780 nm ultrashort-pulsed fiber laser

A fiber laser, comprising:

• a seed laser generating a pulsed fundamental beam having a center wavelength;
• an optical gain fiber arranged to receive the fundamental beam, the fundamental beam propagating through the optical gain fiber from a first end to a second end thereof, the optical gain fiber having a core doped with erbium ions that are energized by a pump beam, the fundamental beam and the pump beam counter-propagating within the optical gain fiber, the pump beam having a power selected to produce population inversion at the second end of the optical gain fiber in a range between 30% and 60% and everywhere in the optical gain fiber of less than 60%, the optical gain fiber having a length selected such that the optical gain fiber absorbs all the power of the pump beam during counter propagation of the pump beam with respect to the fundamental beam, the center wavelength of the fundamental beam increasing between the first end and the second end of the optical gain fiber due to amplification of longer wavelengths within the fundamental beam and absorption of shorter wavelengths within the fundamental beam, the center wavelength increasing to between 1570 nanometers and 1575 nanometers;
• an erbium fiber power amplifier arranged to receive the fundamental beam from the optical gain fiber and to linearly amplify the fundamental beam to generate an amplified fundamental beam, the amplified fundamental beam having a spectral bandwidth that is compressible to a pulse duration less than or equal to 240 femtoseconds;
• and
• a harmonic generator arranged to receive the amplified fundamental beam and to generate a second-harmonic beam having a center wavelength greater than or equal to 780 nanometers.