Diffraction gratings (manufacture)

Abstract

Recent progress in the techniques of manufacture of spectroscopic diffraction gratings is described. Three main topics are discussed in detail: (i) the mechanical ruling of gratings, and the way in which the mechanical aspects of the ruling process affect the spectroscopic performance of the grating; (ii) the development of interference (or 'holographic') techniques for manufacturing gratings, and the relationship between ruled gratings and those made interferometrically; (iii) x-ray gratings for use at grazing incidence, and the different criteria that arise through the use of gratings in this way. 2.7. Electromagnetic theory of gratings 2.8. Wood's anomalies . 2.9. Surface plasmons . 3.1. Introduction . 3.2. The ruling tool . 3.3. Films for ruled gratings 3.4. Recent studies of the ruling process 3.5. Contemporary ruled gratings . 3.6. Ruling engines . 3.7. Replication. 4.1. Introduction . 4.2. The spectroscopic performance of plane interference gratings 4.3. Blazed interference gratings . 4.4. Focusing and aberration-corrected gratings 4.5. Summary . 5 . X-ray gratings .

Prospects for machined immersion gratings in the near infrared and visible

“…Periodic error, essentially modulating the desired grating with a sub-grating, causes spurious "ghost" features in a spectrum. The intensity of a first order Rowland ghost relative to its parent line is given by (πmε/d) 2 , where m is the diffraction order of the grating, ε is the amplitude of the periodic error and d is the groove spacing 28 . Although there is no explicit wavelength dependence, the groove spacing will generally decrease and/or the diffraction order increase in gratings designed for shorter wavelengths, increasing the ghost intensity for a given periodic error amplitude.…”

“…The fraction of power incident on the grating that is lost to this form of scatter is given by (4πε (sin θ B ) /λ) 2 , where ε is the amplitude of the random error, θ B is the blaze angle (assumes Littrow configuration) and λ is the wavelength in the immersed material 28 . We have seen no evidence of random error in germanium gratings operated at 10 µm.…”

On the nature of the unidentified solar emission near 117 nm

“…It is based on the idea that a high diffraction order of the beam propagates along the surface of the grating for certain angles of incidence before it is diffracted off to the detector. Using the detailed theory presented by Palmer et al (1975), we checked the SUMER optical design for potential spectral ranges where the Wood anomaly might have an effect, and found 55.3 nm and 69.5 nm in the second order as well as 92.0 nm and 138.5 nm in the first order, not anywhere near the spectral positions of the humps. Even at the suspected ranges, we could not detect any unusual features, and conclude that SUMER is not susceptible to the effects of the Wood anomaly; in all likelihood, because of the concave grating employed, whereas the Rayleigh theory requires a plane grating.…”

<title>Minimizing Fizeau fringes during the contact printing of diffraction gratings</title>

“…Palmer et. al., 10 have discussed the allowed magnitude of this error. They assume that no imperfection should contribute an error in the diffracted wave front of more than λ/10.…”