To obtain the desired properties, the development of the fabrication process for very thin films, without crystalline defects on various substrates, is required. Single-crystalline VO2 thin films on (0001) plane of a sapphire substrate have been synthesized by a laser ablation method. The quality of VO2 was examined by X-ray diffraction and RBS/C method. The eleetrieal resistanee and the optical transmittance of the VO2 film were measured under inereasing and deereasing temperatures. At a temperature of 68 °C, an abrupt transition of resistanee from metal to... 

Magnetic thin films of nickel-iron (usually deposited at an 80 20 composition by weight) exhibit a number of unusual properties, which have led to many experimental and theoretical studies, as well as to impoitant applications in binary storage and switching, magnetic amplifiers, and magneto-optical Kerr-effect displays,... 

Switching systems based on photochromic behavior,I29 43,45 77-100 optical control of chirality,175 76 1011 fluorescence,[102-108] intersystem crossing,[109-113] electro-chemically and photochemical induced changes in liquid crystals,l114-119 thin films,170,120-1291 and membranes,[130,131] and photoinduced electron and energy transfer1132-1501 have been synthesized and studied. The fastest of these processes are intramolecular and intermolecular electron and energy transfer. This chapter details research in the development and applications of molecular switches based on these processes. 

Fig. 8.18 Total internal reflection thin-film optical switch (after K. Wasa el al. (1984) J. Lightwave Techn. IEEE., LT-2, 710-14).

There are various thin-film optical switch principles based on interference, diffraction or total internal reflection (TIR). The TIR switch, the essentials of which are shown in Fig. 8.18, depends on TIR of light passing from one medium to another of lower refractive index. TIR occurs for small differences in refractive indices when the angle of incidence approaches 90°, i.e. for light almost parallel to the surface of the material with the lower refractive index. 

ICP thin films were used as driving electrodes for polymer-Dispersed Liquid-Crystals (PDLC) display devices. Liquid-crystalline-based display devices, which are commonly made of a liquid-crystal compound sandwiched between two substrates coated with a conducting layer of indium tin oxide (ITO), whose substitution with ICP electrodes could improve the optical and mechanical properties of the display devices. On the way to all-organic displays, PDLC sandwiched between two plastic substrates coated with ICP layers are promising devices for paper-like displays for electronic books which require flexibility, lightness, and low-power consumption. The electro-optical characteristics (transmission properties, drive voltages and switching times) of the PDLC devices depend on the nature of the ICP substrate used [13]. 

The modem silicon-based microelectronics led to the miniaturization of electronic devices. However, delays caused by metallic intercoimec-tions became a bottleneck for the improvement of their performances. One possible solution of this problem is to use optical intercoimections for the transfer of information, and, therefore, silicon compatible materials and devices that are able to generate, guide, amplify, switch, modulate, and detect light are needed. Rare earth silicates with luminescent rare earths and compatibility with silicon may be a good choice for these applications (Miritello et al., 2007). Miritello et al. presented the study on nanocrystalline erbium silicate thin films fabricated on silicon/silica substrates. The obtained films exhibit strong photoluminescence emission around 1540 nm with room temperature excitation by 488 ran Ar laser. 

Most of the phenomena described in this monograph on photoreactive organic thin films are based on the isomerization of units deliberately built into molecules, molecular assemblies, or polymers. Most especially, the spectroscopic and isomerization behavior of these units determines the switching and triggering properties of the photoreactive systems and devices. Information storage and nonlinear optical properties, as well as photo-control of equilibria and of polymer, membrane, and other properties are exploited in applications. 

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