The laboratory is engaged in a fundamental study of fiber lasers that represent a new system, which helps to solve classical problems of hydrodynamics. In particular, fiber lasers allow for the laminar and turbulent generation mode, when having certain conditions a laminar-turbulent transition is implemented in them. Thus experimentally it is possible to get much more information on the example of optical systems than in the case of hydrodynamic systems with the help of modern means of optical measurements.
Nature does not allow to increase the size of the system without the loss of coherence. For example, despite the fact that a coherent laminar flow in the tubes is linearly stable, an increase in the flow rate of fluid through the tube will inevitably lead to the generation of turbulence, which dramatically increases the resistance to the injection and, as a consequence, leads to economic losses. To control the processes of transition from laminar to turbulent flow detailed understanding of the mechanisms of turbulence generation is required, which is extremely challenging.
In addition to this fundamental research area issues connected with the implementation and description of the new modes of fiber lasers generation for a new class of applications are also examined. In particular, new mechanisms to achieve mode locking in linear fiber lasers are explored. Work is also underway to obtain a laminar generation as interpulse radiation in noise pulse fiber lasers, which is an analogue of the system of turbulent "Puffs" on laminar background in pipe flows.
Random fiber lasers attract much attention of researchers because of the wide range of possible applications. Consequently, the ability to predict and control the properties of the radiation spectrum of such lasers is an important achievement both in fundamental and in practical terms. The traditional scheme of a laser includes an active medium placed between two mirrors. The active medium provides amplification and generation of light, while the mirrors provide positive feedback, reflecting the increased radiation back into the resonator. Random lasers do not have mirrors of the laser resonator and the positive feedback is formed by a random multiple reflection of light on the irregularities of the amplifying medium.
In 2010 in the journal Nature Photonics Laboratory researchers have described the concept of random generation in conventional optical fiber which is used in telecommunication data transmission lines. In the proposed random fiber laser, Rayleigh scattering has been used to achieve laser generation without using any additional mirrors. Since that time, the area of random fiber lasers has received significant development and a number of different systems on the basis of random fiber lasers has been developed. Such lasers may be used as simple and convenient laser sources in various applications, including data transmission systems and distributed fiber sensor systems to monitor various physical parameters (temperature, extensions, vibration) at the distance.
Russian physicists within a large collaboration of such institutions as: Novosibirsk State University, Institute of Automation and Electrometry SB RAS, Institute of Theoretical Physics named after L.D. Landau RAS, Aston University (England), Moscow Institute of Physics and Technology, Institute of Nuclear Physics named after G.I. Budker SB RAS, Vaytsmansk Institute (Israel) have reviewed the basics of the wave kinetic approach and built a formalism that allows to describe the properties of the systems, including the properties of random fiber lasers and other optical systems, the description of which is impossible applying the traditional kinetic approach. The nonlinear statistical theory of the laser radiation spectrum formation has been built for the first time, thus the approach of Nobel laureates A. Schawlow and Charles Townes has been expanded, who more than 50 years ago, described the principles of the laser radiation spectrum formation in the linear theory. Special experiments confirmed the predictions of the developed nonlinear theory.
From the standpoint of basic science, the results are of great interest. The results can be used to describe the nonlinear evolution of a broad class of dissipative systems. In addition to optical systems such as lasers with non-stabilized resonator, multimode lasers, periodic systems of data transmission; the proposed approach can be applied in solving problems of meteorology (the description of the long-term average annual temperature fluctuations taking into account daily and annual cycles), describing the process of blood circulation in the body ( e.g., alteration of body functions during the transition from walking to running based on heart rate), and other systems in which there is a circular evolution at a given time scale.
Another result of the laboratory activity deals with the basic understanding of fiber laser generation modes. Experimental study of the spatio-temporal generation modes provides fundamentally new opportunities to study the complex physics of generation and understand the processes leading to the formation of laser emission, which, in turn, allows for the development of lasers emitting in the new generation modes for practical application.
International partners of the laboratory: Aston University (UK), Australian National University (Canberra), University of Electronic Science and Technology (Chengdu, Sichuan, China), Zecotek Co. Ltd (Vancouver).
Head of Laboratory: Ph. D. in Physics and Mathematics, Dmitry Churkin,
novolaser@gmail.com
Section of Quantum Optics NSU
Institute of Automation and Electrometry, Siberian Branch of the Russian Academy of Siences
Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Siences 