Observation of spectral drift in engineered quadratic nonlinear media

Spectral blueshifts of femtosecond pulses induced by quadratic cascaded nonlinearities are experimentally studied in an engineered aperiodically poled stoichiometric lithium tantalate crystal with optimized nonlinear pattern and chirp of the input pump pulses. Starting from nearly Gaussian input pulses centered at 1420 nm with 70 nm spectral width, spectral shifts as high as 40 nm were obtained in combination with an almost unaltered spectral shape and a transform-limited pulse duration.