Terahertz (THz) topological photonic structures are promising for last-centimeter communication in intra/interchip communication systems because they support bit-error-free THz signal transmission with topological robustness. Active and dynamically tunable THz topological photonic components have not yet been experimentally realized. Here, we experimentally demonstrate a THz topological switch (270–290 GHz) based on a valley Hall photonic crystal structured high-resistivity silicon substrate, in which the THz waves can be dynamically turned on/off by an external 447 nm continuous-wave laser. Our device exhibited an on/off ratio of 19 dB under a pumping light intensity of 240 mW / mm 2 . The 3 dB switching bandwidth was ∼ 60 kHz .

Terahertz has significant potential applications in biosensing, but its detection sensitivity still needs to be improved. Metamaterials can effectively improve terahertz sensing sensitivity due to their field-enhancing properties. In this work, we designed and fabricated a double-open hexagonal ring metamaterial with a high refractive index sensitivity of 430 GHz/RIU. The resonant properties of metamaterials were demonstrated by both simulations and experiments. The sensing performance were tested with different concentrations of glucose and bovine serum protein solutions. The results showed that the sensitivity of the metamaterial to glucose and bovine serum protein solution reached 0.37 GHz/(mg/dL) and 36.44 GHz/(mg/mL), respectively, while the detection limits of glucose and bovine serum protein solution reached 9.867 mg/dL and 0.16 mg/mL, respectively. The proposed metamaterial sensor has potential application scenarios in the terahertz biomedical field.

Terahertz (THz) technology has seen significant advancements in the past decades, encompassing both fundamental scientific research, such as THz quantum optics, and highly applied areas like sixth-generation communications, medical imaging, and biosensing. However, the progress of on-chip THz integrated waveguides still lags behind that of THz sources and detectors. This is attributed to issues such as ohmic losses in microstrip lines, coplanar and hollow waveguides, bulky footprints, and reflection and scattering losses occurring at sharp bends or defects in conventional dielectric waveguides. Inspired by the quantum Hall effects and topological insulators in condensed matter systems, recent discoveries of topological phases of light have led to the development of topological waveguides. These waveguides exhibit remarkable phenomena, such as robust unidirectional propagation and reflectionless behavior against impurities or defects. As a result, they hold tremendous promise for THz on-chip applications. While THz photonic topological insulators (PTIs), including wave division, multiport couplers, and resonant cavities, have been demonstrated to cover a wavelength range of 800–2500 nm, research on tunable THz PTIs remains limited. In this perspective, we briefly reviewed a few examples of tunable PTIs, primarily concentrated in the infrared range. Furthermore, we proposed how these designs could benefit the development of THz on-chip PTIs. We explore the potential methods for achieving tunable THz PTIs through optical, electrical, and thermal means. Additionally, we present a design of THz PTIs for potential on-chip sensing applications. To support our speculation, several simulations were performed, providing valuable insights for future THz on-chip PTI designs.

Highly sensitive terahertz (THz) sensing with metasurfaces has attracted considerable attention recently. However, ultrahigh sensing sensitivity remains a huge challenge for practical applications. To improve the sensitivity of these devices, herein we have proposed an out-of-plane metasurface-assisted THz sensor consisting of periodically arranged bar-like meta-atoms. Benefiting from elaborate out-of-plane structures, the proposed THz sensor with high sensing sensitivity of 325 GHz/RIU can be easily fabricated via a simple three-step fabrication process, and the maximum sensing sensitivity can be ascribed to toroidal dipole resonance-enhanced THz-matter interactions. The sensing ability of the fabricated sensor is experimentally characterized by the detection of three types of analytes. It is believed that the proposed THz sensor with ultrahigh sensing sensitivity and its fabrication method might provide great potential in emerging THz sensing applications.

We measured crystalline (C-form) saturated fatty acids with even carbon numbers ranging from 12 to 20 using temperature dependent terahertz time-domain spectroscopy (THz-TDS). Absorption features between 0.5 and 3 THz were identified at temperatures from 96 K to 293 K, and a systematic red-shift was obvserved with the increasing carbon chain length. The origins of these absorption bands were uncovered using state-of-the-art ab initio density functional theory (DFT) calculations. Similar vibrational motions in the absorption bands of the different materials highlight the unique role that THz-TDS has for probing weak non-covalent interactions in these materials. Our results showcase the utility of the terahertz region, which is beyond the scope of related vibrational techniques, providing direct evidence of the effect of chain length on the intermolecular interactions of these molecules.

C-coated SiC nanocomposites (SiC@C NCs) were one-step synthesized under a mixture atmosphere of Ar and CH ₄ using a DC arc-discharge plasma method. The microstructure of the composites could be controlled by varying the volume ratio of Ar and CH ₄ . A strong response to the terahertz (THz) field was observed due to the existence of a graphite shell. The dielectric properties of SiC@C NCs can be enhanced by altering the thickness of the graphite shell. The thicker graphite shell results in a stronger absorption of THz waves and an enhanced real part of conductivity. Fitting the measured conductivity data using the Drude–Smith model reveals that the carrier transport in the SiC@C NCs and its counterpart, the SiC nanoparticles, is dominated by backscattering. The SiC@C NCs with enhanced conductivity are believed to be fundamental materials for various functionalized optoelectronic devices.