Electro-optic characteristics

Depending on composition PLZT ceramics display one of three major types of electro-optic characteristic, i.e. memory , linear or quadratic . These are shown in Fig. 8.11, together with the corresponding hysteresis loops, and are discussed briefly below. 

A typical PLZT exhibiting memory characteristics has the composition 8/65/35 and a grain size of about 2 /an. The general approach to obtaining a hysteresis loop is referred to above the intermediate remanent polarization states (e.g. Prl etc. in Fig. 8.12) necessary to generate the An versus normalized polarization plots (Fig. 8.11 (a)(ii)) are obtained as follows. 

The reduced polarization states /Vh Pr2 etc. are due partly to 180° domain reversals, which do not affect the birefringence, and partly to changes in other domains (71° and 109° in rhombohedral crystals) which reduce both the polarization and the birefringence. The relation between birefringence and remanent polarization is therefore complex and, as indicated in Fig. 8.11, zero remanent polarization does not necessarily correspond to zero birefringence. 

The existence of intermediate polarization states is not of great practical use because the effect of an applied field depends on both its exact mode of application and the previous treatment of a specimen. Reproducible results can be achieved by having an electrode and circuit arrangement that allows the 

Compositions that display the quadratic Kerr effect lie close to the ferroelectric rhombohedral-tetragonal boundary (Fig. 8.8) 9.5/65/35 is typical. At room temperature they are essentially cubic, but the application of a field enforces a transition to the rhombohedral or tetragonal ferroelectric phase, and the optical 

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Figure 18. Electro-optic characteristics of an FM/AM-TN LCD with AgPd nanoparticles (5CB-AgPd 0.1%) where the frequency of operating voltages is used as a parameter. (Reprinted from Ref [236], 2006, with permission from IEEE.)...

Fig. 8.11 Hysteresis and electro-optic characteristics of the three main types of PLZT (a) memory (b) linear (c) quadratic (after G.H. Haertling (1971) J. Am. Ceram. Soc., 54, 303).

The electro-optical characteristics of multiplexed STN-LCDs exhibit a significant dependence on temperature. This has to be compensated in order to avoid variations of the optical performance of the display with temperatures. This can be achieved electronically. However, this problem can also be solved by the use of optically active, chiral dopants. The capacitive threshold voltage of a chiral nematic mixture depends on the pitch of the mixture ... 

Analysis of the electro-optical characteristics of GH-LCDs showed that for all types of guest-host chiral nematic phase change effects the contrast is greatest when... 

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 data reported in this section demonstrate the advantage of investigatii rigid-chain polymers by combining FB and EB becau the combination of the results of these two methods provides complete information on the structural and electro-optical characteristics of these molecules. 

The molecular structure of selected V-shaped oligothiophenes is shown in Scheme 5, while the corresponding electro-optical characteristics are reported in Table 2. The luminance vs. voltage plots and the electroluminescence spectra of the devices fabricated with 9,10 and 11 as the active materials, are shown in Figure 4. 

Electroluminescence from green to near-IR has been demonstrated for oligothiophene-5,5-dioxides [63]. Figure 4.8 shows the electroluminescence spectra of compounds 3-5 (whose molecular shuctures are depicted in Scheme 4.2), 8 and 9 (whose molecular structures are depicted in Figure 4.6) and 11, whose molecular structure is shown in Figure 4.8, The electro-optical characteristics of all compounds are reported in Table 4.12. 

Table 4.12 Electro-optical characteristics of oligothiophene-S,S-dioxide 3-5, 8-9 and 11. rp. PL efficiency EA electron affinity x turn-on voltage LumM. luminance max andcp external EL efficiency...

M. Oh-e and K. Kondo, Electro-optical characteristics and switching behavior of the in-plane switching mode, Appl Phys. Lett., 67, 3895 (1995). 

S. H. Lee, S. L. Lee, and FI. Y. Kim, Electro-optic characteristics and switching principle of a nematic liquid crystal cell controlled by fringe-field switching, Appl. Phys. Lett., 73, 2881 (1998). 

Schade, O.H. 1948. Electro-optical characteristics of television systems. RCA Review 9 5-37, 245-286, 490-530, 653-686. 

Lu Yang, Wei Jie, Shi Yang, et al. Effects of fabrication condition on the network morphology and electro-optical characteristics of polymer-dispersed bistable smectic A liquid crystal device. Liq. Cryst. 40 no. 5 (2013) 581-588. 

K. Yang, K. Kim, D. Kim, and B. C. Choi, The effects of conditions for polymerization induced phase separation processes on the electro-optic characteristics of polymer dispersed liquid crystals. Mol. Cryst. Liq. Cryst. 498,83-88 (2009). 

In display applications, the twist cell is placed between two polarizers. They can either be oriented parallel or perpendicular to each other, the switching modes of these two configurations being complementary. The electro-optic characteristics of nematic twist cells have been studied by several authors [56—59]. Applications will be treated in Part III of this book. 

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