自研（1+1）分布式侧面泵浦光纤实现20 kW激光输出

Abstract

Objective The distributed sidecoupled claddingpumped (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 rareearth ions in the signal fiber s core, thus achieving laser gain amplification. In the realm of highpower singlefiber lasers, the primary challenges limiting power enhancement are pump injection and extremely high thermal loads. Therefore, combining cascaded pumping and distributed sidepumping has emerged as a promising and feasible pathway to achieve ultrahigh power in the tens of kilowatts range. MethodsThe experimental setup is based on a master oscillator power amplifier scheme. A pair of fiber Bragg gratings and 20/400 μm ytterbiumdoped fiber form an optical cavity to generate a hundredwatt seed. A homemade 35 m (1+1) DSCCP fiber with highconcentration Ybdoped in active core and a core/cladding size of 60/300 μm is activated by five groups of 1018 nm pump sources in a counter way from pump core with a core size of 310 μm. 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 DiscussionsThe experimental results demonstrate the highest output power of 20.13 kW from the signal fiber, with an opticaloptical 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 hundredwatt 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 singlefiber laser output using the (1+1) type distributed sidepumping approach. The success not only highlights the efficacy of the distributed sidepumping scheme for realizing highpower outputs but also paves the way for future research on further improving beam quality and achieving highquality 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.