Ryozo Kurosaki

Nano- and Microdot Array Formation of FeSi2 by Nanosecond Excimer Laser-Induced Forward Transfer

Fabrication of FeSi2 nano- and microdot array was performed by utilizing droplet ejection through nanosecond laser-induced forward transfer (ns-LIFT). An amorphous FeSi2 source film on a transparent support was illuminated from the support by a nanosecond excimer laser pulse patterned into migcrogrid form, resulting in size- and site-controlled deposition of microdot array onto a silicon substrate. Micro-Raman spectroscopy confirmed β-FeSi2 crystalline phase even on unheated substrates. Moreover, the dot size was successfully reduced to approximately 500 nm in diameter, smaller than any previously reported by ns-LIFT. This technique is useful for integrating functional nano- and microdots under atmospheric room-temperature conditions.

Etching a Micro-Trench with a Maximum Aspect Ratio of 60 on Silica Glass by Laser-Induced Backside Wet Etching (LIBWE)

We have successfully fabricated a deep micro-trench about 7 µm wide and 420 µm deep on silica glass with a maximum aspect ratio of 60 by laser induced backside wet etching (LIBWE) via KrF laser ablation of a saturated pyrene/acetone solution. The processing time for the microetching was as short as 5 min at a repetition rate of 80 Hz and a fluence of F = 1.0 Jcm-2pulse-1. The etch rate was calculated to be approximately 17 nmpulse-1. The LIBWE method is shown to be very useful for surface microstructuring of silica glass with high aspect ratio and high throughput.

A deep micro-trench on silica glass fabricated by laserinduced backside wet etching (LIBWE)

By using laser-induced backside wet etching (LIBWE), we have fabricated very deep micro-trenches in silica glass of 9-μm width and 300-μm depth (aspect ratio ≈ 33). In this paper, we present the details of fabricating the micro-trenches, and discuss why such a deep micro-trench is available by the LIBWE method.

Laser cutting of carbon fiber reinforced plastics (CFRP) by UV pulsed laser ablation

In this paper, we report on a micro-cutting of carbon fiber reinforced plastics (CFRP) by nanosecond-pulsed laser ablation with a diode-pumped solid state UV laser (DPSS UV laser, λ= 355nm). A well-defined cutting of CFRP which were free of debris and thermal-damages around the grooves, were performed by the laser ablation with a multiple-scanpass irradiation method. CFRP is a high strength composite material with a lightweight, and is increasingly being used various applications. UV pulsed laser ablation is suitable for laser cutting process of CFRP materials, which drastically reduces a thermal damage at cut regions.

Surface microfabrication of fused silica glass by UV laser irradiation

Surface micro-structuring of fused silica glass plates was performed by single-shot irradiation with a single-mode laser beam from a diode-pumped solid state UV laser at 355 nm. Well-defined micropattern without debris and microcrack formations around the etched area was fabricated by laser ablation with a focused laser-beam in the ambient air. The time-resolved optical emission spectra of plume were measured to elucidate the ablation behavior of silica glass induced by nanosecond-pulsed laser irradiation at 355 nm where absorption of silica glass is negligibly small. This method is suitable for rapid prototyping of surface microstructuing without a clean room environment.

Laser cutting of carbon fiber reinforced plastics (CFRP) by fiber laser irradiation

Laser cutting of carbon fiber reinforced plastics (CFRP) with a cw IR fiber laser (λ= 1090 nm, average power: 1kW). A well-defined cutting of CFRP which was free of debris and thermal-damages around the grooves, was performed by the laser irradiation with a fast beam galvanometer scanning on a multiple-scan-pass method.

On-Demand Patterning of Indium Tin Oxide Microdots by Laser-Induced Dot Transfer

Laser-induced dot transfer is an innovative micropatterning technique that realizes on-demand microdot deposition under room-temperature atmospheric conditions. Based on this method, we have developed site- and size-controlled micropatterning of oxide materials. As a model case, indium tin oxide (ITO) microdots were arrayed on a receiver substrate. A nanosecond, 266 nm laser pulse was focused onto the interface between the ITO film and transparent support, causing the ejection of a single ITO microdroplet. The dependence of the transferred structures on the film thickness as well as the laser-induced film temperature distribution has been investigated by both experimental and finite elemental approaches.

Laser-induced backside wet etching of silica glass with ns-pulsed DPSS UV laser at the repetition rate of 40 kHz

Surface micro-structuring of silica glass plates was performed by using laser- induced backside wet etching (LIBWE) upon irradiation with a single-mode laser beam from a diode-pumped solid-state (DPSS) UV laser with 40 kHz repetition rate at 266 nm. We have succeeded in a well-defined micro-pattern formation without debris and microcrack generation around the etched area on the basis of a galvanometer scanning system for the laser beam. Bubble dynamics after liquid ablation was monitored by impulse pressure detection with a fast- response piezoelectric pressure gauge.

Surface microfabrication of silica glass by LIBWE using DPSS-UV laser

Surface micro-structuring of silica glass plates was performed by using laser-induced backside wet etching (LIBWE) upon irradiation with a single-mode laser beam from a diode-pumped solid-state UV laser at 266 nm. We have succeeded in a well-defined micro-pattern formation without debris and microcrack formations around the etched area on the basis of galvanometer-based point scanning system with the laser beam. The behavior of liquid ablation (explosive vaporization) was monitored by impulse pressure detection with a fast-response piezoelectric pressure gauge. LIBWE method is suitable for rapid prototyping and rapid manufacturing of surface microstructuing of silica glass as mask-less exposure system in a conventional atmospheric environment.

Surface microstructuring of transparent materials by laser-induced backside wet etching using excimer laser

Silica glass is an important material in optics and optoelectronics because of its outstanding properties, such as transparence in a wide wavelength range, strong damage resistance for laser irradiation, and high chemical stability. In order to develop simpler processes of micro-fabricating silica glass using a pulsed laser, we have investigated a one-step method to microfabricate a silica glass plate using laser-induced backside wet etching (LIBWE) upon irradiation with a ns-pulsed excimer laser. Our idea of LIBWE is based on the deposition of laser energy on the surface of silica glass using ablation of a dye solution. When the dye solution was ablated upon the laser irradiation, the etching of a surface layer was performed on the silica glass. We have succeeded in the micro-fabrication of such transparent materials as silica glass, quartz, calcium fluoride, sapphire and fluorocarbon resin. The advantages of our LIBWE method are as follows, (1) a lwo laser fluence and constant etch rate, (2) microfabrication without debris and cracks formation, (3) large area irradiation with an excimer laser beam through a mask projection, (4) simple pre/post-treatment on target substrates. This is a one-step process simpler method at ambient pressure, which would be used for mass production.