| Budget Amount *help |
¥48,490,000 (Direct Cost: ¥37,300,000、Indirect Cost: ¥11,190,000)
Fiscal Year 2007: ¥7,800,000 (Direct Cost: ¥6,000,000、Indirect Cost: ¥1,800,000)
Fiscal Year 2006: ¥14,690,000 (Direct Cost: ¥11,300,000、Indirect Cost: ¥3,390,000)
Fiscal Year 2005: ¥26,000,000 (Direct Cost: ¥20,000,000、Indirect Cost: ¥6,000,000)
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| Research Abstract |
A coherent tunable terahertz (THz) source is a key device for applications such as THz frequency-domain spectroscopy and THz imaging. The purpose of this research project is to develop a THz-wave synthesizer based on difference-frequency generation (DFG) using nonlinear optical crystals. The n-conjugated organic crystals such as 4'-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) are promising materials for wideband THz-wave generation using DFG We synthesized a new organic crystal of 4'-dimethylamino-N- methyl-4-stilbazolium p-chlorobenzenesulfonate (DASC), which possessed p-chlorobenzenesulfonate instead of the tosylate of DAST. DASC crystals can be grown using a slow-cooling method in methanol solution, the same as DAST.
Widely tunable THz waves ranging from 2 to 30 THz were generated from DAST and DASC crystals using a dual-wavelength optical parametric oscillator (OPO) with two KTiOPO_4 crystals as the input light source. The OPO has a tunable range from 1340 to 1550 rim and is pumped by a frequency-doubled (532 rim), Q-switched Nd:YAG laser with a pulse duration of 12 ns. The THz output energy exceeding 500 nJ was obtained with a 0.5-mm-thick DAST and DASC crystal. Sub-THz waves in the range of 0.3-2 THz were also generated using an improved dual-wavelength OPO near 990 run with 2-mm-thick DAST crystals. The widely tunable -THz-wave synthesizer could potentially be used for real-time THz-imaging, THz-ranging, and spectroscopic applications.
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