The Slow Wave Structure (SWS), typically fabricated from particle-reinforced composite material, such as Dispersed Oxygen-Free Copper (DOFC), is a core component of terahertz travelling wave tubes. However, machining these high-aspect-ratio, multi-period microstructures with high precision through traditional micro-milling is highly challenging due to significant tool wear when employing micro-cutters with extremely small diameters. This study proposes a novel hybrid fabrication method, termed Water film assisted Laser Pre-channel combined with Micro-Milling (WLPMM), to efficiently produce SWS structures with superior precision and reduce tool wear. In the WLPMM approach, water film assisted laser processing is first utilized to generate a preliminary U-shaped pre-channel, leveraging the enhanced material removal capabilities afforded by water film’s scouring effect, optimized laser power strategies, and scanning methodologies. This initial step significantly reduces material volume, facilitating subsequent micro-milling to refine dimensional accuracy and surface quality with only one micro-cutter consumed. Consequently, this method effectively eliminates clamping errors typically introduced by frequent tool changes. Comparative analyses between WLPMM, pure micro-milling, and laser-assisted micro-milling demonstrate that WLPMM significantly outperforms alternative approaches in terms of reduced tool consumption and improved machining efficiency. Furthermore, WLPMM maintains comparable surface finish and dimensional precision, highlighting its viability and advantages for fabricating high-aspect-ratio slow wave microstructures essential in advanced aerospace and precision instrumentation applications.

The slow-wave structure (SWS) working in the terahertz frequency band features large aspect ratio and long span with characteris-tic dimensions of tens of microns. The development of micro-manufacturing technology for the high-quality fabrication of terahertz SWS is technically essential to promote the advancement of terahertz radiation source devices. In this work, micro-milling approaches were devised to process the 0.34 THz folded waveguide SWS with particle-reinforced metal matrix composite material. The causes of shape error and po-sition error, especially within the arc-shape region, were analyzed in detail, considering the influence from the following error of machine tool and the unfavorable rigidity of milling tools. The optimization of regionalized cutting parameters was achieved, and two productive tool-path-planning schemes were conceived according to the structural features within the processing areas, attempting to minimize the external impact on the shape accuracy of SWS. A practical tool replacement scheme with the orthometric setting slots as a reference for resetting af-ter tool replacement was determined, in order to avoid misalignment at the junction of adjacent units. In consideration of the structural com-plexity of SWS and the position specificity of burrs, the tool path in the horizontal plane was designed in the way of alternately milling of S-shape slot and straight slot, with cutting parameters adaptable to the depth of the processing subregion, which shows excellent suppression effect of burrs. The proposed micro-milling process strategy offers promises to improve the fabrication quality of high-aspect-ratio SWSs with the minimum structure size of ~50μm.