Concave holographic gratings are unique in that each grating has two focusing elements to it, the substrate and the groove curvature. The substrate alone will provide a curvature or focus, combined with the additional degree of wavefront control provided by the grooves. The instrument designer can remove the lens system by using concave gratings. Thus, allowing a reduction in the total number of optics in the system. Associated benefits may include lower total cost through simpler instrument assembly.
In systems based on concave gratings optical aberrations such as coma and astigmatism can be greatly reduced by using a concave grating designed to meet your light collection requirements. Concave holographic gratings may also be important for light collection optimization and in the design of more compact systems. They are regularly used in spectrographs that employ solid-state array detectors. Flat-field spectrograph gratings are typically used in detector array instruments of moderate resolution.
Common trade-offs in performance that only occur with concave gratings are resolution and f number, efficiency and clear aperture. Plano gratings, of course, remove these performance trade-offs giving the customer some additional flexibility as well as additional quantity discount pathways that may not exist with concave gratings. Designers that have access to a full product portfolio and experienced applications personnel will be in the best position to choose the right grating for their own unique set of design requirements. We offer that full product portfolio and one of our applications scientists and engineers will be happy to discuss the use of our gratings for your optical design.
See our Diffraction Grating Handbook for a discussion of concave grating mounts and imaging properties.
