Patent ID: 8731008

Claim:
A source of femtosecond pulses in the wavelength range 900-1000 nanometers, the source comprising: a seed pulse source arranged to generate pulses of lasing radiation at a wavelength in the range 900-1000 nanometers and having a first time duration; a fibre amplifier comprising an Ytterbium doped optical fibre that amplifies the pulses via three level operation and a pump laser operable to generate an optical pump signal at an optical power and wavelength for pumping the Ytterbium doped optical fibre; a nonlinear element adapted to produce spectral broadening of the pulses; and pulse compression apparatus arranged to reduce the temporal duration of pulses output from the fibre amplifier so as to provide output pulses having a femtosecond pulse duration that is shorter than the first time duration and a wavelength in the range of 900-1000 nanometers.