MCS260B
CORNERSTONE 260B MONOCHROMATORS
22
6.1 GRATING TYPES
Ruled grating masters are produced using a ruling engine with an extremely fine cutting tool.
Holographic gratings (also called interference gratings) are produced by recording interference
fringes in photoresist. The two different techniques cause some differences in performance.
Holographic gratings are most frequently available at high groove densities due to manufacturing
limitations inherent in the technology. They are generally favored for work in the UV and through
the visible to about 600 nm. Holographic gratings produce less scattering, thereby reducing stray
light inside the monochromator.
Ruled gratings typically have higher efficiencies. Ruled gratings may have periodic errors in the
grating grooves caused by minor defects in the ruling machine, resulting in anomalous readings or
“ghosts”. Holographic gratings do not suffer from ghosts, so interpretation of line spectra is
simplified.
The signal-to-noise ratio (SNR) is the ratio of diffracted energy to unwanted light energy. Although it
may be assumed that increasing diffraction efficiency will increase SNR, stray light usually plays the
limiting role in the achievable SNR for a grating system. Note that the actual signal to noise ratio will
depend on the spectral content of the incident light and the detector.
GRATING PROPERTIES
Configuration
Grating
Position
Type
Groove
Density
(lines/mm)
Blaze
Wavelength
(nm)
Reciprocal
Dispersion
(nm/mm)
UV-NIR High
Resolution
Quad (-1)
#1
Ruled
1200
250
3.56
#2
Ruled
1200
500
3.43
#3
Ruled
1200
750
3.22
#4
Ruled
1200
1000
2.98
UV-NIR High
Resolution
Dual (-2)
#1
Ruled
1200
500
3.43
#2
Ruled
1200
750
3.22
UV-SWIR
Extended
Range (-Q)
#1
Ruled
600
400
7.16
#2
Ruled
600
650
7.07
#3
Ruled
600
1000
6.86
#4
Ruled
600
1850
6.10
VIS-NIR
Extended
Range (-3)
#1
Ruled
600
400
7.16
#2
Ruled
600
1000
6.86
Figure 16: Grating Properties Table for CS260B Pre-Configured Models.
