We report an environmentally stable nanotube mode-locked fibre laser
producing linearly-polarized, nanosecond pulses. A simple
all-polarization-maintaining fibre ring cavity is used, including 300 m of
highly nonlinear fibre to elongate the cavity and increase intracavity
dispersion and nonlinearity. The laser generates scalar pulses with a duration
of 1.23 ns at a centre wavelength of 1042 nm, with 1.3-nm bandwidth and at
641-kHz repetition rate. Despite the long cavity, the output characteristics
show no significant variation when the cavity is perturbed, and the degree of
polarization remains at 97%
