Self-organized light in multicore optical fibers: a route to scalable high-power lasers and all-optical signal processing

Lead Research Organisation: University of Southampton
Department Name: Optoelectronics Research Centre (ORC)

Abstract

Optical fibers are nowadays ubiquitous and exploited in a multitude of applications, from telecommunications to high-power lasers. The last decade has seen the emergence of a new type of optical fiber, the so called multicore (MC) fiber. Unlike traditional fibers, where only a single core is used to carry the light beam, MC fibers are characterized by having a multitude of cores, each one carrying a different light beam. In each core, light can travel in one direction (forward) or in the opposite direction (backward). When forward and backward light beams are simultaneously present, we refer to a counter-propagating configuration.

This project aims to study the coupling dynamics between beams of different cores in a counter-propagating configuration, and to demonstrate its application in some important technological areas, ranging from high-power lasers through to telecommunications.

Preliminary studies carried out by the team members indicate that when the cores are sufficiently close, then strong coupling induced by the counter-propagating configuration may occur, such that the beams in each core organize themselves in to regular well-defined patterns. For example, the forward beams in each core and exiting the fiber may end up with the same phase irrespective of their initial phase.

These results imply natural application in coherent beam combination, which refers to the ability to combine multiple independent light beams so as to obtain a single beam characterized by a high brightness and beam quality at the system output. It is worth noting that here, differently from current state-of-the-art solutions, beam combination is achieved in an "all-optical" way, that is to say without resorting to the use of complex and power-consuming electronic control systems. Indeed it is the beams themselves in each core that self-organize due to their mutual coupling.

In this project we will design, fabricate and test bespoke MC fibers where the proposed all-optical beam combination is exploited to build high-power optical sources and novel optical devices for the next generation Internet. Moreover, a general theoretical framework will be developed that will find application not only in optics but also in other important disciplines, such as hydrodynamics.

The wide range of skills required for the development of the project will be covered by a multidisciplinary team at the Optoelectronics Research Centre (ORC) of the University of Southampton. The ORC is a world leading academic institution with some of the most advanced laboratories for fiber manufacture and experiments available on the planet.

Planned Impact

The broad nature of the project, ranging from theory, through technology to applications, will lead to impact of various forms

Impact on Industry and Economy:
The project will show that the self-organization process in a counter-propagating configuration in MC fibers represents a powerful and robust method for the generation of high-power, high spatial quality beams. This approach promises unprecedented scalability of high-power sources without the need for complex and power hungry electronic control measures. It will be therefore of great interest to laser companies. Moreover, the project will show that this same approach can be exploited to implement novel all-optical signal processing operations for the next-generation of Internet, which will capture the attention of telecommunications companies. Lasers and telecommunications are vitally important industries in the UK. Since the outcomes of this project have the potential to provide a novel ground-breaking technology for both of these industries, they could considerably strengthen the laser and telecom markets, with obvious impact on the UK economy.
In order to further improve the industrial and economic impact, we have included SPI Lasers as a formal project partner. SPI Lasers are one of the world's leading fiber laser manufacturers, with broad expertise in high-power fiber optical sources and beam combination.


Impact on Knowledge:
This project will build a novel fundamental understanding of the self-organization dynamics of light in MC-fibers. However, we envisage the theoretical outcomes of this project will find application in a variety of domains beyond MC-fibers. Arrays of waveguides and multimode fibers are some examples of optical systems where the project outcomes may apply; water waves in hydrodynamics and multicomponent Bose-Einstein condensates represent further examples beyond the optical domain.
In addition, the self-organization process under study in this project may represent a robust mechanism for the formation of "giant" waves, whose importance goes beyond fundamental science and concerns practical issues (giant waves may be extremely dangerous in ocean).
For these reasons, and since systems with counter-propagating configuration are ubiquitous in nature, the project will have important impact on knowledge.

Impact on Society:
The high-power, narrow-beam optical sources explored in this project find application in high-precision surgery, and can therefore improve the quality of surgical care, which represents a clear example of potential impact on society.
In addition, the study of novel all-optical signal processing operations may represent an important step towards the development of the next generation Internet network, characterized by transmission speeds well beyond the existing technology, which will result in a great improvement of the communication services to be offered to the public.

