2006 Fiscal Year Final Research Report Summary
Generation of ultrashort pulses in unexplored time regions and their measurement
| Project/Area Number |
14102012
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| Research Category |
Grant-in-Aid for Scientific Research (S)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied optics/Quantum optical engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SAKAI Hirofumi The University of Tokyo, Graduate School of Science, Associate Professor, 大学院理学系研究科, 助教授 (20322034)
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| Co-Investigator(Kenkyū-buntansha) |
MINEMOTO Shinichirou The University of Tokyo, Graduate School of Science, Assistant Professor, 大学院理学系研究科, 助手 (90323493)
YABUSHITA Atsushi National Chiao-Tung University, Department of Electrophysics, Research Assistant Professor (The University of Tokyo, Graduate School of Science, Assistant Professor), 電子物理系(東京大学・大学院理学系研究科), 研究助理教授(助手) (20376536)
HIRASAWA Masakatsu Yamagata Promotional Organization, Research Institute for Organic Electronics, Chief Researcher, 有機エレクトロニクス研究所, 主任研究員 (90262162)
KOBAYASHI Takayoshi University of Electro-Communications, Project Professor, 特任教授 (60087509)
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| Project Period (FY) |
2002 – 2006
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| Keywords | non-collinear optical parametric amp / carrier envelope phase (CEP) / visible to near infrared range / aligned or oriented molecules / high-order harmonic generation / coherent vacuum ultraviolet radiation / attosecond pulses / polarization rate technique |
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| Research Abstract |
(Visible to near infrared spectral range)
We have developed a technique of non-collinear optical parametric amplification (NOPA) to generate ultrashort visible pulses. The pulses enable us to observe and analyze ultrafast dynamics of various real-time molecular vibrations whose frequencies are up to 3000 cm^<-1>. The ultrashort pulses have broadband spectrum, therefore the ultrafast dynamics of the real-time molecular vibrations can be observed in the entire broadband spectrum of the laser pulses, which gives the dependence of the ultrafast dynamics on the probe photon energy and clarifies its detailed dynamics. We have developed a multi (128 ch) double lock-in amplifier combined with spectrometer to observe the signal in the entire broadband spectrum of the ultrashort pulses. The multi channel lock-in amplifier can simultaneously measure all of the 128 probe wavelengths, which makes the measurement time 128 times shorter than before. The quick measurement enables to increase the signal
… More
to noise (S/N) ratio increased more than 10 times or measure the signal continuously changing parameters in good S/N ratio. Using the ultrashort visible pulses and the multi channel lock-in amplifier, we could observe the real-time signal of the sample in broadband with a fine time resolution, which can resolve the real-time molecular vibration.
(Vacuum ultraviolet spectral range)
We have developed an original technique to generate ultrashort light pulses in the VUV region by using high-order harmonic generation (HHG) from aligned molecules. First, we have succeeded in the optimal control of multiphoton ionization processes in aligned I_2 molecules with time-dependent polarization pulses. This means that we have developed the most advanced technique to control tunnel ionization which is the first step of HHG. Second, our novel technique to observe both ion yields and harmonic signals under the same experimental conditions enabled us to observe the first clear evidence of quantum interference of electron de Broglie waves in the recombination process, i.e., the third step of HHG from aligned CO_2 molecules. Third, we applied the polarization gate technique to HHG from non-adiabatically aligned N_2 molecules. Contrary to our expectations based on ellipticity dependence of HHG from aligned molecules, we have found that the spectral width of each harmonic tends to be broader when the molecular axis is perpendicular to the major axis of elliptical polarization. Theoretical calculations show that our observations are characteristic of time-dependent polarization pulses. This means that molecular alignment can be used as an important control parameter in addition to the carrier envelope phase when we generate attosecond pulses with polarization gated few-cycle pulses. Less
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Research Products
(84 results)
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[Journal Article] Alignment of neutral molecules by a strong nonresonant linearly polarized laser field2002
Author(s)
Hirofumi Sakai, Jakob Juul Larsen, C.P.Safvan, Ida Wendt-Larsen, Henrik Stapelfeldt, Tsuneto Kanai
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Journal Title
ACS Symposium Series, Laser Control and Manipulation of Molecules( A.D.Bandrauk, Y.Fujimura, R.J.Gordon, Editors) Vol.821, Chapter 21
Pages: 320-335
Description
「研究成果報告書概要(欧文)」より
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