Research On Fabrication, Optical Properties And Applications Of The Novel Mid-infrared Hollow Core Fibers

In this paper, the development history of infrared fiber was reviewed. A lot ofresearch works and a great deal of achievement on the hollow-core fibers with dioxidedielectric layers used in transmission of high-power CO₂laser with the lasing wavelengthof10.6μm were discussed. The characteristic of the ATR fiber with n<1in themid-infrared region was analyzed based on theory. The mechanism of Ge/GeO₂doubledielectric layers hollow-core fiber was discussed through the theories of ray path andwaveguide. The hollow-core micro-structure fibers were designed and drawed based onthe the modified chemical vapor deposition （MCVD） method. The integration processof MCVD and the preparation of the fiber were improved. Moreover，the experimentalresearch on applications in medical diagnosis is carried out.Based on the characterize in mid-infrared region of oxide material （nr <1） thecomplex refractive index （n+ik） was derivated from the calculation procedure on thecomplex refractive index in abnormal dispersion_region that was calculated based on thereflectance spectrum under the addition of normal incidence in material.The hollow-coretransimission energy fiber with photonic bandgap effect and the micro-structure likingphotonic crystal fiber which thenr <1，was designed and fabricated.The hollow-core fiber with the pure GeO₂film was fabricated by the integrationprocess of MCVD and the preparation of the fiber. The part of multi-crystalline GeO₂dielectric layer was reduced to rich Ge layer by oxidation-reduction_reactions. Thedouble dielectric layer hollow-core fiber with ultr-microstructure multi-crystalline GeO₂was fabricated. The losses of the fiber were tested under the different state. The outsurface of the hollow-core fiber was coated with silica gel to protect fiber. In addition, theperformance test and experimental analysis of the optical fiber samples were carried byinfrared spectrometer （Auastar360FTIR） and scanning electron microscopy（KYKY-2800）. Based on the experiment results, the integration equipment of MCVD anddrawing using for the fabrication of the mid-infrared fiber was successful.The experiment measure scheme of the energy distribution in optical fiber for CO₂ laser energy transmission was proposed. In the experiment, the pinhole scanning methodand direct thermal exposure method were used. Moreover, comparing the pinholescanning method, the direct thermal exposure method is proved much better in theexperiment. The relations between the irradiation time of the spot and the change ofoutput light mode were obtained. The optical fiber double lens and three lens focusedsystem with independent intellectual property rights were designed. In addition, the effectof the optical lens systems with different compositions on beam focus is experimentalresearched.The optical fiber with the innovation structure for CO₂laser energy transmission isfabricated and used for medical clinical. Many medical clinical experiments are carriedout. The optical fiber are proved the function of cutting fast and good hemostatic effectthrough animal laparoscopic surgery, which provide the fundamental experiment forentering human body laparoscopic to carry minimally invasive surgery. The spectraltesting of the fiber was implemented by combining the infrared fiber fabricated by ourlaboratory and medical infrared spectrometer. The results found that the transmissionwavelength of the fiber is3-12μm, and the large absorption peaks was not appear in thisregion, which the requirements of clinical application are well met.