In this paper, the transmission properties of the double-walled carbon nanotube (DWCNT) films in terahertz spectrum are simulated and analyzed using the finite element method. Carbon nanotubes (CNTs) have excellent electromagnetic properties, oxidation resistance and flexibility, so it has become a material that has attracted much attention to replacing metal wire grids. The transmission of the transverse magnetic (TM) gives the power transmission of the polarizer for the component parallel to the grating vector and the transmission of the transverse electric (TE) for the perpendicular component. Our simulation results show that the transmission of the TM mode and the TE mode could be modulated by adjusting the diameter and spacing of the DWCNTs. In the range of 0.3-2.5THz, the transmission of the TM can be modulated from 90.7% to 99.3%, and TE can be modulated from 0.3% to 23%, which offers an alternative way of designing a polarizer with the desired degree of polarization. The simulation results provide numerical results in wide-band THz wave modulation with DWCNTs.
A real-time online ranging system is proposed using the frequency domain peak interval measurement method. By utilizing an NPR-locked, all-fiber, wide-spectrum erbium-doped femtosecond laser, a gain distribution with a center wavelength of 1560nm is obtained, with a repetition frequency of up to 14.54MHz, and then a femtosecond laser source with a spectral width of 38nm at -3dB can be obtained by adjusting its polarization state, which can improve ranging accuracy. By a combination of an upper computer system an all-fiber Michelson interferometer, real-time capture and processing of spectral interference data can be achieved, thereby realizing real-time acquisition of relative displacement distance. Experimental results show that within the coherence length, the measurable relative distance is around 2cm, and the measurement accuracy can reach 5μm.
A carbon nanotube (CNT) is a cylinder made of graphene. CNTs possess excellent properties of carbon materials, and the parallel-arranged nanotubes exhibit anisotropy additionally. The finite element method is adopted to simulate single-walled carbon nanotube (SWCNT) array in the terahertz spectrum. Under the standard size parameters we have set, Our simulation results show that between 1-3 THz, P-polarization transmittance, which is perpendicular to the SWCNTs, fluctuates around 0.5, while S-polarization transmittance, which is parallel to the SWCNTs, is around 4.8×10-3. The reflectance parallel to the SWCNTs gradually increases to 0.407, and the reflectance perpendicular to the SWCNTs gradually decreases to nearly 1×10-8 as the frequency increases. The simulation results provide theoretical support for further applications of SWCNTs in optical field.
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