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