Active Tuning of a THz Nano Petal-Shaped Sensor Integrated on a Chip

The existing terahertz (THz) technology uses THz metasurface to design THz waves. In order to produce surface plasmon polaritons (SPP) effect and local surface plasma plasmon (LSP) effect on THz band, there are obvious defects, such as large area, high loss, slow tuning speed, and insensitivity to laser irradiation. To address these limitations, an external field is employed to modulate the designed optical metasurface, exhibiting a strong response to the infrared laser spectrum, and then, the altered carrier concentration and dielectric constant of the material directly influence the performance of the THz devices. This approach results in a substantial increase in the modulation amplitude of responsivity (<inline-formula> <tex-math notation="LaTeX">${R}_{A}$ </tex-math></inline-formula>) and noise equivalent power (NEP). Based on this principle, we propose a petal-shaped, ultrafast, low-loss, all-dielectric optical metasurface THz sensor. The THz irradiated device generates the carriers, traveling to the external circuit, forming a THz current. The laser acts directly on the metasurface to actively modulate the device. Notably, the designed sub wavelength configuration creates a cross-resonator, which induces a local field enhancement effect, leading to a significant increase in optical absorption efficiency and a large modulation amplitude. Experimental results demonstrate that the maximum modulation amplitude of <inline-formula> <tex-math notation="LaTeX">${R}_{A}$ </tex-math></inline-formula> can reach 50% at a wavelength of 633 nm, while the maximum modulation amplitude of NEP can achieve 74% at a wavelength of 532 nm. Moreover, compared to traditional THz-modulated sensors, the laser-modulated THz sensor exhibits ultrahigh-speed characteristics. Due to its rapid tunability, large modulation amplitude, and straightforward fabrication process, this THz sensor is expected to have wide-ranging applications.