Transparent spectral range

In order to improve the evaluation in the range where the cosine function is quite insensitive, an additional phase shift is introduced by placing a retarder in the reflected beam. Usually an internal-reflection prism is employed to produce a phase shift somewhere in the range from 30° up to 150°. Since the refractive index does not change much within the transparent spectral range, the phase shift produced by such a retarder is almost achromatic (Korte et al., 1988). For limited spectral ranges multilayer devices are also suitable (Rdseler and Molgedey, 1984). Provided a phase retardation of exact 90° is applied, one finds with the quotient Q 2 of 7 (45°) and 7 (135°)... 

When both bordering media are transparent, one can apply transmission spectroscopy in polarized radiation (Section 2.1) or, when there is a difference in the refractive indices of these media, the ATR method and IRRAS. For each type of solid-solid interface, except for the metal-metal interface, one can study the layers in the contact zone by IRRAS or ATR in the transparent spectral range of one of the media in the system. To choose the technique with which to investigate dielectric (semiconductor)-liquid, dielectric (semiconductor)-semiconductor, and dielectric-dielectric interfaces, several factors must be considered, including the region of transparency of the media under study and the relationship between their refractive indices. If the medium with the largest refractive index is the most transparent, one should use the ATR method otherwise IRRAS is more appropriate. 

Material Transparency Spectral range Damage Relative Reference... 

The physical and chemical properties of any material are closely related to the type of its chemical bonds. Oxygen atoms form partially covalent bonds with metals that account for the unique thermal stability of oxide compounds and for typically high temperatures of electric and magnetic structure ordering, high refractive indexes, but also for relatively narrow spectral ranges of transparency. 

So the function of special optical fibres for sensing is to produce a sensitive response to changes in the fibre surroundings. Such requirements on optical hardware as durability to the analyte, transparency (i.e. minimum optical losses) in a wide spectral range and common availability should be pointed out. Related to the these requirements, the choice of the fibre material as well as of the fibre coating and fibre structure belong to fundamental tasks in the design of fibre-optic sensors. 

When an intense pulse of monochromatic laser light is focussed on a transparent liquid or solid, there is an emission of white light over a wide continuous spectral range. This process is known as self-phase modulation . We will not consider its physics. For our purpose it is important to note its photochemical implications. On the one hand, this pulse of white light can be used to provide a probe light in ps and fs flash photolysis (sections 8.1 and 8.2). On the other hand, it can be a source of stray light in some luminescence measurements. This comes as a surprise to many users of lasers for luminescence kinetics measurements, but it is an unavoidable problem. 

Transmission arrangements for SI applications follow the classical transmission layout, with a radiation source on one side of a sample and the SI analyser on the other side. The information depth is either constant or can easily be measured, which is an advantage in particular for (semi-)quantitative analysis. Although occasionally applied, such transmission systems suffer from the restriction that the sample must either be freely suspended or rest on a support that is transparent in the investigated spectral range. 

LP-CVD ZnO Total and diffuse transmittance (TT and DT) for boron-doped LP-CVD ZnO films are shown in Fig. 6.17 as a function of the film thickness. TT remains superior to 85% in the spectral range [500-900 nm] for ZnO layers with d < 1.5 pm. Because 15% of the incident light is reflected due to the change of refractive index at the air/ZnO and glass/air interfaces, this means that, for d < 1.5 pm, the absorption of the LP-CVD ZnO B itself is too low to be measured by the spectrometer. TT is reduced by only about 5% for a thickness d = 3 pm. This means that 3 pm-thick ZnO films still have a high transparency, in spite of their relatively high thickness. For A > 900 nm,... 

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