Systems, apparatus, and methods for laser amplification in fiber amplifiers
AssigneeMassachusetts Institute of Technology
InventorSteven J. Augst
Life of this patent
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Abstract
A fiber amplifier includes an isolator, a gain fiber to amplify an input laser signal, and an optical filter disposed between the isolator and the gain fiber. The optical filter transmits the laser signal and reflects amplified spontaneous emission (ASE) propagating from the gain fiber toward the isolator. The reflected ASE reenters the gain fiber and is absorbed by the gain fiber for amplifying the input laser signal. The optical filter in the amplifier can protect the usually expensive isolator and reduce potential damage to the gain fiber induced by fluctuation of the input laser signal power, as well as reduce potential photodarkening at the input of the gain fiber.
Claims29
A system for amplifying an input laser signal at a signal wavelength, the system comprising:
- an isolator to receive the input laser signal;
- a gain fiber, in optical communication with the isolator, to amplify the input laser signal, the gain fiber emitting backwards-propagating amplified spontaneous emission (ASE) at an ASE wavelength;
- at least one pump source, in optical communication with the gain fiber, to pump the gain fiber with at least one pump beam at a pump wavelength;
- and
- an optical filter, in optical communication with the isolator and the gain fiber, to transmit at least 50% of the input laser signal from the isolator to the gain fiber and to reflect at least 20% of the backwards-propagating ASE back to the gain fiber, the gain fiber absorbing at least a portion of the backwards-propagating ASE reflected by the optical filter.
A method of amplifying an input laser signal at a signal wavelength, the method comprising:
- transmitting the input laser signal through an isolator;
- transmitting at least 50% of the input laser signal through an optical filter in optical communication with the isolator;
- amplifying the input laser signal with a gain fiber in optical communication with the optical filter, the gain fiber emitting backwards-propagating amplified spontaneous emission (ASE) at an ASE wavelength;
- and
- reflecting at least 20% of the backwards-propagating ASE to the gain fiber, the gain fiber absorbing at least a portion of the backwards-propagating ASE reflected by the optical filter.
A fiber laser amplifier, comprising:
- an isolator to receive the input laser signal having a signal wavelength within a range of about 1045 nm to about 1100 nm;
- a gain fiber doped with ytterbium, in optical communication with the isolator, to amplify the input laser signal at a gain of at least about 17 dB, the gain fiber further emitting a backwards-propagating amplified spontaneous emission (ASE) at an ASE wavelength within a range of about 1010 nm to about 1045 nm;
- at least one pump source, in optical communication with the gain fiber, to pump the gain fiber with at least one pump beam;
- and
- a fiber Bragg grating (FBG), in optical communication with the isolator and the gain fiber and having a transmissivity of at least 50% at the signal wavelength and a reflectivity greater than 20% at the ASE wavelength, to transmit the input laser signal from the isolator to the gain fiber and to reflect the backwards-propagating ASE back to the gain fiber.
Dependencies are inferred from the claim text.