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論文

Hydrodynamics driven by ultrashort laser pulse; Simulations and the optical pump - X-ray probe experiment

Inogamov, N. A.*; Zhakhovsky, V. V.*; 長谷川 登; 錦野 将元; 山極 満; 石野 雅彦; Agranat, M. B.*; Ashitkov, S. I.*; Faenov, A. Y.*; Khokhlov, V. A.*; et al.

Applied Physics B, 119(3), p.413 - 419, 2015/06

 被引用回数:6 パーセンタイル:55.3(Optics)

Spatial structures of ablative mass flow produced by femtosecond laser pulses are studied. In experiments with a gold film, the Ti:sap laser pulse having a focal size of 100 microns on a target was used, while a soft X-ray probe pulse was utilized for diagnostics. The experimental data are compared with simulated mass flows obtained by two-temperature hydrodynamics and molecular dynamics methods. Simulation shows evolution of a thin surface layer pressurized after electron-ion thermalization, which leads to melting, cavitation and formation of spallation liquid layer. The calculated asymptotic surface velocity of this layer as a function of fluence is in reasonably good agreement with experimental data.

論文

Ablation of insulators under the action of short pulses of X-ray plasma lasers and free-electron lasers

Inogamov, N. A.*; Anisimov, S. I.*; Petrov, Y. V.*; Khokhlov, V. A.*; Zhakhovskii, V. V.*; Faenov, A. Ya.*; Pikuz, T.; Fortov, V. E.*; Skobelev, I. Y.*; 加藤 義章*; et al.

Journal of Optical Technology, 78(8), p.473 - 480, 2011/08

 被引用回数:5 パーセンタイル:67.52(Optics)

An experimental and theoretical study has been carried out of the ablation of a solid insulator with a wide band gap (LiF) under the action of ultrashort laser pulses of the UV range, obtained in a free-electron laser, and the soft X-ray region, obtained in a silver-plasma laser. A comparison is made of the results obtained on the two laser systems. It is shown that the ablation threshold is about the same for both lasers. A theory is presented that explains the weak growth of the ablation mass with increasing surface energy density of the laser radiation (the fluence) in the case of X-ray lasers as a result of the transition from spallation close to the ablation threshold to evaporative ablation at high fluence values.

論文

Two-temperature warm dense matter produced by ultrashort Extreme Vacuum Ultraviolet-Free Electron Laser (EUV-FEL) pulse

Inogamov, N. A.*; Faenov, A. Ya.*; Zhakhovsky, V. V.*; Pikuz, T. A.*; Skobelev, I. Yu.*; Petrov, Y. V.*; Khokhlov, V. A.*; Shepelev, V. V.*; Anisimov, S. I.*; Fortov, V. E.*; et al.

Contributions to Plasma Physics, 51(5), p.419 - 426, 2011/06

 被引用回数:19 パーセンタイル:30.15(Physics, Fluids & Plasmas)

極短パルス,極端紫外自由電子レーザー(EUV-FEL)パルス(波長:50nm,パルス幅:100fs)をフッ化リチウム(LiF)のような誘電体に照射することで、結晶状態にあるLiFの破砕現象を初めて観測した。低フルーエンスの場合ではLiFの破砕現象が起こり、これがLiFの低いアブレーション閾値の原因となっていることを明らかにした。同様の現象は、ピコ秒パルスの関西光科学研究所X線レーザー装置を用いた実験でも観測されている。この破砕現象は、ナノ秒パルスのX線レーザー装置では観測されておらず、フェムト$$sim$$ピコ秒パルス特有の現象であることをモデル計算から明らかにした。

論文

Spallative ablation of dielectrics by X-ray laser

Inogamov, N. A.*; Zhakhovsky, V. V.*; Faenov, A. Ya.*; Khokhlov, V. A.*; Shepelev, V. V.*; Skobelev, I. Y.*; 加藤 義章*; 田中 桃子; Pikuz, T. A.*; 岸本 牧; et al.

Applied Physics A, 101(1), p.87 - 96, 2010/10

 被引用回数:30 パーセンタイル:22.19(Materials Science, Multidisciplinary)

A short laser pulse in wide range of wavelengths, from infrared to X-ray, disturbs electron-ion equilibrium and increases pressure in a heated layer. The case where the pulse duration $$tau$$$$_{L}$$ is shorter than acoustic relaxation time $$t$$$$_{s}$$ is considered. It is shown that this short pulse may cause thermomechanical phenomena such as spallative ablation regardless of wavelength. While the physics of electron-ion relaxation strongly depends on wavelength and various electron spectra of substances. There are spectra with an energy gap in semiconductors and dielectrics opposed to gapless continuous spectra in metals. The paper describes entire sequence of thermomechanical processes from expansion, nucleation, foaming, and nanostructuring to spallation with particular attention to spallation by X-ray pulse.

