Lasers and amplifiers having tapered elements

A laser system for generating optical pulses at an operating wavelength of the laser system, the system having an optical resonator comprising:

• first and second reflectors;
• a length of ytterbium doped optical fiber disposed between the first and second reflectors for providing optical gain within the ytterbium gain bandwidth;
• a tapered optical fiber disposed between the first and second reflectors and having a core which has a tapered input section which tapers from single mode to multimode at the laser operating wavelength, an inner section of substantially constant diameter capable of supporting multiple modes at the laser operating wavelength and a tapered output section which tapers from a first diameter to a second diameter that is smaller than the first diameter;
• wherein said tapered optical fiber provides normal dispersion at the operating wavelength of the laser system;
• wherein the length of the tapered optical fiber comprises at least 80% of the length of the optical resonator;
• and
• wherein the laser system is configured to provide optical pulses having pulse repetition rate of no greater than 15 MHz and a time duration no greater than 1 ns.