With the increasing power of fiber lasers,single chirped and tilted fiber Bragg gratings(CTFBGs)cannot completely mitigate continuously enhanced system-excited stimulated Raman scattering(SRS).Although improving the l...With the increasing power of fiber lasers,single chirped and tilted fiber Bragg gratings(CTFBGs)cannot completely mitigate continuously enhanced system-excited stimulated Raman scattering(SRS).Although improving the loss rate of a single CTFBG or cascading multiple CTFBGs can provide better suppression of the stronger SRS,excessive insertion loss may cause significant attenuation of the output power.Confronting the challenge,we firstly present an SRS mitigation method based on a dual-structure fiber grating in this paper.The dual-structure fiber grating comprises a CTFBG and a fiber Bragg grating structure,which were designed and fabricated on a passive 25/400 double-clad fiber.To evaluate the performance of the grating,a 3 kW fiber master oscillator power amplifier laser is established.The experimental results demonstrate that the SRS mitigation rate of the grating is greater than 30 dB(99.9%),whereas the insertion loss is only approximately 3%,thus allowing for minimal deterioration of the output power.This solves the contradiction between high suppression rate and high insertion loss faced by CTFBGs,which in turn makes dualstructure fiber gratings particularly suitable for mitigating SRS in 3-5 kW high-power fiber lasers.展开更多
基金supported by the Key Laboratory of Optical System Advanced Manufacturing Technology(Chinese Academy of Sciences)(2022KLOMT02-04)the Basic Research Program of Jiangsu Province(BK20201305).
文摘With the increasing power of fiber lasers,single chirped and tilted fiber Bragg gratings(CTFBGs)cannot completely mitigate continuously enhanced system-excited stimulated Raman scattering(SRS).Although improving the loss rate of a single CTFBG or cascading multiple CTFBGs can provide better suppression of the stronger SRS,excessive insertion loss may cause significant attenuation of the output power.Confronting the challenge,we firstly present an SRS mitigation method based on a dual-structure fiber grating in this paper.The dual-structure fiber grating comprises a CTFBG and a fiber Bragg grating structure,which were designed and fabricated on a passive 25/400 double-clad fiber.To evaluate the performance of the grating,a 3 kW fiber master oscillator power amplifier laser is established.The experimental results demonstrate that the SRS mitigation rate of the grating is greater than 30 dB(99.9%),whereas the insertion loss is only approximately 3%,thus allowing for minimal deterioration of the output power.This solves the contradiction between high suppression rate and high insertion loss faced by CTFBGs,which in turn makes dualstructure fiber gratings particularly suitable for mitigating SRS in 3-5 kW high-power fiber lasers.
