Design And Implementation Of New Laser Materials For Large-mode-area Fiber

An all-glass photonic crystal fiber is studied theoretically and demonstrated experimentally by replacing air holes with a glass with a low refractive index contrast relative to background glass.The fiber has a negative index step from core to cladding, combined with an adequately large gain coefficient in a large-diameter core region.This new all-glass design enables not only ease and consistency of fabrication but also convenience of being cleaved and polished like conventional fibers.The dispersion properties of the fiber are investigated by using an effective index method.Modeling results suggest that the fiber can provide robust single transverse mode operation which has very large mode-field diameter above 80μm.Based on an analysis of thermal diffusion mechanisms of high power photonic crystal fiber lasers,the thermal management of all-glass photonic crystal fiber is analyzed numerically by finite element method.The all-glass microstructure will improve the thermal performance of the fiber compared to conventional photonic crystal fiber.It is very useful for a number of industrial and military applications,which require scaling the total output power to between several and hundreds of kW's.A novel Nd³⁺-doped lead fluorosilicate glass is prepared by a two-step melting process.Based on the absorption spectrum a Judd-Ofelt theory analysis is made.The emission line width of NPS glass is 44.2nm.The fluorescence decay lifetime of the ⁴F_3/2 level is 586±6μsec,and a laser oscillation is occurred at 1062nm when pumped by 808nm Diode Laser.A kind of ytterbium(â…¢) doped lead fluorosilicate glass with the same composition was demonstrated.Its fluorescence effective linewidth is about 94.8nm;its fluorescence decay lifetime is 2.36ms.The potential laser property was evaluated and the laser parameters indicates that current Yb³⁺ doped lead fluorosilicate glass is an excellent candidate material for using in high-power laser generation and amplification.The "gain-guided index-antiguided" optical fiber was drawn by using the Yb³⁺-doped lead fluorosilicate glass.The diameter of single mode area is above 100μm. Experimental demonstration of lasing in the fiber is presented with excellent beam quality.The M²-value is characterized to be less than 2.9.In this work,we demonstrate that all-glass endless single-mode PCFs can be made by replacing air holes with a glass(K9) with a low refractive index contrast ofâ–³n=4.2×10^-2 to that of the background glass(wt58).The method of making all-glass PCFs is to stack WT58+K9 glass around a solid core rod,cane the stack,and then draw to fiber.This work may provide a straightforward technique to produce high-quality novel photonic crystal fibers with the potential to serve as a "road map" to future research in the area of micro- and nanostructured fiber development.