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    Photonics

 

Academic Staff: Prof. A. Jha
Prof. A. J. Bell

Brochure:

Areas of research:

Development of fluoride glasses as hosts for the 1.3 µm optical fibre amplifier.

Land-based optical fibre networks operate in the second telecommunication window at the wavelength of 1.3 µm. There is at present no commercially available optical amplifier device at this wavelength. The development of such device is therefore of crucial importance and great urgency.

Development of germanium sulphide glasses for nonlinear applications.

Modern photonic systems require a wide range of nonlinear devices. The vast majority of these use single crystals which are expensive and difficult to grow. Glasses offer and attractive alternative for their ease of manufacture and adjustable properties.

Development of heavy-metal oxide glasses and glass ceramics.

Heavy-metal oxide glasses have good glass-forming properties combined with high refractive indices and attractive spectroscopic characteristics. Glass ceramics offer routes to controlled microstructures.

589 nm Laser sources for satellite communication

Broadband Er-doped fibre amplifiers

 

 

Heavy-metal fluoride glasses for the 1.3 µm Pr3+-doped optical fibre amplifier.


Gain in Pr3+-doped fibre amplifiers based on cadmium halide, gallium-indium fluoride and ZBLAN glasses: a) small-signal gain; b) power amplifier gain.


Fluoride glasses are preferred hosts for Pr3+ due to their low phonon energies which result in higher gain and quantum efficiency.

Achievements:
Pr3+ lifetime of 163 µs in modified ZBLAN glass, 60% longer than in standard ZBLAN;
Pr3+ lifetime of 325 µs in cadmium halide glass, the longest reported in any fluoride host;
fabrication of high purity gallium-indium fluoride and cadmium halide glasses using reactive atmosphere processing.

Additional applications:
optical fibres transmitting in the near-UV to near-IR range;
rare-earth doped fibre lasers in the near IR.

Collaborators:

  ORC, University of Southampton
  University of Rennes
  Merck UK
  BT

 

Fluoroaluminate glasses for the 1.3 µm Nd3+-doped optical fibre amplifier.


Gain curve in Nd3+-doped fluoroaluminate fibres.



Grating efficiency in Ce3+-doped fluoroaluminate glass.

Fluoroaluminate glasses are preferred hosts for Nd3+ due to their low refractive indices and good glass characteristics.

Achievements:
Nd3+ gain peak in fluoroaluminate fibre at 1317 nm, the shortest wavelength ever reported;
over 90% gain in the region 1310-1320 nm;
greatly reduced signal ESA (excited state absorption);
demonstration of efficient Bragg grating in Ce3+-doped fluoroaluminate glass.

Additional applications:
optical fibres transmitting in the near-UV to near-IR range;
rare-earth doped upconversion fibre lasers in the blue-violet;
applications involving fibre gratings, i.e. sensors, WDM;
gain-flattened erbium-doped amplifiers.

Collaborators:

  ORC, University of Southampton
  Merck UK
  Pirelli, Milan
 

Germanium sulphide glasses for nonlinear and active devices, for fibre sensors, and as passive delivery fibres.

Germanium sulphide glasses combine good glass-forming characteristics with strong nonlinear properties, extended infrared transmission, and high refractive indices.

Achievements:
nonlinear refractive index (n2) of 3x10-5
infrared transmission to 10 µm
Pr3+ lifetime of 210 µs

Applications:
nonlinear devices;
optical fibres with extended infrared transmission;
fibre sensors;
rare-earth doped infrared fibre lasers.

Collaborators:

  Heriot-Watt University
  NTO, Netherlands
 

 

589 nm Laser sources for satellite communication

Laser sources at 589 nm are required for satellite communications. The only two available sources are currently a multi-laser system involving frequency mixing and a high-power laser-pumped dye laser. We are developing a small, light and flexible fibre laser at 589 nm using Pr-doped fluoride glass. Figure shows Pr emission in different glass hosts: the chosen host glass has a stronger emission at the required wavelength, sufficient to provide lasing action. Other Pr-dope fluoride glasses, with larger emission at longer wavelength, can also act as amplfiers at the medically important 635 nm wavelength.

 


Broadband Er-doped fibre amplifiers

Worldwide demand for telecommunication bandwidth is increasing rapidly, and can only be satisfied by a widespread introduction of new optical technologies, such as wavelength-division-multiplexing (WDM). WDM requires optical amplifiers with broadband, flat gain. Current state-of-the-art Er-doped fibre amplifiers (EDFA) in silica glass do not provide sufficient bandwidth. We are developing broadband Er-doped amplifiers in modified silica and tellurite glass hosts. The figures below show Er emission in two of our glass compared with commercial alternatives. Our glasses have a broader emission curve and a larger cross-section, signalling higher, flatter gain with a broader bandwidth.


 

 


RESEARCH ON NOVEL OPTICAL FIBRES AND WAVEGUIDES FOR TELECOM AND SENSOR DEVICES


 

 
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