自研(1+1)分布式侧面泵浦光纤实现20 kW激光输出

20 kW Laser Output Based on Homemade(1+1)Distributed Side-Coupled Cladding-Pumped Fiber

基于改进的化学气相沉积预制棒制备技术和多光纤并束拉丝光纤拉制工艺,成功制备了(1+1)型分布式侧面泵浦光纤,其中信号纤芯/包层尺寸为60/300μm,泵浦纤芯尺寸为310μm。通过主振荡功率放大结构搭建反向泵浦放大系统,以1018 nm激光器为级联泵浦源,该光纤激光器最终实现了20.13 kW的最高功率输出,经过拟合后的斜率效率为82.3%,由泵浦纤反向端输出的残余泵浦比例的最大值为6%,信号光受激拉曼散射抑制比达到37.65 dB。在测试中,光纤所有部位均表现出优异的热负载性能,这是首次通过(1+1)型分布式侧面泵浦方式实现了20 kW的单根光纤输出功率。

Objective The distributed side-coupled cladding-pumped(DSCCP)fiber comprises an active signal fiber with gain characteristics and several passive multimode pump fibers,collectively coated to form an integral package.The pump laser injected into the pump fiber couples between the pump and signal fibers in the form of an evanescent wave.Upon entering the signal fiber s cladding,it excites rare-earth ions in the signal fiber s core,thus achieving laser gain amplification.In the realm of high-power single-fiber lasers,the primary challenges limiting power enhancement are pump injection and extremely high thermal loads.Therefore,combining cascaded pumping and distributed side-pumping has emerged as a promising and feasible pathway to achieve ultra-high power in the tens of kilowatts range.Methods The experimental setup is based on a master oscillator power amplifier scheme.A pair of fiber Bragg gratings and 20/400μm ytterbium-doped fiber form an optical cavity to generate a hundred-watt seed.A homemade 35 m(1+1)DSCCP fiber with high-concentration Yb-doped in active core and a core/cladding size of 60/300μm is activated by five groups of 1018 nm pump sources in a counter way from pump core with a core size of 310μm.A Raman suppression array,consisting of a few homemade tilted fiber Bragg gratings,is placed between the oscillator and the amplifier to filter noise within the Raman range.Results and Discussions The experimental results demonstrate the highest output power of 20.13 kW from the signal fiber,with an optical-optical conversion efficiency of 81.0%.The fiber slope efficiency,fitted across the entire power range,reaches 82.3%.Spectral measurements exhibit a 3 dB linewidth of 0.44 nm for the seed laser at the hundred-watt level,expanding to 1.1 nm at the amplified power of 20.13 kW.The experiment also reveals a Raman suppression ratio of approximately 37.65 dB,indicating effective suppression of stimulated Raman scattering components in the spectrum.Conclusions This achievement represents the first publicized report of a 20 kW single-fiber laser output using the(1+1)type distributed side-pumping approach.The success not only highlights the efficacy of the distributed side-pumping scheme for realizing high-power outputs but also paves the way for future research on further improving beam quality and achieving high-quality laser outputs approaching diffraction limits in the tens of kilowatts range.In the next stage,we will focus on the improvement of beam quality by controlling core design and enhancing coupling ability.