All metal sensing based on complementary H-shaped arrays (HSAs) is numerically and experimentally investigated at terahertz frequencies. The symmetry-protected bound states in the continuum (BICs) are activated by adjusting one arm's length of the H-shaped, enabling high-Q quasi-BICs. The Q-factor of quasi-BICs is modulated in terms of structural parameters and metal conductivity. With optimal structural parameters of copper HSAs, the proximity sensing performances are studied as a function of the film thickness and the refractive index. High sensitivity of 151 GHz/RIU and FOM of 18.7 are obtained, respectively, which are high compared with the previous metamaterials with planar substrates. In addition, the HSAs are even sensitive to the ultrathin graphene film. These findings indicate that such HSAs-based sensor has great potential for practical applications in chemical and biomolecular fields.
Simultaneously high quality-factor (Q) and transmission (T) are highly desired in various optical, photonic, and optoelectronic applications such as filters, sensors, photodetectors and lasers. However, a trade-off between high Q and high T exists widely in optical systems thanks to the different physics triggers underneath. Here, as an example, we experimentally demonstrate a Bragg filter composed of niobium pentoxide (Nb2O5) and silica (SiO2) stacks which enable high Q of 183 and high T of 91.3%. Balancing dissipation and radiation rate of the optical system is crucial to the performance of the device, which is validated by modulating the absorption of material (Nb2O5) and the number of stacks. Further, with the principle the tunable Bragg filter is able to work in a similar way at optical wavelengths, i.e., maintaining almost unchanged FWHM (full width at halfmaximum) and T values. We believe our work offers an efficient strategy for achieving high Q and T optical systems to meet diversified application requests.
High-speed optical communication systems are built for real-time, massive, and remote information exchange; however, it is strongly reliant on the applied power. Herein, we developed a self-driven optical communication system based on a high-performance graphene/n-Si (Gr/n-Si) hybrid photodetector. Under zero bias, the Gr/n-Si device presents good performance at a wavelength of 520 nm, including the photoresponsivity of 0.27 A W−1, specific detectivity of 9.39 × 1011 Jones, and on/off ratio of 104 with a rise and fall time of 128 and 131 ns, respectively. This hybrid device also exhibits 3 dB bandwidth of 2.18 MHz as well as a small noise equivalent power of 1.68 × 10−17 W Hz−1/2. Furthermore, an optical communication system was constructed based on this hybrid photodetector, through which the audio and text signals were steadily and accurately transmitted under zero bias. Our work lays a solid foundation to demonstrate a promising application of Gr/n-Si hybrid devices toward self-driven optical communications.
In this study, a terahertz composite slab (TCS) based on metal grating and dielectric films is experimentally and numerically investigated in the terahertz region. By combining a dielectric film, the TCS exhibits different sharp resonances for varied polarization waves. A sharp Fano resonance is excited for transverse magnetic (TM) waves, which originates from the introduced asymmetric factor by dielectric films. The film thickness and refractive index can be used for the Fano resonance tuning. The resonant Q-factor can be improved using thinner and lower refractive index films. For transverse electric (TE) modes, a resonance termed guided modes can also be induced when the dielectric film is thick enough. The effects of film thickness and refractive index on these resonances are analyzed in detail. These results demonstrated that this TCS with high Q-factors or narrow resonances for both TM and TE waves is a promising component for THz filter and sensor applications.
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