The University of Southampton

Silica Fibre Fabrication

Fabrication of silica based optical fibre has been the core of the ORC’s fibre research since the formation of the ORC. Silica optical fibre and devices made from these types of fibre form the majority of the components used in the optical telecommunications industry as well as many other uses in high power lasers, sensing, light transmission etc. 

At the ORC we have access to a multi-million pound cleanroom equipped with several systems for fabrication and research on most aspects of silica fibres. The work of the fibre fabrication group is interdisciplinary. Candidates to work in this group require a background in any one of materials science, physics, engineering and chemistry.

Group webpage 

PhD Projects:

Bismuth-doped fibre amplifiers for extended transmission bands in optical communications

Supervisor: Professor Jayanta Sahu 

Co-supervisor: Dr Naresh Thipparapu

Global internet traffic has been growing exponentially over the past 20 years with a predicted growth rate of around 40% year-on-year. This growth is driven primarily by bandwidth-hungry applications such as cloud computing, Telemedicine, 4K live streaming and is expected to continue in the era of the Internet of Things and 5G. However, the present optical fibre communication network’s capacity is solely based on the 11THz (C and L bands) gain bandwidth of erbium (Er) doped fibre amplifiers (EDFA) invented three decades ago. The scaling of the overall transmission capacity requires next-generation optical fibre amplifiers with ultra-broad gain bandwidths to further utilise the complete low-loss window of silica optical fibres from 1250-1700nm.

In this PhD project, we aim to develop efficient Bi-doped fibres and to demonstrate next-generation ultra-broad Bi-doped fibre amplifiers in the wavelength band covering from 1250-1500nm and 1600-1750nm. In the process of developing Bi-doped fibres, the student will also study spectroscopic properties such as absorption and emission cross-sections, and fluorescence lifetime to understand the near-IR luminescence in these fibres. The focus will be on experimental work but can include simulations/modelling based on the interests of the student. The performance of developed Bi-doped fibre amplifiers will be evaluated in collaboration with our academic partners. Our recent work on record level of gain (40dB) and also first ever wideband (115nm) Bi-doped fibre amplifiers have been well received in the scientific community and grasped significant attention from telecom industries.

The successful applicant will have an opportunity to work in the world-class cleanroom complex with the state-of-the-art fibre fabrication facilities. He/she will also interact with our academic and industrial partners and will present the work on international platforms.

High power visible fibre lasers pumped by down-conversion process

Supervisor: Professor Jayanta Sahu 

Co-supervisors: Dr Bill Brocklesby and Dr Arindam Halder

Visible lasers are indispensable for applications such as display, underwater communication, microscopy and bio-photonics, optical storage, and materials processing. Currently the mainstream of visible lasers development is relied on the frequency conversion techniques. However, often such systems are complex and require incorporation of bulk elements into the cavity, and thus not suitable for making monolithic devices. On the other hand, most of the rare earth (RE) ions exhibit absorption lines in the blue spectral region and the fluorescence in the visible region. The progress in GaN-laser diodes (GaN-LD) covering the wavelength range between 390nm to 460nm are promising as pump sources for RE doped solid state lasers with direct emissions in the visible. To date visible lasers utilising RE doped fibres have been reported in fluoride glassed (such as ZBLAN) due to their lower phonon energy than the oxides. However, the fluoride glass fibres are known for their poor chemical durability, weak mechanical properties, higher background loss than silica fibres, and making them difficult to splice with most fibre components which are developed on silica fibres for an all-fibre laser system are the bottlenecks of these fibre lasers to further improve their performance.

This PhD project aims to investigate a route to high power visible sources through cladding pumping of RE-doped silica fibres using GaN-LDs. The student will develop RE (such as Pr3+, Dy3+ and Tb3+) - doped fibres in a modified silica glass host offering a low phonon energy while maintaining the other characteristics of silica fibres. The student will also perform a detailed spectroscopic characterization of the rare earth doped silicate glass fibres as well as realization of high power lasers to guide the development of visible fibres. At the end of this PhD project, the student will have the opportunity to develop skills in specialty optical fibre fabrication. In addition, the candidate will build a strong base in understanding of optical materials and characterization of rare-earth doped optical fibres, while acquiring knowledge on high power fibre lasers and amplifiers.

Development of new generation rare-earth doped optical fibres for high-power lasers at eye-safe wavelengths

Supervisor: Professor Jayanta Sahu

Co-supervisors:Dr Martin Miguel A Nunez Velazquez 

The new generation of high-power fibre lasers that are increasingly becoming the light source of choice for a wide range of industrial and scientific applications, have spurred the development of different types of rare-earth doped fibres, each with a unique set of properties to match with the specific applications. To date, the highest values of output power and laser efficiency have been achieved at a wavelength of around 1µm from ytterbium-doped silica fibres. There has now been an increasing interest in power scaling of fibre lasers operating in the 2 µm eye-safe wavelength region. Since the fibre design and material properties of the fibre core glass have become critical to the performance of the fibre laser, a more powerful fibre fabrication process is required than the current industry standard MCVD (Modified Chemical Vapour Deposition) and solution doping technique.

In this PhD project, the student will develop novel rare earth doped fibre fabrication techniques, using vapor phase deposition of rare-earths in combination with an MCVD or OVD (outside vapor deposition) process, for producing efficient Tm, and Ho - doped fibres for high power and high brightness 2 µm lasers. The fabrication techniques would offer a highly flexible technology platform for manufacturing advanced rare-earth doped optical fibres with a tailored dopant profile and scaling of the doped core, as required for the new generation of high power fibre lasers and amplifiers. The student will have access to the world-class cleanroom complex with a state-of-the-art fibre fabrication facilities. The project is also required a significant element of high power laser work. At the end of this PhD project, the student will have the opportunity to develop a wide range of skills, including specialty optical fibre fabrication and characterization of rare-earth doped optical fibres, while acquiring knowledge on high power fibre devices.

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