Abstract-Significant enhancement of THz detectivity by lowering ZnTe crystal temperature in electro-optic sampling

Xuewei Ju, Deren Chen, Xingchen Chen, Tao Gao, Ying Chen, Jie Wang, Xiangfeng Wang



https://www.sciencedirect.com/science/article/pii/S0925346719301831

The temperature of the ZnTe detection crystal in a THz time-domain system was tuned continuously from 300 K to 1.5 K to minimize phonon absorption, thus enhance its detectivity. The THz peak amplitude was observed to increase more than 10 times. To explain this phenomenon, the THz transmission spectra of the ZnTe crystal at different temperatures were also measured, and the refractive indexand absorption coefficient of the crystal were extracted. The experiments and theoretic analysis reveal that the significant detectivity enhancement is due to the reduced absorption of the THz field and phase matching change in the detection crystal with temperature decreasing, which makes the ZnTe crystal suitable for integrating with cryogenic applications.

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-Free-standing double-layer terahertz band-pass filters fabricated by femtosecond laser micro-machining

Yanzhang Lin, Haizi Yao, