Photorefractive AlGaAs–GaAs multiple-quantum-well structures perform as ultrafast field autocorrelators during steady-state four-wave mixing by use of femtosecond pulses. The photorefractive thin films operate in the Raman–Nath diffraction regime with thin transmission gratings. The thin gratings permit degenerate and nondegenerate four-wave mixing without the need to satisfy phase-matching conditions. Nondegenerate mixing has several advantages over degenerate four-wave mixing. The autocorrelation is broadband and is viable for photon energies larger than the band gap of the photorefractive sample, and the diffraction efficiency is unaffected by the bandwidth of the femtosecond pulses. In addition, the readout laser can be a low-power low-cost cw diode laser.
© 1994 Optical Society of America
R. M. Brubaker, Q. N. Wang, D. D. Nolte, E. S. Harmon, and M. R. Melloch, "Steady-state four-wave mixing in photorefractive quantum wells with femtosecond pulses," J. Opt. Soc. Am. B 11, 1038- 1044 (1994)