Single Frequency And Single Polarization Fiber Laser With Narrow Linewidth

Comparing with semiconductor lasers and other solid lasers, fiber lasers have low threshold, high coupling efficiency, good heat dissipation, widely tunable range, compact structure and light weight. Because of these advantages, they have been widely used in optical communications, optical sensors, material technique, life science, precision machining and other interrelated fields. And the fiber laser with narrow linewidth is a hot research topic. Besides the advantages above, the fiber laser which has narrow linewidth and low noise, has also been widely used in optical sensors, optical remote sensing, high-accuracy spectral analysis, optical communications and so on. So this paper focuses on the discussion of the narrow-linewidth fiber laser.First, we analyze theoretically how to realize single frequency output using saturable absorber in ring cavity and Bragg gratings in linear cavity, respectively. Then we simulate the polarization variation by Jones Matrix and analyze the mechanism of linewidth narrowing corresponding to the two cavity configuration.Next, we do experimental research on the single-frequency and single-polarization fiber ring laser with narrow linewidth based on theoretical analysis. The results have shown that the laser output reaches 23mW, signal-to-noise ratio is higher than 50dB, side mode suppression ratio is higher than 45dB, linewidth is less than 0.8kHz and polarization extinction ratio is higher than 20dB. So the laser which we present can realize single frequency, stable polarization state and narrow linewidth at the same time.Then, we do experimental research on the single frequency and linewidth narrowing of fiber ultra-short linear cavity laser. Erbium and Ytterbium co-doped phosphate glass optical fiber, which using as gain medium to narrow laser linewidth and increase output power, is pointed out. And we discuss two possible methods for realizing single-polarization state output.Finally, the principle of stimulated Brillouin scattering is analyzed. We present the configuration of Brillouin narrow-linewidth fiber laser and do relevant experiments based on much work on multi-wavelength Brillouin fiber laser previously. At last, we point out the direction that we make efforts for the future.