Selecting a Diffraction GratingĬhoosing a diffraction grating comes down to several key interlinked performance factors, including: While both offer significantly higher efficiency than ruled gratings, VPH grating technology offers the optical engineer more design options to achieve the desired efficiency profile. Etched-in relief gratings comprised of fused silica and volume phase holographic (VPH) diffraction gratings, for instance, are two radically different design paradigms for modern optical systems. Learn more about the advantages of VPH gratings.īut we can extend the different types of diffraction gratings further to discuss the new and emerging manufacturing techniques for holographic gratings. Holography is now the gold-standard manufacturing technique for diffraction gratings. This action then ‘writes’ a periodic structure into the chosen medium. Briefly, they are engineered by selectively exposing a substrate or photoreactive material on the substrate to a laser generated optical interference pattern of outstanding uniformity. Holographic gratings are designed to eliminate many of the errors associated with conventional surface relief components. Dust, fingerprints, or other contamination adds to the inherent scatter of the grating over time. Once manufactured, a ruled grating must be handled with care, as it cannot be cleaned without significant risk of damage. Ruled gratings also suffer from fairly high light scattering. This is an expensive and time-consuming design process that may require multiple test gratings to be fabricated via diamond tooling before the final component is produced via replication. A conventional surface relief grating is engineered by ruling a substrate material with equally-spaced grooves, creating the popular and easily recognizable ‘blazed’ surface. Gratings alter the phase of reflected or transmitted light based on their unique structural properties. transmission is not the final word in diffraction grating selection. Consequently, transmission gratings are preferred over reflective components for many OEM applications.Īlthough important, reflection vs. Due to the ability to better compensate for aberrations, optical systems made with transmission gratings have comparatively low alignment sensitivity, which can be a significant benefit for applications where minute alignment errors or temperature changes could wreak havoc on results. Essentially, a reflection grating diffracts light back into the plane of incidence while transmission gratings transmit dispersed light through. Reflection or transmission is one of the most fundamental distinctions in diffraction grating terminology. Reflection vs Transmission Diffraction Gratings This article is intended to act as a brief primer on the different types of diffraction gratings to help you select the right one for your application needs. There are many types of diffraction gratings, which can make the selection process tricky. This is not the only fundamental design type of diffraction grating, but it has become the widely-used standard for many applications. The most common type of grating structure uses numerous parallel rulings on a surface in a manner similar to a series of slits, resulting in a superposition of waves that diffract light by wavelength, effectively separating it into its colors. They operate on the principle of interference to split multi-spectral light into its constituent wavelengths and, like a prism, disperse them spatially through a range of angles. When you need to separate different wavelengths of light with superb spectral resolution in a compact, efficient manner, you might want to consider a diffraction grating.ĭiffraction gratings are widely used optical components featuring periodic structures that allow dispersion of light in a more compact, convenient format than a prism.
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