Square pulse emission with ultra-low repetition rate utilising non-linear polarisation rotation technique

• Main Authors: Sin Jin Tan, Zian Cheak Tiu, Sulaiman Wadi Harun, Harith Ahmad
• Format: Article
• Language: English
• Published: Wiley 2014-09-01
• Series: The Journal of Engineering
• Subjects: optical harmonic generation; optical pulse generation; fibre lasers; ring lasers; laser mode locking; laser cavity resonators; optical rotation; light polarisation; optical solitons; laser tuning; square pulse emission; ultralow repetition rate; nonlinear polarisation rotation technique; nanosecond square pulse generation; microsecond harmonic pulse generation; passively mode-locked fibre ring laser; single mode fibre; laser cavity; dissipative soliton resonance effect; laser peak intensity; pulse width broadening; pulse width tuning; pulse energy; pump power; time 28.2 ns to 167.7 ns; power 125 mW
• Online Access: http://digital-library.theiet.org/content/journals/10.1049/joe.2014.0188

The generation of nanosecond square pulse and microsecond harmonic pulse in a passively mode-locked fibre ring laser is demonstrated by inserting a 20 km long single mode fibre in the cavity. The laser operates in anomalous region based on the non-linear polarisation rotation process. The square pulse generation is because of the dissipative soliton resonance effect, which clamps the peak intensity of the laser and broadens the pulse width. The pulse width can be tuned from 28.2 to 167.7 ns. It was found that the square pulse can deliver higher pulse energy compared with the harmonic pulse. The highest recorded pulse energy is 249.8 nJ under the maximum available pump power of 125 mW without pulse breaking.