In this paper, we have experimentally demonstrated a 4.45 kW master oscillator power amplification (MOPA) narrow-linewidth fiber laser based on fiber Bragg grating (FBG) with near-diffraction limited beam quality. By optimizing the structure of narrow linewidth fiber oscillator seed, the temporal characteristics of injected seed laser is improved. Combined with optimizing pumping ratio of amplifier stage, multiple nonlinear effects are mitigated. Finally, a 4.45 kW narrow linewidth laser output with near-diffraction limited beam quality is achieved with a slope efficiency of 80.2%. The signal to noise ratio is 24.5 dB at the maximum power. The 3 dB and 20 dB bandwidth are 0.5 nm and 3.63 nm, respectively.
KEYWORDS: Fiber lasers, Optical amplifiers, Signal to noise ratio, Fiber amplifiers, Oscillators, Laser systems engineering, High power fiber amplifiers, Cladding, Composites, Reflectivity
One-stage master oscillator power amplifier (MOPA) is an efficient way to acquire high-power narrow-linewidth fiber lasers (NLFLs), which have wide usage in beam combination and detection. In this paper, we set up a narrow-linewidth one-stage MOPA fiber laser system which utilize a compact fiber oscillator as the seed laser. By optimizing the temporal characteristics of seed laser with a backward pumping structure of amplification stage, we finally acquire a 3.5 kW near single mode laser output with 3 dB and 20 dB linewidth of 0.26 nm and 1.1 nm, respectively. The slope efficiency reaches to 83.4%. At the maximum power, the signal to noise ratio ratio is ~60 dB on the spectrum and the M2 factor is measured about 1.3.
In this paper, the quantitative relationship between the seed Raman suppression and output of Yb-doped fiber amplifier is studied theoretically. The analytical formula showing the relationship between the Raman suppression (in dB) in the seed light and output of the fiber amplifier is derived. It is revealed that Raman suppression of the fiber amplifier increases linearly with that of the seed light. It is found that such a relationship can be well kept regardless of the pumping scheme. By the comparison of analytic results and numerical calculation results, it is revealed that there is indeed a linear relationship between two Raman suppressions with the slope agreeing well with the theoretical prediction. However, such a relationship only occurs when the Raman noise power of the seed light is greater than the microwatts level. Once it is less than the microwatts level, the output Raman suppression of the fiber amplifier will not raise with a further increase of seed Raman suppression. It is also found that the law is independent of the output signal power of the seed light as well as the pumping scheme of the fiber amplifier, which is also coincident with the theoretical result.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.