Design And Characteristic Research For High-working-power Fibers

Optical fibers have been developed for 50 years.More and more new applications of fibers have been developed.The fiber laser developed along with the optical fiber has also become the mainstream of the world,with lower cost and better performance.Fiber lasers are moving towards higher power,including higher average power and higher peak power,then fibers will definitely face power withstand limits.A fiber capable of withstanding high power must has a larger core size or binds most of the energy in the air rather than in the dielectric.The current applications of laser beams are more based on fundamental mode or uniformly polarized light,while vortex beams have been widely used in many research fields and have huge potential.However,lasers that output vortex beams are still in the laboratory stage,so further development and commercialization are needed in the future.In addition to vortex beams in free space,vortex beams in optical fibers are gradually being excavated.This paper studies the leakage loss characteristics and the energy distribution characteristics of the negative curvature hollow core fiber.The design method of this fiber to achieve low transmission loss or effective single mode and the reason why the optical fiber has a high damage threshold are demonstrated.This paper also proposes a new design scheme of the vortex fiber,which uses thermal stress birefringence to cause mode birefringence between higher-order vector fields for the stable transmission of vortex beams,and can achieve low numerical aperture(NA)and large mode area.The new fiber is mainly used for the transmission and even gain of high-power optical vortex beams,and can also be used in other fields of highindex-difference ring-core fiber.The content of this paper mainly covers the following points:1.Some basic theories,applications,and development status of optical fibers and vortex beams are introduced.2.The leakage loss characteristics and the energy distribution characteristics of the negative curvature hollow core fiber are studied.Theoretical research is carried out by numerical simulation using finite element method.3.A design scheme of a new vortex fiber which can stably transmit optical vortex beams and achieve low NA and large mode area is proposed.So,it can support the transmission for high power optical vortex beams.The thermal stress field distribution and birefringence distribution of the new vortex fiber are calculated in detail,and the basic theory of design is provided.And through the finite element method simulation,two design schemes are provided.The advantages and the possibility of realization of the new vortex field fiber are demonstrated theoretically.