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This paper demonstrates the fabrication of superhydrophobic soda-lime glass surface by engineering periodic microgratings with self-formed periodic micro-ripples inside the microgratings using a single beam femtosecond laser. The wetting property of the microstructured surface is improved from hydrophobic to superhydrophobic, presenting a water droplet contact angle ranges from 152° to 155°. The microstructured glass surface shows excellent transparency, which is higher than 77% in the visible spectrum. We strongly believe that our proposed technology can achieve superhydrophobic glass surfaces over a large area for applications in diverse fields.

The scattering physics of photons is traced back to Rayleigh scattering theory in 1871 and Mie scattering theory in 1908. However, the scattering near field and far field have recently emerged again as a new fundamental physics and innovative nanoprocessing technology in quantum electronics and photonic devices. An enhanced near field generated by plasmonic particles can concentrate optical energy into a nanoscale space as a nanolens even with near infrared laser pumping. This plasmonic nanophotonics extends the existing optical science to a new class of photonics inclusive of surface enhanced Raman scattering, nanoprocessing of advanced electronic and photonic materials, etc. The Mie scattering near field also opens up new fields. The Anderson localization of light in a planar random photonic crystal laser is also a new class of quantum electronics devices, where Slow Bloch Mode is scattered by artificial structural randomness in a photonic crystal. In this contribution we will review the recent efforts of our scattering photonics research, which have resulted in significant advances in the plasmonic surface photonics of near-field and far-field nano/micro photonics and the Anderson localization in random lasing.

We propose an idea of fast cutting a display glass plate where the sample is pre-processed micromachining single shot rear-surface and internal void arrays aligned on working plane prior to glass cleaving. Single shot void morphology is investigated varying input pulse energy, focusing depth, and scanning speed. A femtosecond laser with pulse duration of 172 fs, central wavelength of 780 nm, and repetition rate of 1 kHz is used to fabricate voids.

We have developed a pulsed Yb:YAG thin disk green laser for pumping a 100 kHz and 10 W femtosecond laser. We optimized numerically and experimentally the open duration of the acousto-optic (AO) Q-switcher and the internal SHG method, generating stable output energy at a 100 kHz repetition rate. We demonstrated a 515 nm output power of over 80 W with a pulse-to-pulse stability of less than 1% RMS with an LD power to green power conversion efficiency of 24%. With the developed green laser, we obtained 16 W of a Ti:sapphire laser in a cavity dumped mode.

We have developed a 6–12 μm mid-infrared (MIR) femtosecond laser source for glyco-protein structure analysis. The MIR femtosecond laser pulses are generated by a differential frequency generation (DFG) configuration with a combination of Ti:sapphire based regeneratively amplified femtosecond laser pulses (780 nm, 160 fs, 1 mJ) and a β-BaB2O4 (BBO) based optical parametric amplifier (OPA). The MIR pulse energy exceeds 4.5 μJ, where a glyco-protein molecule has resonant absorption lines due to the vibrational–rotational transitions. The pulse width is estimated to be less than 1 ps according to the cross correlation measurement between the two OPA output pulses. Using the MIR femtosecond laser pulses, we demonstrated photo-dissociation of the sialyl Lewis X (sLeX) proton added ion, which is the first time to the best of our knowledge.

We report pure continuous-wave (CW) high-power (>100 mW) deep-ultraviolet (DUV) light sources emitting around 200-nm spectral region based on singly resonant sum-frequency mixing (SRSFM). Efficient DUV generation is made possible by use of a Brewster-cut CsLiB/sub 6/O/sub 10/ (CLBO) crystal near noncritically phase-matched (NCPM) condition for the SFM of 1-/spl mu/m output of neodymium lasers. The CW radiation of fifth-harmonic wavelength of a neodymium laser at 213 nm was generated by the SFM of enhanced 1064-nm radiation with single-passing 266-nm radiation produced by external-resonant frequency doubling of a 532-nm green laser. With 1.8 W of 266-nm radiation incident upon a CLBO crystal, as much as 180 mW of CW 213-nm power has been produced. The sub-200-nm CW radiation with 140-mW power has also been achieved by SFM of 1064 nm with 244-nm radiation from a frequency-doubled Argon-ion laser in the CLBO crystal operated near the NCPM condition.

