Efficient, High Resolution, Phase Diffraction Gratings

Experiments on the sodium D lines and an 0.82-Å separated doublet in the iron spectrum have shown that holographically recorded dichromated gelatin diffraction gratings have resolving powers within 90% of theory. The diffraction gratings are of excellent optical quality, have background scatter less than 10−4 of the signal, are ghost free and have greater than 90% first-order diffraction efficiency. Blazing is accomplished by rotating the grating to the incident angle which satisfies the Bragg condition for the blaze wavelength. The 3-μ-thick transmission gratings can be employed from 0.25 μ to at least 15 μ, with gelatin absorption interfering only at 2.6–4.0 μ and 5.8–8.5 μ.