Broadband Anisotropy in Terahertz Metamaterial With Single-Layer Gap Ring Array

Triple-Band and Ultra-Broadband Switchable Terahertz Meta-Material Absorbers Based on the Hybrid Structures of Vanadium Dioxide and Metallic Patterned Resonators

A bifunctional terahertz meta-material absorber with three layers is designed. The surface of the bifunctional meta-material absorber is a periodically patterned array composed of hybrid structures of vanadium dioxide (VO₂) and metallic resonators; the middle layer is a nondestructive TOPAS film, and the bottom layer is a continuous metallic plane. Utilizing the phase-transition property of VO₂, the responses of the meta-material absorber could be dynamically switched between triple-band absorption and ultra-broadband absorption. When VO₂ is in the metallic state, an ultra-broadband absorption covering the bandwidth of 6.62 THz is achieved over the range from 4.71 THz to 11.33 THz. When VO₂ is in the di-electric state, three absorption peaks resonated at 10.57 THz, 12.68 THz, and 13.91 THz. The physical mechanisms of the bifunctional meta-material absorber were explored by analyzing their near-field distributions. The effects of varying structural parameters on triple-band and ultra-broadband absorption were investigated. It is revealed that by optimizing the structure parameters, the number of absorption peaks could be increased for a certain sacrifice of absorption bandwidth. FDTD Solutions and CST Microwave Studio were used to simulate the data of the absorber, and similar results were obtained.

Flexible Terahertz Metamaterial Biosensor for Ultra-Sensitive Detection of Hepatitis B Viral DNA Based on the Metal-Enhanced Sandwich Assay

The high sensitivity and specificity of terahertz (THz) biosensing are both promising and challenging in DNA sample detection. This study produced and refined a flexible THz MM biosensor for ultrasensitive detection of HBV in clinical serum samples based on a gold magnetic nanoparticle-mediated rolling circle amplification (GMNPs@RCA) sandwich assay under isothermal conditions. Typically, solid-phase RCA reactions mediated by circular padlock probes (PLPs) are triggered under isothermal conditions in the presence of HBV DNA, resulting in long single-stranded DNA (ssDNA) with high fidelity and specificity. Then, the resultant ssDNA was conjugated with detection probes (DPs) immobilized on gold nanoparticles (DP@AuNPs) to form GMNPs-RCA-AuNPs sandwich complexes. The HBV DNA concentrations were quantified by introducing GMNPs-RCA-AuNPs complexes into the metasurface of a flexible THz metamaterial-based biosensor chip and resulting in a red shift of the resonance peak of the THz metamaterials. This biosensor can lead to highly specific and sensitive detection with one-base mismatch discrimination and a limit of detection (LOD) down to 1.27E + 02 IU/ml of HBV DNA from clinical serum samples. The HBV DNA concentration was linearly correlated with the frequency shift of the THz metamaterials within the range of 1.27E + 02∼1.27E + 07 IU/ml, illustrating the applicability and accuracy of our assay in real clinical samples. This strategy constitutes a promising THz sensing method to identify virus DNA. In the future, it is hoped it can assist with pathogen identification and clinical diagnosis.

Reconfigurable terahertz switch using flexible L-shaped metamaterial

The design of a reconfigurable terahertz (THz) switch by using flexible L-shaped metamaterial (FLM), which is composed of dual-layer L-shaped metamaterials on polydimethylsiloxane substrate, which has three resonances at 0.57, 1.05, and 1.52 THz, is presented. By stretching the FLM along the x-axis direction, the transmission intensity is increased gradually at the transverse electric mode (TE) and reduced at the transverse magnetic (TM) mode, respectively. Reversely, by stretching the FLM along the y-axis direction, the transmission intensity is reduced gradually at the TE mode and increased at the TM mode, respectively. These electromagnetic responses of FLM provide the optical-logic behaviors with programmable characteristics by stretching FLM at different polarized light. It indicates that the proposed FLM could be used for the dual/triple-band switching, polarization switching, and programmable switching applications.