Theoretical Analysis Of Four-wave Mixing And Researches On Its Applications In Soft-glass Microstructured Optical Fibers

Four-wave mixing（FWM）has been recognized as a significant technology to generate tunable coherent light covering from the ultraviolet（UV）to mid-infrared waveband.It has extensive applications on biological medicine,atmospheric communication,molecular spectroscopy,gas detection,defense and security and so on.Compared to silica fibers,soft-glass fibers have the advantages of wide spectral transmission window and high nonlinearity.Soft-glass microstructured optical fibers（MOFs）can be optimized with the chromatic dispersion profile,effective mode area and transmission mode,which have been proposed as the ideal gain medium candidate for the FWM effect.The theoretical and experimental researchs on the FWM effect in soft-glass fibers are developed in this paper.The evolution of characteristics of the FWM effect are investigated systematically both in the tellurite photonic crystal fiber（PCF）pumped by the fundamental mode and in the chalcogenide MOF pumped by the optical vector beams.The characteristics of the wide-spectrum multi-wavelength fiber laser generated by Brillouin-comb assisted FWM are studied experimentally.The main contents of this dissertation are as follows:Firstly,we design the tellurite PCF and analysis numerically the influence of the pitch distance and diameter-to-pitch ratio on the zero-dispersion wavelength of the PCF and the phase-matching condition of the FWM.The affects by the fiber length（2-10m）,initial pump power（5-15 W）,initial signal power（-10-30 dBm）,signal wavelength（1.26951-1.27012μm）and idler wavelength（1.99800-1.99950μm）on the signal gain and idler conversion efficiency are investigated.We demonstrate that the increase of the pump power lead to the increase of signal output power and gain.The idler output power can be enhanced by increasing either the initial signal power or pump power.The idler conversion efficiency can be increased only by increasing the initial signal power and the maximum is²6%.Secondly,we design the As₂Se₃ MOF and analysis numerically the influence of the core diameter and pump wavelength on the phase-matching condition pumped by different optical vector beams.The influence on signal gain and the idler conversion efficiency are analyzed numerically in the fibers with different lengths when pumped by different signal optical vector beams.With the core diameter of 6.5μm,the pump wavelength of 2.85μm and the fiber length of 1.2 m,the gain of the signals and the conversion efficiency exceed 27.8 dB and 23.4%,respectively,when the different optical vector signal beams are injected.The idler wavelengths satisfying phase-match conditions are 5.196559,5.229995,5.280924 and 5.325436μm for the optical mode of HE₂₁^even,TE₀₁,TM₀₁ and HE₂₁^odd,respectively.Thirdly,we demonstrate a wide-spectrum multi-wavelength fiber laser generated by Brillouin-comb assisted FWM.More than 110 lines are achieved in 10 nm spectral range with the wavelength spacing of⁰.09 nm.The affects by the output power of EDFA,wavelength and output power of Brillouin pump on the multi-wavelength comb line number are researched experimentally.The multi-wavelength fiber laser exhibits good stability on both the operating wavelengths and output power.The tunability of this multi-wavelength fiber laser was improved significantly by inserting a tunable filter in the cavity.The total line number is kept more than 110 in the whole tunable range of30 nm from 1540 to 1570 nm.