Nonlinear films

Figure 5. Optimization of the cross-section for guided wave second harmonic generation. Phase-matching occurs between two dissimilar modes and the overlap integral is optimized by causing the interference effects to occur in linear regions of the waveguide only. For the case of a single nonlinear film, interference effects occur as the field product is integrated over the thickness dimension.

Another directional influence on the short film is the nonlinear film. The nonlinear feature film that I refer to takes two forms the structural nonlinear film,... 

The nonlinear film is marked by a number of characteristics. From the point of view of resolution, there is none. The form is totally open-ended. There are multiple main characters but they don t share a goal or a dilemma. There may or may not be a plot. Because the characters don t have apparent goals, there is nothing for the plot to work against and so plot in the nonlinear film is background, no more important than dialogue or another information track. 

It may even be useful to think of the nonlinear film as a series of short films about the individual characters who inhabit the narrative. What pulls the stories together may be the voice of the filmmaker or it may be a dilemma the characters share. (The half-dozen characters of the Sprecher sisters 23 Conversations About One Thing, all find themselves living in New York. They share location but differ in their philosophies of living. How fate and the city interplay to challenge those philosophies is the core of each character s story.)... 

Nonlinear (fynamic processes such as episodic and preferential flow, hinneling and divergence of flow pa, transient flow behavior, nonlinearity, film flow along fracture suites, intrafracture water dripping, entrapped air, fracture-matrix interaction, and pore-throat effects. 

If the material is thin (i.e., in nematic liquid crystal fdm), the problem of optical propagation is greatly simplified. In its passage through such a nonlinear film, the laser beam is only phase modulated and suffers negligible amplitude change. In other words, the transmitted far-field intensity pattern is basically a diffraction pattern of the incident field, with the nonlinear film playing the role of an intensity-dependent phase screen. 

Figure 11.11. Nonlinear transverse phase shift and diffraction of a laser beam by a thin nonlinear film.

Another approach is to use the LB film as a template to limit the size of growing colloids such as the Q-state semiconductors that have applications in nonlinear optical devices. Furlong and co-workers have successfully synthesized CdSe [186] and CdS [187] nanoparticles (<5 nm in radius) in Cd arachidate LB films. Finally, as a low-temperature ceramic process, LB films can be converted to oxide layers by UV and ozone treatment examples are polydimethylsiloxane films to make SiO [188] and Cd arachidate to make CdOjt [189]. 

Rasing Th 1998 Nonlinear magneto-optical studies of ultrathin films and multilayers Noniinear Optios in Metais ed... 

Vollmer R 1998 Magnetization-induced second harmonic generation from surfaces and ultrathin films Nonlinear Optics in Metals e6 K H Bennemann (Oxford Clarendon) pp 42-131... 

PPQs possess a stepladder stmcture that combines good thermal stabiUty, electrical insulation, and chemical resistance with good processing characteristics (81). These properties allow unique appHcations in the aerospace and electronics industries (82,83). PPQ can be made conductive by the use of an electrochemical oxidation method (84). The conductivities of these films vary from 10 to 10 S/cm depending on the dopant anions, thus finding appHcations in electronics industry. Similarly, some thermally stable PQs with low dielectric constants have been produced for microelectronic appHcations (85). Thin films of PQs have been used in nonlinear optical appHcations (86,87). 

LB films of CO-tricosenoic acid, CH2=CH—(CH2)2qCOOH, have been studied as electron photoresists (26—28). A resolution better than 50 nm could be achieved. Diacetylenic fatty acids have been polymerized to yield the corresponding poly (diacetylene) derivatives that have interesting third-order nonlinear optical properties (29). 

Serious attempts to use LB films in commercial appHcations include the use of lead stearate as a diffraction grating for soft x-rays (64). Detailed discussion on appHcations of LB films are available (4,65). From the materials point of view, the abiHty to build noncentro symmetric films having a precise control on film thickness, suggests that one of the first appHcations of LB films may be in the area of second-order nonlinear optics. Whereas a waveguide based on LB films of fatty acid salts was reported in 1977, a waveguide based on polymeric LB films has not yet been commercialized. 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

For a monolayer film, the stress-strain curve from Eqs. (103) and (106) is plotted in Fig. 15. For small shear strains (or stress) the stress-strain curve is linear (Hookean limit). At larger strains the stress-strain curve is increasingly nonlinear, eventually reaching a maximum stress at the yield point defined by = dT Id oLx x) = 0 or equivalently by c (q x4) = 0- The stress = where is the (experimentally accessible) static friction force [138]. By plotting T /Tlx versus o-x/o x shear-stress curves for various loads T x can be mapped onto a universal master curve irrespective of the number of strata [148]. Thus, for stresses (or strains) lower than those at the yield point the substrate sticks to the confined film while it can slip across the surface of the film otherwise so that the yield point separates the sticking from the slipping regime. By comparison with Eq. (106) it is also clear that at the yield point oo. 

Thin polymeric films have important industrial apphcations (e.g., as protective coatings, lubricants, adhesives, dielectric or nonlinear optic devices, etc.) and pose many fundamental problems of film stability [1,2,4]. An important question, therefore, is whether these films break up and spontaneously dewett the substrate, resulting in the formation of droplets. The... 

Fig. 8-la. The effect of a nonlinear background on the analysis for silver. Simple subtraction of adjacent background gave inversion observable on curve 1 near ordinate axis. Allowance for variation of background with wavelength gave the more reliable curve 2. (We are indebted to the Eastman Kodak Co. for the films and the results plotted as abscissas.)... 

Pandey, A. K. and Pratap, R., Coupled Nonlinear Effects of Surface Roughness and Rarefaction on Squeeze Film Damping in MEMS Structures," 7. Micromech. Microeng., Vol. 14, 2004, pp. 1430-1437. 

---