The Generation Of Supercontinuum Source And Its Application In Medical Detection Technology

The supercontinuum has the characteristics of ultra-wideband,high brightness and high spatial coherence,and is very suitable for application in optical coherence tomography technology(OCT).The 1.6?m band laser is located in the low valley of the water absorption and scattering spectrum,which can effectively reduce the water absorption and scattering loss,and can be used as an ideal source for OCT.Therefore,based on the 1.6?m mode-locked fiber laser and combined with nonlinear effects,this thesis discusses the generation of supercontinuum in the 1.6?m band and the supercontinuum is applied to OCT scanning technology.The specific research contents are as follows:1.A fiber laser based on the nonlinear polarization rotation(NPR)mode-locking mechanism was designed,and the generation of mode-locked pulses in the C and L bands was studied.First,by designing the resonator,when the net cavity dispersion is-0.024ps~2,the conventional soliton pulse and the switchable noise-like pulse in the 1.5?m band are realized,and the modulation sideband of the noise-like pulse is observed.Then,rationally optimize the structure of the resonant cavity,control the net cavity dispersion is-0.0089ps~2,the 1.6?m band noise-like pulse is realized and analyze the characteristic evolution of the output pulse.The central wavelength of the noise-like pulse was 1613nm,the spectral 3d B bandwidth was 64.4nm,and the pulse width was 303fs.2.Research the generation of supercontinuum based on nonlinear effects.First,a power amplification system is built outside at the laser resonant to amplify the power of the fiber laser.Secondly,three different types of fibers are pumped separately with noise-like pulses to generate supercontinuum.Then,compare and analyze the broadening of the spectrum in the three types of fibers.The results show that in high nonlinear fiber(HNLF),the supercontinuum has the best broadening effect.When the HNLF length is 20m,the supercontinuum with the 3d B bandwidth of 603nm is obtained,and its maximum average output power is 45.85m W.Theoretically,applying this supercontinuum to OCT system can obtain the axial resolution of<2?m.3.Based on the imaging principle of frequency domain OCT,the application research of supercontinuum in frequency domain OCT system was carried out.First,a set of spectral domain OCT system has been constructed.Second,the 1.5?m band broadband source was applied to the OCT system,and the axial resolution can reach 20?m;then the supercontinuum is applied to the OCT system,and the axial resolution can reach 8?m.The axial resolution has been improved by 60%.Finally,an imaging experiment was carried out with a glass slide,and the thickness of the glass slide and the air gap between the slides can be clearly distinguished.