2018 Fiscal Year Research-status Report
Novel terahertz waveguide structure: probing low dimensional materials under extremely strong electromagnetic field
| Project/Area Number |
18K13803
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| Research Institution | Shizuoka University |
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Principal Investigator |
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| Project Period (FY) |
2018-04-01 – 2020-03-31
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| Keywords | Carbone nanotubes / Terahertz spectroscopy / parallel plate waveguide |
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| Outline of Annual Research Achievements |
The interaction of high THz electric field with low dimensional materials would provide an insight of their nonlinear and non - equilibrium response. Though, an important step for the study of the carrier dynamic is to probe their linear response. Then, we have performed THz waveguide spectroscopy experiments with arc discharged carbon nanotubes (CNT). For unaligned CNT on Si substrate, the absorption in the low frequency region is 75% in waveguide spectroscopy compared to 20% for the standard THz spectroscopy. The huge absorption due to the configuration of the sample and the electric field enables to measure the real and the imaginary part of the conductivity. The striking difference with the standard THz spectroscopy is that the conductivity roll-off in the waveguide measurement occurs at lower frequency. This implies that the relaxation time is one to two magnitude slower than the results published in the literatures.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
The first part of the experimental setup used is composed of a high power femtosecond laser with a wavelength of 800 nm at 100 kHz repetition rate. This system is crucial for the continuation of my research of Kakenhi as it is the main setup that I have proposed for the project. This system was in standby and even partially damaged by the earthquake in 2018. On January, 2019, we have finished 30% of the improvement work. The status of the high power laser is On March, 2019, we have succeeded to retrieve the power to 3.5 W. However, we still need to improve the pulse width of this laser system in order to generate THz wave. The remaining part of the High power THz setup is already ready for use including the generation and the detection part, the waveguide system and the samples to measure. On April 2019, Osaka University have contacted the Spectraphysics company in order to check and to maintain the laser.
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| Strategy for Future Research Activity |
The ongoing objective is currently to provide a clear and consistent physical mechanism of “linear” absorption of THz wave by 1D/2D samples. Since the original schedule is delayed, we have shifted the first preliminary test during the month of May and June 2019. The new waveguide device design has been already done. The next step in the research is experiments with intense THz field in the waveguide with CNT. At the same time, we will develop formalism in non -equilibrium THz regime for low dimensional material response. In this scheme, we aim to provide a clear evidence of the dominant nonlinear effect in 2D/1D materials under extremely high electric field. The dissemination of the results is toward the beginning of October 2019.
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| Causes of Carryover |
Due to the delay of the project, the main expense for the fiscal year 2018 was the tools for waveguide simulation and domestic travel. Since the high power THz TDS setup is still under improvement, there is no requirement for new additional optical components at that stage. The direct expense amount for the fiscal year 2018 will be combined with the fiscal year of 2019. As proposed in the original plan, the direct costs for fiscal year 2018 (which is now combined with the fiscal year of 2019) will be assigned to oscilloscope, software license, waveguide component and optical components of the experimental setup.
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Research Products
(1 results)
