This patent relates to the use of an optical fibre for transmitting a pulsed main beam together with an initial dispersion according to wavelength so that the beam transmits the optic fibre to reduce the peak power of the beam within the optic fibre and then a compression means so that the beam arrives at the specimen in a compressed form. The ultra short-pulsed laser can generate two-photon excitation, which can obtain images from a greater depth and have reduced photo bleaching and the ability to excite UV dyes without the use of relatively unreliable UV lasers and special lenses.
