Wavelength shifting and amplification of optical pulses through cascaded second-order processes in periodically poled lithium niobate

We investigate the efficiency of wavelength shifting (generation of a pulse at the wavelength ${\lambda }_p\mathrm{-\Delta \lambda }$ from a signal at ${\lambda }_p\mathrm{+\Delta \lambda }$ 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. Our results show that, in a 19-mm-long sample, at ${\lambda }_p\text{=1.8\hspace{0.17em}μ}\mathrm{m}$ and Δλ as large as 60 nm, wavelength shifting with unit gain can be obtained with a pump intensity of $\text{6\hspace{0.17em}}{\mathrm{MW/cm}}^{\mathrm{2}},$ while amplification by a factor 10 requires $\text{18\hspace{0.17em}}{\mathrm{MW/cm}}^{\mathrm{2}}.$