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Choosing a Spectrometer Grating:
"NIR" Optical Bench

You choose from 2 gratings for each "NIR" Optical Bench spectrometer. With each grating, you consider its groove density (which helps determine the resolution), its spectral range (which helps determine the wavelength range) and its blaze wavelength (which helps determine the most efficient range).

Performance and Stability

Instead of the gratings rotating as they do in instruments such as scanning monochromators, our gratings are permanently fixed in place at the time of manufacture to ensure long-term performance and stability. (Gratings can only be changed at the factory.) A grating must be specified for each spectrometer channel.

Grating Selection Chart

The chart below allows you -- with the help of our Applications Scientists -- to select the best grating.

#	Intended Use	Groove Density	Spectral Range	Blaze Wavelength	Best Efficiency
N1	NIR256 or NIR512	300	900 nm	100 nm	700-2100 nm*
N2	NIR256 only	150	1600	1600 nm	700-2500 nm*

* For optimum performance, we recommend setting the starting wavelength no lower than 900 nm unless absolutely necessary.

To see the efficiency curve of a specific grating, and to compare similar gratings, click on the Grating # in the far left column of the table above.

Groove Density. The Groove Density (mm^-1) of a grating determines its dispersion. The greater the groove density, the better the optical resolution possible, but the more truncated the spectral range.
Spectral Range. The dispersion of the grating across the linear array; also expressed as the "size" of the spectra on the array. When selecting gratings, you must choose a wavelength range with a width equal to the Spectral Range entry in the Spectrometer Grating Selection Chart. The grating's highest efficiency is within the range listed in the Best Efficiency (>30%) column.
Blaze Wavelength. The peak wavelength in the typical efficiency curve for a ruled grating. Also, for a holographic grating, the most efficient wavelength region.
Best Efficiency ( >30%). All ruled or holographically etched gratings optimize first-order spectra at certain wavelength regions; the "best" or "most efficient" region is the range where efficiency is >30%. In some cases, gratings have a greater spectral range than is efficiently diffracted.

Contact an
Ocean Optics
Applications Scientist

Optical Resolution

System Sensitivity

Operating Principles

Choosing a Grating: "HR" Optical Bench

Choosing a Grating: "S" Optical Bench

Choosing a Spectrometer Grating: "NIR" Optical Bench

Performance and Stability

Grating Selection Chart

Choosing a Spectrometer Grating:
"NIR" Optical Bench