Pulse shaping by difference-frequency mixing with quasi-phase-matching gratings

We present a theory of ultrashort-pulse difference-frequency generation (DF G) with quasi-phase-matching (QPM) gratings in the undepleted-pump, unampli fied-signal approximation. In the special case of a cw (or quasi-cw) pump, the spectrum of the generated idler is related to the spectrum of the signa l through a transfer-function relation that is valid for arbitrary dispersi on in the medium. The engineerability of this QPM-DFG transfer function est ablishes the basis for arbitrary pulse shaping. Experimentally we demonstra te QPM-DFG devices operating in a frequency-degenerate type II configuratio n and producing pulse-shaped output at 1550 nm from 220-fs pulses at 1550 n m. (C) 2001 Optical Society of America.