Self-pumped phase conjugation with femtosecond pulses by use of BaTiO_3

Abstract

Self-pumped phase conjugation is generally believed to be attributed to degenerate four-wave mixing. Accordingly, the phenomenon requires the existence of three waves at certain interaction regions for the excitation of the fourth one. Although this condition is not satisfied by a train of femtosecond pulses with a repetition rate of 110 MHz, we have observed self-pumped conjugate pulses retroref lected by a BaTiO(3) crystal. The conjugate character of the pulses is demonstrated with the distorter method.

Characterization of femtosecond self-pumped phase conjugation in BaTiO3

“…National Research Laboratory of Metrology, Tsukuba, Ibaraki 305 Japan ͑Received 10 August 1998; accepted for publication 9 February 1999͒ We report the generation and characterization of the self-pumped phase conjugation of 450 nm femtosecond pulses in BaTiO 3 . The pump beam is incident on the crystal from the Ϫc face of the crystal.…”

“…[1][2][3][4][5][6] demonstrated highefficiency phase conjugation of broadband pulses in photorefractive crystals with a dispersive ''2-f '' system. Lobel, Petersen and Johansen 6 showed that the frequency scanning of the self-pumped phase conjugation ͑SPPC͒ could be avoided if the material dispersion of the photorefractive crystal was compensated by external dispersion devices, such as prisms and/or gratings.…”

“…However, at ϭ800 nm the rise time of the fs SPPC was ϳ100 s with a focused pump beam of 50 mW. 2,3 It is worth noting that the response speed by use of 450 nm is about five times faster than that by the use of 800 nm.…”

“…The SPPC is generated by a pair of dynamic gratings coupled by totally internal reflections at surfaces of the crystal ͑cat mirror͒. 3,21 The refraction at the air crystal interface and the dynamic gratings inside the crystal contribute to the negative angular dispersion. The negative angular dispersion compensates for the positive dispersion caused by the GVD of the crystal, which leads to a smaller total dispersion of the self-pumped phase conjugator.…”

Compression and broadening of phase-conjugate pulses in photorefractive self-pumped phase conjugators

“…Femtosecond self-pumped phase conjugation (SPPC) at various wavelengths has been observed in BaTiO 3 . [18][19][20][21][22][23] But its temporal characteristics have not been investigated yet. Although Yariv et al 24 proposed that the process of nonlinear optical phase conjugation could be utilized to compensate for channel dispersion, they discussed only the phase conjugation achieved by four-wave mixing in nondispersive media.…”