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Abstract
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When a part of an optical wave-front experiences a sharp change in its phase,Fresnel diffraction becomes
appreciable. Sharp change in phase occurs as a wave-front strikes with a phase step. The intensity distributions of diffraction patterns of the phase step is formulated by applying Fresnel– Kirchhoff integral.
For whiletheincidentlightonthestepiscoherent,theFresnel–Kirchhoff integralcanbesolvedbyusing
familiar Fresnelintegrals.But,whentheincidentlightispartiallycoherent,onecannotexpressthe
diffraction integralastheFresnelintegralsandtheproblemissummarizedinsolvingsomeunusual
integrals.Inthisreport,weproposeFouriertransformmethodforsolvingtheFresnel–Kirchhoffintegral.
In thisregardweusediscreteFouriertransformmethodandcalculateFresneldiffractionfromthe1D
phase stepbyFFT-basedalgorithms.Thismethoddoesnothaveanyrestrictiononthecoherenceand
profile shapeoftheincidentlight.Weshowthatthemethodhaveappropriatesolutionsforcoherentand
partially coherentlights.Forthecaseofthecoherentlightilluminationofthestep,theobtainedresults
are ingoodagreementwiththecalculatedresultsbyusingtheFresnelintegralsinreportedliteratures
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