With
the rapid advances in functional optoelectronics, the research
on carbon-based materials and devices has become increasingly important
at the terahertz frequency range owing to their advantages in terms
of weight, cost, and freely bendable flexibility. Here, we report
an effective material and device design for a terahertz plasmonic
metasurface sensor (PMS) based on carbon nanotubes (CNTs). CNT metasurfaces
based on silicon wafers have been prepared and obvious resonant transmission
peaks are observed experimentally. The enhanced resonant peaks of
transmission spectra are attributed to the surface plasmon polariton
resonance, and the transmission peaks are further well explained by
the Fano model. Furthermore, the different concentration gradients
of pesticides (2,4-dichlorophenoxyacetic and chlorpyrifos solutions)
have been detected by the designed PMSs, showing the lowest detection
mass of 10 ng and the sensitivities of 1.38 × 10–2/ppm and 2.0 × 10–3/ppm, respectively. Good
linear relationships between transmission amplitude and pesticide
concentration and acceptable reliability and stability have been obtained.
These materials and device strategies provide opportunities for novel
terahertz functional devices such as sensors, detectors, and wearable
terahertz imagers.
In this work, we present a study of bright-bright mode electromagnetically induced transparency based on carbon nanotube films terahertz metasurface consisting of an array of two asymmetric split rings. Under the excitation of terahertz wave, the electromagnetically induced transparency window can be obviously observed. The simulation results agree with the theoretical results. The formation mechanism of the transparent window in bright-bright mode electromagnetically induced transparency is further analyzed. Moreover, the sensing performance of the proposed terahertz metasurface is investigated and the sensitivity can reach to 320 GHz/RIU. To verify the slow light characteristics of the device, the group delay of the terahertz metasurface is calculated and the value is 2.12 ps. The proposed metasurface device and the design strategies provide opportunities for electromagnetically induced transparency applications, such as sensors, optical memories, and flexible terahertz functional devices.
Perfect metasurface absorbers play a significant role in imaging, detecting, and manipulating terahertz radiation. We utilize all-dielectric gratings to demonstrate tunable multi-band absorption in the terahertz region. Simulation reveals quad-band and tri-band absorption from 0.2 to 2.5 THz for different grating depths. Coupled-mode theory can explain the absorption phenomenon. The absorption amplitude can be precisely controlled by changing the pump beam fluence. Furthermore, the resonant frequency is sensitive to the medium’s refractive index, suggesting the absorber may be of great potential in the sensor detection field. The experimental results exhibit a high detectivity of pesticides.
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