INVESTIGATION OF THE METHOD OF DIRECT LASER WRITING OF OPTICAL ELEMENTS WITH BINARY HIGH-CONTRAST AMPLITUDE-PHASE TRANSMISSION

Abstract

A method is proposed for formation on one substrate of two superimposed optical structures - a binary phase structure and an analog high-contrast amplitude structure made on a thick chromium film in the form of a regular two-dimensional zero-order diffraction grating with a variable fill-factor of cells. A numerical and experimental study of this method is carried out as applied to an optical transparency for generating the structure of a gamma-coupled laser beam. The quality of a high-contrast structure, suitable for practical application, was experimentally achieved, with an optical density of a chromium film of about 4.3, when measured at a wavelength of 532 nm, and with a minimum size of transparent and opaque windows of the order of 1x1 μm. This method can be used to synthesize amplitude-phase transparencies with a large alternating range of change in the amplitude optical transmittance, with a relatively slow (smooth) change in the transmittance (with the carrier spatial frequency of the amplitude modulation determined by the period of the above two-dimensional zero-order diffraction grating).