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.

Ultra-short laser pulses are effective, when high requirements concerning accuracy, surface roughness and heat affected zone are demanded for surface structuring. In particular, picosecond laser systems that are suited to be operated in industrial environments are of great interest for many practical applications. This paper focused on inducing optimum process parameters for higher volume ablation rate by analyzing a relationship between crater diameter and optical spot size. In detail, the dependency of the volume ablation rate, penetration depth and threshold fluence on the pulse duration 8 ps and wavelength of 515 nm was discussed. The experimental results showed that wavelength of 515 nm resulted in less threshold fluence (0.075 J/㎠) on copper than IR wavelength (0.3 J/㎠). As a result, it was possible that optimum fluence for higher volume ablation rate was achieved with 0.28 J/㎠.

Laser drilling is an enabling technology for Through Silicon Via (TSV) interconnect applications. Recent advances in picoseconds laser drilling of blind, micron sized vias in silicon is presented here highlighting some of the attractive features of this approach such as excellent sidewall quality. In this study, we dealt with comparison of heat affection around drilled hole between a picosecond laser and a nanosecond laser process under the UV wavelength. Points which special attention should be paid are that picosecond laser process lowered experimentally recast layer, surface debris and micro-crack around hole in comparison with nanosecond laser process. These finding suggests that laser TSV process has possibility to drill under 10μm via. Finally, the laser drilling platform was constructed successfully.

Due to the extremely short interaction time (＜ 10 × 10^-12sec) between laser pulse and material, which enables the minimization of heat affection, ultrafast laser micro-machining has rapidly widened its applications. In this paper, the characteristics of ultrafast laser micro-machining have been reviewed and experimentally demonstrated in laser drilling of silicon wafer and in laser cutting of rigid PCB.

The micro fabrication on the mold material using picosecond laser ablation processing has been studied. We used the two kind of system with picosecond laser. First one is two mirror type scanner and telecentric f-theta lens. Second one is X-Y stage and objective lens. By using these system, the 100㎛ size chess patterning and 2㎛ size patterning was fabricated. Especially 2㎛ size patterning on the mold material can be used as the decorative rainbow color logo for industrial field. In this paper, it is proved the picosecond laser is effective tool for the laser ablation processing.

In order to achieve and maintain dimensional accuracy in laser micro-machining, dominant parameters such as laser power and laser focus position need to be monitored and controlled real time. Also, in order to selectively machine multi-layered materials, the material being presently machined need to be recognized. This paper presents an auto-focusing (AF) module to keep laser focus on a large-area surface; a real-time laser power stabilizing module based on optical attenuation; and a laser-induced breakdown spectroscopy (LIBS) module. With these monitoring modules, position error in laser focus on a 4” silicon wafer was kept below 4㎛, initially 51㎛, and laser power stability of a UV laser source was improved from 1.6% to 0.3%. Also, the material transition from polyimide to copper in machining of FCCL (flexible copper clad laminate) was successfully observed.