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Bacillus cereus is an opportunistic pathogen that often causes severe infections such as bacteremia, with sphingomyelinase (SMase) being a crucial virulence factor. Although many strains of B. cereus carry the SMase gene, they are classified as SMase-producing and nonproducing strains. The reason for different SMase production among B. cereus strains remains unknown. In this study, we investigated the relationship between SMase and the PlcR transcriptional regulation system to clarify the mechanism leading to varied SMase production among B. cereus strains. We analyzed the sequence of the PlcR box, which is a transcriptional regulator-binding site, located at the promoter region of SMase and phosphatidylcholine-specific phospholipase C. Based on differences in the PlcR box sequences, we classified the B. cereus strains into three groups (I, II, and III). SMase expression and activity were hardly detected in Group III strains. In Group I strains, SMase activity and its expression were maximal at the onset of the stationary phase and decreased during the stationary phase, whereas those were maintained during the stationary phase in Group II stains. On injection of B. cereus strains into mice or incubation with macrophages for phagocytosis assay, the SMase-producing Group I and II strains showed higher pathogenicity than Group III strains. These findings suggest that PlcR box sequence in B. cereus affects the production of SMase, which may provide important clinical information for the detection of highly pathogenic B. cereus strains.

Bacillus cereus is well known as a causative agent of food poisoning but it also causes bacteremia and endophthalmitis in nosocomial infections. However, as an environmental bacterium that lives in soil, it is often treated as simple contamination by hospitals. In recent years, highly pathogenic B. cereus strains that are similar to Bacillus anthracis have been detected in hospitals. The B. cereus sphingomyelinase contributes to its pathogenicity, as do sphingomyelinases produced by Staphylococcus aureus, Pseudomonas aeruginosa, Helicobacter pylori, and B. anthracis. Highly pathogenic B. cereus produces a large amount of sphingomyelinase. In this review, we describe the regulation of sphingomyelinase expression through the PlcR-PapR system, the pathogenicity of bacterial sphingomyelinases, and their potential as therapeutic drug targets.

To obtain important information for fabricating atomic-scale Au thin films that are used for biosensors, we have observed the morphology of Au particles adsorbed on a Si(111)-7 × 7 surface, which is supposed to be the initial stage of Au atomistic thin film formation. Au particles were adsorbed on the clean Si surface using a PLD method, and the adsorbed particles were observed using a scanning tunneling microscope. As the number of laser shots was increased in the PLD method, the size of the adsorbed particle became larger. The larger particles seemed to form clusters, which are aggregations of particles in which each particle is distinguished, so we call this type of cluster a film-shaped cluster. In this work, we have mainly analyzed this type of cluster. As a result the film-shaped clusters were found to have a structure of nearly monoatomic layers. The particles in the clusters were gathered closely in roughly a 3-fold structure with an inter particle distance of 0.864 nm. We propose a model for the cluster structure by modifying Au(111) face so that each observed particle consists of three Au atoms.

Bacillus cereus is well known as a causative agent of food poisoning but it also causes bacteremia and endophthalmitis in nosocomial infections. However, as an environmental bacterium that lives in soil, it is often treated as simple contamination by hospitals. In recent years, highly pathogenic B. cereus strains that are similar to Bacillus anthracis have been detected in hospitals. The B. cereus sphingomyelinase contributes to its pathogenicity, as do sphingomyelinases produced by Staphylococcus aureus, Pseudomonas aeruginosa, Helicobacter pylori, and B. anthracis. Highly pathogenic B. cereus produces a large amount of sphingomyelinase. In this review, we describe the regulation of sphingomyelinase expression through the PlcR-PapR system, the pathogenicity of bacterial sphingomyelinases, and their potential as therapeutic drug targets.

We have demonstrated the photon-stimulated surface spectroscopy using broadband vacuum ultraviolet (VUV) emissions from a laser-produced plasma, in which adsorbed atoms or molecules on material surfaces were to be desorbed and dissociated as a result of absorption of the wavelength-selected VUV photons. Desorbed and dissociated atoms or molecules were then detected by a mass spectrometer. Mass spectra of polyethylene and polyvinyl chloride samples were obtained as a function of the irradiation wavelength. We have found sufficient characteristic differences of the mass spectra in the irradiation wavelength shorter than 200 nm in each sample. The desorption and dissociation of atoms or molecules from material surfaces depended on bond energy or molecular structure.

