Higher-order squeezing in a boson-coupled three-mode system

We consider a cavity model in which the dynamics of photons and phonon modes, as well as their interaction with a boson reservoir, are taken into account. The second- and fourth-order quantum coherence functions are evaluated and examined under various conditions of coupling coefficients, phases, and noise. For the case when the laser-anti-Stokes coupling is larger than the laser-Stokes coupling, the quantum correlations between field operators are identified in the form of sum and ordinary squeezing. The reservoir can be noisy without severely degrading the sum squeezing. (C) 1997 Optical Society of America.