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A blazed diffraction grating reflecting only the green portion of the spectrum from a room's fluorescent lighting. For a diffraction grating, the relationship between the grating spacing (i.e., the distance between adjacent grating grooves or slits), the angle of the wave (light) incidence to the grating, and the diffracted wave from the grating is known as the grating equation.
The wavelength of light is then selected by the slit on the upper right corner. An optical spectrometer ( spectrophotometer , spectrograph or spectroscope ) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum , typically used in spectroscopic analysis to identify materials. [ 1 ]
The free spectral range of a diffraction grating is the largest wavelength range for a given order that does not overlap the same range in an adjacent order. If the ( m + 1)-th order of λ {\displaystyle \lambda } and m -th order of ( λ + Δ λ ) {\displaystyle (\lambda +\Delta \lambda )} lie at the same angle, then
A typical monochromator achieves this through the use of entrance and exit slits, collimating and focus optics, and a wavelength-dispersing element such as a diffraction grating or prism. [6] Modern monochromators are manufactured with diffraction gratings, and diffraction gratings are used almost exclusively in spectroradiometric applications.
Since this condition can only exactly be achieved for one wavelength, it is specified for which blaze wavelength the grating is optimized (or blazed). The direction in which maximum efficiency is achieved is called the blaze angle and is the third crucial characteristic of a blazed grating directly depending on blaze wavelength and diffraction ...
An echelle grating (from French échelle, meaning "ladder") is a type of diffraction grating characterised by a relatively low groove density, but a groove shape which is optimized for use at high incidence angles and therefore in high diffraction orders. Higher diffraction orders allow for increased dispersion (spacing) of spectral features at ...
Replacing the prism with a diffraction grating would result in a grating spectrometer. Optical gratings are less expensive, provide much higher resolution, and are easier to calibrate, due to their linear diffraction dependency. A prism's refraction angle varies nonlinearly with wavelength. On the other hand, gratings have significant intensity ...
Most of the structure in the n(λ) and k(λ) spectra occurs in the deep UV wavelength range and thus to properly characterize a film of this nature, it is necessary that the measured reflectance data in the deep UV range is accurate. The figure shows a measurement example of a photoresist (polymer) material used for 248 nm micro-lithography.