Thermal light by nature exhibits the well-known photon bunching effect with the zero-delay second-order correlation coefficient $g^{\left(2\right)}$ ideally equal to 2. The Photon extra-bunching effect, as a special class of the superbunching effect ($g^{\left(2\right)}>2$), describes the enhanced photon correlation ($g^{\left(2\right)}=3$) through the interference of bright twin beams produced in the spontaneous parametric down-conversion. In this work, we report that this effect can exist in classical beams and that $g^{\left(2\right)}$ can approach 4 in some extended extreme models. We experimentally demonstrate the nontrivial extra-bunching correlation ($\sim 1.4\times$ gain) in pairwise-generated holographic thermal light beams with a Dove prism-embedded balanced Mach-Zehnder interferometer. The interaction of such a pair of conjugated thermal light beams can generate a pair of uncorrelated superthermal light beams, enabling ghost imaging and Young's intensity interference with enhanced visibility. The quantum-inspired interference-induced spatial extra-bunching effect provides novel insights into inducing superbunching correlation in classical light and holds the potential for application in the coherent two-photon Lidar system to enhance sensitivity.

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• Ghost imaging
• Optical coherence