IR-Ruled Diffraction Gratings
|In addition to the IR specific gratings shown here, Thorlabs' offers a complete line of
Ruled Diffraction Gratings
with blaze wavelengths from 300 nm to 1.6 μm.
|GR13-xxxx||12.7 mm||12.7 mm||6 mm|
|GR25-xxxx||25 mm||25 mm||6 mm|
|GR50-xxxx||50 mm||50 mm||9.5 mm|
|GR1325-xxxxx||12.5 mm||25 mm||9.5 mm|
|GR2550-xxxxx||25 mm||50 mm||9.5 mm|
- Blaze Wavelengths from 750 nm to 10.6 µm
- 60% - 80% Efficiency at Blaze Wavelength Peak
- Gratings Available to Efficiently Diffract Light out to 12 μm
- Low Ghosting, <0.5% of Parent Line
- Soda Lime Glass Substrate with 750 to 1200 Grooves/mm
- Produced from Ruled Original
- High Laser Damage Threshold:
- Pulsed: 350 mJ/cm2
- CW: 40 W/cm2
Thorlabs offers a selection of ruled diffraction gratings for IR applications, optimized with blaze wavelengths from 750 nm to 10.6 µm. Ruled gratings are ideal for applications centered at the grating's blaze angle as the gratings typically have a sharp efficiency peak about the blaze wavelength. However, many of these gratings offer high efficiencies at wavelengths far away from the blaze wavelengths. See the efficiency curves below for more info. Ruled gratings typically offer higher efficiencies than holographic gratings, while holographic gratings do not produce ghosting effects. For information regarding the differences between grating types, please click on the Selection Guide tab above.
Mounting the Diffraction Gratings on Kinematic Mounts are easily acheived using the KGM series mount adapter. See the Mounting tab for further info.
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. Any attempt to clean a grating with a solvent voids the warranty. 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.
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' selection of gratings can be mounted in the KGM Series Grating Mount Adapters, as shown in the photograph to the right. These mounts can accommodate gratings and rectangular mirrors up to 60 mm tall and are compatible with all Ø1", front-loading, unthreaded mirror mounts.
To secure the grating, simply slide the upper and lower clamps on the adapter to match the desired optic height. These clamps slide in machined grooves and are tightened into place with two M3 screws that are located on the back side of the mount (see below).
Back Side of KGM Series Adpater
The 3-point, kinetic mounting mechanism consists of two bottom lines of contact and a top flat-spring contact, as shown in the photograph to the right. A nylon-tipped, locking setscrew, which is located on the top clamp, provides added holding force.
Thorlabs offers four lines of gratings: Ruled Holographic, Echelle and Transmission
|Ruled Gratings||These replicated, ruled diffraction gratings are offered in a variety of sizes and blaze angles. Ruled gratings typically achieve higher efficiencies than holographic gratings due to their blaze angles. |
|Holographic Gratings||Holographic gratings do not suffer from periodic errors that can occur in ruled gratings, thus ghosted images are nonexistent. Particularly in applications like Raman spectroscopy, where signal to noise is critical, the inherent low stray light of Holographic Gratings is an advantage.|
|Echelle Gratings||Echelle gratings are special 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. Supplied on precision glass substrates, Echelles have a resolution of 80-90% of theoretical. These Echelle Gratings are ideal for high resolution spectroscopy.|
|Transmission Gratings for UV,|
Near IR and Visible
|These gratings are ideal for simple optical designs that require fixed gratings such as spectrographs. The incident light is dispersed on the opposite side of the grating at a fixed angle. Transmission gratings are very forgiving for some types of grating alignment errors. All of these transmission gratings are ruled and blazed for optimum efficiency. In most cases, the efficiency is comparable to that of reflection gratings typically used in the same region of the spectrum. Transmission gratings are also relatively polarization insensitive.|
Selecting a grating requires consideration of a number of factors, some of which are listed below:
- Efficiency: In general, ruled gratings have a higher efficiency than holographic gratings. Applications such as fluorescence excitation and other radiation-induced reactions may require a ruled grating.
- Blaze Wavelength: Ruled gratings with a "sawtooth" groove profile have a relatively sharp peak around their blaze wavelength, while some holographic gratings have a flatter spectral response. Applications centered around a narrow wavelength range could benefit from a ruled grating blazed at that wavelength.
- Wavelength Range: The spectral range covered by a grating is dependent on groove spacing 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: For applications such as Raman spectroscopy, where signal-to-noise is critical, the inherent low stray light of a holographic grating is an advantage.
- 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.
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. Any attempt to clean a grating with a solvent voids the warranty. 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.