Fabrication of periodic fringe pattern of high spatial frequency for visible light lithography using dual aperture compact holographic lens system

In interference lithography both reflective and refractive beam combiners are used. Due to the achromatic nature of reflection, the angle of reflection and the angle between two interfering waves are identical irrespective of wavelengths related to spectral bandwidth of the laser leading to the generation of fringes of unequal fringe width. Whereas, for a diffractive beam combiner the longer wavelength is bent more than that of the shorter wavelength maintaining the ratio of wavelengths to half the semi angles between the two interfering waves same for all the wavelengths leading to generation of fringes of the same special frequency. In present work theoretical and experimental investigation on design and analysis of a dual aperture holographic diffractive beam combiner is presented for the fabrication of even periodic fringe pattern of high spatial frequency irrespective of wavelengths associated with spectral bandwidth of laser source.