Optical loss visible region

Close to silica fibres are silicate fibres drawn from optical glasses. Silicate fibres are typically applicable in the visible spectral region. Their optical losses in the visible region usually reach much higher values than silica fibres - at least 102dB/km. On the other hand, the refractive index can be tailored in a large interval (from 1.5 for the BK-class to 1.95 for the... 

Optical fibres composed of plastics are also transparent in the visible spectral region but optical losses reach 102 - 103 dB/km13. Their refractive index varies from 1.35 to 1.6 depending on the kind of polymer used (e.g. polymethymethacrylate PMMA -1.49). The chemical resistance is much worse than that of silica fibres and thermal stability is incomparable. On the other hand, low temperature processes of plastic fibre preparation allow us mix the starting polymer with organic dyes which enables the production of luminescent fibres suitable e.g. for fluorescence-based sensing13. 

Evidence for the contribution of the CIO + BrO interaction is found in the detection and measurement of OCIO that is formed as a major product of this reaction, reaction (31a). This species has a very characteristic banded absorption structure in the UV and visible regions, which makes it an ideal candidate for measurement using differential optical absorption spectrometry (see Chapter 11). With this technique, enhanced levels of OCIO have been measured in both the Antarctic and the Arctic (e.g., Solomon et al., 1987, 1988 Wahner and Schiller, 1992 Sanders et al., 1993). From such measurements, it was estimated that about 20-30% of the total ozone loss observed at McMurdo during September 1987 and 1991 was due to the CIO + BrO cycle, with the remainder primarily due to the formation and photolysis of the CIO dimer (Sanders et al., 1993). The formation of OCIO from the CIO + BrO reaction has also been observed outside the polar vortex and attributed to enhanced contributions from bromine chemistry due to the heterogeneous activation of BrONOz on aerosol particles (e.g., Erie et al., 1998). 

In order to develop an integrated optical sensor, it has to be taken into account that the main material used in microelectronics is silicon, which absorbs at wavelengths below 1.12 xm. Then, the first step would be the design of waveguides that could operate in the visible region with acceptable absorption losses while keeping their single-mode behavior. 

DMF precludes using ESR to follow the polymerization because of high dielectric loss due to the solvent. However, the polymerization can be followed by optical density since the system is homogeneous and the monomer absorption does not interfere in the visible region. 

When single layers of clay minerals are dispersed in a polymer matrix to form a nanocomposite, a material optically clear in the visible region can be obtained, but with loss in the UV region (A < 250 nm) mostly due to scattering by layers of the clay mineral. The unique behavior of the nanoparticles when interacting with light leads to spedal applications such as UV and IR absorbers. 

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