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Noble metal/polymer nanocomposites were prepared with homogeneous distribution of the metal nanoparticles in the polymer via in situ polymerization and subsequent thermal reduction. First, noble metal complexes having good compatibility with methyl methacrylate (MMA) were dissolved in MMA. The mixture was pre-polymerized by adding an initiator, and then transferred to a mold to complete the polymerization. The composites obtained were reduced in situ by post-heating at different temperatures, depending on the metal. X-ray CT and transmission electron microscopy were utilized to prove the uniform distribution of noble metal nanoparticles in the poly (methyl methacrylate) (PMMA). The noble metal nanoparticles have average diameters of ∼3.0, 5.9, 12.7, and 24.1 nm for Pt, Pd, Cu, and Au, respectively. Thermogravimetric analysis shows that the weight of the Pd/PMMA nanocomposites increases with increasing initial molar concentration of metal complexes. UV/Visible transmission spectra also show plasmon absorptions characteristic of metals. The tensile strength of Pd/PMMA nanocomposites increased by 18.8% by adding Pd nanoparticles. These results suggest that uniform distribution of noble metal nanoparticles in PMMA can be achieved through in situ polymerization and thermal reduction.

Laser lift-off is one of potential candidates for new additive manufacturing technologies since it would realize additive patterning in micron/submicron resolution under atmospheric and room-temperature conditions. We have developed a variety of laser lift-off processes towards electronics, bio-sensing and medical treatments. In this paper, two kinds of laser lift-off methods were introduced: $\underline{L}$aser-$\underline{I}$nduced $\underline{D}$ot $\underline{T}$ransfer (LIDT) for micro/nanodots printing and $\underline{L}$aser-$\underline{I}$nduced $\underline{F}$orward $\underline{T}$ransfer with $\underline{o}$ptical stamp (LIFTop) for micropatterning of various functional films.

For high quality film printing, we have newly developed a laser-induced forward transfer with optical stamp (shortly, LIFTop), that consists of a two-step transfer process. In the first step, functional films were transferred onto a transparent polymer having high adhesiveness and elasticity like PDMS, which we call “optical stamp”. This stamp helps to avoid the transferred film from pattern spread and fracture. Then, the transferred micro-pattern on the optical stamp was further transferred onto a final target. In this talk, metal and transparent conductive oxide film transfer was demonstrated using our new LIFT process.

Polydimethylsiloxane (PDMS) is a material used for bio-chips and micro total analysis systems / lab-on-chips. For further development, it is inevitable to develop a technique to fabricate precise structures on micrometer scale at high aspect ratio. In the previous works, we reported a technique for high-quality micromachining of PDMS sheets, by means of ablating the PDMS sheets using EUV radiations around 10 nm from laser-produced plasma. In the present work, we have investigated fabricated structures based on wave optics, for fabricating designed strutures at submicrometer precision at high aspect ratio up to 10. We experimentally found that a deep hole with a diamter of 100 nm is formed at the center of flat ablated region after EUV irradiation of a PDMS sheet through a circular aperture with a diamter of two micrometers in a contact mask. In the case of EUV irradiation through square apertures, the deep hole was not found on a PDMS sheet, while narrow dip is formed at the edge of the ablated region. We numerically calculated propagations of EUV plane wave light in PDMS sheets. After traveling one micrometer from a circular aperture, an intense peak appears at the center of the beam, which is caused by diffraction. For the square apertures, the enhancement does not occur, while intense profile near the edge is formed due to the Fresnel diffraction. Interestingly, at 100 micormeters from the aperture, the Frenel peaks are superposed at the center, resulting in a narrow and intense beam.

In this study, the correlation between the stress–strain behavior of a carbon fiber-reinforced plastic (CFRP) and the temperature at which the heat-affected zone (HAZ) is generated is investigated. First, CFRP ([−45/45]2s laminate) specimens were heated at several temperatures to induce thermal damage, i.e. a HAZ. Subsequently, tensile tests were conducted on the specimens with thermal damage. Then, microscopy and X-ray measurements were carried out to discuss the stress–strain responses from a microscopic viewpoint. The results of strain measurement during thermal treatment indicated that the strain increases with increasing temperature. The tensile tests showed that the CFRP specimens subjected to thermal damage during heating at a high temperature fractured in the ductile mode, whereas the fracture mode of the CFRP specimens with low-temperature thermal damage was discontinuous. Microstructure observation using X-ray tomography showed that the debonding between the carbon fibers and the resin matrix in...

