Transmission grating

Small, efficient single monochromators based on concave holographic gratings, transmission holographic gratings or standard Czemy-Turner monochromators in combination with a notch filter. 

These are typical of the results obtained for the other compounds whose spectra are not shown. The shapes of the spectra are influenced by the particular instrument used, because they are uncorrected for variations in detector sensitivity, xenon arc lamp emission or grating transmission with wavelength. 

The diffiaction efficiency foi the transmission geometry is given by equation 12 (24) where is the amphtude of the index grating. 

For both geometries the diffraction efficiency approaches unity in value for Atransmission hologram exhibiting a periodic behavior (24,25) efficiency as a function of the grating strength ( ), whereas the reflection efficiency exponentially approaches unity. 

With development of ultrashort pulsed lasers, coherently generated lattice dynamics was found, first as the periodic modulation in the transient grating signal from perylene in 1985 by De Silvestri and coworkers [1], Shortly later, similar modulation was observed in the reflectivity of Bi and Sb [2] and of GaAs [3], as well as in the transmissivity of YBCO [4] by different groups. Since then, the coherent optical phonon spectroscopy has been a simple and powerful tool to probe femtosecond lattice dynamics in a wide range of solid... 

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... 

Fig. 13.22 (a) MNF/microsphere tool for surface sensing, (b) Transmission power dependence on the position of the microsphere at the diffraction grating surface. Comparison of two measure ments of the same grating region shows the reproducibility of measurements. Reprinted from Ref. 42 with permission. 2008 Optical Society of America... 

Diffraction of light by transmission and reflection gratings was used to demonstrate the existence of light waves and led to the development of the diffraction equation. 

Fluorescence Instrumentation and Measurements. Fluorescence spectra of the FS samples were obtained on a steady state spectrofluorometer of modular construction with a 1000 W xenon arc lamp and tandem quarter meter excitation monochromator and quarter meter analysis monochromator. The diffraction gratings In the excitation monochromators have blaze angles that allow maximum light transmission at a wavelength of 240 nm. Uncorrected spectra were taken under front-face Illumination with exciting light at 260 nm. Monomer fluorescence was measured at 280 nm and exclmer fluorescence was measured at 330 nm, where there Is no overlap of exclmer and monomer bands. 

Figure 2.23 Diffraction gratings. Each line in a grating acts as a separate source of radiation (a) but radiation transmitted at any angle 6 is retarded relative to radiation from the preceding line (b) by the distance x. In the transmitted radiation some wavelengths will undergo constructive interference while the majority will suffer destructive effects. Reflectance gratings (c) are frequently used and the principles of monochro-mation are the same as for transmission gratings.

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