Laser beam addressing

In this paper a laser beam addressed liquid-crystal light valve is described. Its writing speed is limited by the available laser power and by the laser scanning system, but it does have selective erase capability. This feature, which allows local erase and update of information on the screen, is important in large storage displays and is not available with present storage CRT s. 

E. A. Cunningham, A. G. Dewey and G. J. Sprokel, Absorbing Films for Reflective Laser-Beam-Addressed,... 

M. Hareng and S. Le Berre, Formation of Synthetic Images on a Laser-Beam-Addressed Smectic Liquid-Crystal Display, Elec. Letters 11 73 (1975). 

Fig. 23—A laser-beam-addressed thermo-optic liquid-crystal light valve (Ref. [134]).

A. Sasaki, T. Ishibashi, M. Inoda, K. Kawahata, Write-in speed of laser beam address in liquid-crystal large-scale display. Trans. Inst. Electron. Comm. Eng. 63-C, 368 (1980) (in Japanese)... 

The ability to separate the fiber-optic tip and sample by as much space as required makes Raman sampling extremely flexible. For example, 15-foot immersion probes to insert in the top of chemical reactors have been made. The laser beam travels down the 15-foot probe shaft, finally coming to a focus just outside of the optical window at the probe s tip. A photo of such a probe is shown in Figure 5.4(a). Non-contact probes could also be made to come to a focus at similar distances, but then the beam must be enclosed to address safety concerns. 

Therefore, heterogeneous catalysts present a greater potential for the application of HT and Combinatorial methods, because they involve diverse compositional phases that are usually formed by interfacial reactions during their synthesis, which in turn produce a variety of structural and textural properties, often too vast to prepare and test by traditional methods. In this respect the HT and Combinatorial methods extend the capabilities of the R D cycle, which comprises the synthesis, the characterization of physicochemical properties and the evaluation of catalytic properties. The primary screening HT method gives the possibility of performing a rapid test of hundreds or thousands of compounds using infrared detection methods [27-29]. Alternatively, a detection method called REMPI (Resonance Enhanced Multi Photon Ionization) has been used, which consists of the in situ ionization of reaction products by UV lasers, followed by the detection of the photoions or electrons by spatially addressable microelectrodes placed in the vicinity of the laser beam [30, 31]. 

The development of the laser has opened the possibility of addressing memories with optical beams, making it possible to benefit from the rather short access time associated with the short rate of beam modulation and deflection and from the large bit density associated with the ability to focus laser beams to diameters of the order of 1 pm. 

In general, laser writers offer some unique advantages. With multiple laser beams (up to 32 in some systems), these systems are capable of high throughput and are therefore considerably faster than their electron-beam-writer counterparts. They are also more accurate than electron-beam writers because they are more stable, a consequence of the facts that electrons are very sensitive to magnetic fields and also tend to scatter. The very small effective address unit is useful for fine adjustment of line widths on the mask, which makes it easier to implement optical proximity correction schemes in these masks than in masks produced from other mask writers. Furthermore, laser writers operating at 364-nm and... 

The critical propagation problems which are being addressed at the various research centres are Stimulated Raman scattering by air molecules thermal blooming, due to laser heating of the air electrical breakdown of the air, which could generate plasmas that attenuate the beam atmospheric turbulence, which could perturb the focusing of the laser beam. 

D. Maydan, H. Melchior and F. Kahn, Liquid Crystal Graphic Displays Thermally Addressed by Infrared Laser Beams, IEEE Conference Record of 1972 Conference on Display Devices,... 

If confined to a resonator, the wave has to obey the resonance boundary conditions the standing waves in the resonator are called modes. Particular functions U describe the different modes. Because of the nature of laser resonators, which normally are much longer than wide, one may conveniently split the description into longitudinal (often by convention the z-axis) and transverse (the x- and y-axes) components, or modes, with respect to the optical axis of the resonator. As it turns out, to a good approximation, one can use the longitudinal mode components to derive the resonance frequencies in the resonator these then are loosely addressed as longitudinal (frequency ) modes. The transverse mode components can be used to calculate the lateral intensity distribution of a laser beam in general one then speaks of transverse (intensity) modes. 

To conclude this section we address the phenomenon of the stimulated Raman effect and its application to molecular spectroscopy. Stimulated Raman scattering is experimentally different from normal Raman scattering, in that it is observed in the forward direction (the stimulated Raman photon emerges into a very narrow cone to the propagation direction of the laser beam propagation direction). But the effect is normally only observed for high-power laser radiation. 

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