孔径填充——光纤激光阵列相干合成中的关键技术

Aperture Filling——an Important Technique in Coherent Beam Combining of Fiber Laser Array

光纤激光相干合成能够获得高功率、高光束质量的光束输出。目前国内对于相干合成技术的研究集中于各路激光的相位控制,即光束如何"相干"。而相干光束的"合成",即如何提高相干激光阵列的填充因子,作为影响相干合成光束质量的一个重要因素,则较少受到关注。为了保证相干合成激光的光束质量,需辅以相应的孔径填充技术尽可能增大激光阵列的填充因子。跟踪国外近年来发展的孔径填充技术,如幅相转换、自成像波导、光束整形、衍射光学法、光束截断法等,并对每一种技术加以分析和评判。结果表明,光束截断法不需要复杂的光学设计,实施起来最为简单有效,有可能最终用于多路大功率光纤激光的合成。

Coherent beam combining of fiber lasers can achieve high power laser with good beam quality. Most studies on coherent beam combining focus on phase controlling, i.e., how to make the beamlets coherent. Beam combining of the coherent beamlets, i.e., how to improve the fill factor of the coherent laser array, is also an important factor that affects the beam quality, yet it has seldom been taken into account. In order to ensure the beam quality of the coherently combined beam, the aperture filling technique should be employed to improve the fill factor of the fiber laser array. Recent progress on the aperture filling technique, i.e., amplitude-to-phase technique, self imaging waveguide, beam shaping, diffraction optics and beam truncation was introduced. Each technique was analyzed and evaluated in detail. It is shown that the beam truncation technique is free of complicated optical system design and easy to implement, which holds great potential in coherent beam combining of high power fiber laser array.