Photon superbunching of classical light in the Hanbury Brown–Twiss interferometer

Two-photon superbunching of classical light is observed with single-mode continuous-wave laser light in a linear optical system. By adding more two-photon paths via rotating ground glasses, pinholes, lens, etc., g⁽²⁾(0) = 7.10 ± 0.07 is experimentally observed. The second-order temporal coherence function of the superbunching pseudothermal light is theoretically and experimentally studied in detail. It is predicted that the degree of coherence can be increased dramatically by adding more multi-photon paths. For instance, the degree of the second- and third-order coherence of the superbunching pseudothermal light with five rotating ground glasses can reach 32 and 7776, respectively. The results are helpful to understanding the physics of superbunching and improving the visibility of thermal light ghost imaging.