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Journal Articles

Observation of the laser-induced surface dynamics using the single-shot soft X-ray laser probe

Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; Morita, Toshimasa; Sasaki, Akira; Terakawa, Kota*; et al.

X-Ray Lasers 2012; Springer Proceedings in Physics, Vol.147, p.117 - 120, 2014/00

 Times Cited Count:0 Percentile:0

We have developed the femto-second laser pump and soft X-ray laser probe system in order to observe the dynamical processes of the femto-second laser ablation. By using this system, we succeed to obtain the temporal evolution of the soft X-ray reflectivity from the laser induced Pt surface. The results lead that the rate of decrease in the reflectivity of the probe beam has a non-linear relation with the pump laser fluence.

Journal Articles

Measurement of femtosecond laser ablation by soft X-ray laser interferometory and reflective imaging

Nishikino, Masaharu; Hasegawa, Noboru; Ishino, Masahiko; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Minami, Yasuo*; Terakawa, Kota*; Takei, Ryota*; Baba, Motoyoshi*; Suemoto, Toru; et al.

JAEA-Conf 2013-001, p.16 - 19, 2013/09

The dynamics of the femtosecond laser ablation is still not clear at the early stage. Several studies on the time-resolved imaging of femtosecond laser ablation process have been performed on various materials. In this study, we have demonstrated a pump and probe imaging of the metal surface morphology during the femtosecond laser ablation by using the laser-driven plasma induced soft X-ray laser (SXRL) as a probe beam. The pumping laser used for ablation was a Ti:Sapphire laser system based on chirped pulse amplification. The pump beam had a Gaussian profile and the focal spot size on the metal surface was about 70 micron at FWHM. The dependence for the pump laser fluence of the ablation surface expansion and the surface condition (roughness and density gradient) were observed from the soft X-ray interferogram and reflective image, respectively.

Journal Articles

Experimental verification of femtosecond laser ablation schemes by time-resolved soft X-ray reflective imaging

Tomita, Takuro*; Yamamoto, Minoru*; Hasegawa, Noboru; Terakawa, Kota*; Minami, Yasuo*; Nishikino, Masaharu; Ishino, Masahiko; Kaihori, Takeshi*; Ochi, Yoshihiro; Kawachi, Tetsuya; et al.

Optics Express (Internet), 20(28), p.29329 - 29337, 2012/12

 Times Cited Count:18 Percentile:69.28(Optics)

Pump and probe reflective imaging using a soft X-ray laser probe was applied to the observation of the early stage of femtosecond laser ablation process on platinum. In strongly excited area, drastic and fast reflectivity drop was observed. In moderately excited area, the decay of the reflectivity is slower than that in the strongly excited area, and the reflectivity reaches its minimum at t = 160 ps. In weakly excited area, laser-induced reflectivity change was not observed. These results give the critical information about the femtosecond laser ablation.

Journal Articles

Development of the X-ray interferometer and the method of temporal synchronization of X-ray and optical pulse

Hasegawa, Noboru; Yamamoto, Minoru*; Terakawa, Kota*; Nishikino, Masaharu; Ochi, Yoshihiro; Minami, Yasuo*; Tomita, Takuro*; Kawachi, Tetsuya; Suemoto, Toru

AIP Conference Proceedings 1465, p.23 - 27, 2012/07

 Times Cited Count:0 Percentile:0.13

We have developed a soft X-ray laser (SXRL) interferometer capable of the single-shot imaging of nano-scaled structure dynamics. The depth and lateral resolutions of the interferometer were about 1 nm and 1.8 micron, respectively. We observed the initial stage ($$sim$$50 ps) of the ablation process of the Pt surface pumped by a 70 fs Ti:Sapphire laser pulse. The expansion speed of the Pt surface (34 nm/50 ps) indicated that the nano-bubble structures were formed in the initial stage of the ablation. In order to observe the detailed dynamics, the precision of temporal synchronization between the pump and probe pulses was improved to be 3 ps by adopting a portion of the SXRL and pump beams as the time fiducials.

