Holographic diffraction gratings can have very high diffraction efficiency, even above that of flat aluminum reflectors, at the design wavelengths and orientation. Diffraction efficiency is highly dependent on the polarization state. Planar holographic gratings typically feature narrower spectral bandwidth, and have their peak efficiency at a shorter wavelength for P-polarization compared to S-polarization. For laser cavity applications this property may be used to feed light from a specifically chosen wavelength and polarization state back into the laser gain medium to control the output of the laser. Conversely, applications such as spectrometers designed to operate using unpolarized light may require the use of two gratings in conjunction with a polarizing beamsplitter to obtain optimum results.

Pairs of identical diffraction gratings that are tuned to the polarization and output wavelengths of a laser may be used to temporally compress ultrafast laser pulses, greatly increasing the peak power. When a spectrally broad laser pulse is incident on a diffraction grating, the various wavelength components will disperse, or diffract in different directions. If this pulse has its wavelength chirped (i.e. its frequency progressively increases during the length of the pulse) the first grating will diffract the leading portion of the pulse (consisting of longer wavelengths) at a greater angle compared to the trailing portion of the pulse (consisting of shorter wavelengths). When the light reaches the second grating with same periodicity the dispersion will be reversed from symmetry and the light will be collimated. Light from the leading edge of the pulse will travel a longer optical path through the pair of gratings, requiring more travel time. If the separation between the gratings is chosen so that the travel time difference matches the pulse duration, the laser power will be compressed into a nearly instantaneous pulse.

Like their ruled counterparts, holographic gratings are most efficient when used in the Littrow configuration, or aligned so that the diffraction angle of the dominant diffraction order is coincident with the input beam, effectively behaving as a retroreflector at a specific wavelength. This geometry is especially useful for applications using a diffraction grating inside a laser cavity to select a particular wavelength. Only the exact chosen wavelength will reflect into the laser cavity. Holographic gratings are particularly useful because they have peak efficiency only at a particular polarization, allowing them to be used as a substitute for a Brewster window to control the laser output polarization.

Holographic gratings are patterned surface relief gratings, the surface cannot be touched with without damaging the fringe pattern and potentially seriously degrading the optical performance. Damage to the grating can take the form of contamination or distortion of the microscopic groove profile. Damage to this microscopic groove profile is, unfortunately, irreversible. The resin layer like modeling clay, will retain a permanent imprint. Contamination with finger oils, moisture, etc. is also often permanent. Because of the sensitive nature of the grating groove profile, it is imperative that the user take precautions in handling gratings. Do not touch the surface of the grating; handle the grating by the edges and always wear gloves or finger cots. Use a non-contact cleaning method such as dry, compressed air or a dust bulb to remove excess dust from a grating.

Float glass is made by floating molten glass over a bed of molten metal. While this is a low cost material that is used in commercial windows, the production method yields a very flat surface of uniform thickness making it a good choice for optics.

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.