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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 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.

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.

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.

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.