Groove density:
(or groove frequency):
the number of grooves contained on a grating surface, expressed in grooves per mm (g/mm) or lines per mm (l/mm). |
Groove density affects the mechanical scanning range and the dispersion properties of a system. It is an important factor in determining the resolution capabilities of a monochromator. Higher groove densities result
in greater dispersion and higher resolution capabilities.Select
a grating that delivers the required dispersion when using
a CCD
or array detector, or the required resolution
(with appropriate slit width) when using a monochromator. |
Mechanical scanning range:
the wavelength region in which an
instrument can operate. |
Refers to the mechanical rotation capability (not the operating or optimum range) of a grating drive system with a specific grating installed.
Select a grating groove density that allows operation over your required wavelength region. |
Blaze wavelength:
the angle in which the grooves are
formed with respect to the grating
normal, often termed blaze angle. |
Diffraction grating efficiency plays an important role in monochromator or spectrograph throughput. Efficiency at a particular wavelength is largely a function of the blaze wavelength if the grating is ruled, or modulation if
the grating is holographic. Select a blaze wavelength that encompasses the total wavelength region of your application(s), and if possible, favors the short wavelength side of the spectral region to be covered (see Grating Efficiency Curves). |
Quantum wavelength range:
the wavelength region of highest
efficiency for a particular grating. |
Normally determined by the blaze wavelength.
Select a grating with maximum efficiency over the required wavelength region for your application(s). |
Advantages of Multiple-Grating Turrets
Quite often it becomes necessary to select two or three gratings to achieve efficient light throughput over a broad spectral region. That's why SpectraPro monochromators and spectrographs are equipped with multiple-grating turrets as a standard feature. Turrets make grating changes an easy push-button or computer-controlled operation, while reducing the risk of handling the delicate gratings. |
