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Top Image: On one edge of the grating, an arrow parallel to the grating's surface indicates the blaze arrow.
Bottom Image: On the opposite edge of the grating, an arrow perpendicular to the grating's surface, indicates the transmission direction.

Features

• Optimum Performance in the Visible Spectrum
• Ideal for Fixed Grating Applications such as Spectrographs
• Schott B270 Substrate
• Custom Sizes Available Upon Request

Thorlabs' Visible Transmission Gratings are ideal for fixed grating applications such as spectrographs. The incident light is dispersed on the opposite side of the grating at a fixed angle. Transmission gratings offer low alignment sensitivity, which helps minimize alignment errors. In most cases, the efficiency of these gratings is comparable to that of reflection gratings such as Ruled Gratings or Holographic Gratings when used in the same wavelength range.

Transmission gratings require relatively low groove densities to maintain high efficiency. As the diffraction angles increase with higher groove densities, the refractive properties of the substrate material limits the transmission at the higher wavelengths and performance drops off. The grating dispersion characteristics, however, lend themselves to compact systems utilizing small detector arrays. These gratings are also relatively polarization insensitive. Our visible transmission gratings are offered with four different groove densities in five different sizes.

Please see the Selection Guide tab to choose the right grating type for your application.

Warning:

Optical gratings can be easily damaged by moisture, fingerprints, aerosols, or the slightest contact with any abrasive material. Gratings should only be handled when necessary and always held by the sides. Latex gloves or a similar protective covering should be worn to prevent oil from fingers from reaching the grating surface. No attempt should be made to clean a grating other than blowing off dust with clean, dry air or nitrogen. Solvents will likely damage the grating's surface.

Thorlabs uses a clean room facility for assembly of gratings into mechanical setups. If your application requires integrating the grating into a sub-assembly or a setup, please contact us to learn more about our assembly capabilities.

Thorlabs offers 3 types of Reflection Gratings:

Ruled

Ruled gratings can achieve higher efficiencies than holographic gratings due to their blaze angles. They are ideal for applications centered at the blaze angle. Thorlabs offers replicated ruled diffraction gratings in a variety of sizes and blaze angles.

Holographic

Holographic gratings have a low occurance of periodic errors which results in limited ghosting, unlike ruled gratings. The low stray light of these gratings make them ideal for applications where the signal-to-noise ratio is critical, such as Raman Spectroscopy.

Echelle

Echelle gratings are low period gratings designed for use in the high orders. They are generally used with a second grating or prism to separate overlapping diffracted orders. The are ideal for applications such as high-resolution spectroscopy.

Thorlabs offers 3 types of Transmission Gratings:

UV Transmission

As with all of our transmission gratings, Thorlabs' UV transmission gratings disperse incident light on the opposite side of the grating at a fixed angle. They are ruled and blazed for optimum efficiency in the UV range, are relatively polarization insensitive, and have an efficiency comparable to that of a reflection grating optimized for the UV spectrum. They are ideal for applications that require fixed gratings such as spectrographs.

VIS Transmission

As with all of our transmission gratings, Thorlabs' VIS transmission gratings disperse incident light on the opposite side of the grating at a fixed angle. They are ruled and blazed for optimum efficiency in the VIS range, are relatively polarization insensitive, and have an efficiency comparable to that of a reflection grating optimized for the VIS spectrum. They are ideal for applications that require fixed gratings such as spectrographs.

Near IR Transmission

As with all of our transmission gratings, Thorlabs' NIR transmission gratings disperse incident light on the opposite side of the grating at a fixed angle. They are ruled and blazed for optimum efficiency in the NIR range, are relatively polarization insensitive, and have an efficiency comparable to that of a reflection grating optimized for the NIR spectrum. They are ideal for applications that require fixed gratings such as spectrographs.

Selecting a grating requires consideration of a number of factors, some of which are listed below:

Efficiency:
Ruled gratings generally have a higher efficiency than holographic gratings. However, holographic gratings tend to have less efficiency variation accross their surface due to how the grooves are made. The efficiency of ruled gratings may be desireable in applications such as fluorescence excitation and other radiation-induced reactions.

Blaze Wavelength:
Ruled gratings have a sawtooth groove profile created by sequentially etching the surface of the grating substrate. As a result, they have a sharp peak around their blaze wavelength. Holographic gratings are harder to blaze, and tend to have a sinusoidal groove profile resulting in a less intense peak around the design wavelength. Applications centered around a narrow wavelength range could benefit from a ruled grating blazed at that wavelength.

Wavelength Range:
Groove spacing determines the optimum spectral range a grating covers and is the same for ruled and holographic gratings having the same grating constant. As a rule of thumb, the first order efficiency of a grating decreases by 50% at 0.66λB and 1.5λB, where λB is the blaze wavelength. Note: No grating can diffract a wavelength greater than 2 times the groove period.

Stray Light:
Due to a difference in how the grooves are made, holographic gratings have less stray light than ruled gratings. The grooves on a ruled grating are machined one at a time which results in a higher frequency of errors. Holographic grooves are made all at once which results in a grating that is virtually free of errors. Applications such as Raman spectroscopy, where signal-to-noise is critical, can benifit from the limited stray light of the holographic grating.

Resolving Power:
The resolving power of a grating is a measure of its ability to spatially separate two wavelengths. It is determined by applying the Rayleigh criteria to the diffraction maxima; two wavelengths are resolvable when the maxima of one wavelength coincides with the minima of the second wavelength. The chromatic resolving power (R) is defined by R = λ/Δλ = nN, where Δλ is the resolvable wavelength difference, n is the diffraction order, and N is the number of grooves illuminated.

For further information about gratings and selecting the grating right for your application, please visit our Grating Tutorial.

Caution:

The surface of a diffraction grating can be easily damaged by fingerprints, aerosols, moisture or the slightest contact with any abrasive material. Gratings should only be handled when necessary and always held by the sides. Latex gloves or a similar protective covering should be worn to prevent oil from fingers from reaching the grating surface. Solvents will likely damage the grating's surface. No attempt should be made to clean a grating other than blowing off dust with clean, dry air or nitrogen. Scratches or other minor cosmetic imperfections on the surface of a grating do not usually affect performance and are not considered defects.