1996 Fiscal Year Final Research Report Summary
Encoding and decoding of amplitude or phase informations with a liquid-crystal array on femtosecond light pulses
| Project/Area Number |
07650401
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
電子デバイス・機器工学
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| Research Institution | Keio University |
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Principal Investigator |
KANNARI Fumihiko Keio University, Faculty of Science and Technology, Assosiate Professor, 理工学部, 助教授 (40204804)
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| Project Period (FY) |
1995 – 1996
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| Keywords | femtosecond laser / amplitude shaping / phase shaping / coherent phonon / coherent function shaping / multiplexed holography |
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| Research Abstract |
1. Arbitrarily shaped femtosecond laser pulses are produced with a Fourier-transform synthesis using a commercially available liquid-crystal spatial light modulator (SLM) controlled by a IBM-PC.The modulator consists of 128 individually programmable pixels of 100 mum wide with a 3 mum gap between each elements. The pulse-shaping apparatus consists of a grating pair placed at the focal planes of a unit magnification confocal lens-pair with a focal length of 15cm.
(1) Phase-only masks formed with the SLM in the experiments were designed with simulated annealing optimization algorithm for arbitrarily shaped amplitude and phase time histories. Even asymmetric shapes in time domain can be synthesized with four gray levels of 0, (]SY.+-。[)pi/2, and pi.
(2) Successful shaping of -100 fs input laser pulse was obtained in our experiments such as THz pulse trains shaped with 7-length M-sequence, unsymmetrical pulse trains, and linearly frequency-chirped pulses.
2. Selective coherent phonon mode was excited in Bi with THz pulse trains synthesized with our pulse shaping apparatus.
3. Utilizing this pulse shaping apparatus, we succeeded to shape coherent function of a cw light from a super luminescent diode with a spectrum width of -17nm.
4. Multiplexed holograms were recorded with spatial phase encoding method as a preliminary experiments of femtosecond spectrum holography. Holograms recorded by a beam encoded with a quasi-noise phase pattern and a single lobe formation pattern, successfully produce a single lobe beam pattern only when a read beam is encoded with the same quasi-noise phase pattern.
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