Abstract
Ultraweak, ∼300-fs pulses at 1.5 μm are measured by second-harmonic generation intensity autocorrelation and frequency-resolved optical gating using aperiodically poled LiNbO 3 waveguides. Our reference-free scheme can retrieve complex fields with 120-aJ coupled pulse energy, corresponding to a sensitivity of 2 × 10 -6 mW 2 , ∼5 orders of magnitude better than the previous record. © 2006 IEEE.