We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

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Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

The rise in output power from rare-earth-doped fiber sources over the past decade, via the use of cladding-pumped fiber architectures, has been dramatic, leading to a range of fiber-based devices with outstanding performance in terms of output power, beam quality, overall efficiency, and flexibility with regard to operating wavelength and radiation format. This success in the high-power arena is largely due to the fiber’s geometry, which provides considerable resilience to the effects of heat generation in the core, and facilitates efficient conversion from relatively low-brightness diode pump radiation to high-brightness laser output. In this paper we review the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in terms of high-power performance. We then review the current status and challenges of extending the technology to other rare-earth dopants and associated wavelengths of operation. Throughout we identify the key factors currently limiting fiber laser performance in different operating regimes—in particular thermal management, optical nonlinearity, and damage. Finally, we speculate as to the likely developments in pump laser technology, fiber design and fabrication, architectural approaches, and functionality that lie ahead in the coming decade and the implications they have on fiber laser performance and industrial/scientific adoption.

High power fiber lasers: current status and future perspectives [Invited]

Recent research on fibre optic long-period gratings (LPGs) is reviewed with emphasis placed upon the characteristics of LPGs that make them attractive for applications in sensing strain, temperature, bend radius and external index of refraction. The prospect of the development of multi-parameter sensors, capable of simultaneously monitoring a number of these measurands will be discussed.

https://iopscience.iop.org/article/10.1088/0957-0233/14/5/201/pdf

Optical fibre long-period grating sensors: characteristics and application

The spectroscopic properties, structure and interconversions of optically active oxygen-deficiency-related point defects in vitreous silica are reviewed. These defects, the E′-centers (oxygen vacancies with a trapped hole or 3-fold-coordinated silicons), different variants of diamagnetic `ODCs' (oxygen-deficiency centers), and their Ge-related analogs play a key role in the fiber-optic Bragg grating writing processes. The controversy surrounding the structural models for the Si- and Ge-related ODCs is discussed and the similarity between the bulk and surface point defects in silica is emphasized. The possible interconversion mechanisms between 2-fold-coordinated Si, neutral oxygen vacancies and E′-centers are discussed. The effects of glassy disorder have a profound effect on defect properties and interconversion processes in silica.

Optically active oxygen-deficiency-related centers in amorphous silicon dioxide

2D layered materials (2DLMs) are a subject of intense research for a wide variety of applications (e.g., electronics, photonics, and optoelectronics) due to their unique physical properties. Most recently, increasing research efforts on 2DLMs are projected toward the nonlinear optical properties of 2DLMs, which are not only fascinating from the fundamental science point of view but also intriguing for various potential applications. Here, the current state of the art in the field of nonlinear optics based on 2DLMs and their hybrid structures (e.g., mixed-dimensional heterostructures, plasmonic structures, and silicon/fiber integrated structures) is reviewed. Several potential perspectives and possible future research directions of these promising nanomaterials for nonlinear optics are also presented.

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Nonlinear Optics with 2D Layered Materials.

A brief review is given of the state of the art in the research on the photosensitivity of fibres and photoinduced fibre gratings. The most important properties of fibre gratings are considered and the main methods of their production and their applications are discussed. The photosensitive compositions of silica glasses are presented and methods for increasing their photosensitivity are indicated.

Fibre gratings and their applications

Continuous-wave lasing of Bi-doped fiber lasers in a wavelength range of 1150-1215 nm with a power of up to 15 W has been obtained for the first time. The unsaturable optical losses in Bi-doped fibers have been revealed and their influence on the Bi-laser operation is investigated. Frequency doubling of the Bi-fiber laser radiation is demonstrated that can be used as a yellow light source (wavelength of 580 nm).

/pdf/high-power-cw-bismuth-fiber-lasers-koc5dmod84.pdf

High-power cw bismuth-fiber lasers

Bismuth-doped fiber lasers operating in the range 1300–1470 nm have been demonstrated for the first time, to our knowledge. It has been shown that Bi-doped alumina-free phosphogermanosilicate fibers reveal optical gain in a wavelength range of 1240–1485 nm with pumping at 1205, 1230, or 808 nm.

Bi-doped fiber lasers and amplifiers for a spectral region of 1300-1470 nm.

The authors propose a new simple configuration for 1.24 and 1.48 /spl mu/m Raman fibre lasers which are promising pumping sources for 1.31 /spl mu/m Raman amplifiers and Er-doped fibre amplifiers, respectively. Efficient resonant conversion of CW 1.06 /spl mu/m radiation to the first (1.24 /spl mu/m) and second (1.48 /spl mu/m) Raman Stokes in a phosphosilicate fibre is demonstrated for the first time.

CW high power 1.24 [micro sign]m and 1.48 [micro sign]m Raman lasers based on low loss phosphosilicate fibre

We report a laser-diode-pumped 1407-nm Raman fiber laser with an output power of 1 W. In this three-cascaded cw Raman laser, based on a single active phosphorus-doped silica fiber, for the first time to the authors’ knowledge successive generation of Stokes components of essentially different frequency shifts (1330 and 490 cm-1) has been realized. These Stokes components are associated with both constituents (P2O5 and SiO2) of the fiber core glass.

/pdf/three-cascaded-1407-nm-raman-laser-based-on-phosphorus-doped-3s4jv1x27w.pdf

Oleg I. Medvedkov

Papers

Fibre gratings and their applications

High-power cw bismuth-fiber lasers

Bi-doped fiber lasers and amplifiers for a spectral region of 1300-1470 nm.

CW high power 1.24 [micro sign]m and 1.48 [micro sign]m Raman lasers based on low loss phosphosilicate fibre

Three-cascaded 1407-nm Raman laser based on phosphorus-doped silica fiber.