  Generation of nonclassical light suitable for interaction with atoms
corresponds to a crucial goal pursued across the broad quantum optics
community. We present the generation of nonclassical photon pairs using the
process of spontaneous four-wave mixing in warm atomic vapor with an
unprecedentedly high degree of nonclassical photon correlations. We show how
the unique combination of excitation of atoms in the proximity of the vapor
cell viewport, single excitation laser beam, double-$\Lambda$ energy level
scheme, auxiliary optical pumping, and particular optical filtering setups,
allow for the spectral bandwidth of generated nonclassical light fields of up
to $560 \pm 20$ MHz and low two-photon noise. We provide a quantitative
analysis of particular noise mechanisms which set technological and fundamental
limits on the observable photon correlations. The overall technological
simplicity of the presented scheme together with the availability of spectrally
matched quantum memories implementable with warm atomic vapors promises the
feasibility of realization of GHz bandwidth on-demand nonclassical light
sources and efficient quantum communication nodes.
