SUM SQUEEZING IN 4-WAVE SUM-FREQUENCY GENERATION

Sum squeezing is a higher-order multimode squeezing effect. Sum squeez ing of the electromagnetic field in four-wave sum frequency generation is investigated under short-time approximation based on a fully quant um mechanical approach. It is shown that for uncorrelated modes the no rmal squeezing in the sum frequency field depends directly on the sum squeezing of the input field modes and that sum squeezing can be turne d into normal squeezing through it. Further, the occurrence of sum squ eezing in the three input modes is found to be dependent on the normal squeezing in any one or more of the modes.