Recently, the laser processing of carbon fiber reinforced plastics (CFRPs) has attracted attention owing to the high processing speed and less tool wear. A problem in the laser processing of CFRPs is the lower strength than that of CFRPs processed by machines. This is considered to be due to the heat-affected zone (HAZ) generated during laser processing. In this study, the stress distributions of CFRPs processed by a laser obtained was evaluated by using infrared thermography. X-ray CT images were also obtained, which enabled us to discuss the stress distribution in terms of the HAZ. The stress distribution showed that the area with reduced stress generated in the HAZ which was introduced by laser processing. The region of low stress in the HAZ was visualized by infrared thermography. It is shown that the regions with reduced stress induce the conventionally reported decrease in strength of laser-processed CFRPs.

Laser-induced dot transfer (LIDT) is one of promising additive manufacturing techniques because it can realize flexible patterning of micron and submicron-sized dots even at atmospheric room-temperature conditions. In the LIDT process, a laser pulse is tightly focused onto a source film, leading to a transient melting of the film followed by sub-spot transfer using one-to-one microdot deposition with laser-illuminated area. Recently, we have developed a novel double-pulse LIDT process using the first pulse for preheating the source film and the second pulse for dot transfer. To investigate the double-pulse effect on microdot transfer of oxides, temporal high-temperature distributions of a thick indium tin oxide source film during double-pulse irradiation have been simulated using a Finite Element Method (FEM) approach. As a result, preheating by the first pulse decreased a difference in film temperature along both the film thickness and in-plane directions. This is effective to avoid film fracture, leading to high-quality patterning of a wide variety of microdots.

Polydimethylsiloxane (PDMS) is a material used for cell culture substrates / bio-chips and micro total analysis systems / lab-on-chips due to its flexibility, chemical / thermo-dynamic stability, bio-compatibility, transparency and moldability. For further development, it is inevitable to develop a technique to fabricate precise three dimensional structures on micrometer-scale at high aspect ratio. In the previous works, we reported a technique for high-quality micromachining of PDMS without chemical modification, by means of photo direct machining using laser plasma EUV sources. In the present work, we have investigated fabrication of through holes. The EUV radiations around 10 nm were generated by irradiation of Ta targets with Nd:YAG laser light (10 ns, 500 mJ/pulse). The generated EUV radiations were focused using an ellipsoidal mirror. It has a narrower incident angle than those in the previous works in order to form a EUV beam with higher directivity, so that higher aspect structures can be fabricated. The focused EUV beam was incident on PDMS sheets with a thickness of 15 micrometers, through holes in a contact mask placed on top of them. Using a contact mask with holes with a diameter of three micrometers, complete through holes with a diameter of two micrometers are fabricated in the PDMS sheet. Using a contact mask with two micrometer holes, however, ablation holes almost reaches to the back side of the PDMS sheet. The fabricated structures can be explained in terms of geometrical optics. Thus, we have developed a technique for micromachining of PDMS sheets at high aspect ratios.

For higher cell-to-module efficiency in Cu(In,Ga)Se2 (CIGS) thin-film solar cells, it is important to reduce the loss of active area due to integrated connection. The integrated connection contains three scribing processes: P1 (back contact insulation), P2 (electrical connection) and P3 (transparent conductive oxide, shortly TCO front contact insulation). In this work, we focused on ultrashort-pulse laser scribing (λ=1034 nm, Δτ=300 fs) of TCO via lift-off process as damage-less P3 scribing of CIGS thin-film solar cells. The lift-off of TCO was caused by laser ablation of only an upper part of CIGS light-absorbing layer. The dependence of lift-off behavior on the laser pulse energy and TCO film thickness has been investigated. It was observed that the lift-off of TCO formed a heat-affected zone (HAZ) with a thickness up to 250 nm beneath the trench bottom, where the CIGS experienced to melt. Further, thinner TCO film required lower laser energy threshold for the TCO lift-off, which is favorable to higher solar cell efficiency due to smaller HAZ. Using the TCO liftoff as P3, a submodule with an active area of approximately 3.5 cm2 made by all laser scribing exhibited the conversion efficiency of 11.6 %. After post-annealing at 85 °C for 15 h in vacuum for recovering laser-induced damages, the efficiency was successfully improved to 15.0 %, which is comparable to mechanically-scribed one.

