Preparation And Optical Performances Of Rare Earth Ions Doped Tellurite Microstructured Fibers

Infrared fiber lasers have wide applications in optical communication,biomedicine, environmental pollution monitoring, machine finishing field, militaryaffairs, and basic researches. Since gain fibers are the key components of the infraredfiber lasers, the selection and preparation of them would affect the performances ofthe lasers. The characteristics of traditional silica fibers as narrow transmissionwindows (300~2500nm), relative low nonlinear coefficients, and high phononenergies have somewhat limited their applicotions, especially in the mid-infraredregion. So explore new fiber materials and fiber structures, invesgate optialperformances in novel fibers would be of great values for the development of infraredfiber lasers.Tellurite fibers have attracted many interests for their broad gain bandwidth,high nonlinear coefficient, and good thermal and chemical stabilities. In theory,broadband amiplifiers and mid infrared fiber lasers could be realizes by takingtellurite fibers as the gain media. While there are still some urgent problems in thepreparation of tellurite fibers and the researchments on relative devices:(1) Er3+doped tellurite fibers have been considered as the optimal workingmedium for broadband fiber amplifier (EDFA). However, there was still a gapbetween the current bandwidth of Er3+doped tellurite fiber amplifiers and thetheoretical value. So further expanding the working bandwidth of the Er3+dopedtellurite fiber amplifiers would be of great value.(2) For broadband supercontinuum (SC) light soureces, there exists afundamental tradeoff between the output spectral bandwidth and the average power.New approaches are needed for further improving the characteristics of broadband SClight sources.(3) The existence of hydroxyl (OH) groups in the glass matrix severely limitsthe applications of tellurite fibers in the mid infrared region. Introducing somefluoride components into the tellurite glasses can effectively reduce or even remove the OHin the glasses, while the introduction of Fwould also break down thethermal stabilities of the glass matrix, and bring some trouble for fiber drawing. Soexploring thermally stable fluorotellurite glasses with low OH for preparingfluorotellurite fibers would be beneficial for extending their applications in themid-infrared region.Based on the issues above, the author proceeded a series of research work on thepreparation and optical performances of rare earth doped tellurite microstructurefibers. Some innovative research results on the broadband Er3+doped fiber amplifiers,the SC generation in rare earth doped fibers and the development of fluorotelluritefibers were achieved. Detailed descriptions as below:(1) Based on the TeO2ZnO Na2O Bi2O3(TZNB) glasses, we fabricated Er3+doped tellurite microstructure fibers (EDTMFs) by using a rod in tube method. Bytaking the EDTMFs as the gain media, a broad positive net gain bandwidth of113nm(1524–1637nm) is obtained under the pumping of a1480nm laser. Compared to thepreviously reported result (1634nm), its longer operational wavelength is extended tothe theoretical limits (1637nm) of erbium doped tellurite fiber amplifiers. Meanwhile,highly efficient lasing and self Q switched lasing in EDTMFs are also obtained.(2) Tm3+doped tellurite microstructure fibers (TDTMFs) were fabricated by usingby using a rod in tube method. Under the pumping of a1560nm pulsed laser, SCgeneration in TDTMFs was investigated. Experimental results show that, theamplificaotion of Tm3+is benefitial for further extending the SC spectral rangetowards the longer wavelengths. In addition, as the broadening of the SC spectra,intense upconversion (UC) emission of800nm (Tm3+:3H4â†'3H6) in the EDTMFspumped by the pulsed laser. Compared to that pumped by a continuouswave laser, theUC emission intensity is enhanced~4.1times.(3) A fluorotellurite glass system of TeO2BaF2Y2O3(TBY) with good thermalstability and low OH groups was developed, and based on it, Er3+dopedfluorotellurite microstructured fibers (EDFTMFs) were fabricated by using a rod in tube method. Under the pumping of a1480nm or a980nm laser, highlyefficient lasing and broadband optical amplification at~1.5μm are obtained in theEDFTMFs. Moreover, intense mid infrared emissions at~2.7μm are also obtained.These results show that the EDFTMFs are promising candidates for broadband fiberamplifiers and mid infrared fiber lasers.