We propose a laser-diode-pumped Yb:YAG laser as a novel practical fiber amplifier pump source, and describe its first successful application of high-output-power operation (850 mW=+29.3 dB m) of an Er3+,Yb3+-codoped fiber amplifier at 1.55 μm. We have developed both bulk and microchip Yb:YAG lasers and obtained 3.3 W and 2.7 W, respectively, in the cw mode at room temperature. Laser-diode-pumped Yb:YAG lasers are shown to have a potential applicability to such fiber amplifiers as Pr3+-doped amplifiers and Tm3+-doped amplifiers, as well as Er3+,Yb3+-codoped fiber amplifiers.

A new medical fiber laser oscillating at two useful wavelengths (3 and 2 /spl mu/m) is reported. We have demonstrated highly efficient and high-power continuous-wave cascade oscillation at room temperature with a holmium ion-doped fluoride glass fiber laser pumped with a 1.15-/spl mu/m fiber Raman laser. The simultaneous oscillation wavelengths were 3 and 2 /spl mu/m, and their combined output power was 3.0 W with a slope efficiency of 65%. To our best knowledge, this is the first achievement of watt-level-output power in the mid-infrared region with ZrF/sub 4/-BaF/sub 2/-LaF/sub 3/-AlF/sub 3/-NaF (ZBLAN) glass fiber. In experiments to evaluate potential for medical applications, we tested the two wavelength beam as a laser surgical knife on soft rabbit tissues and demonstrated that it had strong cutting capability, and that the coagulation layer thickness could be controlled by varying the power ratio of the two-wavelength laser.

We describe a simple-design laser-diode-pumped CW Nd:YAG active-mirror laser and a thermal analysis in the crystal. A CW output power of 2.4 W and an M2 beam-quality value of less than 1.9 at an incident pumping power of 8.9 W have been obtained. From the thermal analysis, we predict that the output power can be increased by increasing the pump beam diameter at a constant pump-power density. We also calculate the maximum temperature rises and the focal lengths of thermal lenses for various cylindrical laser crystals with different radius-to-length aspect ratios.

Generation of microwave radiation from a long-pulse rotating electron beam in a circular wiggler magnetic field (circular free electron laser) has been studied. The beam energy is 300–400 kV, typically, and the beam current is 200 A. The radiation frequency is measured with the grating spectrometer to be 12.7 GHz. Measured values agree with the theoretical prediction. The interaction between the beam mode and the TM waveguide mode is discussed, based upon the dispersion relation.

As a pump laser of a Ti:sapphire femtosecond laser, the authors developed high power, high repetition rate and highly stable Yb:YAG thin disk green laser. We achieved 200 kHz, 73 W operation.

A potential method for precise and fast dicing of display glass plates is proposed in this study. This technique facilitates the micromachining of cavities in both front and rear surfaces for a single pass of laser beam. The influences of focusing depth, input pulse energy, and scanning speed of the laser beam are investigated to study the morphology of the front and rear surface cavities. A commercial femtosecond laser with pulse duration of 172 fs, center wavelength of 780 nm, and repetition rate of 1 kHz is used for introducing the cavities.

We propose and demonstrate a 1.50-mum- band gain-shifted thulium-doped fiber amplifier (TDFA) by using a novel dual-wavelength (1.05and1.56 -mum) pumping scheme for what we believe is the first time. By providing a small amount of 1.56-mum power to a conventional upconversion-pumped TDFA, we successfully demonstrated a small-signal gain larger than 25 dB and a noise figure of 5 dB in a 1475-1510-nm band.

We solved the stability, life-time and cost problems of femtosecond lasers and opened the door to their huge commercial market in near future. Femtosecond lasers will be used in the semiconductor and LCD manufacturing factory.

Femtosecond laser ablation using the combination of 260 nm pulses and 780 nm pulses is explored for the high speed and high quality selected removal of insulating layers.