Carbon fiber-reinforced plastics (CFRP) composite is most attractive materials to reduce the weight of transportations. To increase the production volume and the efficiency in the field of CFRP component, fast, highly precise and cost-efficient technologies are required. Although laser cutting meets these requirements, it is not used because of insufficient knowledge about the effect of thermal damage on the material behavior. In this study, the effect of several cutting processes on the static tensile strength and the fatigue strength was evaluated for CFRP consisting of thermoset resin matrix and carbon fibers. The CFRP was cut using two different-type of lasers; a CO2 gas laser and single-mode fiber lasers, and a conventional mechanical tool. The mechanical cutting specimen produced a cut of high quality. While, the laser cutting specimens clearly showed a heat-affected zone (HAZ). The static tensile strength and the fatigue strength by laser cutting specimens clearly decreased in comparison with mechanical cutting specimen. The laser cutting specimen exhibited a linear dependency of the tensile strength on the HAZ, indicating that the main effect resulted from thermal destruction of CFRP within the HAZ.

We have newly developed a double-pulse laser-induced dot transfer technique to realize ondemand deposition of functional oxide microdots under room-temperature atmospheric conditions. In our double-pulse system, the first pulse was irradiated to preheat an oxide source film, and then the second pulse was more tightly focused on the same position to deposit an oxide microdot onto a receiver substrate. As a model case, indium tin oxide microdots with much smaller lateral dimensions than the laser focal area were reproducibly arrayed on a silica glass substrate by the doublepulse process, while there were microdot vacancies at a rate of approximately 30 % in the case of a single-pulse process without preheating. In order to explore the effect of double-pulse, laser-induced temperature distribution was also investigated from a finite elemental approach.

Neutral fragments from a nanosecond KrF excimer laser-ablated carbon fiber reinforced plastic (CFRP, carbon fiber/epoxy resin composite) were investigated by laser-ionization time-of-flight (TOF) mass spectrometry in order to explore the laser ablation dynamics of CFRP. The neutrals were detected after the post-ionization by an ArF excimer laser pulse at variable delay times, td, relative to the ablation KrF excimer laser pulse. Depending on the ablation fluence, TOF mass spectra and laser-etched surface morphology drastically changed. At the laser fluence of 0.3 J·cm -2 , the resins were preferentially ablated. The TOF mass spectra contained a main peak at 36 amu assigned to C3 + in early delay times, and then the main peak changed to 39 amu assigned to C3H3 + . At 1.0 and 1.5 J·cm -2 , both of carbon fibers and resins were ablated. The most prominent peak was C3 + independent of the delay time. The delay-time distribution of C3 + exhibited a single peak at 0.3 J·cm -2 and then changed to two peaks at 1.5 J·cm -2 . The fits with shifted Maxwell-Boltzmann distribution gave good agreement, suggesting transient maximum CFRP temperature of 4700, 6400, and 7100 K at 0.3, 1.0 and 1.5 J·cm -2 , respectively.

were fabricated with a fluence of 1.3 J/cm 2 , a pulse repetition of 80 Hz, and various pulse numbers. Special care was directed to maintaining in-focus conditions for etching. In the fabrication of 5-µmwide microtrenches, etch rates of 5.3 nm/pulse evaluated for trenches with depths of less than 4 µm increased by a factor of 2.55 to 13.5 nm/pulse when the trenches became deeper than 16 µm. Such variation in the etch rate reduced with width and became negligibly small for 20-µm-wide microtrenches. Based on a similar dependence on width, the variation in etch rate with depth can be related to the size effect observed in LIBWE. As a factor causing the size effect as well as the variation in etch rate with depth, the interaction between the laser-heated surface and the solution in an early time region of the laser-induced phenomena is proposed.

