Researches Of The Forward Brillouin Scattering And The Sagnac Loop Filter

The acoustic waves form optical-phonon-like modes of forward Brillouin scattering has a flat dispersion curve; so it is suggested that the process may be used in a wide variety of photonic applications, such as frequency comb generation, active phase modulation, optical frequency conversion, and high-frequency mode locking of fiber lasers. In this paper, the transverse acoustic mode and forward Brillouin scattering are theoritecal and experimentally studied in standard fibers of125μm. The filter chacteristics of Sagnac loops are studied with the fabrication of rare-earth doped fibers. And the main achievements of this thesis are listed as follows:1. An analytical model of transverse acoustic mode, polarized GAWBS and depolarized GAWBS is established. The polarized and the depolarized GAWBS are observed in a2-km-long highly nonlinear fiber (HNLF) respectively. And the scattering efficiency and the frequency agree with the calculation.2. An analytical model of forward stimulated Raman-like Brillouin scattering (SRLS) and forward stimulated inter-polarization scattering (SIPS) is established, considering all the acoustic modes. It is revealed that the influency of Kerr nonlinearity on the gain and lineshape of SRLS. The gain of (anti-) Stokes beam increases; the linewidth of (anti-) Stokes beam broadens and the profile on the anti-Stokes side of the pump beam have lineshapes that are asymmetric; peak of gain deviating from centual frequency shifts to lower frequency.3. A SRLS gain specture is observed first time. When a pump of8mW is launched into HNLF, the tight confinement of the light and acoustic field enhances the interaction and results in a large gain coefficient of34.7W'1at a frequency of933.8MHz; which is three times of Kang's report in Nature Physics. It is releaved that the generation machine of lineshape and the influence of initial phase of input signals on the gain.4. A multi-polarization controlled Sagnac loop is proposed; and an analytical method of multi-order Jones matrix is established. And the results show that the more polarization controls the more flexible the transmission spectrum is; the interval tunability and the side-frequency restriction are shown. The experimental results are in great agreement with theory. 5. A kind of new type high features single cladding highly rare-earth doped silica optical fiber was fabricated by a new furnace round heating MCVD process.; and the erbium-doped ring fiber lasers based on a single polarization controlled Sagnac loop filter and a double polarization controlled Sagnac filter are proposed. In experiment Stable single-, double-and triple-wavelength are achieved respectively. The stable laser with20%slope efficiency,0.016nm3dB line-width,0.097nm30dB line-width and40dB SMSR is obtained by using a single polarization controlled Sagnac. By using double polarization controlled Sagnac, the3dB line-width is less than0.03nm, and the fluctuation of wavelength and peak power is less than0.05nm and0.1dB in30minutes. The side-frequency restrain characteristic is shown in a ring fiber laser for its application in our paper; and the SMSR enhances5dB.