HOLOGRAPHIC OPTICAL-ELEMENT FABRICATION USING CHALCOGENIDE LAYERS

Investigations in the field of diffractive optical element (DOE) fabrication using optical methods and registering media based on chalcogenide vitreous semiconductors are reviewed. The peculiarities of the holographic diffraction grating (HDG) fabrication processes using such resists are investigated and the factors that influence the groove profiles are determined. Ways of optimizing media parameters, exposure, and treatment processes are shown. High-quality HDGs are obtained with spatial frequencies in the range 600 to 3600 mm(-1), diffraction efficiencies of 80 to 85% in polarized light, and a stray light level of 10(-6). The processes of Fresnel lense formation by the holographic method with the consequent diffraction pattern transfer into the substrate are developed and investigated. This provides an opportunity to obtain binary lenses with high numerical apertures and small sizes. The results of investigations of the fabrication processes of DOEs with blazed profiles are discussed. Most promising is the method of direct DOE recording using a sharply focused laser beam, which enables one to obtain kinoform elements with micrometer-sized distant zones. Additional treatment methods (wet or dry) enable one to obtain blazed gratings using the initial HDG with a symmetrical profile fabricated on the base of the chalcogenide layers.