  In general, the typical approach to discriminate antibunching, bunching or
superbunching categories make use of calculating the second-order coherence
function ${g^{(2)}}(\tau )$ of light. Although the classical light sources
correspond to the specific degree of second-order coherence ${g^{(2)}}(0)$, it
does not alone constitute a distinguishable metric to characterize and
determine light sources. Here we propose a new mechanism to directly classify
and generate antibunching, bunching or superbunching categories of light, as
well as the classical light sources such as thermal and coherent light, by
Gamma fitting according to only one characteristic parameter $\alpha$ or
$\beta$. Experimental verification of beams from four-wave mixing process is in
agreement with the presented mechanism, and the in fluence of temperature $T$
and laser detuning $\Delta$ on the measured results are investigated. The
proposal demonstrates the potential of classifying and identifying light with
different nature, and the most importantly, provides a convenient and simple
method to generate light sources meeting various application requirements
according to the presented rules. Most notably, the bunching and superbunching
are distinguishable in super-Poissonian statistics using our mechanism.