論文

Interaction of short laser pulses in wavelength range from infrared to X-ray with metals, semiconductors, and dielectrics

Inogamov, N. A.*; Faenov, A. Ya.*; Zhakhovskii, V. V.*; Skobelev, I. Y.*; Khokhlov, V. A.*; 加藤 義章*; 田中 桃子; Pikuz, T. A.*; 岸本 牧; 石野 雅彦; et al.

Contributions to Plasma Physics, 51(4), p.361 - 366, 2010/05

 被引用回数:18 パーセンタイル:31.79(Physics, Fluids & Plasmas)

Laser-matter interaction is defined by an electric band structure of condensed matter and frequency of electromagnetic radiation. The thermalization processes are different for optical as compared with X-ray quanta and for metals relative to semiconductors and dielectrics, since the light absorption and electron-electron, electron-ion dynamics are sensitive to the electron population in a conduction band and the width of a forbidden gap. Although the thermalization processes are different, the final state is simply a heated matter. Laser heating creates powerful stresses in a target if duration of laser pulse $$tau$$$$_{L}$$ is short in acoustic time scale. Nucleation and material removal take place under such stresses. Such way of removal is called here the spallative ablation. Thus the spallative ablation is an ablation mechanism universally important for qualitatively different materials and quanta.

論文

Low-threshold ablation of dielectrics irradiated by picosecond soft X-ray laser pulses

Faenov, A. Y.; Inogamov, N. A.*; Zhakhovskii, V. V.*; Khokhlov, V. A.*; 西原 功修*; 加藤 義章*; 田中 桃子; Pikuz, T. A.*; 岸本 牧; 石野 雅彦; et al.

Applied Physics Letters, 94(23), p.231107_1 - 231107_3, 2009/06

 被引用回数:41 パーセンタイル:16.73(Physics, Applied)

Ablation of LiF crystal by soft X-ray laser pulses with wavelength 13.9 nm and duration 7 ps is studied experimentally and theoretically. It is found that a crater appears on a surface of LiF for XRL fluence, exceeding the ablation threshold 10.2 mJ/cm$$^{2}$$ in one shot, or 5 mJ/cm$$^{2}$$ in each of the three XRL shots. This is substantially below the ablation thresholds obtained with other lasers having longer pulse duration and/or longer wavelength. A new mechanism of thermomechanical ablation in large bandgap dielectrics is proposed. The theory explains the low ablation threshold via small attenuation depth, absence of light reflection, and electron heat conductivity.

口頭

Low threshold ablation of large bandgap LiF dielectrics induced by picosecond soft X-ray laser pulses

Faenov, A. Y.; Inogamov, N. A.*; Zhakhovskii, V.*; Khokhlov, V. A.*; 西原 功修*; 加藤 義章*; 田中 桃子; Pikuz, T.*; 岸本 牧; 石野 雅彦; et al.

no journal, , 

Experimental and theoretical investigations of large bandgap LiF dielectrics ablation threshold induced by 7 ps 13.9 nm XRL pulses were performed. LiF crystal threshold is about 1600, 210 and 8 times smaller compare with LiF crystal thresholds measured previously for ns and fs visible lasers and ns 46.9 nm soft XRL, correspondently.

口頭

Low-threshold ablation of dielectrics irradiated by picosecond soft X-ray laser pulses; Observation and modeling

Faenov, A. Y.; Pikuz, T. A.*; Inogamov, N. A.*; Zhakhovski, V.*; Khokhlov, V.*; Anisimov, S. I.*; Fortov, V. E.*; 加藤 義章*; 福田 祐仁; 田中 桃子; et al.

no journal, , 

The results of theoretical and experimental studies of ablation of LiF crystal by X-ray beam having photons with 89.3 eV and very short duration of pulse 7 ps are presented. It is found that the crater is formed for fluencies above the threshold 10 mJ/cm$$^{2}$$. Such a small threshold is one order of magnitude less than the one obtained for X-ray ablation by longer (nanoseconds) pulses. The theory explains this dramatic difference as a change-over from more energy consuming evaporative ablation to spallative ablation, when the pulse duration decreases from ns to ps time ranges.

口頭

Observation and modeling ablation threshold features of dielectrics irradiated by ultrashort pulses of soft X-ray transient collisional and free electron lasers

Inogamov, N. A.*; Faenov, A. Y.; Pikuz, T.*; Zhakhovski, V.*; Skobelev, I.*; Khokhlov, V.*; Anisimov, S. I.*; Fortov, V. E.*; 福田 祐仁; 加藤 義章*; et al.

no journal, , 

The results of theoretical and experimental studies of ablation of LiF crystal by X-ray laser and FEL beams having photons with 89.3 eV and 20 eV with very short duration of pulse 7 ps and 300 fs are presented. It is found that the crater is formed for fluencies above the threshold Fabl about 10 mJ/cm$$^{2}$$: Such a small threshold is one order of magnitude less than the one obtained for X-ray ablation by longer (nanoseconds) pulses. The theory explains this dramatic difference as a change-over from more energy consuming evaporative ablation to spallative ablation, when the pulse duration decreases from ns to ps time ranges. We demonstrate that tensile stress created in dielectrics by short X-ray pulse can produce spallative ablation of target even for drastically small X-ray fluencies, which open new opportunities for material nano processing.

