Patent ID: 7830596

Claim:
A method comprising: providing a first photonic-crystal optical device that includes a first photonic-crystal-defined waveguide having a diameter of at least about 40 microns, and a second photonic-crystal-defined waveguide, wherein the first and second photonic-crystal-defined waveguides each maintain a single transverse mode, and are each surrounded by a cladding to contain pump light so the pump light can enter each waveguide over its length; generating a pulsed single-frequency narrow-linewidth seed laser signal light; directing the pulsed seed signal light into the second waveguide of the photonic-crystal optical device; directing pump light into the second waveguide of the photonic-crystal optical device in a counter-propagating direction relative to the pulsed seed signal light; amplifying the pulsed seed signal light in the second waveguide while maintaining a single transverse mode to obtain second amplified pulsed signal light; directing the second amplified pulsed signal light from the second waveguide of the photonic-crystal optical device to the first waveguide of the photonic-crystal optical device; directing pump light into the first waveguide of the photonic-crystal optical device in a counter-propagating direction relative to the signal light; and further amplifying the second amplified pulsed signal light in the first waveguide to obtain a first pulsed output beam while maintaining a single transverse mode to a peak power of at least about 300 kW and a spectrally narrow signal bandwidth of less than 50 GHz.