Fiber lasers have advantages, such as high conversion efficiency, good beam quality, convenient thermal management, and flexible transmission. They are widely used in industrial processing, national defense research, and other fields. In recent years, with the development of fiber technology, fiber devices, and pump source technology, the output power of high-power fiber lasers has been rapidly improved. Currently, the output power of the fiber oscillator exceeds 9 kW. For fiber amplifiers, solutions with an output power exceeding 10 kW have become more mature, and multiple research teams have reported on fiber amplifiers with an output power exceeding 20 kW. With the increasing demand for laser size, weight, cost, and reliability in industries and other fields, the traditional concept of size, weight, and power (SWaP) is gradually becoming unsuitable for a wide range of application scenarios. Moreover, it is difficult to simultaneously consider multiple application scenarios using traditional fiber oscillators and amplifiers. Now, bidirectional output fiber laser (BOFL) and oscillating-amplifying integrated fiber lasers (OAIFL) are quickly receiving widespread attention as new structure fiber lasers, with obvious advantages in efficiency, nonlinear effect suppression, transverse mode instability (TMI) suppression, system size, cost, and weight. Currently, a BOFL can achieve a 2×4 kW laser output, and an OAIFL can achieve a 6 kW high beam quality laser output. In this study, we introduce new indicators with which to evaluating the performance of fiber lasers: cost‒size‒weight per unit power (CSWpP) and cost‒size‒weight per unit brightness (CSWpB). In addition, we analyze the application potential of the two new structure fiber lasers in different demand scenarios via theoretical and experimental methods.

First, based on the rate equation system of fiber lasers, the theoretical models of BOFL and OAIFL are established. Based on theoretical models, the advantages of the two new structure fiber lasers are analyzed in terms of efficiency, temperature control, and nonlinear effect suppression. In an experiment, a BOFL is designed, based on a double cladding ytterbium-doped fiber with a core/cladding diameter of 30/600 µm. In addition, an OAIFL is designed, based on a self-designed low NA (numerical aperture) double cladding ytterbium-doped fiber with a core cladding diameter of 30/600 µm. Finally, by combining the bidirectional output structure with the oscillating amplifying integrated structure, a scheme of using an oscillating‒amplifying integrated bidirectional output fiber laser (OAI-BOFL) to simultaneously reduce the CSWpP and CSWpB of the laser system is proposed, and experimental verification is conducted.

Theoretical simulation results show that, compared with UOFL, BOFL has a higher efficiency, lower fiber temperature, and better stimulated Raman scattering (SRS) suppression ability under the same conditions. If the strength of the SRS is controlled similarly, the total output power of the BOFL is more than twice that of the UOFL. The OAIFL also has a higher efficiency, better temperature control ability, and better SRS suppression ability, compared with UOFL. In an experiment, SRS mutual feedback is suppressed by shortening the length of the passive fiber. A 2×5 kW laser output is achieved with a total efficiency of 81.0%, and the beam quality values at both ends are 2.59 and 2.74, respectively. Based on a self-designed low NA double cladding ytterbium-doped fiber with a core cladding diameter of 30/600 µm, an OAIFL with an output power of over 10 kW with an efficiency of 70.6% is achieved. Finally, based on the OAI-BOFL, a high beam quality 2×4 kW laser output is achieved, thereby demonstrating the potential to simultaneously balance CSWpP and CSWpB.

In this study, the concepts of CSWpP and CSWpB in fiber lasers are proposed, based on SWaP. Low CSWpP fiber lasers focus on improving output power while reducing the size, weight, and cost of the laser, which confers obvious advantages in industrial applications. Moreover, low CSWpB fiber lasers focus on improving the beam quality of the output laser while reducing the size, weight, and cost of the laser, which confers obvious advantages in the field of national defense. In response to application requirements in different fields, the concepts of BOFL that are beneficial for reducing CSWpP and those of OAIFL that are beneficial for reducing CSWpB are proposed. In an experiment, a double cladding ytterbium-doped fiber with a core/cladding diameter of 30/600 µm is used to achieve a total power of over 10 kW using a BOFL. Based on a self-designed low NA double cladding ytterbium-doped fiber with a core/cladding diameter of 30/600 µm, an OAIFL with an output power of over 10 kW is achieved. An OAI-BOFL is developed based on the above two structures, which can simultaneously balance the CSWpP and CSWpB of laser systems and is an important development direction for future high-power fiber lasers.