مشخصات پژوهش

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