Sum squeezing in four-wave sum frequency generation

Abstract

Sum squeezing is a higher-order multimode squeezing effect. Sum squeezing of the electromagnetic field in four-wave sum frequency generation is investigated under short-time approximation based on a fully quantum mechanical approach. It is shown that for uncorrelated modes the normal squeezing in the sum frequency field depends directly on the sum squeezing of the input field modes and that sum squeezing can be turned into normal squeezing through it. Further, the occurrence of sum squeezing in the three input modes is found to be dependent on the normal squeezing in any one or more of the modes.