Abstract

Crystals whose quadratic susceptibility, χ⁽²⁾, is modulated periodically in space can be used to phase match two or more counterpropagating beams of different frequencies provided that the wave vector of the modulation is sufficiently large. Conceivably, such crystals can allow second-harmonic generation or optical parametric amplification in a counterpropagating geometry.^1,2 This configuration, while still just beyond present-day poling technology, is very interesting because it can exhibit a range of behaviors including amplification and oscillation.

© 1998 Optical Society of America