Intensity Distribution of the Radiation Diffracted by the Variable Depth Echelette Gratings

概要

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Taking the effect of the wavelength into consideration, formulae for the intensity distribution of the light, diffracted by various kinds of variable depth echelette gratings have been derived from the Kirchhoff theory. The formula for the variable single depth echelette (VSDE) grating agrees with the formulae which have hitherto been derived for an ordinary echelette grating, except the normalization constant. It has been made clear that this constant is inversely proportional to the wavelength. The operation of the VSDE grating slightly away from the blaze, gives the light of the desired wavelength effectively in a wide spectral region, reducing the intensities of the higher order spectra. Resolving power is proportional to the total number of plate and to the order, while the angular dispersion is inversely proportional to the width of plate and becomes larger with the increase of the order. By adding the rotation to the VSDE grating, it can serve as a dispersive medium as well as a filter for the higher order spectra at the same time. Variable depth filter grating is its special case. By menas of the variable double depth echelette grating which has the depth ratio of 2 m-1 : 1, it is possible to eliminate perfectly the light with the wavelength which is 1/m of that of the light to be wanted.
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