The demand for high-speed processing and big data has accelerated the adoption of three-dimensional integrated circuits (3D ICs), where interposers serve as essential components for chip-to-chip connectivity. However, silicon interposers using the through-silicon via (TSV) technology have structural limitations. As alternatives, glass-based interposers employing the through-glass via (TGV) technology are gaining attention. This study explored the fabrication of via holes in glass substrates using the selective laser etching (SLE) process. A spatial light modulator (SLM) was used to generate donut- shaped bessel beams by inserting an image pattern without relying on phase modulation. The machinability of via holes fabricated with these beams was compared to that of holes formed using phase-modulated beams. Effect of pulse energy on taper angle was also investigated. Hourglass-shaped holes were observed at lower pulse energies. However, taper angles approaching 90° were observed at higher energies, indicating an improved verticality.

Lasers are widely used in precision metrology, defense, and micromachining. The rise of GHz burst processing has increased interest in high-repetition-rate laser sources. Electro-optic (EO) frequency combs are promising due to their excellent controllability and GHz-range tunability. However, the modulation process that generates EO combs produces M-shaped spectra with pronounced side peaks containing high-order chirped components. These can degrade amplification efficiency and limit pulse distribution quality due to incomplete temporal compression. In this study, we implemented a 24-W EO comb-based picosecond laser system and applied programmable spectral shaping with a 0.7-nm Gaussian-filter to suppress spectral side peaks. As a result, temporal energy confinement of compressed pulse was significantly improved from 53.1 to 92.8% while maintaining comparable output power and pulse duration. These findings demonstrate that spectral shaping can effectively enhance the temporal quality of EO comb pulses, supporting their application in high-precision GHz-burst micromachining.