HOLOGRAPHIC DIFFRACTION GRATINGS WITH ASYMMETRICAL GROOVE PROFILES
1977; Elsevier BV; Linguagem: Inglês
10.1016/b978-0-08-021625-6.50058-0
AutoresStefan Johansson, Lars‐Erik Nilsson, Klaus Biedermann, Kent Leveby,
Tópico(s)Solid State Laser Technologies
ResumoGratings with a sinusoidal profile, as they are obtained in photoresist by holographic interference techniques, can provide very high efficiency values for wavelengths of about the same dimension as the groove spacing. When the high dispersion following from the high groove density is undesirable and broadband efficiency is required, asymmetrical groove profiles become necessary. We report on a method of Fourier synthesizing an asymmetrical profile by superimposing two sinusoidal exposure distributions of spatial frequency ratio 1:2. Amplitudes and the relative phase of the two interference exposures are obtained from a calculation optimizing diffraction efficiency by optimizing the combined action of the diffracted fields. The technical realisation of the method, comprising, e.g., exact phase control of the two individual exposures, is described in detail. As an example, experimental results are reported for a grating of 600 grooves/mm blazed for λ = 340 nm The diffraction efficiency obtained in the +1 order is 67 per cent, and this value is higher by a factor of 9.5 than that of the −1 order.
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