Research On 1?m Single Frequency Ytterbium-doped Fiber Amplifier Based On Master-Oscillator Power-Amplifier System

The single-frequency laser has found its wide use in laser ranging,laser communications,coherent detection,coherent light phase locking.And 1?m single frequency laser is the base of single-frequency lasers with other wavelengths.However,the 1?m laser with single frequency and high output power is less researched.Fiber Master-Oscillator Power-Amplifier?MOPA?system is a feasible scheme of improving the output features of single-frequency?SF?lasers because of its many advantages,such as high slope efficiency and easily manageable output characteristics via control of the seed source.In this article,MOPAs based on ytterbium-doped fibers and non-planar ring oscillators?NPRO?are studied both theoretically and experimentally.And the main content of this thesis is:1.The working principle of NPRO is analyzed by Jones matrix of polarization state and the round trip transmission matrix of the NPRO is worked out.Next,the round trip loss of four modes is calculated.The NPRO can be processed out,once the design parameters are obtained by optimizing the loss and loss difference.Finally,we measured performance parameter of NPRO laser.And a 1?m single frequency LASER with the maximum single-frequency output power of 282 m W,optical conversion efficiency of 11.7%,slope efficiency of 14.1%,beam quality of 1.29 was achieved.2.We studied the spectrum characteristic of Yb³⁺ ions and established Yb³⁺-doped fiber laser rate equation model.Ignoring the influence of ASE about LMA highly doped fiber amplifier output characteristics,we established the Yb³⁺ doped fiber amplifier rate equation model and studied the steady-state amplification numerically.Based on the simple steady-state model of Yb³⁺-doped amplifier,the influence of fiber length,concentration and pump power on the output characteristics and the relations of optimal fiber length with pump power are analyzed through numerical simulation.3.The MOPA?master-oscillator-power-amplifier?technique has been adopted to carry out the amplification of the signal 1064 nm through Yb³⁺-doped fiber amplifier.The maximum CW 3.5W,the gain 21 dB,the beam quality of 1.85 at the wavelength 1064 nm has been achieved.Finally,the FPI and oscilloscope show that it is still a single frequency laser.