High-power narrowed-linewidth fiber laser system

A narrow linewidth fiber laser system comprising:

• a seed oscillator;
• and
• an amplifier coupled to the seed oscillator,
• said seed oscillator comprising:
• an active gain fiber configured to absorb pump light at a first wavelength λ1 and to emit signal light at a second wavelength λ2;
• a pump source configured to introduce pump light at said first wavelength λ1 into said active gain fiber;
• a single-mode output fiber arranged at a first end of active gain fiber,
• a first resonant cavity including said active gain fiber;
• and
• a second resonant cavity including said active gain fiber,
• said first and second resonant cavities cooperating to reduce modal beating of the seed oscillator;
• said amplifier comprising:
• an active multimode gain fiber capable of supporting a single fundamental mode at the signal wavelength λ2, and a pump source configured to introduce pump light into said active multimode fiber,
• said single mode output fiber of said seed oscillator and said multimode gain fiber of said amplifier being mode-matched and coupled without a mode converter.

A narrow-linewidth fiber laser system comprising:

• a seed oscillator comprising:
• a single-mode active gain fiber configured to absorb pump light at a first wavelength λ1 and to emit signal light at a second wavelength λ2;
• a pump source configured to introduce pump light at said first wavelength λ1 into said active gain fiber;
• a single-mode output fiber arranged at a first end of active gain fiber, said single-mode output fiber including an output reflector,
• a fiber coupler arranged at a second end of said active gain fiber, said coupler splitting light from said second end of said active gain fiber into a first coupler output fiber and a second coupler output fiber;
• a first end reflector arranged on said first coupler output fiber, wherein a first resonant cavity including said active gain fiber is defined between said first end reflector and said output reflector;
• and
• a second end reflector arranged on said second coupler output fiber, wherein a second resonant cavity including said active gain fiber is defined between said second end reflector and said output reflector,
• said first and second resonant cavities supporting a substantially single fundamental mode, narrow linewidth optical signal, while cooperating to reduce modal beating;
• and
• an amplifier coupled to the single mode output fiber of said seed oscillator, said amplifier comprising:
• an active multimode gain fiber capable of supporting a single fundamental mode at the signal wavelength λ2, said single mode output fiber and said multimode gain fiber being mode-matched and coupled without a mode converter.