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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.
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Contact
an
Ocean Optics
Applications Scientist
Optical
Resolution
System
Sensitivity
Operating
Principles
Choosing a Grating:
"HR" Optical Bench
Choosing
a Grating: "S" Optical Bench
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