Pseudomonas aeruginosa can penetrate the layer of mucus formed by host intestinal epithelial cells, often resulting in sepsis in immunocompromised patients. We have previously demonstrated that P. aeruginosa can penetrate the mucin layer by flagellar motility and the degradation of the mucin layer. However, it remains unclear how P. aeruginosa initially recognizes epithelial cells. Using the human epithelial colorectal adenocarcinoma (Caco-2) cell line, we investigated extracellular signaling that could facilitate the penetration of P. aeruginosa through the mucin layer. The supernatant from Caco-2 cell cultures increased penetration of P. aeruginosa through an artificial mucin layer. The Caco-2 cell supernatant increased bacterial flagella-dependent swarming motility, but it did not influence P. aeruginosa growth or protease activity. Filtering of the Caco-2 cell supernatant indicated that proteins weighing

We have observed the initial stage of the film deposition process by pulsed laser deposition method (PLD) on the Si(1 1 1)-7 × 7 surface to obtain the information of the interface between the substrate and the films. In the present work, we have concentrated to observe the initial stages for β-FeSi2 and SiC thin films fabricated by PLD method. We used an ultra-high-vacuum scanning tunneling microscope (UHV-STM) for the observation. Fe, Si, e-FeSi, HOPG and C60 targets were used for the PLD experiment. Our results suggest that particles ablated from Fe, Si and HOPG targets adsorbed onto the substrate surface as single atom, e-FeSi as a pair and C60 as a cluster of three molecules. We also found that the particles ablated from the Fe, Si, e-FeSi and HOPG targets which has a dangling bond preferred to adsorb onto adatom that has a dangling bond as well, whereas the particles ablated from the C60 target which is electrically neutral preferred to adsorb onto the mechanical structures of the surface. These results are expected to be useful information for fabrication of the β-FeSi2 and SiC thin films of good quality.

Laser surface modification of Si wafer is a well-known method in the semiconductor industry. It has been repoted that scratching of the surface by an AFM probe induces surface phase transition on silicon (Si) wafer. This can act as an etching mask against potassium hydroxide (KOH) solution. In this study, a combination of formation of laser-induced surface periodic structure by low fluence femtosecond laser irradiation on crystalline Si wafer and anisotropic wet etching achieved the formation of the structures with different morphology from the conventional. Femtosecond laser pulses (800nm, 120fs) were irradiated on the surface of Si (110) in order to form periodic structures with the lowest fluence possible. After the structures formation, anisotropic wet etching by KOH solution was performed. The structures played as an etching mask to form the periodic structures with the aspect ratio more than 0.6 and the separation about the irradiated wavelength.

Fiber Bragg Grating (FBG) strain-sensing system has been paid much attention for the advantages of its light weight, anti-explosion, and harmlessness for electromagnetic noise, but it has not been widely used in practical applications with the high price. We have developed a new concept of wavelength meter in which the transmission center wavelength is monitored by mechanically applying a certain strain to a scanning FBG. The accuracy and stability are found to be ±0.01 nm for 12 days running, which is enough for the most applications.

Fiber Bragg Grating(FBG)を用いた土木計測用の多段式傾斜計を開発した。基本性能を実験にて確認し、測定範囲±1.5°において、±0.5%F.S以内の偏差を示し、一般的な電気式の傾斜計と同等の結果を示した。実際の盛土工事現場で開発したFBG多段式傾斜計を1mピッチで25台をボーリング孔に設置し計測を行った。測定結果は、G.L.-13m付近の微少変位を検出することができ、変位速度0.03mm/日の地盤変位速度を検知できることが明らかとなった。その結果、地すべりモニタリングなどへの応用に関する知見を得た。

