Picosecond pulse-width ultra-low repetition rate passive mode-locked fibre ring laser.

The authors experimentally demonstrate an ultra-low repetition rate passive mode-locked fibre ring laser with a semiconductor optical amplifier works like as a gain medium and non-linear polarisation rotation. A unidirectional erbium-doped fibre amplifier provides additional gain to increase cavity power. By exploiting non-linear polarisation rotation combined with dispersion management stable 5.18 ps optical pulses with 67.2 kHz repetition rate and energy of 1.75 nJ were generated with an extinction ratio >35 dB. The central wavelength is 1557.89 nm and the optical 3-dB bandwidth 1.82 nm very appropriate for optical applications that often require high-peak-power, low repetition rate and picosecond pulses. [ABSTRACT FROM AUTHOR]