The present technical status and an understanding of the discharge-pumped rare-gas halide excimers are reviewed. Much emphasis is placed on the energy scaling of the discharge-pumped XeCl lasers, long pulse excimer lasers and high efficiency operation of excimer lasers. The problems to be solved are presented along with the future prospect s of the discharge pumped excimer lasers.

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A peak power of one terawatt has been obtained in XeCl with a pulse width of 310fs. Amplified spontaneous emission (ASE) was investigated extensively by changing the gain of wide aperture discharge amplifiers. As a result, the ASE content was suppressed to less than 3% in energy by using an appropriate spatial filter before the final amplifier along with operating at a low gain level of 4.8%/cm.

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Several discharge-pumped excimer lasers which constitute a short-pulse excimer laser amplification system have been developed for XUV laser research. These are a compact oscillator generating ns pulses, three automatically-preionized laser devices with an output pulse energy of 1-1.6J and a high-power X-ray preionized laser device with an output energy of 50 J in 85 ns pulses. The coherent VUV/XUV generation systems have also been developed using excimer laser pumped dye lasers, which can produce coherent radiation in a wavelength region of 70-200 nm by two-photon resonant four wave mixing.

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The spectral-narrowing techniques and the present status for narrow-bandwidth rare-gas-halide excimer lasers are described. First, various spectral-narrowing techniques for the directly tuned excimer lasers are described. Second, the present status for the narrow-bandwidth excimer lasers and other related UV-lasers is summarized. Last, various techniques for these high-beam-quality high-power operation are described.

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Discharge excited high repetition-rate excimer lasers will be useful to the material process of a next generation. In this paper, the technologies for the discharge excited high repetition-rate excimer lasers including gas circulation system, magnetic pulse compressor, pre-ionizer and gas recycling system, are discussed. We wish to report a high power KrF excimer laser with a new capacitor-transfer-type configuration, which delivered an average power of 150W at a high efficiency of-3.8% and a high repetition-rate of 700Hz.

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Electron beam pumped rare gas excimer lasers which oscillate in the VUV wavelength region are reviewed. High output power operation with various resonator mirrors made of. quartz glass (SiO₂), Si, Mo orcoated with SiC, tunable oscillation with a rotatable MgF₂ prism and wavelength conversion by Raman shifter containing molecular hydrogen gas are discussed.

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A basic module for large scale KrF laser amplifiers having four electron beam diodes has been developed in order to confirm the scalability of KrF lasers. The KrF laser module produces 580J output in 100ns pulse duration with high intrinsic efficiency around 10%. The experimental results are consistent with the prediction based on calculations using the 3D ASE code. The criterion for the high efficiency operation of high power KrF lasers is defined as goD≤3 and goL=10 in double pass configurations. According to the pump rate scaling, high efficiency operation of the high pump rate KrF laser module gives the conclusion that high power output of 500kJ will be delivered from a large scale amplifier having a large active volume of 60m³ excited by long pulse electron beams.

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Coherent tunable VUV and XUV sources by frequency up-conversion using nonlinear optical effects are one of the important applications of high-power UV excimer lasers. Various techniques of frequency upconversion in non-linear gas mediums, are reviewed, emphasizing two-photon resonant four-wave mixing and anti-Stokes stimulated Raman emission.

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