Impact on People:
The project will involve interdisciplinary collaboration between research fellows (RF) that are specialized in different domains. However, they will work closely together, providing mutual feedback. This strong interaction will ensure that the RFs are actively involved across the whole scientific process, from the initial theoretical models up to the fabrication and testing of the prototypes. This will allow them to gain basic skills and knowledge in those areas where they are not typically involved, therefore strengthening their scientific profile and ability to undertake research with broader scope and impact.
 
Description University of Bourgogne-Picozzi & Fatome 
Organisation University of Burgundy
Country France 
Sector Academic/University 
PI Contribution Discussion about the project objectives with Dr. Picozzi and Fatome( Univ. of Burgundy ) have stimulated them to expand upon their previous results in the all-optical control of light in single-mode systems, and so to undertake further studies in the framework of multimode systems like multicore fibers, which is the reference platform in this project.
Collaborator Contribution Dr.J.Fatome from Univ. of Burgundy (Dijon) is sharing his expertise to shape the next complex set of experiments on multicore fibers to be undertaken within the project. This includes suggesting the most suitable setups and components as well as specific experimental tips/techniques for the excitation of multiple spatial modes and the ability to observe and quantify them at the fiber output. Dr. A.Picozzi from Univ. of Burgundy (Dijon) is sharing his expertise in complex nonlinear multimode systems to shape the theoretical framework, which includes the development of the proper set of dynamical equations describing the interaction among the different beams of a multicore fiber as well as the related Matlab software to implement numerical simulations.
Impact 1) Definition of the set of experiments to undertake 2) Development of the theoretical framework
Start Year 2020
 
Description University of Brescia 
Organisation University of Brescia
Country Italy 
Sector Academic/University 
PI Contribution This collaboration is with Pr. C.De Angelis, Dr.L.Carletti and Dr. M.Gandolfi from the Department of Information Engineering at the University of Brescia, Italy. While project EP/T019441/1 deals with the study of nonlinear interactions in strongly coupled cores of multicore fibers, the abovementioned collaboration deals with the study of similar nonlinear interactions but at the nanoscale, in short submicron-sized arrays of coupled waveguides (nano-arrays). The target is the design of nano-arrays with tens of coupled elements to scale up the nonlinear conversion, and then ultimately the emitted power at the nanoscale. Both co-propagating and counter-propagating setups are envisaged (as in project EP/T019441/1). This collaboration fits and complements very well the objectives of project EP/T019441/1. Indeed, the design of such a complex platform requires a novel theoretical understanding. The theoretical tools developed in project EP/T019441/1 can provide useful theoretical tools to study the nonlinear dynamics in these nano-arrays. At the same time, some of the theoretical and numerical tools developed in the framework of nano-arrays may complement the theoretical analysis for project EP/T019441/1. The main contribution I made so far has been to set up the collaboration with Pr.De Angelis and M.Gandolfi, envisaging the analogies among the optical fiber setup and the nano-array setup that underlie the future work within this collaboration.
Collaborator Contribution Pr.C.De Angelis is a worldwide recognized expert in nonlinear optics at the nanoscale, and the recipient of several national and international grants on this topic. He brings a wide understanding of the physics investigated in this collaboration, as well as a broad network of academic peers that may significantly improve the quality of the research (especially in terms of fabricating the nano-arrays). Dr.M.Gandolfi and L.Carletti are respectively researcher and assistant professor in the group of Pr.De Angelis. Their main contribution comes from their excellent skills in numerical simulations. They are in charge of the complex and time-consuming finite-element method (FEM) simulations of the nano-arrays.
Impact 1) Definition of the analogies between the multicore fiber and the nano-array. 2)Definition of the steps to undertake within the collaboration, from the investigation of the simplest setup up to the most complex ones. 3)Identification of possible grants that may be targeted in the future to expand the outcomes of this collaboration
Start Year 2021
 
Title Nonlinear multicore - bidirectional simulations 
Description Matlab numerical tool to investigate the linear and nonlinear coupling among the supermodes of a multicore fiber with strongly coupled cores, with forward and backward beams propagating and interacting. 
Type Of Technology Physical Model/Kit 
Year Produced 2021 
Impact This code allows investigating the complex nonlinear dynamics of multicore fibers with forward and backward beams. This is a key-tool to determine the most appropriate set of parameters (e.g. lasers powers and wavelengths, fiber refractive index, number of cores, pitch and core radius) to be used in the experiments.