Photon number squeezing due to two-photon absorption in internal and external fields of a microcavity

The amplitude and phase noise spectra of the internal and external field of a microcavity are calculated using the quantum mechanical Langevin equatio ns. We assume that two-photon absorber works inside a cavity, which brings photon-number squeezing in the internal field as well as the external field . The individual frequency components of the output. field have strong sque ezing at cavity resonance due to the interference between the input and the cavity field, which is similar to the quadrature squeezing in a parametric oscillator and the photon number squeezing in a saturated laser oscillator . However, the degree of the squeezing is not perfect becuase the material fluctuation remains.