Abstract-Broadband THz to NIR up-converter for photon-type THz imaging

Peng Bai, Yueheng Zhang, Tianmeng Wang, Zhanglong Fu, Dixiang Shao, Ziping Li, Wenjian Wan, Hua Li, Juncheng Cao, Xuguang Guo,  Wenzhong Shen

https://www.nature.com/articles/s41467-019-11465-6

High performance terahertz imaging devices have drawn wide attention due to their significant application in healthcare, security of food and medicine, and nondestructive inspection, as well as national security applications. Here we demonstrate a broadband terahertz photon-type up-conversion imaging device, operating around the liquid helium temperature, based on the gallium arsenide homojunction interfacial workfunction internal photoemission (HIWIP)-detector-LED up-converter and silicon CCD. Such an imaging device achieves broadband response in 4.2–20 THz and can absorb the normal incident light. The peak responsivity is 0.5 AW−1. The light emitting diode leads to a 72.5% external quantum efficiency improvement compared with the one widely used in conventional up-conversion devices. A peak up-conversion efficiency of 1.14 × 10−2 is realized and the optimal noise equivalent power is 29.1 pWHz−1/2. The up-conversion imaging for a 1000 K blackbody pin-hole is demonstrated. This work provides a different imaging scheme in the terahertz band.

Abstract-Surface-phonon-polariton-mediated photon response of terahertz quantum-well infrared photodetectors

DiXiang Shao, XuGuang Guo, YiMing Zhu, SongLin Zhuang, ZhangLong Fu,  JunCheng Cao

http://iopscience.iop.org/article/10.1088/1361-6463/aaeb77/meta

A surface-phonon-polariton (SPHP)-mediated photon response near the longitudinal optical (LO) phonon frequency of GaAs is investigated in a terahertz GaAs/AlGaAs quantum-well infrared photodetector, integrated with a one-dimensional metal grating. For a contrast device without a grating coupler, no SPHP-related signature is found in the photocurrent spectrum, because the incident radiation from free space cannot excite the SPHP, due to the mismatch of momentum. The intensity of the electric field component along the growth direction of the device absorption layer is numerically calculated. The results show that the photocurrent response peaks near the LO phonon frequency band (8.8–9.0 THz) are attributed to the local field enhancement induced by SPHP. Our results are useful to realize high performance SPHP-mediated terahertz photodetectors and other related terahertz devices.

Abstract-Multicolor T‐Ray Imaging Using Multispectral Metamaterials

Zhitao Zhou  Tao Zhou  Shaoqing Zhang  Zhifeng Shi  Ying Chen  Wenjian Wan  Xinxin Li Xinzhong Chen  Stephanie N. Gilbert Corder  Zhanglong Fu  Liang Chen  Ying Mao  Juncheng Cao Fiorenzo G. Omenetto  Mengkun Liu  Hua Li,  Tiger H. Tao,

https://onlinelibrary.wiley.com/doi/abs/10.1002/advs.201700982

Recent progress in ultrafast spectroscopy and semiconductor technology is enabling unique applications in screening, detection, and diagnostics in the Terahertz (T‐ray) regime. The promise of efficaciously operation in this spectral region is tempered by the lack of devices that can spectrally analyze samples at sufficient temporal and spatial resolution. Real‐time, multispectral T‐ray (Mul‐T) imaging is reported by designing and demonstrating hyperspectral metamaterial focal plane array (MM‐FPA) interfaces allowing multiband (and individually tunable) responses without compromising on the pixel size. These MM‐FPAs are fully compatible with existing microfabrication technologies and have low noise when operating in the ambient environment. When tested with a set of frequency switchable quantum cascade lasers (QCLs) for multicolor illumination, both MM‐FPAs and QCLs can be tuned to operate at multiple discrete THz frequencies to match analyte “fingerprints.” Versatile imaging capabilities are presented, including unambiguous identification of concealed substances with intrinsic and/or human‐engineered THz characteristics as well as effective diagnosis of cancerous tissues without notable spectral signatures in the THz range, underscoring the utility of applying multispectral approaches in this compelling wavelength range for sensing/identification and medical imaging.

Abstract-Multicolor T‐Ray Imaging Using Multispectral Metamaterials

Zhitao Zhou, Tao Zhou, Shaoqing Zhang, Zhifeng Shi, Ying Chen, Wenjian Wan, Xinxin Li, Xinzhong Chen, Stephanie N. Gilbert Corder, Zhanglong Fu, Liang Chen, Ying Mao, Juncheng Cao, Fiorenzo G. Omenetto, Mengkun Liu, Hua Li, Tiger H. Tao,


https://onlinelibrary.wiley.com/doi/full/10.1002/advs.201700982

Recent progress in ultrafast spectroscopy and semiconductor technology is enabling unique applications in screening, detection, and diagnostics in the Terahertz (T‐ray) regime. The promise of efficaciously operation in this spectral region is tempered by the lack of devices that can spectrally analyze samples at sufficient temporal and spatial resolution. Real‐time, multispectral T‐ray (Mul‐T) imaging is reported by designing and demonstrating hyperspectral metamaterial focal plane array (MM‐FPA) interfaces allowing multiband (and individually tunable) responses without compromising on the pixel size. These MM‐FPAs are fully compatible with existing microfabrication technologies and have low noise when operating in the ambient environment. When tested with a set of frequency switchable quantum cascade lasers (QCLs) for multicolor illumination, both MM‐FPAs and QCLs can be tuned to operate at multiple discrete THz frequencies to match analyte “fingerprints.” Versatile imaging capabilities are presented, including unambiguous identification of concealed substances with intrinsic and/or human‐engineered THz characteristics as well as effective diagnosis of cancerous tissues without notable spectral signatures in the THz range, underscoring the utility of applying multispectral approaches in this compelling wavelength range for sensing/identification and medical imaging.

Abstract-Two-colour THz quantum well photodetectors

 Haixia Wang,  Rong Zhang, Feng Wang, Zhejing Jiao, Dixiang Shao,   Zhanglong Fu, Tao Zhou,  Zhiyong Tan, Jungcheng Cao.

http://ieeexplore.ieee.org/document/8011679/

Two-colour terahertz (THz) quantum-well photodetectors are designed, fabricated, and characterised. To realise two-colour detection, a stacked structure is adopted by sequentially growing two one-colour detectors. It is found that the spectra of the stacked device are in accordance with those of the two individual detectors connected in series. The relatively broad spectral bandwidth may enable its use in a THz spectrometer