Second-order optical nonlinearity was found to be generated in high-purity silica glasses when they were exposed to x-ray radiation and then thermally poled. Two kinds of second-order optical nonlinearity, near-surface nonlinearity localized in a thin layer near the sample surface and bulk nonlinearity spreading throughout the whole sample, were observed. The maximum χ33(2) values of near-surface and bulk nonlinearity were 0.20 and 0.43 pm/V, respectively. Further, a change in refractive index of Δn=4×10−3 was also observed in the sample. The χ33(2) value of the bulk nonlinearity and the change in refractive index increased with the x-ray intensity. On the other hand, the χ33(2) value of the near-surface nonlinearity had a tendency to saturate when the intensity was higher than 1.3 mW/cm2. Based on absorption spectra of the samples, both the bulk nonlinearity and the refractive index change were found to be associated with point defects such as the E′ center (≡Si⋅) and nonbridging oxygen ions (NBO−,≡Si–O−).

Recently, a novel method of photochemical vapor deposition using vacuum ultraviolet (VUV) excimer lamps (VUV-CVD) has been developed. We have been attempting to make thin films from organic precursors at room temperature by VUV-CVD. We present the characteristics of VUV-CVD films and the reaction properties of VUV-CVD as a function of the addition of O2, the substrate temperature, and the illumination intensity, examining the growth rate, film quality, and gap-filling properties when various organic siloxane gases are used as chemical precursors. VUV photons dissociate the organic precursor and produce radical reactants that consist of Si-O and impurities such as C-H and O-H. They finally condense into deposition films including SiO2 and impurities. Therefore, the VUV-CVD films are very similar in composition to the precursors. The reaction is altered by adding O2, which produces ozone and activated oxygen as a result of dissociation by VUV photons. The deposition efficiency is improved by both a low substrate temperature and the higher light intensity of the excimer lamp. Film deposition at room temperature in VUV-CVD without thermal- or plasma-induced damage constitutes an important innovation in thin film preparation. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(4): 43–50, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10325

Tetraethoxysilane (TEOS : SiO4(C2H5)4) is widely used to fabricate silicon-dioxide insulator thin films in LSI device technologies. We have already reported that TEOS is photo-dissociated to result in oxide layer deposition at room temperature by a vacuum ultraviolet excimer lamp (λ=172 nm). In this paper, we have observed the initial stages of oxide layer deposition on silicon clean surfaces with the scanning tunneling microscope (STM) and time-of-flight (TOF) mass spectrometer. An argon excimer lamp (λ=126 nm) is used for the photo-chemical vapor deposition (CVD). TEOS molecules have been dissociated to be SiO4(C2H5)n(n=1, 2, 3) groups on the clean surfaces. The 126 nm photons dissociate the molecules or radicals to Si-Om(m=1, 3, 4) after 2 min. Finally, the Si-Om adsorbed molecules and Si atoms in the substrate are re-arranged to be a disorder structure by the photons.

Thin semiconductor wafer is more required for portable devices due to its mechanical flexibility or space gain. In dicing process for this thin wafer, suppression of micro-cracks is indispensable, which result in starting point of substrate breakage. In this research, laser cutting was performed for thin silicon wafer as a new dicing technique to conventional diamond blade dicing. Nano-, pico- and femtosecond laser were used to cut substrates in order to investigate the dependence of the flexural strength on the pulse width and the irradiated laser energy. As a result of that, the average strength of the diced wafer with the femtosecond laser was about three times larger than that with the nanosecond laser. In the case using the femtosecond laser, moreover, the minimum strength was about three times as large as that of the conventional blade dicer.

