The diffraction properties of plane reflection gratings

Chapter 1 outlines the development of both ruling and holographic techniques for the production of diffraction gratings. The evolution of theoretical formulisms for describing the diffraction by gratings is also described. The experimental techniques available for testing the theories are considered, and an account is given of investigations into "anomalous" properties of gratings. In Chapter 2, five theoretical formulations are considered in some detail. The improvements in accuracy and domain of applicability given by each new method over its predecessor are demonstrated numerically, for four of the five formulisms. (The fifth formulism does not lend itself to direct comparison with the others.) The rigorous theories are validated by comparisons of their predictions with experimental measurements. Chapters 3 and 4 consider the theoretical properties of diffraction grating anomalies. In Chapter 3, attention is confined to gratings whose grooves are shallow compared with the wavelength of the incident radiation, and thus to S polarization anomalies. In Chapter 4, the behaviour of gratings having deeper grooves is examined, and properties of both P and S polarization anomalies are investigated. Chapters 5 and 6 discuss the results of theoretical studies of blaze optimization. For triangular profile gratings, it is shown that, in general, groove apex angles close to 90 degrees are to be preferred, rather than the larger angles 1100 to 120°(as recommended by G.W. Stroke). In Chapter 6, diffraction gratings having optimized sinusoidal groove profiles are shown to have blaze properties comparable with those of triangular profile gratings of the same line density. In Chapter 7, a theoretical method for the calculation of the profiles of holographic diffraction gratings produced in photoresist is described. This method is shown to give results in good agreement with all experimental observations of such profiles. Consideration is then given to the flexibility of arrangements for the formation of holographic gratings and an experimental system is discussed which fully utilizes this flexibility. The wide range of profiles which may be generated with such a system is demonstrated. Chapter 8 is devoted to a study of the agreement between experimental efficiency measurements and theoretical calculations for the three most important types of grating profile - the triangular form, the same form including land, and the quasi-sinusoidal shape. Profile distortion is demonstrated to have pronounced effects on Wood anomalies. It is shown that, by appropriate utilization of the non-linear characteristics of A21350 photoresist, improvements of at least 70% in the spectral performance of holographic gratings can be achieved