Second order cascaded frequency shifting and signal amplification in organic and inorganic crystals

We report wavelength shifting (generation of a pulse at the wavelength,lambda(p)-Delta lambda from a signal at lambda(p)+Delta lambda under the action of a pump at lambda(p)) and parametric amplification through a cascaded second order process in a periodically poled lithium niobate crystal and also in an organic crystal N-(4-nitrophenyl)-L-prolinol (NPP), NPP could convert signal pulse (from 1.16 to 1.14 mu m) with unit gain under the action of a pump pulse (at 1.15 mu m) of peak intensity as low as 9 MW/cm(2). In the limit of negligible conversion where the cascading effect can be described through an affective chi(eff)((3)),we derive for NPP \chi((3)) \ approximate to 2.4 x 10(-17) m(2)/V-2, which is similar to 10(2) larger than chi((3)) of conjugated polymers or semiconductors. In a 19 mm long PPLN sample, at lambda(p)=1.8 mu m and Delta lambda as large as 60 nm, we could obtain unit gain with a pump intensity of 6 MW/cm(2), while amplification by a factor of 10 requires 18 MW/cm(2). We also present a theoretical comparison between frequency mixing and cascading.