Controllable superbunching effect from four-wave mixing process in atomic vapor

Correlation property of light limits the performance in related applications such as the visibility of ghost imaging or intensity interferometry. To exceed these performance limits, we here manipulate the degree of second- and higher-order coherence of light by changing controllable variables in four-wave mixing (FWM) process. The measured degree of second- and third-order coherence of the output light beams considerably exceed those of the incident pseudothermal light. Namely superbunching effects, g (2) (0) value up to 7.47 and g (3) (0) value up to 58.34, are observed experimentally. In addition, strong second- and third-order cross-correlation exist between the output light beams. Further insights into the dependence of superbunching light on the temperature of Rb vapor, the laser detuning and the optical power of all the incident light beams show that it can serve as a light source with a tunable superbunching degree.