Flexible and rapid preparation of FeSi2 microdots and indium tin oxide (ITO) microstructure patterns was performed using laser-induced forward transfer with a nanosecond high-frequency diode-pumped solid-state laser/galvanometer-based point-scanning system. Different types of source materials, i.e., FeSi2 and ITO, were used to explore the materials dependence of transfer. FeSi2 spheres with a lateral diameter of 5.5 μm were successfully arrayed on a micrometer scale. Sub-spot transfer was achieved, and we refer to this as laser-induced dot transfer (LIDT). In the case of ITO, although the transferred shape is flower-like rather than spherical, site-controlled transfer was achieved. The LIDT technique is useful for integrating functional micro-patterns with sub-spot resolution under room-temperature atmospheric conditions.

An indirect laser processing, laser-induced backside wet etching (LIBWE) is one of effective techniques for flexible laser-direct-write (LDW) type micromachining of transparent materials. Micromachining by LIBWE employing a diode-pumped solid state (DPSS) green laser and a galvanometer-based point scanning system was examined with employing organic dye solution and liquid metal as laser-absorbing media. LIBWE using liquid metal absorber showed smaller threshold pulse energies for etching (9.1 μJ/pulse) than that using organic dye solution (33 μJ/pulse). Different morphologies of etched surfaces were observed for different laser-absorbing media, indicating different mechanisms involved in the etching processes. The laser-induced dynamic phenomena were investigated by means of transient reflection measurements. The different contribution of direct and indirect actions of laser pulses was indicated for LIBWE employing different laser-absorbing media.

*1 Institute of Applied Physics, University of Tsukuba, 1-1-1 Ten'nodai, Tsukuba, Ibaraki 305-8573, bk200820379@s.bk.tsukuba.ac.jp *2 Graduate School of Information Sciences and Electrical Engineering, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395,Japan *3 Department of Health Sciences, School of Medicine, Kyushu University, 3-1-1 Maidashi, Fukuoka 812-8582, Japan *4 Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki305-8565, Japan

Silica glass can be ablated using focused laser plasma soft X-rays. The ablation technique enables us to fabricate trenches with a width as narrow as 50 nm. In the present paper, we have investigated the nano-ablation process. The soft X-ray irradiation causes a silica surface broken into almost atomic species. Ionic species have kinetic energies higher than that gained by heating to the boiling point. We measured the ablation depth as a function of the soft X-ray fluence. The depth analysis revealed that soft X-rays are absorbed in a silica surface with an effective absorption depth of 10 nm. The result indicates that the energy density of the soft X-rays per unit volume at the threshold fluence is comparable to that required for breaking silica glass into atomic species. Further, the results suggest that ablation occurs before diffusion of absorbed energy into the surrounding region. In addition to energy absorption, repulsive forces between ionic species may cause ablation of the silica surface by soft X-ray irradiation. These properties of soft X-ray ablation may make possible the nano-ablation of silica glass. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(9): 30–35, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10354

We investigated a simple and productive micromachining method of silica glass by ablation using a TEA CO2 laser (10.6 μm) with a spatial resolution down to sub-wavelength scale. The silica glass was irradiated by the TEA CO2 laser light through a copper grid mask with square apertures of 20×20 μm2 attached to the silica glass surface. After the irradiation, circular holes with a diameter of several μm were formed on the silica glass surface at the centers of the apertures due to the Fresnel diffraction effect. The minimum diameter of the holes was 3.4 μm. The characteristics of the micromachining are discussed based on the electric field distributions of the CO2 laser light under the mask using a three-dimensional full-wave electromagnetic field simulation.

