The productivity and quality of laser micromachining depend on multiple laser parameters that are intricately correlated. For these optimizations, a quick survey of laser parameters is vital. Recently, the authors developed a Yb-doped fiber chirped-pulse amplification system that can control various laser parameters in a wide range (pulse duration: 0.4–400 ps, repetition: single shot to 1 MHz, etc.). In this work, using this laser system, percussion microdrilling of three types of advanced ceramics, AlN, Al2O3, and Y2O3-doped ZrO2, was explored. In the case of the microdrilling of the Al2O3 ceramic, the ablation volume increased about 2–3 times as the pulse repetition increased from 100 Hz to 1 MHz. This suggests a different mechanism because the volume removal became dominant at 1 MHz. Scanning electron microscope observation confirmed a drastic melt formation at 1 MHz. From these, there is an additional volume removal due to the heat accumulation by multipulse irradiation on the Al2O3 ceramic at a higher repetition rate. It was also found that the variation of ablation volume with the pulse duration and fluence exhibited a big difference among these ceramics. A comprehensive survey of ultrafast laser ablation of ceramics was demonstrated.

Laser-induced forward transfer (LIFT) is a direct-writing technique capable of depositing a single dot smaller than the laser wavelength at small shot energy through the laser-induced dot transfer (LIDT) technique. To deposit a single nanodot in a single shot of laser irradiation, a liquid nanodrop is transferred from donor to receiver and finally solidified via a solid–liquid–solid (SLS) process. In conventional LIDT experiments, multi-shots with step scanning have been used to form array structures. However, interference laser processing can achieve an arrayed process and generate a periodic structure in a single shot. In this study, a femtosecond laser interference pattern was first applied to LIDT, and an array of nanodots was successfully deposited in a single shot, producing the following unit structures: a single dot, adjoining dots, and stacking dots. The diameter of the smallest nanodot was 355 nm, and the narrowest gap between two adjoining nanodots was 17.2 nm. The LIDT technique produces high-purity, catalyst-free that do not require post-cleaning or alignment processes. Given these significant advantages, LIDT can expand the usability of nanodots in a wide range of fields.

Noble metal nanodots have been applied to plasmonic devices, catalysts, and highly sensitive detection in bioinstruments. We have been studying the fabrications of them through a laser-induced dot transfer (LIDT) technique, a type of laser-induced forward transfer (LIFT), in which nanodots several hundred nm in diameter are produced via a solid–liquid–solid (SLS) mechanism. In the previous study, an interference laser processing technique was applied to LIDT, and aligned Au nanodots were successfully deposited onto an acceptor substrate in a single shot of femtosecond laser irradiation. In the present experiment, Pt thin film was applied to this technique, and the deposited nanodots were measured by scanning electron microscopy (SEM) and compared with the Au nanodots. A typical nanodot had a roundness $f_r=0.98$ and circularity $f_{circ}=0.90$. Compared to the previous experiment using Au thin film, the size distribution was more diffuse, and it was difficult to see the periodic alignment of the nanodots in the parameter range of this experiment. This method is promising as a method for producing large quantities of Pt particles with diameters of several hundred nm.

We demonstrated beam shaping to top-flat and square by phase-only Spatial Light Modulator (SLM) and spatial frequency filtering. Spatial phase distribution of a femtosecond laser beam was modulated by a phase grating pattern reflecting a transfer function for beam shaping. By filtering the higher spatial frequency component at Fourier plane in 4f system, the spatial amplitude distribution of the zero-order beam was shaped to top-flat and square. This result enables us to fabricate large area and uniform devices by using multi-shot processing.

Carbon nanotubes (CNTs) are considered remarkable low-dimensional materials that can overcome the problems associated with bulk semiconductors. The development of CNT processing technology complementing conventional processing technology is required to advance research on CNT devices. We assessed the potential and application of laser-based micro-processing for patterning micrometre-thick CNT films. We discovered that the laser ablation method can pattern micrometre-thick CNT films in micrometre spatial resolution and can directly pattern the CNT films inside the protective film—features not achievable by competing processing technologies. Thus, the laser ablation method is uniquely advantageous and applicable in manufacturing functional CNT devices.