Before the 1960s, all anti-Stokes emissions, which were known to exist, involved emission energies in excess of excitation energies by only a few kT. They were linked to thermal population of energy states above excitation states by such an energy amount. It was the well-known case of anti-Stokes emission for the so-called thermal bands or in the Raman effect for the well-known anti-Stokes sidebands. Thermoluminescence, where traps are emptied by excitation energies of the order of kT, also constituted a field of anti-Stokes emission of its own. Superexcitation, i.e., raising an already excited electron to an even higher level by excited-state absorption (ESA), was also known but with very weak emissions. These types of well-known anti-Stokes processes have been reviewed in classical textbooks on luminescence.1 All fluorescence light emitters usually follow the well-known principle of the Stokes law which simply states that excitation photons are at a higher energy than emitted ones or, in other words, that output photon energy is weaker than input photon energy. This, in a sense, is an indirect statement that efficiency cannot be larger than 1. This principle is

Upconversion and Anti-Stokes Processes with f and d Ions in Solids

We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.

Fiber grating sensors

The historical beginnings of photosensitivity and fiber Bragg grating (FBG) technology are recounted. The basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described. The many applications of fiber grating technology are tabulated, and some selected applications are briefly described.

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Fiber Bragg grating technology fundamentals and overview

Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) “soft” luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references).

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Lanthanide luminescence for functional materials and bio-sciences

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

High gain amplification of up to 28 dB has been observed in a 3m-long erbium-doped fibre. The amplifier has a spectral bandwidth of greater than 300GHz in the region of 1.536µm and a measured sensitivity of -42dBm at a bit rate of 140 Mbit/s.

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Low-noise erbium-doped fibre amplifier operating at 1.54μm

The spectral behaviour of two superimposed fibre gratings having different Bragg wavelengths (850 and 1300 nm) with respect to strain and temperature has been studied. The results show that the ratio of sensitivity at two Bragg wavelengths is dependent on strain and temperature, which can be used for simultaneous measurement of these parameters using a single sensing element.

/pdf/discrimination-between-strain-and-temperature-effects-using-1xlw6ng6ys.pdf

Discrimination between strain and temperature effects using dual-wavelength fibre grating sensors

A high pressure fibre optic sensor using an in-fibre grating has been constructed. The wavelength of peak reflection from an in-fibre grating is tracked as it is pressurised, and a wavelength shift of 0.22nm at 70MPa hydraulic pressure has been observed. This sensor is expected to be an attractive choice for ultrahigh-pressure monitoring.

/pdf/optical-in-fibre-grating-high-pressure-sensor-1sb25jzmh2.pdf

Optical in-fibre grating high pressure sensor

We report what is to our knowledge the first fiber distributed-feedback laser using a single Bragg grating at 1.5 microm written directly into a 2-cm-long Er(3+)-doped fiber codoped with Yb(3+). We obtained robust single-frequency operation by either using one end reflector or locally heating the center of the grating to create the necessary phase shift.

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Er(3+):Yb(3+)-codoped fiber distributed-feedback laser.

We report the first CW operation of a neodymium-doped silica single-mode fibre laser pumped by a GaAIAs laser diode. A laser threshold of less than 1 mW has been obtained.

/pdf/neodymium-doped-silica-single-mode-fibre-lasers-2jifjjxz18.pdf

Laurence Reekie

Papers

Low-noise erbium-doped fibre amplifier operating at 1.54μm

Discrimination between strain and temperature effects using dual-wavelength fibre grating sensors

Optical in-fibre grating high pressure sensor

Er(3+):Yb(3+)-codoped fiber distributed-feedback laser.

Neodymium-doped silica single-mode fibre lasers