Waveguide filtering technique

This chapter will focus on one-dimensional physical models, and on the techniques known as waveguide filters for constracting very simple models that yield expressive soimd synthesis. First weTl look at the simple ideal string, and then refine the model to make it more reahstic and flexible. At the end we will have developed models that are capable of simnlating an interesting variety of one-dimensional vibrating objects, inclnding stiff stmctures such as bars and beams. 

In this chapter we will shortly summarize the nonlinear optical properties of macromolecular systems and some of the main experimental techniques for their optical characterization. Some basic optoelectronic patterns will be reported in order to give a brief account of the advances in the realization of active waveguide systems and telecommunication devices based on organic materials. The main optoelectronic devices based on nonlinear optical properties of chromophores in polymeric and hybrid matrices will be illustrated. In particular Mach-Zehnder modulators, microring resonators, switches and wavelength filters will be reviewed. 

A polymeric waveguide-type wavelength filter based on a Bragg grating has been fabricated using a simple nanoimprint technique by Ahn et al. [170] They obtained a maximum reflection of 25 dB at 1,569 nm and the bandwidth at 3 dB was about 0.8 nm for a device length of 1.5 cm. 

The filters were designed for operation at 530 nm, and preliminary estimates for monolayer thickness I and refractive index Wq for both materials were obtained by ellipsometry, reflectometry and waveguiding techniques (Table 3.2). Reasonable agreement was obtained between these techniques, particularly for the polysiloxane. The thickness and refractive index data were then refined to give more accurate initial layer thickness f and refractive index values (Table 3.3) by taking account of the dispersion of the materials over the wavelenth range 400-800 nm (Fig, 3.12). 

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