2000 Fiscal Year Final Research Report Summary
Photochemistry by femtosecond pulse-train
| Project/Area Number |
11440173
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
WADA Akihide Tokyo Inst. of Tech., Chem. Res. Lab., Assoc. Pro, 資源化学研究所, 助教授 (20202418)
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| Co-Investigator(Kenkyū-buntansha) |
KUBOTA Jun Tokyo Inst. of Tech., Chem. Res. Lab., Res. Assoc, 資源化学研究所, 助手 (50272711)
ONDA Ken Tokyo Inst. of Tech., Chem. Res. Lab., Res. Assoc, 資源化学研究所, 助手 (60272712)
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| Project Period (FY) |
1999 – 2000
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| Keywords | pulse shaping / Genetic Algorithm / ultrafast phenomena / pulse train / coherent phonon / femtosecond laser / パルストレイン / コヒーレントフォノン |
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| Research Abstract |
In this research project, we have constructed a pulse-shaping system consisting of a mode-locked femtosecond laser and pulse-shaper. The control of pulse shape is accomplished using a programmable pulse shaper based on a Fourier transform technique where a liquid crystal spatial light modulator (LCSLM), consisting of the polarizer and liquid crystal display (LCD) which has the rectangular pixels with the width of 0.1 mm, adjusts the intensity and the phase of each spectral component of the laser pulses in the frequency domain. Furthermore, the system was controlled by the a genetic algorithm (GA) which is a powerful tool to find a pulse shape suitable for a specific physical/chemical process without the knowledge of the input pulses and the detailed structure of samples.
The GA is a multi-objective optimization method which mimics process actually taking place in the biological evolution process consisting of selection, crossover, and mutation of individuals. For the pulse shaping system controlled by the GA, the modulation pattern printed on the LCD in the SLM is regarded as the pattern of nucleotide sequence in gene by considering the pixel of the SLM as the base pair of gene. Then, the system evolves the modulation pattern in search of the pulse shapes suitable for a specific process on the basis of feedback from the experiment. In the progress of the pattern evolution, the value of the experimental output corresponds to the fitness for the environment of the organism.
We tried to control the STE creation process in perylene crystal using the system. It was found that the intensity ratio of E-type STE emission to Y-type STE emission could be changed as a function of the pulse shape.
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