We have developed a high-repetition, 1-W, and 70 fs regenerative amplifier system. The stable operation was obtained due to a seeding fiber laser, a compact folded cavity, and a green pump source built by ourselves.

We demonstrated stable operation of the femtosecond laser continuously over 10,000 hours only with compensation of power loss of LDs.

We describe true continuous-wave (CW), high-power, line-narrowed, deep-ultraviolet (DUV) light sources for the high-resolution metrology tools such as wafer inspection and mask inspection systems. The 198.5-nm CW radiation with 300-mW power has also been achieved by sum-frequency mixing (SFM) of 1064-nm output from a single-frequency Yb 3+ fiber amplifier with the 244-nm radiation from a frequency-doubled argon-ion laser. The 266-nm CW DUV radiation with 5 W of maximum power has been generated by frequency doubling of 532-nm green laser output. Both sources utilize Brewster-cut CsLiB 6 O 10 (CLBO) crystal for efficient and stable DUV light generation.

We have successfully developed a highly-stable commercial femtosecond laser. We achieved continuous operation of femtosecond laser over 4,000 hours.

An efficient optical frequency mixer employing a Brewster-cut CLBO crystal has been developed for the generation of high-power CW DUV coherent radiation. DUV light of 180mW at 213nm and 140mW at 198.5nm have been produced.

We have been working on the tailored ablation processing of advanced materials using femtosecond lasers. Here we would like to focus on the femtosecond laser processing tailored for hydroxyapatite. Hydroxyapatite is a key material of human tooth and human bone. The human bone is made of hydroxyapatite oriented along the collagen. The micromachining of human bone is highly required for medicine. The medical issue is how to preserve the chemical property of the laser-ablated surface. By use of pulsewidth tunable femtosecond laser (50fs - 2ps, 1.5mJ, 1kpps), we compared the relative content of calcium and phosphorus. The relative content of calcium and phosphorus is kept unchanged before and after laser ablation. For these medical applications, the intense femtosecond laser delivery through optical fibers is required. It is theoretically shown that it is possible to deliver the 900 fs pulses of 0.1 mJ/pulse through a 1 m-lohng graded index fiber with a 200 μm core diameter if the fiber has the optimum refractive index profile. We therefore conclude that graded index multimode fibers give better spatial distributions of the output transverse mode than hollow fibers or step index multimode fibers, and can deliver larger pulse energy than single mode fibers.

We report on the experimental and analytical study of fiber delivery of femtosecond laser pulse through a step index (SI) and graded index (GI) multimode fiber. The 1.1 ps pulses of 8.7 μJ at 800 nm were delivered through a 10 cm GI multimode fiber with a 0.6 dB transmission loss. In the meantime, the output beam profile is nearly Gaussian and is independent of bending of the fiber. It is also shown that the prospect that the frequency pre-chirped pulse is usable for the utlrashort laser pulse delivery through GI multimode fibers by the numerical analysis.

Summary form only given, as follows. We demonstrated function variability to living soft tissue of the mid-IR cascade oscillation Ho/sup 3+/ fiber laser at 3 μm and 2 μm operation of continuous wave radiation for surgical applications. Our study was both experimental and theoretical.

We developed a medical surgical system with function variability and flexible delivery of dual-wavelength infrared fiber laser that simultaneously oscillated 3 and 2 micrometers radiation. We studied the function variability (cutting/coagulation) of this fiber laser using a specially designed filter which contained two adjacent areas with different transmission for 2 micrometers radiation. When the power of 3 micrometers radiation was set to 0.6 W and the power of 2 micrometers radiation was changed from 0 W to 0.77 W using this filter at the beam traveling speed of 0.25 mm/s, the cutting groove formed in myocardium tissue increased from 0.80 mm to 0.89 mm and the coagulation layer thickness increased from 0.41 mm to 0.85 mm. We successfully developed a filter system that could continuously control coagulation layer thickness with cutting capability constant. We studied a flexible beam delivery using a single crystal sapphire fiber. The transmission efficiency per meter for 3 and 2 micrometers radiation using a 200-micrometers core-diameter sapphire fiber was 58.0% and 60.4%, respectively. The bending loss at 3-cm loop radius was 5.6%. The high flexibility and low bending loss of the sapphire fiber might make it possible to apply the dual-wavelength infrared fiber laser to endoscopic treatment. In summary, these results may encourage the possibility for practical use of the fiber laser.

