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Mangini F, Ferraro M, Gemechu WA, Sun Y, Gervaziev M, Kharenko D, Babin S, Couderc V, Wabnitz S. On the maximization of entropy in the process of thermalization of highly multimode nonlinear beams. OPTICS LETTERS 2024; 49:3340-3343. [PMID: 38875615 DOI: 10.1364/ol.521563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 05/13/2024] [Indexed: 06/16/2024]
Abstract
We present a direct experimental confirmation of the maximization of entropy which accompanies the thermalization of a highly multimode light beam, upon its nonlinear propagation in standard graded-index (GRIN) optical fibers.
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Ferraro M, Mangini F, Zitelli M, Wabnitz S. On spatial beam self-cleaning from the perspective of optical wave thermalization in multimode graded-index fibers. ADVANCES IN PHYSICS: X 2023; 8. [DOI: 10.1080/23746149.2023.2228018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 06/16/2023] [Indexed: 09/02/2023] Open
Affiliation(s)
- Mario Ferraro
- Department of Information Engineering, Electronics and Telecommunications, DIET, Sapienza University of Rome, Rome, Italy
- Department of Physics, University of Calabria, Rende, Italy
| | - Fabio Mangini
- Department of Information Engineering, Electronics and Telecommunications, DIET, Sapienza University of Rome, Rome, Italy
- CNR-INO, Istituto Nazionale di Ottica, Pozzuoli, Italy
| | - Mario Zitelli
- Department of Information Engineering, Electronics and Telecommunications, DIET, Sapienza University of Rome, Rome, Italy
| | - Stefan Wabnitz
- Department of Information Engineering, Electronics and Telecommunications, DIET, Sapienza University of Rome, Rome, Italy
- CNR-INO, Istituto Nazionale di Ottica, Pozzuoli, Italy
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Mangini F, Ferraro M, Sun Y, Gervaziev M, Parra-Rivas P, Kharenko DS, Couderc V, Wabnitz S. Modal phase-locking in multimode nonlinear optical fibers. OPTICS LETTERS 2023; 48:3677-3680. [PMID: 37450723 DOI: 10.1364/ol.494543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 06/19/2023] [Indexed: 07/18/2023]
Abstract
Spatial beam self-cleaning, a manifestation of the Kerr effect in graded-index multimode fibers, involves a nonlinear transfer of power among modes, which leads to robust bell-shaped output beams. The resulting mode power distribution can be described by statistical mechanics arguments. Although the spatial coherence of the output beam was experimentally demonstrated, there is no direct study of modal phase evolutions. Based on a holographic mode decomposition method, we reveal that nonlinear spatial phase-locking occurs between the fundamental and its neighboring low-order modes, in agreement with theoretical predictions. As such, our results dispel the current belief that the spatial beam self-cleaning effect is the mere result of a wave thermalization process.
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Podivilov EV, Mangini F, Sidelnikov OS, Ferraro M, Gervaziev M, Kharenko DS, Zitelli M, Fedoruk MP, Babin SA, Wabnitz S. Thermalization of Orbital Angular Momentum Beams in Multimode Optical Fibers. PHYSICAL REVIEW LETTERS 2022; 128:243901. [PMID: 35776459 DOI: 10.1103/physrevlett.128.243901] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 04/20/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
We report on the thermalization of light carrying orbital angular momentum in multimode optical fibers, induced by nonlinear intermodal interactions. A generalized Rayleigh-Jeans distribution of asymptotic mode composition is obtained, based on the conservation of the angular momentum. We confirm our predictions by numerical simulations and experiments based on holographic mode decomposition of multimode beams. Our work establishes new constraints for the achievement of spatial beam self-cleaning, giving previously unforeseen insights into the underlying physical mechanisms.
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Affiliation(s)
- E V Podivilov
- Novosibirsk State University, Novosibirsk 630090, Russia
- Institute of Automation and Electrometry SB RAS, 1 academician Koptyug avenue, Novosibirsk 630090, Russia
| | - F Mangini
- Department of Information Engineering, University of Brescia, Via Branze 38, 25123 Brescia, Italy
- Department of Information Engineering, Electronics, and Telecommunications, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy
| | - O S Sidelnikov
- Novosibirsk State University, Novosibirsk 630090, Russia
| | - M Ferraro
- Department of Information Engineering, Electronics, and Telecommunications, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy
| | - M Gervaziev
- Novosibirsk State University, Novosibirsk 630090, Russia
| | - D S Kharenko
- Novosibirsk State University, Novosibirsk 630090, Russia
- Institute of Automation and Electrometry SB RAS, 1 academician Koptyug avenue, Novosibirsk 630090, Russia
| | - M Zitelli
- Department of Information Engineering, Electronics, and Telecommunications, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy
| | - M P Fedoruk
- Novosibirsk State University, Novosibirsk 630090, Russia
| | - S A Babin
- Novosibirsk State University, Novosibirsk 630090, Russia
- Institute of Automation and Electrometry SB RAS, 1 academician Koptyug avenue, Novosibirsk 630090, Russia
| | - S Wabnitz
- Novosibirsk State University, Novosibirsk 630090, Russia
- Department of Information Engineering, Electronics, and Telecommunications, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy
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Mangini F, Gervaziev M, Ferraro M, Kharenko DS, Zitelli M, Sun Y, Couderc V, Podivilov EV, Babin SA, Wabnitz S. Statistical mechanics of beam self-cleaning in GRIN multimode optical fibers. OPTICS EXPRESS 2022; 30:10850-10865. [PMID: 35473042 DOI: 10.1364/oe.449187] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 02/14/2022] [Indexed: 06/14/2023]
Abstract
Since its first demonstration in graded-index multimode fibers, spatial beam self-cleaning has attracted a growing research interest. It allows for the propagation of beams with a bell-shaped spatial profile, thus enabling the use of multimode fibers for several applications, from biomedical imaging to high-power beam delivery. So far, beam self-cleaning has been experimentally studied under several different experimental conditions. Whereas it has been theoretically described as the irreversible energy transfer from high-order modes towards the fundamental mode, in analogy with a beam condensation mechanism. Here, we provide a comprehensive theoretical description of beam self-cleaning, by means of a semi-classical statistical mechanics model of wave thermalization. This approach is confirmed by an extensive experimental characterization, based on a holographic mode decomposition technique, employing laser pulses with temporal durations ranging from femtoseconds up to nanoseconds. An excellent agreement between theory and experiments is found, which demonstrates that beam self-cleaning can be fully described in terms of the basic conservation laws of statistical mechanics.
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