口頭

Low-threshold ablation of dielectrics irradiated by ultrashort pulses of soft X-ray transient collisional and free electron lasers; Observation and modeling

Faenov, A. Y.; Pikuz, T.*; Inogamov, N. A.*; Zhakhovski, V.*; Skobelev, I.*; Khokhlov, V.*; Anisimov, S. I.*; Fortov, V. E.*; 福田 祐仁; 加藤 義章*; et al.

no journal, , 

Theoretical and experimental studies of ablation of LiF crystal by X-ray laser and FEL beams were provided. It was found a very low ablation threshold for both types of irradiation. Such a small threshold is one order of magnitude less than the one obtained for X-ray ablation by longer (nanoseconds) pulses or 2 orders smaller than arradiated by fs visible pulses. The theory explains this dramatic difference as a change-over from more energy consuming evaporative ablation to spallative ablation, when the pulse duration decreases from ns to ps time ranges.

口頭

軟X線レーザーを集光照射した金属表面の観察

石野 雅彦; Faenov, A. Y.*; 田中 桃子; 保 智己*; 河内 哲哉; Inogamov, N. A.*; Pikuz, T. A.*; 大場 俊幸; 海堀 岳史; Khokhlov, V.*; et al.

no journal, , 

軟X線レーザーによるアブレーション基礎過程の理解を目的として、アルミニウム表面の照射痕を走査型電子顕微鏡で観察したところ、照射領域にアブレーション構造とは異なる微細構造が形成されていることを確認した。この領域には200nm程度の直径を持つ円錐状の構造物が多数確認できる。これまでにレーザープラズマから発生する軟X線を連続照射した有機高分子表面に微細構造が形成されることが報告されているが、軟X線レーザーの照射においても同様の現象が金属表面に起こることが明らかとなった。軟X線レーザーによるアブレーションは、熱的な蒸発描画よりも破砕的な過程が原因と考えられているが、アルミニウム表面に形成された微細構造は、照射領域の熱的融解に起因するものと考えられる。

口頭

EUVレーザーによる固体のアブレーションしきい値の観測

河内 哲哉; Faenov, A.*; 石野 雅彦; 田中 桃子; Inogamov, N. A.*; Khokhlov, V.*; Anisimov, S. I.*; Pikuz, T.*; 長谷川 登; 錦野 将元; et al.

no journal, , 

EUVレーザーを固体に照射した場合のアブレーションしきい値を観測した。アブレーションしきい値は、従来の可視赤外領域のレーザーを用いた場合に比べて2$$sim$$3桁低かった。観測結果を説明するために分子動力学と流体コードを組合せた計算機シミュレーションを行い、実験との比較を行った。その結果、EUV領域の高輝度レーザーパルス照射を行った場合には、従来の可視赤外レーザーの場合のように試料が個々の原子として蒸発する描像ではなく、局所的に高温高圧状態になった試料内部が破断することで表面部分が破砕することが示された。

口頭

ピコ秒EUVレーザー照射による低アブレーションしきい値の観察

河内 哲哉; Faenov, A.*; 田中 桃子; 石野 雅彦; Pikuz, T.*; 長谷川 登; Bulanov, S. V.; Inogamov, N. A.*; Khokhlov, V.*; Anisimov, S. I.*

no journal, , 

ピコ秒の時間幅を持つEUVレーザーを固体に照射した場合のアブレーションしきい値を観測した。観測から得られたアブレーションしきい値は、従来の可視赤外領域のレーザーを用いた場合に比べて2桁以上低かった。観測結果を説明するために分子動力学と流体コードを組合せた計算機シミュレーションを行い、実験との比較を行った。その結果、EUV領域の高輝度レーザーパルス照射を行った場合には、従来の可視赤外レーザーの場合のように試料が個々の原子として蒸発する描像ではなく、局所的に高温高圧状態になった試料内部が破断することで表面部分が破砕することが示された。

口頭

Surface nanodeformations caused by ultrashort laser pulse

Inogamov, N. A.*; Zhakhovsky, V. V.*; Ashitkov, S.*; Eminov, Yu.*; Faenov, A.*; Petrov, Y. V.*; Khokhlov, V.*; 石野 雅彦; Demaske, B.*; 田中 桃子; et al.

no journal, , 

Results of investigations of surface nanomodification caused by ultrashort laser pulses from infrared will be presented and discussed.

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