Squeezing in the sum and difference fields in second harmonic generation

In this article we show that, in intracavity second harmonic generation, a combined quadrature can be chosen which exhibits considerably more squeezin g than the amplitude quadratures of the fundamental or second harmonic indi vidually. We also investigate squeezing in single-pass travelling wave seco nd harmonic generation, showing that previously published results are not a ccurate for arbitrary interaction length, with the behaviour obtained being qualitatively different. (C) 1999 Elsevier Science B.V. All rights reserve d.