Electrooptic materials applications

Since this chapter is focused on electrooptic materials and two-photon absorption, we will not consider measurement techniques for y and y(31 in detail, but refer the interested reader to Ref. [19]. In this section, we will briefly describe some of the techniques that have been used for the measurement of the two-photon cross-section, d. We first recall that the 2PA behavior of a molecule is characterized by a spectrum entirely analogous to a one-photon absorption (1PA) spectrum. Although, from the point of view of an application at a particular wavelength, measurements of d at only that wavelength may contribute to a figure-of-merit for that application, more generally, to understand structure-property relationships, it is helpful to acquire 2 PA data over as wide a frequency range as permitted by the lasers available and by the onset of 1PA. 

This is certainly the most advanced potential application of FLCPs. Taking advantage of the processability of FLC polymers, Idemitsu Kosan Co. has fabricated a large-area, static-driven display (12x100 cm) and a dynamically driven simple matrix display (13x37 cm) [7, 19]. The performance of these two demonstrators is summarized in Table 8. The electrooptic material used was plasticized polyoxyethylene XVIII (Fig. 26). 

Agullo-Lopez, R, Cabrera, J.M., and Agullo-Rueda, F. (1994) Electrooptics Phenomena, Materials, and Applications, Academic Press, London. Gives a very detailed description of aU aspects of electrooptic materials. Two of the chapters cover applications. It also provides information about how electrooptic coefficients are determined experimentally. 

Much of this early effort dealt with modulator technology that is considered too slow (1-100 kilohertz) for high-speed applications such as optical interconnection and memory read/write. This includes modulators based on electrooptic effects in ferroelectric liquid crystals (ELCs) and in a ceramic containing lead, lanthanum, zinc, and titanium (PLZT). These electrooptic materials are bonded in some fashion to Si circuits to create hybrid SPAs. 

Applications, especially those in analytical chemistry (e.g. bio-, photo- or electrochemical sensors) [17, 18] have currently been developed, as has the preparation of photochromic, thermochromic, luminescent or electrooptical materials [19-24],... 

Preliminary studies of the stability of organic electrooptic materials to high energy (gamma ray) radiation and particles (protons) carried out by Lockheed Martin (Palo Alto) and by researchers at the Air Force Research Laboratory (Wright Patterson Air Force Base) suggest that space application of polymeric electrooptic materials should proceed without problems. 

The main limitation to general deployment of organic electrooptic materials is that they have been optimized to this point in time for applications at telecommunication wavelengths. Inorganic materials such as lithium niobate are still the materials of choice for applications at visible wavelengths. Such inorganic modulators are likely going to continue to dominate the laboratory market for modulators to be used with research laser systems. 

Avnir, D Braun, S Lev, 0 Levy, D and Ottolenghi, M. (1994) Organically doped sol-gel porous glasses chemical sensors, enzymatic sensors, electrooptical materials, luminescent materials and photochromic materials, in Sol-Gel Optics Processing and Applications... 

PM spectra and their decays in DOO-PPV films and dilute solutions, we conclude that the primary excitations in DOO-PPV films are also singlet excitons [26]. The long excitonic lifetime and a corresponding high PL quantum efficiency [27] indicates that DOO-PPV is a high quality polymer material, which is very suitable for electrooptics and laser action applications [28],... 

We recognize that there are applications in two- and three-dimensional waveguides (12,13) which do not have the same criteria of phase-matching as in simple crystals or that one may just as well be interested in screening these materials for the related electrooptic performance by the simple SHG powder method. (It has been shown for several organic materials that although the electro-optic and SHG x tensors are in principle unequal, due to dispersion and due to the possible contribution of atomic and molecular distortions... 

Thermotropic cholesterics have several practical applications, some of which are very widespread. Most of the liquid crystal displays produced use either the twisted nematic (see Figure 7.3) or the supertwisted nematic electrooptical effects.6 The liquid crystal materials used in these cells contain a chiral component (effectively a cholesteric phase) which determines the twisting direction. Cholesteric LCs can also be used for storage displays utilizing the dynamic scattering mode.7 Short-pitch cholesterics with temperature-dependent selective reflection in the visible region show different colors at different temperatures and are used for popular digital thermometers.8... 

LiNbOj is a widely used ferroelectric crystal with various applications in the nonlinear optics and integrated optics (10). Another attractive material for 10 devices is LiTaOs. Its electrooptic (EO) and nonlinear (NL) coefficients are comparable to those of LiNbOj, and its photorefractive damage threshold is more than an order of magnitude higher than that of LiNbOj in the visible range. 

Approximately ten years ago, it was first reported by Haertling and Land (jj that optical transparency was achieved in a ferroelectric ceramic material. This material was, in reality, not just one composition but consisted of a series of compositions in the lanthanum modified lead zirconate-lead titanate (PLZT) solid solution region. The multiplicity of compositions, each with different mechanical, electrical and electrooptic properties has led to a decade of study in defining the chemical and structural nature of these materials in understanding the phenomena underlying their optical and electrooptic properties and in evaluating the practicality of the large number of possible applications (2-12),... 

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