We demonstrate an electrically tunable superconducting metamaterial capable of modulating terahertz waves dynamically. The device is based on electromagnetically induced transparency-like metamaterials, and the maximum modulation depth reaches 79.8% in the transmission window. Controlled by an electrical sinusoidal signal, such a device could achieve a modulation speed of approximately 1 MHz. The superior property and simplicity of design make this device promising for the development of high performance THz systems.

Fabricating resonant cavities with conventional methods to improve the coupling efficiency of a detector in the terahertz (THz) region is difficult for the wavelength is too long. Here, we propose a solution by using the substrate cavity effect given that the substrate wavelength and thickness of the preparation device are in the same order. The planar dipole antenna-coupled NbN microbolometers with different substrate thicknesses were fabricated. The interference effect of the substrate cavity on the optical voltage response of the detector is analyzed experimentally and theoretically. The experimental results show that the optical response of the detector is determined by the length of the substrate cavity. Thus, the THz devices with different detection frequencies can be designed by changing the substrate cavity length. Furthermore, on the basis of this substrate cavity effect, an asymmetric coupled Fabry-Pérot (FP) cavity is constituted by simply placing a movable metallic planar mirror at the backside of the Si substrate. The incident THz radiation on the NbN microbolometer can be effectively manipulated by changing the substrate-mirror distance to modulate the phase relation between the reflect wave and the incident wave. The distinct radiation control can be observed, and the experiments can be well explained by numerically analyzing the responsivity dynamics that highlights the role of the FP cavity effect during radiation. All of the results discussed here can be extended to a broad range of frequency and other type of THz detectors.

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Room-temperature thermal detection at a wavelength of 2 µm in the short-wave infrared range (1.7-3 µm) was demonstrated for the first time using a NbN microbolometer. The photothermal responses of two types of NbN microbolometers were evaluated. By suspending NbN microwires in the air above the substrate, a reduction in thermal conductance of the device by a factor of 39 was achieved. The measured optical voltage responsivity R of the NbN microbolometer reached the value of 61.5 V/W. A noise equivalent power of 8.5 × 10 W/√Hz (at 1 kHz) and a detectivity D* = 2.0 × 10 cm√Hz /W with a typical response time as small as 0.17 ms was obtained at a wavelength of 2 µm for a 10 × 30-µm device. The performance could be improved further by optimizing the design and operating parameters. This study revealed a simple low-cost technique to develop a large-scale focal plane array in silicon for infrared detection.

We present an electrically tunable superconducting metamaterial capable of modulating terahertz (THz) waves. The device consists of two concentric ring resonators, which exhibits the electromagnetically induced transparency-like spectral response. A relatively high modulation depth of 86.8% and a group delay of 25.4 ps were achieved at the transmission window. The experimental and simulated transmission spectra show good agreement. The hybrid coupling model could well explain the physical mechanism. The tuning of group delay of THz waves is of great significance to the applications of THz technology.