Simultaneous squeezing of coherent fields using coherent population trapping

We study the effects of equal and unequal Rabi frequencies as well as cavity bandwidth on the optimal noise of the output fields from a two-mode optical cavity, which is fed by two coherent fields and encloses a collection of three-level Λ atoms. Each of the output modes is shown to be highly squeezed in the case of smaller symmetrical atomic detunings compared to the spontaneous-emission rates, where the system is in the vicinity of perfect coherent population trapping (CPT). We find that the squeezing on each output mode is larger than that reported by Dantan et al (2006 Phys. Rev. Lett. 97 023605) when adjusting the equal Rabi frequencies. The cavity bandwidth affects, not the degree of squeezing, but the linewidth of the spectral components. In an alternative way, the squeezing of each outgoing mode can be understood as a consequence of the enhanced cross-phase modulation, different from the nonlinear Faraday effect in Dantan's paper (2006 Phys. Rev. Lett. 97 023605). The application of squeezed light is to obtain high-precision measurement, optical communication, and interferometric detection of gravitational radiation.