Recently, semiconductor substrates for integrated circuits (ICs) have been required to be as thin as 50 µm, because many electronic devices must be miniaturized and light in weight. Machining of such thin substrates with conventional dicing techniques is very difficult. Therefore, we have proposed processing them using femtosecond laser ablation. In this work, we investigate the influence of conditions of a double pulsed laser such as the delay time and fluence on the depth and diameter in order to develop a new dicing technique for very thin ICs. A double pulsed laser (λ = 780 nm, τ = 150 fs, f = 10 Hz, Δt = 0 to 100 ps, E1 + E2 = 100 µJ) was focused on the Si substrate with a plano-convex lens having a nominal focal length of 100 mm. At a delay time of 10 ps, singularly shallow and flat-bottomed holes were obtained. When the substrates were diced under these conditions, the bottom of the processing groove was flat and very smooth, whereas many microcracks starting from the bottom of the groove formed by the conventional method have been observed. From these results, we were able to identify femtosecond laser processing conditions that were applicable to dicing of thin Si substrates. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(3): 43–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20028

Recently, much attention has been paid to novel photochemical vapor deposition using vacuum ultraviolet excimer lamps (VUV-CVD), because thin films can be deposited at room temperature. We show some characterization of films and discuss about the reaction mechanism using organic siloxane gases in VUV-CVD. VUV photons dissociate organic gases into radical reactants of Si-O and impurities such as C-H and O-H in the gas phase. The reactants finally condense on the surface into films included SiO2 and impurities. The reaction is different by adding O2. It is caused by the behaviors of ozone and activated oxygen that VUV photons dissociate O2 and are generated. The deposition efficiency is improved both by the low substrate temperature and the higher light-intensity of an excimer lamp. The film deposition at room temperature in VUV-CVD that either thermal or plasma induced damages are completely avoided must become a novel technique in thin films preparations.

Femtosecond laser can minimize the undesirable thermal effected zone, and hence is suitable for the processing of brittle materials. Taking advantage of this method, some glassy materials can be cut without any micro-cracks on the surface. This paper presents the drilling of ultra thin silicon wafers irradiated with femtosecond laser. In order to understand fundamental characteristics of the ablation using femtosecond laser, influence of laser parameters such as pulse energy, pulse separation time, etc. is investigated. As the pulse energy increased, the distribution of the air breakdown grew only to the side of the focusing lens and the ablation depth was saturated by the breakdown plasma which causes scattering of the laser. Therefore the highest processing rate was obtained with the maximum pulse energy not to generate the breakdown plasma. Double pulse method was useful for restraint of the swelling around the ablation crater. The swelling height was within 0.5μm with the most suitable pulse separation time (10ps-20ps).

Precise periodic structures have been generated on the surface of Si, Cu and acrylic resin by femtosecond laser (τ=120fs, λ=800nm, F=1kHz) of energies nearby ablation threshold. The direction of the periodic structures on the ablated surface of Si and Cu is perpendicular to the polarization of the incident beam. On acrylic resin surface, however, the direction of those has nothing to do with the polarization. It is possible to produce the periodic structures continuously in wide area by overlapped laser scanning with a cylindrical lens. The periodic structures have a function of spectroscope, and hence are composed of the ripples with constant space. The ripple spacings on Si and Cu surface depend on laser incident angle and almost correspond with irradiated laser wavelength at normal incidence, but on the other hand the ripple spacings on acrylic resin are always 20μm at various incident angles.

We have developed photon-stimulated desorption surface spectroscopy system using broadband VUV emissions from a laser-produced plasma. Observed desorbed atoms or molecules from material surfaces depended on bond energy or molecular structure.

A large second-order optical nonlinearity has been found to be generated in various kinds of silica glasses in which an even-order optical nonlinearity is inherently prohibited. Thermal poling is a typical procedure to generate such a second-order optical nonlinearity, but a mechanism behind the generation is not elucidated completely. It should be pointed out, however, that the nonlinearity was not added to high-purity silica glasses by poling. In this article, we show that the nonlinearity is generated in high-purity silica glasses irradiated by a KrF excimer laser before poling. We also show that the laser pulses erase the nonlinearity induced in the glasses. In addition to the laser irradiation effects on the generation and erasure, optical absorption and luminescence spectra in the glasses show that point defects of ≡Si–O− play a key role for the nonlinearity.

