Researchers at EEEL have developed a new method to measure second-, third-, and fourth-order temporal coherences (g(2), g(3), g(4)) using a four-element superconducting nanowire single-photon detector (SNSPD). This technique allows for continuous measurement of all delay times, providing new insights into higher-order photon bunching.
The new method, which uses four SNSPD elements to sample an optical beam, offers several advantages over traditional beamsplitter and discrete detector approaches. It enables continuous measurement of all delay times, rather than just fixed nonzero delays, and can be more advantageous in some cases.
The researchers demonstrated their technique using both chaotic, pseudo-thermal light and coherent, attenuated laser light. The results showed good agreement with theoretical predictions, and the technique could potentially be used to test the long-held assertion that laser light is coherent to all orders (g(n) = 1).
The ability to measure higher-order coherences could have important applications in studying fundamental properties of optical sources, time-dependent scattering media, and improving visibility or signal-to-noise ratio in certain conditions.
Keywords: coherence, superconducting, nanowire, photon, coherences
