Light transmission spectra

Figure 6 shows the white light transmission spectra through two arrays of nanoholes with different periodicities. The experimental setup used in these measurements has been described elsewhere [25,26]. 

Figure 4.9 Light transmission spectra of PMMA/FPEOF pseudo-SIPN films (see text for details). Path length 0.2 mm. Cso concentration (wt%)-from right to left 1.1,1.5, 2.7 and 4.5.

Figure 6.10 Light transmission spectra of 5 p.m DHF-FLC cell placed between two crossed polarizers versus applied voltage at a frequency of color switch of 100 Hz the horizontal size of the micrographs is 500 p.m [19]. Reproduced from E. P. Pozhidaev, G. Hegde, P. Xu, and V. G. Chigrinov, Electrically controlled birefringent colors of smectic C deformed helix ferroelectric liquid crystal cells. FLC 07 Program, FLC International Conference on Ferroelectric Liquid Crystals, 0-36 (2007)...

UV-visible light transmission spectra were obtained using an HP UV-vis spectrophotometer operated at scan speed 240 nm/min, slit width 2.0 nm, using bottle sidewall polyester parts. 

The intensity transmission of the weak probe laser versus the frequency detuning (Ac=As) are plotted in Fig. 9. Fig. 9 (a) presents the measurement without the control field and represents the EIT manifested absorption spectra in the four-level system observed before [39]. The light transmission spectrum with both the signal and control fields present is plotted in Fig. 9(b), which shows that the absorption at the resonance (Ap=Ac=0) is suppressed by the destructive interference, which results in simultaneous EIT for both the signal field and the control field. 

Two scans are required to obtain an absorption spectrum. First, a blank reference scan is taken that characterizes the broadband light source. Then a scan with the sample in place is recorded. The ratio of the sample power spectrum to the reference power spectrum is the transmission spectrum. If the source has stable output, then a single reference scan can be used with many sample scans. 

Fig. 2.10 Normalized transmission spectrum of a microring resonator made by e beam bleaching. The input light is TE polarized. Reprinted from Ref. 15 with permission. 2008 Institute of Electrical and Electronics Engineers...

Fig. 2.15 (a) The change in the transmission spectrum of a fiber Bragg grating coated with DH6/ PMMA in response to DNT. The sensor was exposed to saturated DNT vapor at room temperature. The measurements were taken at time intervals of one hour. The last measurement was taken after the sensor was exposed to DNT for 16 h. (b) The change of optical power at the output end of the fiber sensor for light of the wavelength of 1,562.9 nm. Reprinted from Ref. 33 with permission. 2008 American Chemical Society... 

Infrared spectra of zeolitic samples can be measured in several different modes. These include transmission, diffuse reflectance, attenuated total internal reflection (ATR) and emission. Transmission and diffuse reflectance are by far the most widely used of these techniques. In the transmission mode, the sample is placed directly in the infrared beam of the instrument and the light passing through or transmitted is measured by the detector. This transmitted signal (T) is ratioed to the open beam (no sample) signal (To) to get the transmission spectrum of the sample. The transmission spectrum is converted to an absorbance spectrum ... 

At infrared wavelengths extinction by the MgO particles of Fig. 11.2, including those with radius 1 jam, which can be made by grinding, is dominated by absorption. This is why the KBr pellet technique is commonly used for infrared absorption spectroscopy of powders. A small amount of the sample dispersed in KBr powder is pressed into a pellet, the transmission spectrum of which is readily obtained. Because extinction is dominated by absorption, this transmission spectrum should follow the undulations of the intrinsic absorption spectrum—but not always. Comparison of Figs. 10.1 and 11.2 reveals an interesting discrepancy calculated peak extinction occurs at 0.075 eV, whereas absorption in bulk MgO peaks at the transverse optic mode frequency, which is about 0.05 eV. This is a large discrepancy in light of the precision of modern infrared spectroscopy and could cause serious error if the extinction peak were assumed to lie at the position of a bulk absorption band. This is the first instance we have encountered where the properties of small particles deviate appreciably from those of the bulk solid. It is the result of surface mode excitation, which is such a dominant effect in small particles of some solids that we have devoted Chapter 12 to its fuller discussion. 

Diffuse Reflection. Using a set of flat and elliptical mirrors, this device can measure a sufficient amount of light diffused by a sample dispersed in KBr powder (Fig. 10.20). By comparing the diffused reflection obtained with neat KBr, a result resembling the transmission spectrum is obtained. Kubelka-Munk s correction can be used to improve the spectrum. 

Selenium and cobati arc used in Him glass to add ted and blue hues m amounts only sufficient to balance the green hue resulting from iron oxide present as impurity in most naturally occurring taw materials. The intended result is an even light transmission over the whole visible spectrum. 

The considerable changes in the optical absorption of CPs during the dopingundoping process are at the basis of many proposals for electrochromical devices, such as smart windows, whose light transmission can be electrically controlled, and various display devices. Due to the drastic change that appears in their visible spectrum, PTh [122-124] and PAni [125] are... 

Polymers with very low light transmission properties give highly inadequate spectra, which are difficult to evaluate. The lower curve in Fig. 5.1-14, for instance, shows the spectrum of polyethylene, including 2% soot. The upper portion of Fig. 5.1-14 shows that the scale expansion considerably enhances the accessible information content of the spectrum (Peitscher, 1979). 

Figure 5.1-14 Enhancing the information content of the IR spectrum of a polymer with very poor light transmission properties using difference spectroscopy and ordinate scale expansion Spectrum of polyethylene containing 2% soot d = 140 pm.

I suggest the use of infrared spectroscopy for the laboratory tests. Samples of the him can be mounted in the path of the infrared light beam in an infrared spectrometer and the resulting infrared transmission spectra recorded. If your staff is not familiar with infrared spectroscopy or the interpretation of infrared transmission spectra, you might allow them some time to read some basic reference material on this technique. I can provide that for you. The transmission spectrum recorded by the spectrometer is like a fingerprint of the material in the path of the light. It is a pattern that is observed each time that material is tested. 

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