1996 Fiscal Year Final Research Report Summary
Research on generation of lightwave with ultra-wide sidebands and its conversion to THz electromagnetic wave
| Project/Area Number |
07455039
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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 |
Applied optics/Quantum optical engineering
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| Research Institution | Osaka University |
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Principal Investigator |
KOBAYASHI Tetsuro Osaka University, Faculty of Engineering Science, Professor, 基礎工学部, 教授 (10029522)
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| Co-Investigator(Kenkyū-buntansha) |
KITAGAWA Masahiro Osaka University, Faculty of Engineering Science, Assistant Professor, 基礎工学部, 講師 (20252629)
MORIMOTO Akihiro Osaka University, Faculty of Engineering Science, Associate Professor, 基礎工学部, 助教授 (00142307)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Tera Hertz / beat / sideband / electro-optic modulation / electro-optic deflector / injection locking / SHG autocorrelation |
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| Research Abstract |
(a) Generation of ultra-wide optical sidebands
i.Electro-optic phase modulators with quasi velocity matching (QVM) by periodic domain inversion of LiTaO_3 crystal have been developed, Ultra-wide optical sidebands over 3THz have been generated a modulation frequency 16GHz.
ii.A new electro-optic deflector with traveling phase grating by tilt periodic domain inversion of LiTaO_3 crystal has been proposed and developed. Ultra-wide modulation sidebands have been generated by Raman-Nath diffraction. Ultrafast deflection has been done with the help of Fourier transform optics.
(b) Control of THz sidebands : Both electro-optically generated phase modulation sidebands and sidebands from modelocked laser have been spectrally resolved, spatially separated, selected and/or phase shifted by liquid crystral spatial phase modulator and then recombined. The pulse trains with the repetition rate equal to a multiple of modulation frequency have been generated.
(c) Generation of coherent THz optical beat :
… More
Superposition of lightwaves from two single-mode lasers exhibits intensity beat at the difference frequency of the two lasers which can easily be made to be THz. However, THz electromagnetic wave generated from the optical beat decoheres due to phase diffusion of the lasers. It is therefore essential to fix the phase relation of two lasers with frequency difference of the order of THz.
i.Selective injection locking : Modulation sidebands or mode-locked sidebands are guaranteed to be coherent.with each orther. DBR laser diode can be selectively locked to the one of the injected sidebands. By locking two laser diodes to the sidebands separated by THz, coherent THz optical beat can be generated.
ii.SHG autocorrelation negative feedback : Deviation of optical beat phase is show to be detected by non-collinear SHG autocorrelation. By negative feedback of the beat phase deviation to the one of the laser phase, the beat coherency is sustained. The scheme has been successfully demonstrated by using microwave delay-line and mixer in place of SHG autocorrelation. Less
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