Processing strategy for symmetrical ablation profile in pulsed laser patterning of high-performance broadband spiral antennas

Abstract

High-performance broadband spiral antennas are considered as non-substitutable parts in the field of aerospace, and the nanosecond pulsed laser (NPL) patterning has shown a broad prospect in the processing of the high-performance broadband spiral antennas, in which the characteristic of ablation profile is always considered as the most significant issue. However, for the pattern of antenna with complex curve feature, the position for the highest overlapping rate of laser spot offset from the spot center to the curvature center of scanning trajectory, and then the laser energy cumulative loses the symmetry for the complex curve scanning trajectory on the machining parts surface, which induces the location deviation of the maximum ablation depth for the curve pattern. Meanwhile, the curve with the maximum ablation depth will deviate from the ideal designed antenna line, resulting in a direct impact on the antenna performance. In this study, the curvature characteristic of the scanning trajectory is innovatively taken into consideration in the NPL processing of pattern with complex feature. Thus, the ablation profile symmetry and the according assessment are proposed with mathematical model, and the asymmetry of ablation profile is carefully revealed to obtain the deviation of maximum ablation depth for pattern with both large and fine radius feature. Furtherly, based on the proposed model, the processing strategies are extended that the side-step distance is generated in pulsed laser ablation of pattern with large radius feature and the scanning trajectory is optimized for the downsized pattern with finer radius feature. As a consequence, the experimental results satisfactorily verify the theoretical side-step distance and also verify that the position curve of maximum ablation depth is optimized with a deviation distance reduction of more than 74%. With the proposed processing strategies, a good and concerned guide is provided for the precise NPL patterning of high-performance broadband spiral antennas.