Build to Order Echelle Diffraction Gratings

An echelle diffraction grating differs from a conventional grating (called an echelette) in many ways. An echelle is coarse with fewer grooves per millimeter and is used at high angles in high diffraction orders. The virtue of an echelle lies in its high efficiency and low polarization effects over large spectral intervals. Together with high dispersion, this leads to compact, high-resolution instruments. An important limitation of echelles is that the orders overlap unless separated optically, for instance by a cross-dispersing element. A prism or echelette grating is often used for this purpose. This combination leads to an output format well matched to CCD arrays.

  • Coarse design with fewer grooves per millimeter
  • High-blaze-angle gratings used in high diffraction orders
  • High diffraction efficiency in both polarization states
  • Provides very high dispersion and resolution
  • Special size, substrate and coating options


Master Grating Options

Echelle gratings are listed in order of groove frequency, with the lowest blaze angle listed first. The maximum ruled area is groove length x ruled width. Click on a Master Grating Code (last 4 digits of a grating's part number) below to view master grating efficiency curves. Use the request a quote to get a quote based on your requirements. For additional diffraction grating options and custom capabilities, please see the Features section.

Master Grating Code Grooves per mm Nominal Blaze Angle Maximum Ruled Area (mm) Overstock Availability Request a Quote
182E 13.33 80.7° 198 x 412 Yes Quote
412E 23.2 63° 154 x 306 Yes Quote
419E 24.35 70° 97 x 102 Yes Quote
413E 27 70° 64 x 153 Quote
411E 31.6 63.9° 204 x 408 Yes Quote
453E 31.6 71° 308 x 408 Quote
414E 31.6 75° 154 x 313 Yes Quote
303E 31.6 76° 310 x 413 Quote
174E 31.6 76° 200 x 400 Quote
425E 41.59 76° 204 x 410 Quote
418E 44.41 70° 101 x 103 Quote
407E 46.1 32° 102 x 102 Quote
292E 48.39 68.2° 130 x 206 Quote
275E 50.7 64.2° 154 x 306 Quote
422E 52.13 32° 102 x 102 Quote
415E 52.67 63.5° 128 x 254 Quote
424E 52.67 65° 204 x 410 Quote
417E 52.67 69° 204 x 408 Yes Quote
053E 52.91 64° 102 x 102 Yes Quote
416E 54.49 46° 102 x 102 Yes Quote
153E 62 41.65° 154 x 184 Quote
454E 72 44° 95 x 90 Yes Quote
408E 79 62° 210 x 411 Quote
401E 79 63° 204 x 408 Yes Quote
402E 79 74° 128 x 254 Yes Quote
406E 85.84 76° 128 x 254 Quote
127E 87 63° 308 x 413 Yes Quote
291E 91.7 58.9° 154 x 208 Quote
488E 94.74 44° 104 x 104 Yes Quote
304E 97.11 56° 102 x 102 Quote
403E 98.7 63° 154 x 206 Quote
002E 101.95 45° 100 x 100 Quote
121E 110 64° 310 x 413 Quote
071E 112.96 79° 128 x 258 Yes Quote
084E 117.94 79° 128 x 258 Quote
187E 124.93 66° 154 x 206 Quote
141E 154.51 76° 128 x 260 Quote
404E 158 63° 127 x 203 Quote
405E 158 70° 128 x 256 Yes Quote
420E 171.66 78° 102 x 102 Yes Quote
149E 180 41.8° 154 x 206 Quote
451E 316 63° 204 x 408 Yes Quote
452E 316 70° 128 x 256 Yes Quote


Echelle Grating Geometry

For a conventional (echelette) grating, the longer groove facet (of length t) would face toward the incident and diffracted light; for an echelle, the shorter, steeper groove facet (of length s) is facing toward the light. Echelles are often used in or near the Littrow configuration (shown), in which the angle of incidence α equals the angle of diffraction β, though they have been used with as much as α – β = 40° between the beams.

The two design parameters that define an echelle grating are its groove frequency G (= 1/d) and its blaze angle θ. Echelles presently range in groove frequency from 23 to 316 mm–1. Blaze angles include, but are not limited to, 32°, 44°, 63.4°, 71.5°, 76° and 79°; the last four are chosen because their tangents are 2, 3, 4 and 5. Often echelles are specified by their "R number", which equals this tangent; for example, an R4 echelle in one with blaze angle arctan(4) = 76°.

Geometry of an echelle grating (Littrow).

