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Fibre lasers research

Aston  Institute  of  Photonic  Technologies  (AIPT)  has  a  well  established  track  record  in  many  optical  fibre  related  research  areas.  The  recent  development  in  fibre lasers by exploiting the nonlinear effects, polarised fibre gratings and nanomaterials has put AIPT in a leading position in novel optical fibre laser technology and applications.

Interesting fact: Aston University has developed the world’s longest fibre laser, stretching to a length of 270 kilometres!

Key research areas  

  • Ultralong Raman fiber lasers
  • Random distributed feedback fiber lasers
  • Real time spectral and temporal characterization of fiber lasers

Possible applications

  • Development of ultralong lasers for telecommunications 
  • Development of next-generation high repetition rate mode locked laser sources 
  • Lasers for biophotonics 
  • Fiber optic analogues for fluid dynamics and turbulence studies
aipt_fibrelaser2
AIPT  was  the  world  first  proposed  and 

developed  ultralong  fibre  lasers  with  cavity 
length  up  to  tens  and  hundreds  km  by 
uniquely  exploiting  Raman  amplification 
effects in the fibre.  Recently, a world record 
of  270  km  has  been  reported  by AIPT.  The 
demonstration  of  the  ultralong  fibre  lasers 
leads to a radical new outlook on information 
transmission and secure communications.


aipt_fibrelaser3
Principle of the random distributed feedback fibre laser
The  concept of random lasers has attracted a great
deal  of  attention  in  recent  years,  however,  the
properties of their output radiation are rather special
and  usually  characterized  by  complex  features  in
the  spatial,  spectral  and  time  domain.  At  AIPT,  a
new  type  of  the  random  fibre  laser  that  is  tunable
over  a  broad  wavelength  range  with  uniquely  flat
output  power  and  high  efficiency  has  been
developed,  which  outperforms  traditional  lasers  of
the same category.  AIPT proposed and demonstrated the random fibre lasers have opened
up a new field in laser physics research

aipt_fibrelaser1
Soliton is an ultra-short optical pulse with
properties having significant impact on the
optical communication. AIPT has recently
studied  the  Carbon  Nanotube  enabled
ultrafast  fibre  laser  technology  which  is
able to produce soliton pulses with a more
compact  structure.  With  the  nanomaterial
enabled  photonics  technology,  AIPT  is
considering    both  commercialisation  and
fundamental research in this type of laser.

Truly all fibre
  • Light weight and compact
  • Ultrashort pulse generation (10-15s)
  • Soliton pulse shape 
  • Low cost
  • Environmentally stable

Laser dynamics are usually interpreted by measuring its output intensity as a function of time. In a laser, the light is trapped in the cavity, making round trips as it bounces back and forth between the mirrors. We developed in AIPT a real-time measurement technique which uses this internal periodicity of radiation in the laser cavity to reveal two-dimensional spatio-temporal intensity patterns (over fast time and slow evolution time) instead of usual one-dimensional intensity dynamics. In experiments carried out at AIPT, dark and grey solitons of picosecond-order temporal width were found in radiation emitted by different lasers. In addition, bright coherent structures were also revealed in the radiation previously thought to be completely stochastic. The developed technique allows for the precise characterization of laser dynamics on different scales and can potentially reveal mechanism of pulse formation and destruction, rogue wave formation and other interesting manifestations of nonlinear interactions in a laser cavity.

Studying transition to a highly disordered state of turbulence from a linearly stable coherent laminar state is conceptually and technically challenging and immensely important, e.g. all pipe and channel flows are of that type. In optics, understanding how systems lose coherence with increase of spatial size or excitation level is an open fundamental problem of practical importance. We identified, arguably, the simplest system where this classical problem can be studied: we learnt to operate a fibre laser in laminar and turbulent regimes. We showed that laminar phase is an analogue of a one- dimensional coherent condensate, and turbulence onset appears through a spatial loss of coherence. We discovered a new mechanism of laminar-turbulent transition in laser operation: condensate destruction by the clustering of dark/grey solutions.

Ultrashort pulse fibre lasers play an important role in the modern research and industrial applications, ranging from telecom and metrology to biological/chemical applications and machining. Typical pulse widths can range from anywhere between a few nanoseconds, to hundreds of femtoseconds. There are various ways by which ultrashort pulsing can be achieved, each with its own merits and limitations. At AIPT, we use 45-degree tilted fibre Bragg gratings (TFBGs) in our lasers to realize sub-picosecond pulses. The 45-degree TFBG is essentially an all-fiber polarizer operating on the ‘pile of plates’ principle. Being of an all-fiber nature, it has very low insertion losses – much less than bulk polarizers. Furthermore, TFBGs can withstand high powers and temperatures – a property that is very conducive towards high power laser applications where very few alternatives for mode-locking exist. Very recently, our group demonstrated a sub-100 femtosecond mode locked fiber laser based on this grating technology. Our all-fiber approach to laser design strives to meet the high demands of stability and repeatability placed by real-world applications.

The random distributed feedback fibre laser was first demonstrated at the AIPT in 2010. Instead of point reflectors as in conventional fibre lasers, random fibre lasers employ distributed Raman amplification to amplify Rayleigh backscattering events occurring along the length of the fiber. Remarkably, this generates the necessary feedback to sustain lasing. This unique characteristic gives the laser many interesting properties, making it an attractive proposition for real world applications. Spectral tailoring of the radiation of random fibre lasers is a highly desirable property, and is being actively studied presently at the AIPT. With the use of filtering elements, sub-nanometer line-widths can be routinely obtained in the random lasing configuration. Further, by the use of fibre based polarisation devices, multiwavelength generation in the system can also be obtained in a quite straightforward manner. Apart from the motivation to find real world applications, the random fiber laser provides a unique laboratory for the study stochastic nonlinear dynamics – a nascent area which holds a lot of potential.