We theoretically investigated variable-function (cutting/coagulating) characteristics of the continuous wave 3 μm, 2 μm cascade Ho3+:ZBLAN fiber laser using 3D heat-conduction calculation with finite element method. We have modified a commercial-available simulator in order to calculate heat conduction and thermal ablation process in soft tissue. In this calculation we considered specific heat rise due to the thermal denaturation of protein and volume shrinkage caused by temperature elevation. Beam profile, beam traveling speed, output power, and absorption coefficient were employed to describe the laser beam. The configuration of cutting groove and temperature distribution were calculated by varying the power ratio of the two wavelengths. Coagulation layer was defined as the region that was over 60°C for 1 second because we found that birefringence loss in porcine myocardium observed by a polarizing microscope occurred on this temperature history. When we increased the power ratio of 2 micrometers radiation to the total power of 0.9 W from 0% to 100% at the traveling speed of 0.5 mm/s, the incision depth decreased form 1.45 mm to 0.25 mm, while the coagulation layer thickness increased from 0.17 mm to 0.70 mm. We experimentally performed laser cutting on the same condition by our calculation using extracted porcine myocardium and compared this experimental results with the calculated results. We demonstrated that the incision depth and coagulation layer thickness estimated by our calculation indicated good agreement with the experimental results within 20% differences regarding the function variability by 3 μm/2 μm light mixing.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We studied coagulation layer controlled incision with newly developed continuous wave 2 micrometer, 3 micrometer cascade oscillation fiber laser in vitro. Since this laser device simultaneously oscillates 2 micrometer and 3 micrometer radiation, we could change tissue interaction by arranging power ratio of 2 micrometer to 3 micrometer radiation. About one watt of total irradiation power with various power ratios was focused to extracted fresh porcine myocardium or anesthetized rabbit on an automatic moving stage to obtain line incision. Macro photograph and microscopic histology were used to observe tissue interaction phenomenon. The incised specimen showed that precise cutting groove with thin coagulation layer was attained by a 3 micrometer based radiation, meanwhile addition of 2 micrometer radiation to 3 micrometer radiation made coagulation layer thicker. A heat conduction simulator using finite-element method was used to qualitatively explain obtained coagulation layer thickness. This precise incision with controllable side coagulation layer may effective to control bleeding during incision, for instance, for skin, liver, and kidney incisions. Pure continuous wave radiation of 2 micrometer and 3 micrometer may eliminate stress wave induced tissue damage which is frequently found in Ho:YAG and/or Er:YAG tissue interactions. Moreover, sapphire fiber might offer flexible power delivery to this new laser to establish endoscopic application and/or to improved beam handling.

Accepted: 1990-11-17, 資料番号: SA1002140000

We propose and demonstrate a 1.50-µm-band gain-shifted thulium-doped fiber amplifier (TDFA) by using a novel dual wavelength (1.05/1.56 µm) pumping scheme for the first time. By providing a small amount of 1.56-µm power to the conventional TDFA, we successfully demonstrated a small-signal gain of >25 dB and a noise figure of 5 dB in the 1475- to 1510-nm band.

We have demonstrated the temperature-optimized operation of 970-nm diode-pumped Yb:YAG and Yb:LuAG lasers at approximately 160K by taking into account Yb-crystal absorption spectra narrowing at low temperatures.

We have developed an ArF excimer laser exposure system that combines a monochromatic quartz projection lens system and a spectrally-narrowed ArF excimer laser. The bandwidth of the laser was narrowed to 0.7 pm by using three prisms and an etalon. We fabricated 0.12 micrometers lines-and-spaces using an alternating phase shifting mask and a top surface imaging resist.

