Optical properties waveguiding

Chemical properties of deposited monolayers have been studied in various ways. The degree of ionization of a substituted coumarin film deposited on quartz was determined as a function of the pH of a solution in contact with the film, from which comparison with Gouy-Chapman theory (see Section V-2) could be made [151]. Several studies have been made of the UV-induced polymerization of monolayers (as well as of multilayers) of diacetylene amphiphiles (see Refs. 168, 169). Excitation energy transfer has been observed in a mixed monolayer of donor and acceptor molecules in stearic acid [170]. Electrical properties have been of interest, particularly the possibility that a suitably asymmetric film might be a unidirectional conductor, that is, a rectifier (see Refs. 171, 172). Optical properties of interest include the ability to make planar optical waveguides of thick LB films [173, 174]. 

Guided mode calculations were also carried out to compare the sensor response of several waveguide systems. In these simulations a model molecular monolayer is represented by a 2-nm thick layer with a refractive index of n 1.5. The optical properties of this model layer are typical of a dense layer of organic molecules on a substrate1 41, and are a reasonable approximation for a streptavidin protein layer bound to a biotinylated surface, the experimental model system we use to characterize our sensors. The ambient upper cladding was assumed to be water with a refractive index of n 1.32. For all examples, the lower cladding was assumed to be Si02 with an index of n 1.44. In the simulations, the effective index of... 

These characteristics show that perfluorinated polyimides are promising materials for waveguides in integrated optics and optical interconnect technology. The thermal, mechanical, and optical properties of perfluorinated polyimides can be controlled by copolymerization in the same manner as partially fluorinated polyimides. ... 

The main characteristic of non-guided radiation devices is that the recognition element or the chemical membrane is not physically integrated in any waveguide structure. Variations of the membrane optical properties lead to variations of the transmission of a non-guided light beam (Fig. 4a). 

We should make it clear from the start that we define the word "image" in the very broad sense of a spatial variation of the optical properties of a sample in such a way as to cause a desired modification of an optical beam passing through the sample. Our definition thus includes a number of optical elements or devices, such as holographic lenses or optical waveguide circuits, that superficially bear little resemblance to more familiar absorption images. 

A basic waveguide structure, which is sketched in Fig. 1, is composed of a guiding layer surrounded by two semi-infinite media of lower refractive indices. The optical properties of the stmcture are described by the waveguiding layer refractive index Hsf, and thickness t, and by the refractive indices of the two surrounding semi-infinite media, here called (for cover) and (for substrate). Application of Maxwell s equations and boundary conditions leads to the well-known waveguide dispersion equation [6] ... 

Absorbance calculations in the above configuration are implemented by introducing the absorbing species as a small perturbation to the initial configuration (see Fig. 2). Either a small extinction coefficient is introduced to the optical properties of the cover material (as shown in Fig. 3) or a thin absorbing layer is introduced between the waveguide and the cover (Fig. 4). A critical assumption for the... 

Next, we consider the absorbance due to a dichroic adlayer adsorbed onto the waveguide surface with the optical constants as indicated in Fig. 4. The optical properties of the dichroic layer are described by the different extinction coefficients k, ky, and k in each Cartesian direction. The reflectance of the waveguide-adlayer-cover system follows the analysis found in Macleod [9] with the anisotropic coefficients taken from Horowitz and Mendes [10]. By assuming a thin and weakly absorbing adlayer, the following expressions are obtained for the absorbance as measured through a guided mode at each polarization [8] ... 

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