Broadening of the sum-frequency phase-matching bandwidth by temperature gradient in MgO:PPLN.

We demonstrate bandwidth broadening in cascaded MgO-doped periodically poled lithium niobate (MgO:PPLN) crystals (Λ=10.3  μm) using the temperature-gradient technique. Up to 2.8 nm bandwidth at 600 nm spectral region is achieved using two 50 mm long cascaded MgO:PPLN crystals via sum frequency generation. This technique combines the merits of high conversion efficiency attributed to cascaded nonlinearity and the reconfigurability of temperature-gradient-induced chirp for broadening of the input wavelength acceptance range.