Single-frequency fiber amplifier with distal cladding stripper

A method of amplifying a beam of light, the method comprising:

• coupling the beam of light into a first gain fiber having a first core diameter and a first absorption at a pump beam wavelength;
• guiding the beam of light through the first gain fiber while pumping the first gain fiber with pump light at the pump beam wavelength;
• coupling the beam of light from the first gain fiber into a second gain fiber having a second core diameter smaller than the first core diameter and a second absorption at the pump beam wavelength lower than the first absorption;
• and
• guiding the beam of light through the second gain fiber while pumping the second gain fiber with additional pump light at the pump beam wavelength,
• wherein the first gain fiber and the second gain fiber have non-overlapping Stokes shifts.

A method of amplifying a beam of light, the method comprising:

• coupling the beam of light into a first gain fiber having a first core diameter and a first absorption at a pump beam wavelength;
• guiding the beam of light through the first gain fiber while pumping the first gain fiber with pump light at the pump beam wavelength;
• coupling the beam of light from the first gain fiber into a second gain fiber having a second core diameter smaller than the first core diameter and a second absorption at the pump beam wavelength lower than the first absorption;
• and
• guiding the beam of light through the second gain fiber while pumping the second gain fiber with additional pump light at the pump beam wavelength,
• wherein coupling the beam of light from the first gain fiber into the second gain fiber comprises adapting a transverse dimension of a fundamental mode guided by the first gain fiber to a size matching a fundamental mode guided by the second gain fiber.