Spatial-temporal photon bunching in spontaneous parametric light scattering

Alexander N. Penin, T. A. Reutova, Alexander V. Sergienko

А. А. Малыгин, Alexander N. Penin, Alexander V. Sergienko

Filip Sośnicki, Michał Mikołajczyk, Sanjay Kapoor +3 more

Photons emitted by incoherent sources exhibit temporal bunching, a fundamental manifestation of Bose-Einstein statistics first observed by Hanbury Brown and Twiss (HBT). While intensity correlation measurements originated in astronomy and are now central across quantum technologies, biophysics, and spectroscopy, observing temporal bunching in broadband thermal light remains limited by detector temporal resolution. Conventional approaches - such as streak cameras or optical upconversion - introduce severe trade-offs in efficiency, bandwidth, or setup versatility. Here, we propose and demonstrate a third route: pre-detection temporal magnification of the optical field prior to measuring its intensity autocorrelation function in a conventional HBT setup. Using an electro-optic time lens with a temporal magnification of 660, we resolve the temporal intensity autocorrelation of broadband thermal light generated via non-degenerate spontaneous parametric down-conversion with a bandwidth of 250 GHz. This enables direct observation of thermal photon bunching on sub-3.5 picosecond timescales without narrow spectral filtering, establishing pre-detection temporal imaging as a general platform for broadband statistical optics, with applications spanning ultrafast quantum optics, biophysical imaging, and potentially stellar intensity interferometry.

Chen‐Xin Ding, Ruiqing He, Zhiyuan Ye +6 more

Thermal light by nature exhibits the well-known photon bunching effect with the zero-delay second-order correlation coefficient ${g}^{(2)}$ ideally equal to 2. The Photon extra-bunching effect, as a special class of the superbunching effect (${g}^{(2)}>2$), describes the enhanced photon correlation (${g}^{(2)}=3$) 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 ${g}^{(2)}$ can approach 4 in some extended extreme models. We experimentally demonstrate the nontrivial extra-bunching correlation ($\ensuremath{\sim}1.4\ifmmode\times\else\texttimes\fi{}$ 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.

Xi Jie Yeo, Justin Yu Xiang Peh, Darren Ming Zhi Koh +2 more

Thermal light, including blackbody radiation and spontaneous emission, exhibits photon bunching. Thermal light sources, however, typically yield low spectral densities, limiting their practical utility. Pseudothermal light sources with higher brightness and longer coherence time are often employed instead. While pseudothermal light also exhibits photon bunching, this property may not suffice to fully replicate the behavior of genuine thermal light. Here we demonstrate a method to directly test the Siegert relation for two sources of photon-bunched light, laser light scattered from a rotating ground glass and spontaneously emitted light from a gas discharge lamp, probing a fundamental criterion expected of thermal light.

Boris Ya Zel'dovich