Journal Articles

Picosecond soft-X-ray laser interferometer for probing nanometer surface structure

Ochi, Yoshihiro; Terakawa, Kota*; Hasegawa, Noboru; Yamamoto, Minoru*; Tomita, Takuro*; Kawachi, Tetsuya; Minami, Yasuo*; Nishikino, Masaharu; Imazono, Takashi; Ishino, Masahiko; et al.

Japanese Journal of Applied Physics, 51(1), p.016601_1 - 016601_3, 2012/01

 Times Cited Count:10 Percentile:44.63(Physics, Applied)

We have developed a soft X-ray laser interferometer based on the double Lloyd's mirror and obtained a single shot interferogram by a 7-ps pulse at the wavelength of 13.9 nm. Micrometer grooves with 5-nm depth were successfully reconstructed from the interferogram. The lateral and depth resolutions were estimated to be 1.5 $$mu$$m and better than 1 nm, respectively. This interferometer will be an attractive diagnostic device for observing transiently changing nano-scale deviations on solid surfaces.

Journal Articles

Source development and novel applications of laser-driven plasma X-ray lasers in JAEA

Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Oba, Toshiyuki; Kaihori, Takeshi; Kishimoto, Maki; Ochi, Yoshihiro; Tanaka, Momoko; et al.

X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.15 - 24, 2011/12

This paper reviews recent improvement in the source development of laser-driven X-ray lasers and the applications in the research fields of material science, laser processing, X-ray imaging, and radiation damage in biological cells. In the application for material science, we have firstly observed temporal correlation between the domain structures of ferro-electric substance under the Curie temperature. In the laser processing, new X-ray laser interferometer reveals us the nano-scale surface distortion of substance pumped by a femto-second optical pulse. In the X-ray diffraction image, we have taken several static images of micro-structure of samples: now we are trying to extend the objective to nano-scale dynamics using pump and probe method. In the radiation damage of biological cells, we observed double strand break in DNA using X-ray laser exposure; this results are compared with the case using incoherent several KeV X-ray exposure.

Journal Articles

Development of the X-ray interferometer and the method of spatial and temporal synchronization of XRL and optical pulse

Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Terakawa, Kota*; Tomita, Takuro*; Yamamoto, Minoru; Nishikino, Masaharu; Oba, Toshiyuki; Kaihori, Takeshi; Imazono, Takashi; et al.

X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.353 - 358, 2011/12

The understanding of the dynamics of the initial process is important for the micro processing and welding by the ultra-short laser pulse. The X-ray laser is suitable for probing this initial process because it has short wavelength (Ni-like Ag, 13.9 nm) and short duration (7 ps). For this investigation, the origin of time of the pumping pulse is quite important. In this study, we used the scintillation plate and the plasma gate technique to realize the spatial and temporal synchronization of the pump and probe pulses. For the spatial alignment, a CsI scintillation plate that was set at the sample position was illuminated by both the X-ray laser pulse, and the fluorescence light were detected by the CCD camera. For the temporal synchronization, we set a thin foil at the sample position. We measured the transmission of the X-ray laser while changing a temporal delay of the pumping laser with respect to the time of X-ray laser pulse to obtain the origin of the irradiation time.

Journal Articles

Observation of the laser-induced surface dynamics by the single-shot X-ray laser interferometer

Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; Sasaki, Akira; Terakawa, Kota*; Minami, Yasuo*; et al.

Proceedings of SPIE, Vol.8140, p.81400G_1 - 81400G_8, 2011/10

 Times Cited Count:3 Percentile:84.58

We have developed a soft X-ray laser (SXRL) interferometer capable of the single-shot imaging of nano-scaled structure dynamics. The interferometer consisted of the reflection optics including double Lloyd's mirrors and focusing optics, and the interference fringes are produced on the detector surface. By using this interferometer, the initial stage ($$sim$$50 ps) of the ablation process of the Pt surface pumped by a 70 fs Ti:Sapphire laser pulse was observed. The expansion speed of the surface estimated from the result (34 nm/50 ps) indicated that the nano-bubble structures were formed in the initial stage of the ablation. In order to observe the detailed dynamics, the temporal synchronization between the pump and probe pulses was improved to be 3 ps by adopting a portion of the SXRL and pump beams as the time fiducials, to which the pump and probe timing was adjusted by using the X-ray streak camera.

