Investigation on hybrid processing of picosecond laser and micro milling of the 340 GHz folded waveguide.

Hao, Xiuqing; Hu, Zhiwen; Pan, Pan; Li, Shangshang; Wan, Yafang; Wei, Chengfeng; Qiu, Zhenyu; Li, Liang; He, Ning

The traveling-wave tube (TWT) is widely used in the terahertz domain due to its outstanding efficiency in amplifying microwave signals. The micrometer-scale slow-wave structure (SWS), the core structure of the TWT, is extremely difficult to manufacture because of its complex processing paths and high-precision requirements. A novel hybrid processing of picosecond laser and micro milling (PLMM) for manufacturing the SWS was introduced in this paper. In order to figure out the influence of surface roughness and sidewall verticality on the electromagnetic performance of folded waveguide and determine the requirements for processing the SWS, a beam-wave interaction simulation of the folded waveguide was conducted. PLMM was used in the fabrication of a 79-period 340 GHz folded waveguide with a groove depth of 0.28 mm and an aspect ratio of 2.8. The optimized milling parameters were obtained using response surface method. The processing results showed that PLMM outperformed the conventional micro milling (COMM) in terms of bottom surface roughness, average sidewall verticality, and the electromagnetic performance of the folded waveguide microgrooves. In contrast to COMM, the PLMM fabricated the microgroove with 47.5% smaller surface roughness value and 0.38° larger inlet and outlet verticality. The folded waveguide manufactured by PLMM had a broader operating bandwidth with a 8.7 dB larger S11 and a 9.9 dB smaller S21 than that produced using COMM.

TRAVELING-wave tubes; SURFACE roughness; LASERS; BANDWIDTHS; MICROWAVES

International Journal of Advanced Manufacturing Technology, 2025, Vol 136, Issue 3, p1439

0268-3768

Academic Journal

10.1007/s00170-024-14878-w