Subpicosecond vacuum ultraviolet (VUV) pulses at the wavelength of 126 nm have been generated in rare gases as a result of the 7th harmonic radiation of a subpicosecond Ti:Sapphire laser oscillating at 882 nm. The VUV harmonic intensity was optimized in Xe at the pressure of 1.2 Torr. The behavior of the harmonic emission was qualitatively reproduced by the classical nonlinear optics. The increase of the harmonic intensity was limited by multiphoton ionization of Xe.

We determined that refractive index change of Ge-doped silica can be induced by vacuum ultraviolet (VUV) light irradiation from Xe2*, Kr2*, and Ar2* excimer lamps using fabricated fiber Bragg grating (FBG) in the core of the hydrogen-loaded fiber as the material. It was found that irradiation with light from Xe2* and Kr2* excimer lamps can change the refractive index in the core and irradiation with light from Ar2* excimer lamps cannot. The change in refractive index under 146 nm light irradiation was greater than that under 172 nm light irradiation. The change in refractive index induced by irradiation with VUV light can be maintained up to approximately 130 °C.

By using a photochemical vapor deposition method with a Xe 2 excimer lamp (172 nm, 20 mW cm −2 output power), silica films have been prepared by means of a single precursor process from Tetraethoxyorthosilicate (TEOS) at room temperature. Transparent thin films of SiO 2 were obtained on sapphire and quartz single crystal substrates with a deposition rate of 0.9 nm min −1 . They were mainly composed of amorphous SiO 2 , although small amounts of residual organic materials were contained. The refractive index was 1.476 at 632.8 nm. The surface roughness decreased with the film thickness and reached 0.2 nm-rms. These findings indicate that the VUV excimer lamp CVD is a promising method for preparing smooth, dense and fine thickness-controllable films of SiO 2 at room temperature.

Rare gas excimer lamps using dielectric-barrier discharge are a new type of compact and high-efficient light source for vacuum ultraviolet wavelength region. Since the lamps produce incoherent and quasi-continuous radiation, uniform processing over large sample areas is expected to be possible without thermal effects and speckling or interference fringes. The purpose of this paper is to exploit a new technique of material processing by use of the newly developed incoherent rare gas excimer lamps. We will describe some findings obtained by applying the excimer lamps to preparation of silica thin films. A photochemical vapor deposition using a Xe2 excimer lamp has made it possible to prepare silica films by means of a single precursor process from tetraethoxyorthosilicate (TEOS) at room temperature. Transparent SiO2 thin films were obtained with a deposition rate of 0.9nm/min. The refractive index was 1.476 at 632.8nm and the surface roughness reached 0.2nm-rms. These findings indicate that the VUV excimer lamp CVD is a promising method for preparing smooth and fine thickness-controllable films of SiO2 at room temperature. We confirmed that, this technique provides a very promising photo-quantum process for the fabrication of semiconductors and opt-electronic devices, and others.

In this paper, we report the deposition of silicon nitride (SiNx) films for the production of semiconductor devices and flat panel displays, by chemical vapor deposition with vacuum ultraviolet excimer lamps (VUV-CVD) using SiH4 and NH3 as raw materials. An Ar2* excimer lamp (λ=126 nm, hν=9.8 eV) with a high photon energy was used to directly excite and dissociate SiH4 through a photochemical reaction. SiNx films were successfully formed at a low temperature of 100 °C with the Ar2* excimer lamp. Although the Si-rich films were obtained using an Ar2* lamp, they showed a quality almost similar to that of films obtained by conventional plasma-CVD at 400 °C.

Room temperature (RT) deposition of silica thin films is available with vacuum ultraviolet (VUV) chemical vapor deposition (CVD) technique. However, the quality of the films with VUV-CVD was inferior to that with conventional methods. In this work, we have investigated the photochemical reaction using an Ar2* excimer lamp. After 1-min deposition, the irradiation of Ar2* excimer lamp to the obtained film was operated with the evacuation in the chamber. From the result of Fourier transmission infrared spectrometer spectra and an X-ray photoelectron spectroscope measurement, it was found that hydrogen and hydrocarbon, such as CH3, was reduced with the irradiation of Ar2* excimer lamp. Therefore, it was considered that the film with low impurities could be obtained at RT by this technique. This technique is considered to be effective, because the operation could have performed at RT. We can conclude that this method will be a very useful method for no damage process of ultra large scale integration production in the semiconductor industry.

