High efficiency ultrashort pulse measurement with aperiodically poled lithium niobate (A-PPLN) waveguides

This study reports autocorrelation measurements using quasi-phase-matched (QPM) lithium niobate waveguides, which permit much higher second harmonic generation (SHG) efficiency by confining the optical beam within a small area for a long distance. By longitudinally chirping the poling period of the waveguides, the group velocity mismatch (GVM) problem is solved by broadening the SHG bandwidth to be compatible with that of input pulses. This leads to a substantial increase in sensitivity, which may be particularly useful for measurements of ultrafast lightwave communication signals.