Calorimetry of Photon Gases in Nonlinear Multimode Optical Fibers
Year: 2024
Authors: Ferraro M., Mangini F., Wu F.O., Zitelli M., Christodoulides D.N., Wabnitz S.
Autors Affiliation: Sapienza Univ Rome, Dept Informat Engn Elect & Telecommun, Via Eudossiana 18, I-00184 Rome, Italy; Univ Cent Florida, CREOL Coll Opt & Photon, Orlando, FL 32816 USA; Ist Nazl Ottica, CNR INO, Via Campi Flegrei 34, I-80078 Pozzuoli, Italy.
Abstract: Recent studies have shown that light propagating in a nonlinear, highly multimode system can thermalize in a manner totally analogous to that encountered in traditional statistical mechanics. At thermal equilibrium, the system’s entropy is at a maximum, in full accord with the second law of thermodynamics. In such arrangements, the entropy is extremized once the statistical power allocation among modes associated with this photon gas attains a Rayleigh-Jeans distribution that is fully characterized by an optical temperature T and a chemical potential mu. However, it has been theoretically argued that the variables T and mu represent actual thermodynamic forces that control the exchange of the respective conjugate quantities between two subsystems. In this work, we report, for the first time, optical calorimetric measurements in nonlinear multimode fibers, which unambiguously demonstrate that both the temperature T and the chemical potential mu dictate the flow of their associated extensive quantities, i.e., the energy and the optical power. Specifically, we study the process of light thermalization associated with two orthogonally polarized laser beams. Our observations are enabled by recently developed techniques that allow one to judiciously multiplex/demultiplex the optical power within various mode groups. Our results indicate that because of photon-photon collisions, heat only flows from a hot to a cold photon gas subsystem-thus providing an unequivocal demonstration of the second law in such all-optical thermodynamic arrangements. In addition to being fundamental, our findings provide a new approach to manipulate laser beams using thermodynamic principles.
Journal/Review: PHYSICAL REVIEW X
Volume: 14 (2) Pages from: 21020-1 to: 21020-13
More Information: M. F., F. M., and S. W. acknowledge NextGenerationEU, partnership on Telecommunications of the Future (PE00000001-program RESTART), and Sapienza University (Grants No. RG12117A84DA7437, No. SP12218480C7D1E9, and No. AR2221815ED243A0). The work of D. N. C. was partially supported by Air Force Office of Scientific Research (MURI: FA9550-20-1-0322, S004112), Office of Naval Research (MURI: N00014-20-1-2789), Army Research Office (W911NF-23-1-0312), Israel Ministry of Defense (IMOD: 4441279927) , National Science Foundation (CCF-2320937), and MPS Simons collaboration (Simons grant 733682). All authors acknowledge D. S. Kharenko, M. Gervaziev, and Y. Sun for helping in the development of the mode decomposition setup.KeyWords: Calorimetry; Chemical potential; Entropy; Laser beams; Multimode fibers; Nonlinear optics; Statistical mechanics; Multimode optical fibers; Multimode system; Non-linear multimodes; Optical power; Optical-; Photon gas; Power allocations; Second Law of Thermodynamics; Statistical power; Thermal-equilibriumDOI: 10.1103/PhysRevX.14.021020Citations: 2data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2025-04-27References taken from IsiWeb of Knowledge: (subscribers only)