Journal Articles

Observation of femtosecond laser ablation process by using the soft X-ray laser interferometer

Yamamoto, Minoru; Hasegawa, Noboru; Terakawa, Kota*; Umeda, Yoshifumi*; Tomita, Takuro*; Ochi, Yoshihiro; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; et al.

Proceedings of 12th International Symposium on Laser Precision Microfabrication (LPM 2011) (Internet), 4 Pages, 2011/06

Femtosecond lasers have been used for material processing. However, the physical processes responsible for femtosecond laser ablation have not been understood completely. These processes involve melting, vaporization, re-solidification or ablation, which occur in a very short time from pico- to nano-seconds. To understand the physical processes, it is essential to reveal the dynamics of ultrafast surface morphological change after laser irradiation. At JAEA, the laser-driven plasma soft X-ray laser (SXRL) that has extremely high spatial and spectral purity was constructed. It delivers soft X-ray photons at 89.2 eV (13.9 nm) with a photon number of exceeding $$10^{10}$$, which is sufficient to obtain a single shot interferogram. By using this system, the soft X-ray laser interferometer with the lateral resolution of 1.8 $$mu$$m and a depth resolution of 1 nm was developed. We report on demonstration of time-resolved measurement of femtosecond-laser ablation dynamics by using the soft X-ray laser interferometer.

Journal Articles

Single-shot picosecond interferometry with one-nanometer resolution for dynamical surface morphology using a soft X-ray laser

Suemoto, Toru; Terakawa, Kota*; Ochi, Yoshihiro; Tomita, Takuro*; Yamamoto, Minoru; Hasegawa, Noboru; Deki, Manato*; Minami, Yasuo*; Kawachi, Tetsuya

Optics Express (Internet), 18(13), p.14114 - 14122, 2010/06

 Times Cited Count:33 Percentile:82.72(Optics)

Using highly coherent radiation at a wavelength of 13.9 nm from a Ag-plasma soft X-ray laser, we constructed a pump-and-probe interferometer based on a double Lloyd's mirror system. The spatial resolutions are evaluated with a test pattern, showing 1.8 micrometers lateral resolution, and 1-nm depth sensitivity. This instrument enables a single-shot observation of the surface morphology with a 7-ps time-resolution. We succeeded in observing a nanometer scale surface dilation of Pt films at the early stage of the ablation process initiated by a 70 fs near infrared pump pulse.

Oral presentation

Observation of nano-scale fluctuation on solid surface by soft X-ray laser interferometer with highly temporal resolution

Ochi, Yoshihiro; Terakawa, Kota*; Suemoto, Toru*; Kawachi, Tetsuya; Hasegawa, Noboru; Tomita, Takuro*; Yamamoto, Minoru*; Deki, Manato*; Oba, Toshiyuki; Kaihori, Takeshi

no journal, , 

We developed a soft X-ray laser interferometer dedicated to the solid state physics. The interferometer enabled us to observe dynamical changes on the solid surface such as the photo-induced phase transition with picoseconds temporal resolution and nanometer special resolution (in z-axis). We carried out a performance test using static test pattern and confirmed the performance.

Oral presentation

Development of 0.1-Hz double-target X-ray laser and its application

Ochi, Yoshihiro; Hasegawa, Noboru; Kawachi, Tetsuya; Terakawa, Kota*; Suemoto, Toru*; Tomita, Takuro*; Yamamoto, Minoru*; Deki, Manato*; Tanaka, Momoko; Nishikino, Masaharu; et al.

no journal, , 

We have developed a chirped pulse amplification laser with zigzag slab Nd:glass power amplifiers which provides two synchronized beams with energy of $$sim$$10 J and duration of a few ps at 0.1-Hz repetition-rate. Using this laser as a driver, fully spatial coherent X-ray laser at a wavelength of 13.9 nm is generated at 0.1 Hz. Typical energy, beam divergence and duration of the X-ray laser are $$sim$$1 $$mu$$J, 0.5 mrad and 7 ps, respectively. Hence, a quite high peak brilliance is achieved. Using this X-ray laser, various application researches have been started.

