TY - GEN

T1 - Self-induced generation of absolute negative temperatures in a multimode dense photon gas

AU - Ferraro, Mario

AU - Mangini, Fabio

AU - Stefanska, Karolina

AU - Gemechu, Wasyhun A.

AU - Gervaziev, Mikhail D.

AU - Kharenko, Denis S.

AU - Babin, Sergey

AU - Wabnitz, Stefan

N1 - Mario Ferraro, Fabio Mangini, Karolina Stefanska, et al. "Self-induced generation of absolute negative temperatures in a multimode dense photon gas", Proc. SPIE 13908, Quantum Sensing and Nano Electronics and Photonics XXII, 1390807 (5 Mar 2026); https://doi.org/10.1117/12.3076478 This work was supported by Russian Science Foundation (RSF) grant 25-72-31018.

PY - 2026/3/5

Y1 - 2026/3/5

N2 - Statistical mechanics connect macroscopic properties of matter with the laws governing the evolution of its microscopic constituents. In a classical gas, different thermodynamic laws apply to the weakly or strongly interacting particles of an ideal or real gas, respectively. Here, we demonstrate that a similar situation occurs for a gas of photons, which is contained in a multimode waveguide. We use a few-mode system provided by a standard step-index fiber operated below cutoff, which permits to prepare a high-density gas of photons. We show that, owing to the attractive potential energy contribution to the photon energy induced by the nonlinear Kerr effect, the mode population exhibits a spontaneous inversion from the fundamental to the highest order mode, as the input laser beam power grows larger. This inversion of the mode power distribution leads to a stable attractor for the output beam, and is associated with a progressive increase of the optical temperature until a flip of its sign leads to new regime of negative absolute temperatures. Our work demonstrates a new means to all-optically control the shape of laser beams.

AB - Statistical mechanics connect macroscopic properties of matter with the laws governing the evolution of its microscopic constituents. In a classical gas, different thermodynamic laws apply to the weakly or strongly interacting particles of an ideal or real gas, respectively. Here, we demonstrate that a similar situation occurs for a gas of photons, which is contained in a multimode waveguide. We use a few-mode system provided by a standard step-index fiber operated below cutoff, which permits to prepare a high-density gas of photons. We show that, owing to the attractive potential energy contribution to the photon energy induced by the nonlinear Kerr effect, the mode population exhibits a spontaneous inversion from the fundamental to the highest order mode, as the input laser beam power grows larger. This inversion of the mode power distribution leads to a stable attractor for the output beam, and is associated with a progressive increase of the optical temperature until a flip of its sign leads to new regime of negative absolute temperatures. Our work demonstrates a new means to all-optically control the shape of laser beams.

KW - Multimode Fibers

KW - Mode decomposition

KW - Kerr effect

KW - Four-wave mixing

KW - Transverse effects

KW - Beam shaping

KW - Statistical physics

UR - https://www.scopus.com/pages/publications/105039584259

UR - https://www.mendeley.com/catalogue/192c55e7-0488-3b4d-8826-83f87ee23cc9/

U2 - 10.1117/12.3076478

DO - 10.1117/12.3076478

M3 - Conference contribution

SN - 9781510697331

T3 - Proceedings of SPIE - The International Society for Optical Engineering

BT - Proceedings of SPIE - The International Society for Optical Engineering

A2 - Razeghi, Manijeh

A2 - Khodaparast, Giti A.

A2 - Vitiello, Miriam S.

PB - The International Society for Optical Engineering

T2 - SPIE Photonics West

Y2 - 17 January 2026 through 23 January 2026

ER -