Spectrometer components diffraction grating

Both dispersive and nondispersive spectrometers can exhibit preferential transmission of light depending on its polarization. The efficiency of diffraction gratings and the polarization sensitivity of the beamsplitter can cause errors in the observed depolarization ratio, depending on several variables such as experimental geometry and Raman shift region. For this reason, it is often important to place a polarization scrambler between the sample and any polarization-sensitive components of the spectrometer other than the polarization analyzer itself. In addition, it is good practice to measure p for a few known systems to verify accuracy of the apparatus. 

Spectrometer is an instrument with a component, such as a prism or diffraction grating, which can break radiation extending over a part of the spectrum into discrete wavelengths and/or separate them. 

Color Plate 23 Polychromator for Inductively Coupled Plasma Atomic Emission Spectrometer with One Detector for Each Element (Section 21-4) Light emitted by a sample in the plasma enters the polychromator at the right and is dispersed into its component wavelengths by grating at the bottom of the diagram. Each different emission wavelength (shown schematically by colored lines) is diffracted at a different angle and directed to a different photomultiplier detector on the focal curve. Each detector sees only one preselected element, and all elements are measured simultaneously. [Courtesy TJA Solutions, Franklin, MA.J... 

Figure 3.1-6 The main components of a grating spectrometer N is the number of interfering rays, given by the number of rules so is the half width of the diffraction pattern of the collimator lens with the diameter D and the focal length /, it determines the optimal slit width (Laqua, 1980), h is the slit length.

According to Equation 3.1 all diffraction orders of the echelle grating superimpose and cannot be initially distinguished by the detector of a spectrometer. Consequently order separation by an additional dispersing component is essential for unambiguous wavelength determination. 

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