Echelles Efficiency Behavior

The high efficiency of echelles is maintained near the Littrow angle. This means moving progressively through a series of diffraction orders to cover the entire spectral range. Within each order, the efficiency will be maximum in the middle (typically reaching 50 to 75%), but drop to about one-half of these values at the crossover points. Interorder efficiency behavior closely follows scalar theory; however, when the diffraction order of use is low, or when the diffraction angles are high, the detailed efficiency properties are governed by electromagnetic (vector) theory. An accurate theoretical formulation of this case is a recent achievement.

Testing of Echelles Gratings

Echelle gratings are subject to careful testing. Resolution close to the theoretical limit can be verified by interferometric and Foucault wavefront tests, and also by observation of the hyperfine spectra of mercury. Efficiency is determined with mercury and laser light sources, to ensure narrow spectral line widths. Exact blaze angles are derived by one of several methods.

Echelles Diffraction Gratings Applications

Echelles are most often used in applications where their high dispersion and resolution are important. This covers atomic spectrometry, laser tuning, and astronomy. Since they operate in many diffraction orders, echelles are capable of wide wavelength coverage, being used from 100 nm into the infrared. Echelles are found on several space spectrographs, including the Hubble Space Telescope.

Catalog Part Number System

All standard Richardson gratings have a part number according to the following format:


  • AA indicates the type of grating (e.g., diced, plano, grism).
  • BBB indicates the size of the grating substrate.
  • CC indicates the substrate material
  • DD indicates the type of coating
  • EEE indicates the master grating groove parameters
  • x indicates the master grating type (e.g., ruled, holographic, echelle)

Please see Diffraction Grating Part Number System for additional information.

Grating Size Options

Commonly used sizes vary from 50 by 100 mm to 308 by 408 mm, where the shorter number specifies the groove length and the longer number the ruled width. Because dispersion is high, it is important to maintain constant groove spacing, which is why echelles are often replicated onto low thermal expansion materials. A recent development has been to make echelles larger than the standard 408 mm ruled width limit, in order to satisfy the needs of large astronomical spectrographs. This can be accomplished by the precise double replication of a single ruling onto a larger substrate; the resulting grating is called a mosaic.

Size Code BBB Substrate Dimensions (mm) Ruled Area (mm)
114 50 x 100 x 16 46 x 96
019 60 x 150 x 25 56 x 142
015 110 x 110 x 16 102 x 102
025 110 x 220 x 30 102 x 206
032 135 x 265 x 45 128 x 254
044 165 x 320 x 50 154 x 306
036 220 x 265 x 45 204 x 254
043 220 x 420 x 74 204 x 410
045 320 x 420 x 74 306 x 410

Grating Substrate Material Options

The standard substrate material for small and medium-sized gratings is specially annealed borosilicate crown glass. Low expansion material can be supplied on request. Float glass may be used for small, diced gratings. In addition, replicas may be furnished on metal substrates, such as copper or aluminum, for applications with extreme thermal conditions. The substrate material codes CC are given below:

Substrate Material Code CC Substrate Material
AL Aluminum
BF Borosilicate float or equivalent
BK BK-7 glass or equivalent
CU Copper
FL Float glass
FS Fused silica or equivalent
LE Low-expansion glass
SP Special glass (unspecified)
TB BK-7, transmission grade
TF Fused silica, transmission grade
UL Corning ULE® glass
ZD Schott Zerodur®

Diffraction Grating Coating Options

All reflection gratings include a standard aluminum (Al) reflectance coating (Coating Code "01"). Gratings can also be replicated in gold (Au), or overcoated with magnesium fluoride (MgF2) or silver (Ag), to enhance reflectivity in certain spectral regions. The coating material codes DD are shown below:

Coating Code DD Coating Material Application
01 Aluminum (Al) General purpose applications.
02 Gold (Au) Offers higher reflectivity in the infrared.
03 Magnesium Fluoride (MgF2) Used to prevent oxidation of aluminum (Al) coatings, which helps maintain high reflectivity in the ultraviolet over time.
06 Protected Silver (Ag) Offers higher reflectivity in the visible and near infrared. Silver is protected from tarnishing by a dielectric coating, which helps maintain reflection over time.

Custom Diffraction Gratings

Newport is pleased to discuss special and unusual applications that are not addressed by our build to order catalog diffraction gratings. In some instances, none of the hundreds of master gratings we have in stock meet specifications, so a new master may be required. Please see Custom Diffraction Gratings for additional information on our capabilities.


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