High repetition rate operation technology and spectral narrowing technology with compact excimer lasers whosecross-sectional dimensions are around 120 x 120 mm. High repetition rate operation over 1 .5 kHz and spectral narrowing to 1pm are reported.These technologies are essential to promising applications of ArF excimer lasers. High resolution pattem of 0.16 imline and space is demonstrated by an optical laser lithography with the compact ArF excimer laser. The smallest AsP excimerlaser specific to the photo-chemical surgery of cornea is also presented.Keywords: excimer laser, ArF, high repetition, spectral narrowing, lithography, projection optics, DRAM, PRK, cornea 1. INTRODUCTION Excimer laser market has been growing up remarkably due to the maturity of excimer laser technologies and to alarge growth in its applications, in recent years. Most of excimer lasers which are applied to excimer laser-stepper for 64Mbit and 256 Mbit dynamic random access memory (DRAM), laser drilling of print-heads for ink-jet printers, photo chemi-cal surgery for cornea and so on. However, technologies such as the high repetition rate oscillation and spectral narrowingare immature for ArF excimer laser, and essential to promising applications of next generations.The innovation in the field of a LD pumped solid state laser and harmonic generation with a nonlinear crystal is alsoremarkable. Ultraviolet(UV) light source are obtained with harmonics generation of the infrared-red LD pumped solid statelaser with high efficiency of several tens percent. Part of KrF and XeCl excimer lasers will be replaced by solid state lasersafter their improvements in the average power in the near future. Replacement of ArF excimer lasers by solid state lasers isdifficult ,because vacuum ultra-violet (VUV) radiation with solid state lasers is problematic. Low conversion efficiency andlow damage threshold of a nonlinear crystal have not been improved yet in the wavelength range shorter than 200 am.Our researches have been focused on ArF excimer laser by reasons described above. Advanced technologies aredescribed in section 2. Compact ArF excimer lasers specific to hot applications such as an optical lithography and a photo-chemical surgery are described in section 3.

We describe a simple design, laser-diode-pumped cw Nd:YAG active-mirror laser and present a thermal analysis of the crystal. A cw output power of 2.4 W and an M(2) beam quality value of less than 1.9 at an incident pumping power of 8.9 W were obtained. From the thermal analysis we predict that the output power can be increased by increasing the pump beam diameter and the pump power at a constant excitation density.

We have investigated the temperature dependence of output performances for 970-nm diode-pumped Yb:YAG (Yb(3+):Y(3)Al(5)O(12)) and Yb:LuAG (Yb(3+):Lu(3)Al(5)O(12)) lasers over the wide temperature range from 80 to 310 K. Temperature-optimized operation was experimentally demonstrated at around 160 K and was theoretically confirmed by taking into account the absorption spectra change of Yb crystals at low temperatures. Cooling the crystal to below 160 K caused a narrowing of the absorption bandwidth and led to a decrease in output power and efficiency.

We have demonstrated dual-wavelength continuous-wave oscillation at 3 and 2 mum with a Ho-doped ZrF(4)- BaF(2)- LaF(3)- AlF(3)- NaF fluoride-glass fiber laser by use of a cascade oscillation scheme. We have shown that the fiber laser operates with a high slope efficiency of 52% (at 3 and 2microm) with respect to the absorbed pump power. With a 6.5-m-long fiber we achieved an output power of 90 mW at each of the wavelengths that was limited only by the pump power, and the 3-microm output power is to our knowledge higher than any previously reported level with 3-mum Ho(3+) -doped fiber lasers.

We have developed an ArF excimer laser exposure system that combines a monochromatic quartz projection lens system and a spectrally-narrowed ArF excimer laser. The bandwidth of the laser was narrowed to 0.7 pm by using three prisms and an etalon. We delineated 0.2 µm lines-and-spaces using a chemically amplified resist and 0.16 µm lines-and-spaces using a top surface imaging resist.

Generation of microwave radiation from a rotating electron beam in a circular wiggler magnetic field (circular free-electron laser) has been studied. The electron beam is emitted by a velvet-covered cathode; its energy is typically 300-500 keV and its beam current is 160 A. Measured frequency, power and pulse width of the radiated microwave are 12.7 GHz, 11 kW and 500 ns, respectively. Measured frequency agrees with the theoretical prediction. The interaction between the beam mode and the traveling magnetic waveguide mode is discussed based upon the dispersion relation.