Slanted microstructures were fabricated on silica glass by laser-induced backside wet etching (LIBWE) with gradual shift of the area irradiated by normal incidence. Slanted microtrenches with tilting angles up to about 30 degrees could be fabricated by lateral shift of the irradiated area with the speed of ~5.0 nm·pulse under the conditions showing the vertical etching with rate of 7.0 11 nm·pulse. Tilting angle could be controlled by the speed of lateral shift the irradiated area during the etching. Such structures were formed as a result of both lateral and vertical etching at the etch front. The trench structure fabricated by drastic shift of the irradiated area indicated that the etching of the sidewalls occurred at the area with height of around 400 nm.

A simple and productive micromachining method of a silica glass using a TEA (transversely excited atmospheric) CO2 laser (10.6 μm) was investigated. A copper grid mask with a thickness of 2 μm, square apertures of 20×20 μm was attached to the silica glass surface, and it was irradiated by the TEA CO2 laser light. As a result, circular holes were formed on the silica glass surface at the center of each aperture in a spatial resolution down to the sub-wavelength scale. The minimum diameter of the hole was less than 3 μm, which is less than one third of the wavelength of the TEA CO2 laser. A depth of the holes ranging from 100 nm to 600 nm could be micromachined on silica glass surface. The mechanism of the micromachining was discussed based on electric field distributions of the CO2 laser light by a 3D full-wave electromagnetic field simulation solver. The simulation results are in good agreement with the experimental results. It was found that the micromachining of the circular holes were caused by Fresnel diffraction of the CO2 laser light at the apertures.

The well-controlled fabrication of microtrenches including inclined features using normal incidence with gradual shifting of the irradiated area was demonstrated. Based on the variation of trench width depending on the laser fluence, the existence of gaps between the edge of the irradiated area and sidewall of the trench was shown. Because of these gaps, the shifted laser pulse can stay at the bottom of the trenches in the fabrication of the inclined features. In laser-induced backside wet etching (LIBWE), the photo-activated region generated within organic solution would act on the glass surface and results in etching. It was indicated that the photo-activated region generated at the bottom of the trenches acted not only on the bottom of the trench but also on the sidewalls. Based on such etching of the sidewall, fabrication of inclined features becomes possible. In this method, the tilting angle can be changed within one deep trench. Flexible structure formation deep inside the silica glass can be achieved.

The effect of laser-induced heat on Cu(In,Ga)Se2 solar cells was evaluated by scanning spreading resistance microscopy (SSRM) to improve the laser scribing (LS) quality. Two types of LS were examined for electrical isolation; that using transparent conductive oxide (TCO) lift-off resulted in a higher conversion efficiency of 17.4% and shunt resistance of 5 × 103 Ωcm2. SSRM images confirmed the absence of shunt paths between the laser-induced low-resistance layer at the trench bottom and the top TCO layer, which resulted in the high shunt resistance. Ultrashort-pulse LS would be a promising tool for reducing the dead area and increasing the throughput by high-speed scribing.

We are investigating the micromachining of silica glass using extreme ultraviolet (EUV) light from laser-produced plasma (LPP). The present investigation deals with the ablation using EUV light of around 13.5 nm and 11 nm generated in laser-produced Sn plasma and Xe plasma, respectively. CO2 laser and Nd:YAG lasers were used as pump lasers. The EUV radiation was focused on the surface of silica glass through the meshed mask using an ellipsoidal mirror coated with gold film. The results showed that the silica glass was successfully ablated by EUV light from the Nd:YAG-LPP. The maximum ablation rate was 42 nm per shot for 11-nm light, and 25 nm per shot for 13.5-nm light. On the other hand, EUV radiation from the CO2-LPP did not ablate the silica glass. This is presumably caused by the lower EUV irradiation intensity due to the long pulse duration of the CO2 laser.

Fabrication of FeSi2 nano- and microdot array was performed by utilizing droplet ejection through laser-induced forward transfer, which we named laser-induced dot transfer (LIDT). An amorphous FeSi2 alloy 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 dot deposition. Micro-Raman spectroscopy confirmed β-FeSi2 semiconducting crystalline phase even on unheated substrates. Moreover, the microdots exhibited near-infrared photoluminescence at the peak wavelength of 1.57 μm, which comes from the β-FeSi2 crystalline phase precipitated during the LIDT process. The dot size was successfully reduced to approximately 500 and 300 nm in diameter and height, respectively. This technique is useful for integrating functional nano- and microdots under atmospheric room-temperature conditions.

