Since the invention of the laser in 1960s, the stability of the laser frequency has been improved which is stabilized in reference to the molecular absorption or the resonance of the Fabry-Perot cavity, and frequency-stabilized lasers have been used for precision spectroscopy or precise interferometric measurement. In 1990s, the optical frequency standards have been proposed using cooled atoms or a single ion confi ned in small area, and among them, the optical lattice clock is one of the most promising candidates for the next-generation international optical frequency standards whose frequency stability is rapidly improved to reach 10^‒18 level that is higher than that of the cesium atomic fountain clock. The key technology for further improvement of the optical lattice clock is a probe laser with extremely narrow linewidth that is limited by the thermal noise of the Fabry-Perot cavity. The cryogenic cavity, the silicon single-crystal cavity or crystalline coating decrease the thermal noise limited level to reach the laser linewidth of a few mHz level. The highly frequency-stabilized lasers can be easily transfer its stability to another frequency by using optical frequency comb, and disseminate its stability by using precision optical fi ber links. The frequency stability of the 10^‒18 level of the laser makes it possible to verify fundamental physics such as time variations of fundamental constant or isotropy of the speed of light, and also to apply to the geodesy or gravitational wave detection.

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Semiconductor high volume manufacturing (HVM) was expected to start from 2012. However now a delay of around three years is expected, due to challenges in the development of high power EUV light sources. Also recent M&A activity is very aggressive. Since 2003, we have been developing the CO2- Sn-LPP EUV light source, which is the most promising solution as the 13.5 nm high power light source for HVM EUVL. We have made remarkable progress on EUV source development, and we are seeing hopeful prospects. We will report latest engineering data from our test tools

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New types of high-energy X-ray sources coupled with a high-power laser and an electron accelerator have been developed, including a laser Compton scattering (LCS) X-ray or γ -ray sources, and an X-ray free electron laser. The development of LCS X-ray and γ -ray sources and their applications to the medical imaging and the nondestructive inspection are reviewed. The development of all-optical, compact, ultrashort X-ray sources using laser electron acceleration is also reviewed.

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Laser-driven γ -ray is expected to be a very useful nondestructive diagnostic tool for large-scale structures because of its potential for high energy, short pulse, high spatial resolution, compactness, and easy control. CRIEPI has proposed a radiographic testing system that consists of a compact laser-driven γ -ray generator and a compact radiographic imaging system. It can be applied to a very narrow space (10 cm) in plant facilities, which are often crowded with pipes and other components. Here we review the recent progress of our research on a laser-driven γ -ray source for nondestructive testing.

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This paper describes the biological effect of an intense pulsed electric fi eld and electromagnetic radiation that varies by frequency band. A fi eld with less frequency than 1 MHz provides an electrical stress to the plasma membrane, but that with higher frequency is likely to affect the intracellular components. A laser plasma soft x-ray microscope, which is a combination of highly intense laser plasma soft x-ray sources and a contact type soft x-ray microscope, has been developed. The laser plasma soft x-ray microscope captures an x-ray image of live hydrated biological cells with 80-nm spatial resolution in a 600-ps time duration. Cellular organelles such as chromatin, mitochondria and actin fi laments have been observed with the laser plasma soft x-ray microscope in combination with a fl uorescence microscope to identify cellular organelles. We also observed such life phenomenon as an apoptotic process and detailed structural deformation.

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X-ray ablation has been recently achieved using plasma soft X-ray lasers, laser plasma soft X-rays, and X-ray free electron lasers. Nanosecond laser plasma soft X-rays sources allow us to fabricate highquality micro- and nano-structures of poly (methylmethacrylate) (PMMA), poly (dimethylsiloxane) (PDMS), and SiO₂. Even after the soft X-ray irradiation, the surfaces of these materials have the same chemical structures as those of unirradiated surfaces. We found that ablation of SiO₂ occurs more efficiently than linear optical absorption and energy accumulation to break all of the bonds in SiO₂ surfaces. Picosecond plasma soft X-ray laser sources allow us to ablate LiF crystals at a low threshold fluence. The ablation is explained in terms of spallative ablation, that is, removal of a surface layer by tensile stress induced by the short-pulse X-ray irradiation, without breaking the layer into atomic species. It should be noted that nanostructures such as nano-cones on Al surfaces can be fabricated by irradiation with the plasma soft X-ray laser light

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The materials used in the exterior surfaces of spacecraft encounter severe erosion due to hyperthermal (8 km/s) collisions with chemically reactive O-atoms, which are the major composition of the Earth’s upper atmosphere. Laser-induced plasma has been used to simulate these atom/surface reactions in the ground-based facilities. A 5-7 J/pulse CO₂ laser is used to form intense hyperthermal O-atom pulses. The confi guration of the apparatus resembles LPP EUV sources, and strong EUV emission is observed as side products. We explain the material degradation phenomena in space by hyperthermal collisions with O-atoms and the current status of ground-based studies using laser-induced plasma.

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Picosecond time-resolved Laser pump/X-ray probe experiments using pulsed nature of synchrotron radiation sources are becoming general and powerful tools to explore structural dynamics in materials and biological sciences. Experimental protocols for time-resolved X-ray solution scattering measurements are presented in detail.

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The considerable progress in the development of soft x-ray / extreme ultra-violet (EUV) sources such as laser produced plasma, high-harmonic generation, synchrotron radiation, x-ray free electron laser will create new scientifi c fi eld and new industrial technology fi eld. These soft x-ray/EUV sources research have also led to progress in the development of soft x-ray/EUV optical devices such as multilayer mirrors and Fresnel zone plates. This paper reviews the recent these optics.

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Transverse-fl ow CO₂ laser amplifi ers were constructed to generate a high-power pulsed CO₂ laser for an extreme ultraviolet light source of nano-lithography. We evaluated the amplifi ers using a short-pulse seed laser. The pulse tandem amplifi ers emitted an average output power of 8.3 kW with an electrical power 200 kW discharge. The input short-pulse laser had an average power of 20 W, the repetition rate was 100 kHz, and the pulse duration was 15 ns. Our experiment showed that the electrical-to-optical effi ciency was higher than that of the axial-fl ow amplifi ers at the same laser input power.

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We measured in-situ temporal decay and the spatial distribution of the transmission of a Cr:YAG saturable absorber in a passively Q-switched Nd:YAG laser by a scanning transmission focused laserbeam method. An excited ion decay time of 4 μs and top hat (saturated) transmission distribution were observed. By a theoretical fi tting for the transmission distributions, the ground state absorption cross sections were found to be 1.0 × 10^‒17 and 2.3 × 10^‒19 cm² for π and for σ -polarized light to the S₄ local symmetry axis of Cr⁴⁺ center. The excited-state absorption cross section was estimated to be 2.4 × 10^‒18 cm².

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