Optical transmittance spectrum

Fig. 16. Optical transmittance spectrum of a typical DNQ—novolac resist. ( ), The transmittance of a 1 ftm film after coating. (-), the transmittance of...

Fig. 7 shows the optical transmittance spectrum of the entire ZnO-TFT in the wavelength range between 200 nm and 2500 nm (including the glass substrate with 1.1 mm thickness). The average optical transmission in the visible part of the spectrum is 80% while at 550 nm (maximum sensitivity for the human eye) it is 85%, which indicates that transmission losses due to the ZnO-TFTs in comparison with the uncoated glass substrate are negligible... 

The transmittance spectrum of a titania nanotube-film (transparent) on glass is shown in Fig. 5.33. The optical behavior of the Ti02 nanotube-arrays is quite similar to that reported for mesostructured titanium dioxide [133], The difference in the envelope-magnitude encompassing the interference fringe maxima and minima is relatively small compared to that observed in titania films deposited by rf sputtering, e-beam and sol-gel methods [134],... 

Smaller values of are obtained for interferometers operated in a double-beam mode, since the moveable mirror must be left stationary for a fraction of the cycle time to allow the detector to stabilize each time the beam is switched from the sample to the reference position. With an optical null grating spectrometer the chopper is used not only to modulate the beam but also to alternate the beam between sample and reference channels. Thus, it takes approximately the same time to measure a transmittance spectrum using a double beam optical null spectrometer as it takes to measure a single-beam spectrum with the same S/R. Hence, for this type of spectrometer may be assigned a value of 2. 

Optical polished Nd Lu20j transparent samples were used for the spectroscopic measurement. Linear optical transmittance of 3at.%Nd Lu203 transparent ceramic was measured in region of 190-1100 nm on a UV. VIS/NIR spectrophotometer (Lambda 2, Perkin Elmer, U.S.A.). The fluorescence spectrum of the specimen was recorded by a spectrofluorometer (Fluorolog-3, Jobin Yvon, Edision, U.S.A.) equipped with a Hamamatsu R928 photomultiplier tube. A 808nm continuous wave diode laser was used as the excitation source. 

Step 4. The approximate values of n and k of the solution are used as starting values in the exact Fresnel equations (see Section 9.2.2) to calculate the theoretical transmittance spectrum. This spectram is computed as the ratio of the simulated spectrum, corresponding to the analyte solution, and the simulated background spectrum of the pure solvent. Both spectra are calculated using a thin layer of solution, situated between the two optical windows, as the model of the transmission cell. In one case, the layer is represented by the optical constants of the pure solvent and in the other case it has the optical constants of the solution, calculated using Eqs. (40) and (41). 

Step 5. The attenuation coefficients of the analyte k, are perturbed at each wavelength and used to calculate the refractive indices using Eq. (39). Both optical constants are then used to calculate the optical constants of the solution using Eqs. (40) and (41). The attenuation coefficients of the solution are later used to calculate another theoretical transmittance spectrum using the approach described in Step 4. 

Fig. 9.14 Optical constants of pyridine, calculated from the transmittance spectrum of a 0.1 M solution in D2O. n is the refractive index, k is the attenuation coefficient. Taken with permission from Refs. [36] and [40].

Fig. 10. Optical transmittance of the PANI-CSA/PMMA blend (10% PANI-CSA in PMMA wM) (o) and electroluminescence spectrum of PPV (-) ...

Most reports in the published literature calculate the absorbance of a sample from either its transmittance or the reflectance spectra, assuming that all the light that is not transmitted (if we are calculating it from the transmittance spectrum) is absorbed. The absorbance calculated in this fashion is effectively the attenuation that sample exerts on the light, i.e. its optical density, when transmitting or reflecting the light, see Sect. 2.2.2.1 above. 

The detector must be sensitive to the radiation falling on it, and the spectrum is very often displayed on a chart recorder. The spectrum may be a plot of absorbance or percentage transmittance (IOO///0 see Equation 2.16) as a function of frequency or wavenumber displayed linearly along the chart paper. Wavelength is not normally used because, unlike frequency and wavenumber, it is not proportional to energy. Wavelength relates to the optics rather than the spectroscopy of the experiment. 

This diagram shows the energy spectrum of a given source, coupled with a filter of defined transmittance, which is established by a detector of known spectral response, as modified by a standard source and modified to that of a Standard Observer. Once an instrument has been set up properly with the proper optical... 

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