<title>New optical systems for holographic recordings of aberration-corrected diffraction gratings</title>

Abstract

A spherical concave diffraction grating was chosen as the dispersing element for a number of spectroscopic deices. More recent application of these grating is designing of multiplexers/demultiplexers for wavelength routed optical networks. Concave grating acts as the focusing element and can be the sole optical element of a device, which simplifies its adjustment and increases the transmittance. However, it possesses aberrations. Conventional method of concave diffraction grating recording using interference of two spherical waves formed using dividing an depending of laser beam, gives possibility to minimize three main types of aberrations, the defocusing, the meridional coma and the first order astigmatism. For the wide range of spectrometers these gratings can be used with rather good results. However, if we want to design spectrometer with increased aperture, wide spectral region or extremely high resolving power, we have to take into consideration per limit more than two aberrations - the sagittal coma and the spherical aberration. We also have this problem in designing of wavelength routers, where aberration geometric size of image should be not more than the optical fiber diameter. We can resolve this problem using aspheric wavefront recording systems. Since refraction optics is not good for holographic recording because of scattering, this system can include mirrors or other diffraction gratings. In present work different recording systems are discussed from the point of view of geometric theory of grating and from the point of view of reality of experimental installing and using of these systems as well.