In order to greatly promote impressive applications in terahertz (THz) photonics, research on active optoelectronic THz devices with high performance such as modulators is still a vital work. Electrically controlled THz modulators with a large modulation depth and wide modulation bandwidth are urgently needed for THz technology. Herein, a bismuth (Bi) nanofilm is rationally designed as an electrically controlled THz modulator combining the advantages of high electron mobility and near zero bandgap. The Bi nanofilm devices are produced by the magnetron sputtering deposition method, and the maximum modulation depth reaches 70% in the transmission spectrum. We have demonstrated an electrically tunable Bi nanofilm of modulating THz waves dynamically. Moreover, the Bi nanofilm modulator exhibits broadband modulation performance within a wide frequency range from 0.1 to 1.1 THz. Taking advantage of the excellent modulation property and simple approach to design, semimetal based devices are promising components for the development of high performance THz applications.

Due to the low photon energy in the relevant frequency band, fewer materials can directly excite carriers, and an extreme lack of high‐performance, large‐area detectors, limit the promotion, and development of 6G technology. In addition, flexible detectors with the integration of 6G communication and Internet of Things technology has good prospects for application in the development of optoelectronic devices, which are also urgently needed. A large‐area flexible thin layer terahertz detector is designed that combines the advantages of excellent optoelectronic performance in the detection of electromagnetic waves with low photon energy and the localized surface plasmon (LSP) effect in a sub‐wavelength structure detector. Due to the large effective area, the spiral electrode device demonstrates the best performance at room temperature. The noise equivalent power (NEP) and photoresponsivity (R_V) are achieved with 0.4 pW Hz^−1/2 and 154 MV W⁻¹ at 0.28 THz. In addition, the bending experiments show that the device has extreme advantages for flexible 6G detector applications.

The next generation of communication 6G technology in the terahertz band is crucial for the development of the future high-speed information society. How to achieve a highly sensitive response to low power density terahertz signals at room temperature has been one of the frontier research hot issues within this field. In addition, the reproducible line height of the device and its availability for mass production are also urgent issues to be addressed. Here, We have proposed a 6G detector based on combining the advantages of sub-wavelength micro-structures, 3D micro-cavity, and Weyl-semimetallic films. The localized surface plasmon (LSP) effect by the micro-stud array is used for the enhancement of the light-matter interaction. Also, the 3D structure leads to a micro-cavity allowing for a near enhancement of the interaction on a small scale. Furthermore, the 0-band gap of the Weyl-semimetal and the enhanced response to low-energy photon displacement currents near makes the Weyl-semimetal more suitable for detecting terahertz waves. In addition, the use of projection micro stereolithography 3D print technology combined with magnetron sputtering of thin films makes this terahertz detection technology solution reproducible, low cost, simple processing, and promising for industrial production, contributing to the development and diffusion of 6G technology.

Planar waveguide devices based on silicon-on-sapphire are emerging as a bridge between mid-infrared (IR) and near-IR wavelength through frequency conversion process. We analyze the limits of indirect detection of mid-IR signals by wavelength conversion in such waveguides and investigate signal-to-noise ratio improvement that is attainable with respect to direct detection using state of the art commercial detectors. Our calculation shows that, in addition to room temperature and high speed operation, the proposed indirect detection can improve the electrical signal-to-noise ratio up to 40 dB compared to direct detection by PbSe, HgCdTe, and InSb detectors, especially in detection of weak mid-IR signals.

Based on femtosecond laser ablated processing, one-dimensional arrays with different line spacings were fabricated on titanium disulfide (TiS2) nanosheet. Optical modulated measurements with these devices were demonstrated. Photo-induced complex conductivity changes of the TiS2 nanosheet devices were studied by an optical-pump THz-probe (OPTP) measurement system. For the 700 μm line spacing device, the optically introduced modulation depth (MD) reached up to 70%. Our experimental results have demonstrated the ultrafast dynamics and photoconductivity for the TiS2 nanosheet devices in the THz frequency range. TiS2 nanosheet based devices would be suitable as the photoelectric modulators of THz wave.

Instead of utilizing commercial detectors and a detection scheme based on 2D layer semiconductors or surface plasmon enhancement effect, we have developed a novel THz detector consisting of an array of microgrooves. This device combines the exceptional performance of materials with the localized surface plasmon (LSPs) effect in a sub-wavelength structure electromagnetic induced well detector. At room temperature, our device achieves a detectivity (D*) of 6.3×10 ⁸ cm Hz ^1/2 pW ^-1 and a responsivity (Rv) of 3.31×10 ⁵ V W ^-1 at 0.1 THz, with a 20 μm line spacing array. Furthermore, the effective detection area of our device is 6.5 mm × 2 mm, making it much more suitable for practical applications. These high-performance THz wave photodetectors open up possibilities for the effective detection of THz waves, which have wide-ranging applications in areas such as high-capacity communications, THz radar, biological diagnosis, and THz detection.