We attempted silicon nitridation that continuously deposits silicon with monosilane (SiH4) and nitrides the silicon with ammonia (NH3) at a low temperature using a vacuum ultraviolet excimer lamp. We used an argon excimer lamp (λ=126 nm, h ν=9.8 eV) so that SiH4 and NH3 can absorb photons and dissociate. Nitrogen exists only near the film surface at a low temperature, and its concentration increases at a high temperature. This photon-assisted process is very feasible for the nitridation of semiconductor devices and flat panel displays in the near future, because it is a low-temperature and low-damage process.

We considered the influence of the core and cladding diameters on the simultaneous measurement of the refractive index and temperature of liquids using a tilted fiber Bragg grating (TFBG). When the cladding diameter of a TFBG was only reduced from 125 to 123 µm, the calculated refractive index differed by 0.0068 from the expected value. When the core diameter was reduced from 9.6 to 7.8 µm, the change was less than 0.0005. We found that equalization of cladding diameter is required to improve the precision of the simultaneous measurement of the refractive index and temperature of liquids.

Potassium titanyl phosphate (KTP) crystals were grown from the K 6 P 4 0 13 (K6) flux using a temperature falling method. Real-time mesurement of the weight of the crystal during the growth was carried out with an electronic load cell in order to estimate the bulk growth rate. It was found that the growth rate of the crystal became too fast and liquid that inclusions were formed during a certain growth term in the growth period by excessively high supersaturation when the temperature falling rate was constant. In order to avoid this process, by changing the temperature cooling rate, a KTP crystal, 32 x 42 x 87 mm ( a x b x c ) without liquid inclusion was successfully obtained. The refractive indices, which were measured by means of laser interferometry, were found to be varying along the growth direction. Variation of the refractive indices was approximately 1.6 x 10 -4 for n z and 7.1 x 10 -6 for n xy , giving rise to a change of the phase matching direction of up to 0.38°.

We have demonstrated an argon excimer vacuum ultraviolet (VUV) amplifier at 126 nm by using the optical-field induced ionization (OFI) of argon. The gain-length product of 5.6 was achieved as a result of the optical feedback inside the amplifier with a VUV mirror. Plasma self-channeling caused by the high-intensity pump laser was simultaneously observed when the maximum gain-length product was observed. We have also optimized the output power of a subpicosecond VUV seed beam at 126 nm produced in low-pressure rare-gases as a result of the seventh harmonic nonlinear wavelength conversion of a Ti:Sapphire laser at 882 nm.

Optical inhomogeneities in potassium titanyl phosphate crystals grown from different fluxes have been investigated. In the crystals grown from a flux which contains tungsten, striations parallel to the {011} faces were observed. The main reason for forming striations is the change in tungsten concentration with change in growth rate. In the case of a potassium phosphate flux, no striations were observed in the crystal which was grown at almost the same temperature and stirring conditions as for the tungstate flux. We can conclude that the phosphate flux is more suitable for the growth of optically good crystals for KTP as laser harmonic converters.

We report the optical amplification in a compact OFI rare-gas excimer VUV amplifier and the generation of femtosecond VUV seed pulses using the harmonic conversion of an infrared Ti:Sapphire laser.

In vacuum ultraviolet (VUV) spectral region, coherent light sources are being thus in high demand for advanced precise and microscopic processing. A sub-picosecond VUV light source at 126 nm has been produced by the nonlinear wavelength up-conversion of a near infrared femtosecond Ti:Sapphire laser at 882 nm in rare gases. We obtained the maximum output of the 7th harmonic at 126 nm in Xe at the pressure of around 2 Torr. The 126 nm beam will be amplified by an optical-field-ionization produced Ar 2 medium and then high-power sub-picosecond VUV pulses will be obtained.