Silica glass can be ablated using focused laser plasma soft X-rays. The ablation technique enables us to fabricate trenches with a width as narrow as 50 nm. In the present paper, we have investigated the nano-ablation process. The soft X-ray irradiation cause silica surface broken into almost atomic species. Ionic species have kinetic energies higher than that gained by heating up to the boiling point. We measured ablation depth as a function of soft X-ray fluence. The analysis of the depth revealed that soft X-rays are absorbed in silica surface with a effective aborption depth of 10 nm. The result leads to that the energy densty of the soft X-rays per unit volume at the threshold fluence is comparable to that required for breaking silica glass into atomic species. Futher, the results suggests that ablation occurs before diffusion of absorbed energy into the surroudning region. In addition to the energy absorption, repulssive force between ionic species may cause ablation of silica surface by soft X-ray irradiation. These properties of soft X-ray ablation may achieve nano-ablation of silica glass.

We have investigated a one-step method to fabricate a microstructure on a silica glass plate by using laser-induced backside wet etching (LIBWE) that consists of diode-pumped solid state (DPSS) laser beam scanning system. The focused laser beam of a DPSS UV laser at λ = 266 nm on the repetition rate of 10 kHz was directed to the sample cell of the glass. Deep vertical microtrenches having an aspect ratio of ca. 6 were fabricated on the surfaces of silica glass. Inclined trench structures at the angle of 60 degree were successfully fabricated by changing the incident angle of the laser beam onto the glass surface through an equilateral prism at the normal incidence of the laser baem.

We have investigated nanomachining of inorganic materials using laser plasma soft X-rays. The soft X-rays were generated by irradiating Ta targets with pulsed Nd:YAG laser light. The laser plasma soft X-rays were focused using an ellipsoidal mirror, which is designed so as to focus soft X-rays at around 10 nm efficiently. The focused soft X-rays were incident to the surfaces of inorganic materials such as silica glass, LiF, CaF2, and LiNbO3. It is found that these materials are ablated by soft X-ray irradiation. In particular, silica glass can be ablated at rates of 0.2 to 150 nm/shot, which can be controlled by the intensity of soft X-rays. It is remarkable that silica can be ablated smoothly with a roughness of 1 nm after 10 shots of soft X-ray irradiation at a rate of 50 nm/shot. In order to demonstrate nanomachining of silica glass, we used contact masks on top of silica glass plates fabricated by electron beam lithography technique. The silica glass plates were irradiated with laser plasma soft X-rays through the windows of the contact masks. We found that nanofabrication of trenches with a width of 70 nm was performed clearly. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(4): 45– 51, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10080

We have investigated a one-step method to fabricate a microstructure on a silica glass plate by using laser-induced backside wet etching (LIBWE) that consists of excimer laser mask projection system and diode-pumped solid state (DPSS) laser beam scanning system. Well-defined deep microtrenches without crack formations on a fused silica glass plate were fabricated by LIBWE method with the UV lasers. We have demonstrated the micro- fabrication of pits-array and patterned grating on the surface of silica glass plates by LIBWE method at 248 nm and 266 nm with dye solutions. The two new systems allow us to use rapid prototyping of high precision surface microfabrication of silica glass as laser direct-write processing.

Deep microtrenches having a high aspect ratio on the surfaces of silica glass were fabricated by laser-induced backside wet etching (LIBWE). The focused laser beam of a diode-pumped solid state (DPSS) UV laser at λ = 266 nm on the repetition rate of 30–40 kHz was directed to the sample cell of the glass by a galvanometer-based point scanning system. Vertical and inclined trench structures were successfully fabricated on the glass by changing the incident angle of the laser beam. The depth of filed (DOF) in LIBWE was analyzed by inclined laser irradiation. Flexible rapid prototyping by the mask-less exposure system was demonstrated.

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.

