Breaking through the limits of a single fiber laser amplifier - Coherent Beam Combination

High-power, high-energy ultrafast fiber lasers are indispensable tools in various fields, from basic and applied science research to industrial processing. However, due to thermal effects, nonlinear effects, there is always a limit to the power/energy expansion of a single fiber laser amplifier. Coherent Beam Combination (CBC) technology is an effective strategy to break through the limits of a single fiber laser amplifier and further achieve power/energy scaling. Under the conditions of mutual coherence and stable phase relationship, multiple laser beams can be superimposed and mutually interfere with each other. This approach allows for an improvement in average power and pulse energy by a factor almost equal to the total number of combined channels. However, with the increase of beam combining channels, the complexity of CBC systems also increases, bringing negative impacts such as decreased beam combining efficiency, degraded beam quality, and increased operational difficulty to the system.

Researchers from Huazhong University of Science and Technology reported the use of filled aperture coherent beam combining technology to achieve an ultrafast fiber laser system with an average power output of 403 W, 0.5 mJ pulse energy, and 260 fs. Excellent beam quality (M²<1.2) was achieved while ensuring good power stability (RMS<0.5%). By utilizing integrated electronic dispersion hardware, effective compensation has been achieved for the incomplete compensation of high-order dispersion after grating compression, optimizing pulse width while also achieving superior improvement in pulse quality. In addition, CBC operates at an average power of over 230 W per channel, simplifying system complexity and operational difficulty. In the future, it is expected that using only four channel coherent synthesis can increase power to the kw level and pulse energy to the mJ level. The work entitled “260 fs, 403 W coherently combined fiber laser with precise high-order dispersion management” was published on Frontiers of Optoelectronics (published on Jan. 22, 2024).