VPH Transmission Gratings: Robust diffractive elements with many advantages

21 Apr 2023

VPH transmission gratings offer many benefits over traditional ruled reflection gratings, ranging from superior and consistent optical performance to design flexibility and easy handling. VPH gratings are ideal for applications like laser pulse compression, spectroscopy, hyperspectral imaging, optical coherence tomography, and astronomy. Wasatch Photonics offers gratings for wavelengths ranging from 300 nm to 2500 nm, with bandwidths 5-800 nm, and line frequencies 150-5000 lines/mm.

Volume phase holographic (VPH) gratings are made by holographically imaging a grating’s ‘grooves’ into optical gelatin, which is hermetically sealed between two windows to allow easy cleaning and handling. This process can be used to manufacture very high quality diffraction gratings in volumes of 1 to 1000 pieces or more, with consistent performance.

VPH gratings offer high peak 1^st order diffraction efficiencies, ranging from >80% for a 200-300 nm bandwidth (Wasatch Photonics' patented HD design) to >99% for a single wavelength (typical laser pulse compression grating design). This is up to 40% greater than reflective surface relief gratings, which tend to have asymmetric efficiency profiles that impact system performance. A VPH grating’s efficiency, in contrast, varies smoothly with wavelength, and can be modeled at the design stage for inclusion in system performance models, then manufactured dependably to the specifications of that design.

The flexible nature of the manufacturing process also makes it possible to easily and cost-effectively customize and optimize VPH gratings for each application. Wasatch Photonics offers multiple patented design technologies to meet these needs, both as stock gratings for R&D to custom gratings for our many OEMs and unique applications. We also manufacture grisms to enable straight pass optical designs.

Learn more about the advantages of VPH transmission gratings, or contact us to discuss your needs today.