Abstract-Design of double-slot antennas for terahertz array detectors in flip chip packaging

Peng Xiao, Xuecou Tu, Lin Kang, Zhenjie Li, Pengfei Chen, Shuyu Zhou, Xiaoqing Jia, Jian Chen, and Peiheng Wu

 (a) Unit cell of the double-slot antennas designed for THz array detectors. (b) Results of E at the center (x=125 µm, y=125 µm, z=350 µm) of the antenna for different values of W1. (c) Distribution of E on the cross-section of the model in a periodic unit cell at 0.6255 THz.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-6-8783

In flip chip packaging, the performance of terahertz (THz) array detectors is directly influenced by the flip chip. In addition, predicting this effect is difficult because the readout circuits in the flip chip are very complex. In this study, to reduce the influence of the flip chip, we design a new type of double-slot antennas for THz array detectors. For comparison, we designed and analyzed dipole antennas with the same period. Numerical simulations showed that the coupling efficiency of the double-slot array antennas at approximately 0.6255 THz does not degrade, if the flip chip structure is changed. However, in the case of dipole array antennas with the same period of 250 µm, coupling efficiency was severely affected by the flip chip structure. These results revealed that double-slot antennas are more applicable to THz array detectors compared with dipole antennas, as they can more effectively reduce the influence of the flip chip. Furthermore, we integrated the double-slot antennas into Nb5N6 THz array detectors using the micro-fabrication technology. Measurement results indicated that double-slot antennas possess the advantages of facile preparation and large-scale integration, which provide great potential for THz array detectors in flip chip packaging.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Low-Noise Readout Integrated Circuit for Terahertz Array Detector

 Zhou Jiang,  Liang Men,  Chao Wan,  Peng Xiao.  Chengtao Jiang, Xuecou Tu, Xiaoqing Jia,   Lin Kang,  Lianming Li,  Jian Chen , Peiheng Wu


https://ieeexplore.ieee.org/document/8340872/

In the field of terahertz (THz) imaging applications, using a 0.18-μm CMOS process, a 1 × 16 low-noise readout integrated circuit (ROIC) is developed for a 1 × 64 Nb 5 N 6 microbolometer array detector. This circuit consists of a digitally programmable current digital-to-analog converter and an amplifier module, which are responsible for biasing the microbolometer and amplifying its output signals with minimum added noise, respectively. Test results show that the ROIC achieves an average gain of ~47 dB and a voltage noise spectral density of ~9.34 nV/√Hz at 10 kHz, which meet the requirements for the THz array detector. Moreover, the responsivity of the Nb 5 N 6 microbolometer detector is -580 V/W, and the corresponding noise equivalent power is 17 pW/√Hz. Together with the ROIC, the 1 × 64 Nb 5 N 6 microbolometer array detector is preliminarily used for THz imaging applications. The imaging results prove that the ROIC can be used with the detector to develop an efficient and low-cost THz imaging system.

Abstract-Reflective grating-coupled structure improves the detection efficiency of THz array detectors

Peng Xiao, Xuecou Tu, Lin Kang, Chengtao Jiang, Shimin Zhai, Zhou Jiang, Danfeng Pan, Jian Chen, Xiaoqing Jia, Peiheng Wu

https://www.nature.com/articles/s41598-018-26204-y

A reflective grating-coupled structure on the silicon substrate was designed to improve the detection efficiency of terahertz detectors for the frequency ranging from 0.26 THz to 0.36 THz. By using finite difference time domain (FDTD) solutions, the simulation and optimized design of the grating-coupled structure were carried out. The results showed that the signal was effectively reflected and diffracted by the reflective grating-coupled structure which significantly enhanced the electric field in the place of the detector. The maximum electric field can be increased by 2.8 times than that of the Fabry-Perot resonator. To verify the design results, the reflective grating-coupled structure was applied in the preparation of the Nb5N6 array detector chip and compared with the Nb5N6 array detector chip with the F-P resonator. The results showed that the maximum voltage responsivity of the Nb5N6 detector with the reflective grating-coupled structure was 2 times larger than the Nb5N6 detector with the F-P resonator. It indicates that the reflective grating-coupled structure can efficiently improve the detection efficiency of THz detectors.

Abstract-Investigation of antenna-coupled Nb5N6 microbolometer THz detector with substrate resonant cavity

Xuecou Tu, Chengtao Jiang, Peng Xiao, Lin Kang, Shimin Zhai, Zhou Jiang, Run Feng Su, Xiaoqing Jia, Labao Zhang, Jian Chen, and Peiheng Wu

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-7-8990

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 Nb5N6 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 Nb5N6 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.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-The design of Nb5N6 microbolometer detector for 0.3 THz detector

Chengtao Jiang; Xuecou Tu,  Peng Xiao,  Shimin Zhai,  Xiaoqing Jia,  Lin Kang, Jian Chen,  Peiheng Wu

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10531/1053123/The-design-of-Nbsub5-subNsub6-sub-microbolometer-detector-for-03/10.1117/12.2292539.short

We design and simulate planar antenna structure on the high- resistivity silicon substrate(ρ=1000Ω·cm) for the Nb5N6 micro- bolometer at the frequency range from 0.265 THz to 0.365 THz by CST Studio Suite. We have obtained the center frequency of the antenna at 0.3 THz by optimizing parameters of the antenna structure and the antenna has the very good radiation directivity. And the maximum directivity of the antenna is around 8.634 dBi at 0.3THz. The measured best voltage response of the Nb₅N₆ micro-bolometer detector is at 0.307 THz. The measured response frequency and the simulated S-parameter are in substantial agreement.

© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Abstract-Terahertz superconducting metamaterials for magnetic tunability

Dongyang Wang1, Zhen Tian1, Caihong Zhang2, Xiaoqing Jia2, Biaobing Jin2, Jianqiang Gu1, Jiaguang Han1 and Weili Zhang1,3

http://iopscience.iop.org/2040-8986/16/9/094013

jiaghan@tju.edu.cn weili.zhang@okstate.edu

1 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology, Tianjin 300072, People's Republic of China
2 Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, People's Republic of China
3 School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA 

We present the magnetic tunability of a metamaterial made from superconducting niobium nitride film. The inductive-capacitive resonance excited by a normally incident terahertz wave was found to be continuously modulated through an external magnetic field at temperatures below the superconducting transition point. A giant resonance modulation was observed due to a strong magnetic effect, where the variation of the magnetic field alters the intrinsic conductivity of the superconducting film. The high sensitivity of the metamaterial allows us to observe the temperature-dependent magnetic effect, and the magnitude of resonance modulation decreases with increasing temperatures. This work demonstrates that a strong magnetic effect could be implemented as an active control modality in superconducting integrated devices functioning at terahertz frequencies