We have demonstrated an OFI Ar 2 * excimer VUV amplifier at 126 nm pumped by a high-intensity laser in the table top size. We observed the Ar 2 * excimer emission centered at 126 nm with the spectral bandwidth of 10 nm (FWHM), which was produced in the OFI plasma. Significant amplification was observed inside the OFI Ar 2 * excimer as a result of the optical feedback provided by a VUV reflector. The gain-length product of 5.6 was observed at the Ar pressure of 11 atm. The population inversion density on the order of 10 17 cm -3 was evaluated inside the OFI plasma, which would be sufficient for the amplification of a subpicosecond VUV pulse at 126 nm produced by the harmonic generation.

We have been developing an ultrashort-pulse high-intensity vacuum ultraviolet (VUV) laser. Ultrashort VUV pulses at 126 nm have been produced in rare-gases by nonlinear wavelength conversion of an infrared Ti:sapphire laser at 882 nm. This pulse will be amplified inside an Ar 2 * amplifier excited by optical-field-induced ionization electrons. The amplification characteristics of the Ar 2 * amplifier has been improved by plasma channeling induced by a high-intensity plasma-initiating laser.

Hydroxyapatite (HAp) is a biocompatibility material. We have successfully obtained the nano-particles of hydroxyapatite by the underwater laser ablation. A sintered HAp ceramics target was made of commercially available HAp powder and it was placed in the purified water. The focused KrF excimer laser outputs were irradiated on the target surface at the fluence from 7 J/cm2 to 23 J/cm2 at the repetition rate of 100 Hz. We found that the amount of the particles increased in proportional to the laser fluence. However, the rate of content of sub-micron particles was became larger at the lower laser fluence. The particles made by 7J/cm2 laser ablation were dispersing in the water for 12 hours after stopping the laser irradiation.Hydroxyapatite (HAp) is a biocompatibility material. We have successfully obtained the nano-particles of hydroxyapatite by the underwater laser ablation. A sintered HAp ceramics target was made of commercially available HAp powder and it was placed in the purified water. The focused KrF excimer laser outputs were irradiated on the target surface at the fluence from 7 J/cm2 to 23 J/cm2 at the repetition rate of 100 Hz. We found that the amount of the particles increased in proportional to the laser fluence. However, the rate of content of sub-micron particles was became larger at the lower laser fluence. The particles made by 7J/cm2 laser ablation were dispersing in the water for 12 hours after stopping the laser irradiation.

L-arginine phosphate monohydrate (LAP) is a promising nonlinear organic crystal for higher harmonic generation in place of the conventional KDP. It has a large absorption at 1.06 μm. Deuterated LAP (DLAP) has been synthesized to decrease this absorption. The absorption coefficient was reduced from 0.09 to 0.02 cm -1 Microbes which easily multiply in the growth solution were successfully inhibited by Hadding H 2 O 2 . Damage thresholds of LAP and DLAP crystals are much higher than that of KDP and fused silica. We suggest that DLAP can be used in place of KDP in high power lasers.

The growth of huge KDP crystals which have a 40 cm × 40 cm cross section for a frequency converter for high power laser system for nuclear fusion experiments is described. The main factor limiting the growth rate is spontaneous nucleation. We could successfully grow a crystal by a three-vessel method (TVM) at the rate of 2.9 mm/day over half a year without nucleation by setting the temperature of the crystallizer lower than room temperature. The TVM proved to be superior to a conventional temperature reduction method. The bulk laser damage threshold was improved two to three times that of conventionally grown crystals by reducing organic impurities in the growth solution. These techniques are very important for the growth of large KDP crystals of good quality for high power lasers.

Hydroxyapatite (HAp) is a biological and bioactive material, which has promise as a coating material for orthopedic and dental implants. Some HAp coating methods have been investigated and the pulsed laser deposition (PLD) method is one of the most candidate. Previous PLD researchers deposited the HAp coatings on heated Ti and Ti-alloy substrates in order to crystallize the coatings. However, the deposition condition, high substrate temperature and water atmosphere, should promote the oxidation of the substrate surface prior to the growth of the HAp layer, which degrades the adhesion of the coating to the substrate. Therefore, HAp coatings should be deposited at lower temperature to avoid extensive oxidation of the substrates.