Oral presentation

Development of high-rep soft-X-ray laser and its application on solid state physics

Ochi, Yoshihiro; Kawachi, Tetsuya; Hasegawa, Noboru; Terakawa, Kota*; Suemoto, Toru; Tomita, Takuro*; Yamamoto, Minoru*; Deki, Manato*; Tanaka, Momoko; Nishikino, Masaharu; et al.

no journal, , 

no abstracts in English

Oral presentation

Observation of ultra-high-speed phenomena on solid surface by using soft X-ray laser

Ochi, Yoshihiro; Terakawa, Kota*; Suemoto, Toru*; Yamamoto, Minoru*; Deki, Manato*; Tomita, Takuro*; Hasegawa, Noboru; Kawachi, Tetsuya

no journal, , 

no abstracts in English

Oral presentation

Development of high-repetition soft-X-ray laser and its application in solid state physics

Ochi, Yoshihiro; Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Tanaka, Momoko; Oba, Toshiyuki; Kishimoto, Maki; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; et al.

no journal, , 

no abstracts in English

Oral presentation

Development of soft-X-ray laser probe system for investigating dynamics on solid surfaces

Ochi, Yoshihiro; Terakawa, Kota*; Suemoto, Toru*; Kawachi, Tetsuya; Tomita, Takuro*; Yamamoto, Minoru*; Deki, Manato*; Hasegawa, Noboru; Oba, Toshiyuki; Kaihori, Takeshi

no journal, , 

no abstracts in English

Oral presentation

Applications of laser driven plasma soft X-ray laser in JAEA

Ochi, Yoshihiro; Kawachi, Tetsuya; Terakawa, Kota*; Suemoto, Toru*; Yamamoto, Minoru*; Tomita, Takuro*; Deki, Manato*; Hasegawa, Noboru

no journal, , 

Oral presentation

Development and applications of plasma X-ray lasers

Nishikino, Masaharu; Ochi, Yoshihiro; Hasegawa, Noboru; Kawachi, Tetsuya; Ishino, Masahiko; Imazono, Takashi; Tanaka, Momoko; Sato, Katsutoshi; Yamamoto, Minoru; Oba, Toshiyuki; et al.

no journal, , 

Recent Progress in the development of laser-driven plasma soft X-ray laser (XRL) and the applications are presented. In the source development, TOPAZ laser using Nd:glass zigzag slab amplifiers with 10 J, 0.1 Hz repetition-rate routinely provides the fully spatial coherent X-ray laser at 13.9 nm for the applications. The bright, coherent, and picoseconds X-ray pulse can be used in a variety of applications such as X-ray speckle measurement and interferometer for probing materials, diffraction imaging, nano-scale fabrication, radiation biology, and so on. In order to extend the use of XRLs, now we are constructing new XRL beam lines for the optical pump and XRL probe experiment.

Oral presentation

Observation of the laser ablation process by the soft X-ray laser interferometer

Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Oba, Toshiyuki; Kaihori, Takeshi; Suemoto, Toru*; Terakawa, Kota*; Tomita, Takuro*; Yamamoto, Minoru*

no journal, , 

In this study, we developed the shingle-shot soft X-ray laser interferometer at the wavelength of 13.9 nm by use of the double Lloyd's mirror geometry to measure the dynamics of the laser ablation. The lateral resolution and depth sensitivity of this interferometer were measured to be less than 1.5 micron and 1 nm, respectively. We combined this interferometer with Ti;Sapphire laser for this experiment. After 50 ps from laser irradiation, 35 nm expansion of the platinum sample was measured. And the expansion speed of the ablation front was estimated to be 700 m/s. The result of it shows there is low density structure (like as bubble structure) under the ablation front.

Oral presentation

Incubation effect of femtosecond-laser ablation

Yamamoto, Minoru; Hasegawa, Noboru; Terakawa, Kota*; Umeda, Yoshifumi*; Tomita, Takuro*; Ochi, Yoshihiro; Kawachi, Tetsuya; Oba, Toshiyuki; Kaihori, Takeshi; Minami, Yasuo*; et al.

no journal, , 

no abstracts in English

32 (Records 1-20 displayed on this page)