We have investigated micromachining of a variety of materials by irradiation with laser plasma soft X-rays (LPSXs) at around 10 nm. The pulsed LPSXs were generated by irradiation of a Ta target in a vacuum chamber with Nd:YAG laser light at 532 nm, with a pulse duration of 7 ns, at a fluence of ~104 J/cm2. The LPSXs were focused on the surfaces of samples using an ellipsoidal mirror that is designed so that LPSXs at around 10 nm are focused efficiently. We found that quartz glass plates are ablated by LPSX irradiation at a typical rate of 48 nm/shot. Furthermore, the ablated regions have smooth surfaces with a roughness less than 10 nm after 10 shots of LPSX irradiation. It is demonstrated that quartz glass is machined with a lateral resolution higher than 100 nm. In addition to quartz glass, the LPSX processing can be applied to micromachining of a variety of materials such as Pyrex, CaF2, LiF, LiNbO3, Si and silicone.

We have investigated nanomachining of inorganic materials using laser plasma soft X-rays. The soft X-ray was generated by irradiating Ta targets with pulsed Nd:YAG laser light. The laser plasma soft X-rays were focused using an ellipsoidal mirror, which is designed so as to focus soft X-rays at around 10 nm efficiently. The focused soft X-rays were incident to the surfaces of inorganic materials such as silica glass, LiF, CaF2 and LiNbO3. It is found that these materials are ablated by soft X-ray irradiation. In particular, silica glass can be ablated at rates of 0.2-150 nm/shot, which can be controlled by the intensity of soft X-rays. It is remarkable that silica can be ablated smoothly with a roughness of 1 nm after 10 shots of soft X-ray irradiation at a rate of 50 nm/shot. In order to demonstrate nanomachining of silica glass, we used contact masks on top of silica glass plates fabricated by electron beam lithography technique. The silica glass plates were irradiated with laser plasma soft X-rays through the windows of the contact masks. We found that nanofabrication of trenches with a width of 70 nm are performed clearly.

We report on the laser cutting of carbon fiber reinforced thermo-plastic (CFRTP) and carbon fiber reinforced plastic (CFRP) with a cw IR fiber laser (average power: 2 kW). CFRTP and CFRP are a composite material which contains carbon fibers and binding plastics. A well-defined 2D laser cutting of CFRTP and CFRP flat plates which were free of debris around the groove was performed by the laser irradiation with a fast beam galvanometer scanning on a multiple-scan-pass method. The area of laser-induced damages in the samples was observed by microscopic X-ray Computed Tomography. Laser cutting with a high speed beam scanning exhibits a clean top and an excellent sidewall quality along with a negligible heat affected zone. In addition, the laser cutting of CFRP for a three-dimensional molded sample was performed with a five-axis laser cutting machine.

For high-resolution printing, we have developed a novel way of functional microdots deposition based on laser-induced forward transfer, which is referred to laser-induced dot transfer (LIDT). LIDT is one of promising additive manufacturing techniques because it can realize flexible patterning of micron and submicron-sized dots at atmospheric room-temperature conditions. Recently we have achieved printing of functional oxide microdots by a double-pulse LIDT with the first pulse for preheat and the second pulse for transfer, resulting in more precise control of laser-induced hightemperature and thermal-stress in a source film. In this paper, temporal temperature distributions during the transfer process have been investigated using a finite element method approach. High-resolution printing of functional microdots is promising for future optoelectronic integrations.

We have developed a novel design for a microfluidic device incorporating a two-dimensional microbead array by using silica glass plates structured by the laser-micromachining method, Laser-Induced Backside Wet Etching (LIBWE). Surface functionalized borosilicate glass and polymer microbeads 10 µm in diameter, which act as detectors, were fixed in etched microstructures and sealed with a polydimethylsiloxane plate to form a microfluidic system. The beads are regularly arranged in a two-dimensional manner without being in contact with any other. Analytes are supplied as a solution flowing in microchannels. The pressure-driven flow in the microchannels was investigated. The successful capture of fluorescein isothiocyanate by amino groups as well as that of biotin by avidin on the beads' surface was confirmed by fluorescence microscopy.