Beam Tilt Aberration Detection of the Seven-Unit Phased Fiber Laser Array

In this paper, we present a method based on the conjugate image principle and micro-nano optics to detect tilt aberrations of a phased fiber laser array system. A co-aperture optics system was adapted to detect the tilt aberrations of a seven-element phased fiber laser array system simultaneously. A Kepler telescope was designed to construct the conjugate relation between the exit pupil of a fiber optic laser array system and a microlens array and also to match the size of the seven beams and the microlens array. The apochromatic theory was used to meet the multispectral (1064 ± 0.3 nm, 1030 ± 0.3 nm, and 633 ± 0.2 nm) detection needs. A far-field detection unit was also designed to evaluate beam quality. When the actual beam was offset by 1 pixel, the beam tilt was about 0.7 µrad. The maximum detection error of the seven-element system was about 7 µrad. It could not only directly detect the beam's tilt angle but also maintained detection accuracy while reducing the algorithm complexity.