在高功率激光系统中,大口径连续相位板(CPP)元件是用来进行光束整形的关键衍射光学器件,由于其毫米量级的空间周期、大相位梯度的波前特征,大口径干涉仪无法满足检测需求。提出采用小口径高分辨率干涉仪结合子孔径拼接实现相位板元件透射/反射波前的检测,采用了误差均化的拼接方法,设计了针对圆形孔径的数据融合新算法,研制了子孔径拼接检测装置,实现了一块330 mm×330 mm的连续相位板元件透射波前的检测。实验结果表明,针对其毫米量级的周期,最大可检测到的波前梯度接近3 μm/cm,检测重复性精度优于6 nm[均方根(RMS)] ,波前数据模拟焦斑计算结果与高功率激光系统中的远场焦斑特性检测结果获得了较好的一致性。

Continuous phase plate(CPP) is critical diffractive optical element used for beam shaping in high-power laser system. But the large-aperture interferometer is unsuitable for testing it for its spatial period with several millimeters and the large phase gradient. A sub-aperture stitching method by small-aperture and high lateral-resolution interferometer is proposed to realize wavefront testing of CPP. A novel interpolation algorithm is developed for circular aperture and the equipment is set up. It tests a CPP with size of 330 mm×330 mm.The experimental result shows that the maximum testable slope of this CPP reaches 3 μm/cm with millimeter period,while the testing repeatability is 6 nm(root mean square). The simulated spot diagram result of far field based on tested wavefront is in good agreement with tested result in high-power laser system.