Phase-dependent fluctuations of resonance fluorescence beyond the squeezing regime

Phase-dependent quantum features of the light scattered by a two-level atom driven by a monochromatic laser were investigated theoretically using the method of conditional homodyne detection [Carmichael, Castro-Beltran, Foster, Orozco, Phys. Rev. Lett. 85 (2000) 1855]. The splitting of fluctuations into terms of second and third order correlations of the dipole noise is obtained analytically. For the out-of-phase quadrature and weak laser driving the former are known to be squeezed. The third order fluctuations, newly found in this paper, grow with the laser intensity, contaminate squeezing below saturation, and dominate above it. They are responsible for the non-classicality and non-Gaussianity of the fluorescence for moderate to strong driving. Conditional homodyne detection, in both time and frequency domains, illustrates more general phase-dependent effects than squeezing, and is much less restricted by finite collection and quantum detector efficiencies than standard homodyne detection schemes.