Low noise FM fiber laser amplifier

A fiber amplifier system comprising:

• an optical source providing an optical seed beam;
• an optical component responsive to the seed beam and causing frequency modulation (FM) to amplitude modulation (AM) conversion to the seed beam that creates a non-uniform spectral transmission of the seed beam having peaks and nulls;
• a spectral shift polarization actuator causing a shift in the spectral transmission of the seed beam created by the optical component;
• a fiber amplifier responsive to the seed beam after the spectral shift polarization actuator and the optical component and generating an amplified output beam;
• a beam sampler responsive to the amplified output beam that provides a sample beam;
• a detector sub-system responsive to the sample beam, said detector sub-system detecting an amount of amplitude modulation in the sample beam and generating a control metric signal identifying the amount of amplitude modulation;
• and
• a spectral shift polarization controller responsive to the control metric signal from the detector sub-system and controlling the spectral shift polarization actuator to cause the spectral shift polarization actuator to make polarization adjustments to the seed beam to cause the spectral transmission created by the optical component to shift so that the peaks or nulls in the non-uniform spectral transmission align with a center frequency of the seed beam to reduce the amplitude modulation in the seed beam.

A fiber amplifier system comprising:

• an optical source providing an optical seed beam;
• an optical component responsive to the seed beam and causing frequency modulation (FM) to amplitude modulation (AM) conversion to the seed beam that creates a non-uniform spectral transmission of the seed beam having peaks and nulls;
• a spectral shift temperature actuator coupled to the optical component, and heating or cooling the optical component to cause a shift in the spectral transmission of the seed beam created by the optical component;
• a fiber amplifier responsive to the seed beam after the spectral shift temperature actuator and the optical component and generating an amplified output beam;
• a beam sampler responsive to the amplified output beam that provides a sample beam;
• a detector sub-system responsive to the sample beam, said detector sub-system detecting an amount of amplitude modulation in the sample beam and generating a control metric signal identifying the amount of amplitude modulation;
• and
• a spectral shift temperature controller responsive to the control metric signal from the detector sub-system and controlling the heating/cooling device to cause the heating/cooling device to make temperature adjustments to the optical component to cause the spectral transmission created by the optical component to shift so that the peaks or nulls in the non-uniform spectral transmission align with a center frequency of the seed beam to reduce the amplitude modulation in the seed beam.