Ultra-narrow and strong squeezing in the resonance fluorescence of a V configuration three-level atom

We investigate steady-state squeezing in the phase quadratures of the resonance fluorescence emitted from a three-level V-type atom driven by two coherent fields and damping in common vacuum. Quantum fluctuation spectra of the optimum-phase quadratures are calculated. We find that the steady-state squeezing of the observed driven transition between the excited state and the ground state is strongly affected by the decay rate of the controlling transition, detuning and intensity of driven fields, and the phase quadrature of fluorescent light. When the decay rate of the controlling transition approaches zero, and the driving fields are not resonant simultaneously, the squeezing peak can be extra narrow and the squeezing can be deeply enhanced to exceed the degree of squeezing for the driven two-level atom. We provide numerical results in support of our arguments for arbitrary values of the atomic and field parameters and also develop an analytic description in the limit of strong driving fields that leads to explicit lineshape and linewidth formulae.