Spatio-temporal dynamics of random lasing in multimode/multicore fibers in comparison with traditional 3D random lasers

Project leaders

Neda Ghofraniha, Sergey Babin

Agreement

RUSSIA - RFBR-suspended - Russian Foundation for Basic Research

Call

CNR/RFBR triennio 2018-2020 2018-2020

Department

Physical sciences and technologies of matter

Thematic area

Physical sciences and technologies of matter

Status of the project

New

Research proposal

The history of random lasers (RLs) dates back to 1966 when Ambartsumyan et al. proposed the use of lasers with nonresonant feedback [1]. Recent developments in RLs include, besides the significant improvement of random laser performance, the demonstration of lasing in different types of disordered media, ranging from fluidic paper-based systems [2] to cold-vapor atoms [3], granular media [4] and biological tissues [5,6]. These results enabled the progress of advanced technologies for a wide range of applications, including the mapping of malignant tumors [7], and speckle-free full-field microscopy [8].
In spite of their already widespread applications, a comprehensive understanding of the mechanism behind the emission of RLs is still demanding. Developing such a model is the first key objective of our project. Since RL emission was observed over a wide range of scattering strengths, a comprehensive model must handle the action of resonances for different degrees of spatial localization. A preliminary theoretical analysis satisfying such requirement, and not limited by the dimensionality of the system, was provided by Conti and co-workers [9]. They proposed an electromagnetic (EM) approach to predict the main RL spectral features, attributing the lasing action to coupling between overlapping resonances with different degrees of spatial confinement. Mathematically, the problem reduces to the Haus master equation that is formally identical to a Gross-Pitaevskii equation with a parabolic potential. The experimental agreement with such theory gives a proof of the resonant modes structure, which is on the basis of RLs; it also demonstrates that such resonances emit according to a mode-locking behavior.
There is a formal analogy between the model used for RLs, and equations modeling the spatio-temporal dynamics of extreme events, such as rogue waves and solitons, in Raman fiber lasers [10]. Such analogy stimulates the interest in studying the emergence of extreme events and their statistics in random fiber lasers (RFLs). RFLs are the 1D version of the most general case of 2D/3D RLs. Similarly to conventional fiber lasers, gain (associated with stimulated emission by doping atoms or stimulated Raman scattering) is induced by an optical pump source. Feedback is provided by a random array of embedded in-fiber reflectors/scatterers such as random fiber Bragg gratings (RFBG) [11], or Rayleigh backscattering (RBS) naturally present in any fiber [12], respectively. Due to their waveguide properties, fiber-based RLs are recognized as light sources with superior performances for many applications. At the same time, the properties of radiation generated in RFLs, especially when based on RBS in long passive fibers exhibiting modeless spectra [12], are quite different from the properties of traditional 2D/3D RLs. So, a fundamental challenge to be tackled by our project is the study of the correspondences between the physical mechanisms of RLs and RFLs, as well as analogies between RLs/ RFLs and other complex systems. As first step in this direction, the analogy between RLs and the spin-glass phenomenon, which is typical for highly-disordered magnetic systems, was just recently demonstrated in [13]. Similar observations in random FBG based RFL have also been reported in [14], and the analogies with wave turbulence phenomena in hydrodynamics have been treated in both types of RFLs [15,16].
In this project, we will carry out comparative studies of the spatiotemporal dynamics and of the statistical properties (including turbulence-like behavior and rare-events generation) of 1D RFLs based on either strong (RFBG) or weak (RBS) scattering. Moreover, we also aim to launch a principally new type of quasi-3D RFL, or spatiotemporal RL (STRL), based on random refractive index 3D structures embedded in multimode and/or multicore fibers (analogous conventional 3D RLs).
It is especially important, that the project will be performed jointly by Italian and Russian teams with world-leading positions and complementary experience in RLs [2,4,9,12,17] and RFLs [12,15]. Specifically, the Russian team will bring in the project the recently developed techniques of random FBG or FBG array fabrication in active and passive fibers [17] and fs-inscribed 3D structures in multimode/multicore fiber lasers [18]. The Italian team will contribute to the project with its expertise on the mode structure of RLs, reached through the development of theoretical models and experimental investigations of several aspects of RLs, ranging from the time dynamics of phase-locking in RLs [9], to the statistical behavior of resonant modes [13], and the effect of geometrical confinement [19].
1.Ambartsumyan, R.V., et al., JETP Lett. 3, 167 (1966).
2.Ghofraniha, N., et al., Laser & Photonics Reviews 7, 432 (2013).
3.Baudouin, Q., et al., Nat. Phys. 9, 357 (2013).
4.Folli, V., et al.,. Scientific Reports 3, 2251 (2013).
5.Wang, C.-S., et al., Scientific Reports 4, 6736 (2014).
6.Gather, M. C., et al., Nature Photonics 5, 406 (2011).
7.Polson, R., et al., J. Opt. 12, 024010 (2010).
8.Redding, B., et al., Nature Phot. 6, 355 (2012).
9.Leonetti M., Conti C., PRA 88, 043834 (2013). Leonetti, M., Conti, C., Lopez, C., Nature Photonics, 5(10), 615 (2011). Leonetti M., Conti C., JOSAB 27,1446 (2010). Conti C., Leonetti M., et al., PRL 101, 143901 (2008).
10.Sugavanam S et al., Laser & Photonics Reviews 9, L35 (2015).
11.Gagné, M., et al., Opt. Expr. 17, 19067 (2009).
12.Turitsyn, S.K., et al., Nat. Phot. 4, 231 (2010).
13.Ghofraniha, N., et al. Nat. Com. 6, 6058 (2015).
14.Gomes, A.S.L., et al., Phys. Rev. A 94, 011801 (2016).
15.Churkin, D. V., et al., Nat. Com. 2, 6214 (2015).
16.González, I.R.R., et al., Nat. Com. 8, 15731 (2017).
17.Abdullina, S.R., et al. Laser Phys. Lett. 13, 075104 (2016).
18.Zlobina, E. A., et al. Opt. Lett. 42 (1), 9 (2017).
19.Ghofraniha, N., et al., Opt. Lett., 38(23), 5043 (2

Research goals

Specific objectives of the project are:
1. Carrying out experiments and analysis in order to provide evidence of extreme phenomena, such as rogue waves and solitons, in RFLs. We also aim to characterize their static behavior, in analogy with conventional/bulk RLs, for increasing dimensionalities of the laser system.
2. Developing a spatiotemporal (3D+1) general model, based on the Gross-Pitevskii equation (PDE) with a quadratic spatio-temporal (ST) potential, able to predict the RL action in multimode RFL. Specifically, we aim to link the fundamental features and physical mechanisms of different types of RLs through comparative studies of their ST dynamics and statistical properties. In particular, we will consider 1D to 3D RFLs based on strong (RFBG) and weak (RBS) scattering.
3. Analyzing, designing, fabricating and experimentally demonstrating a primarily new type of quasi-3D RFL, i.e. the spatio-temporal random laser, based on random refractive index 3D structures embedded in multimode and/or multicore fibers, which could be more closely related to traditional 3D RLs, but providing a cleaner beam quality coupled with higher efficiency.
In what follows, we outline the skeleton of our research plan. In the first year, we shall study the problem at low dimensionality (1D & 2D). In the second year, we foresee the extension of the study to the full 3Dcase. This leads to our proposed demonstration of a very new type of random laser: the spatiotemporal random laser (STRL).

Last update: 08/07/2025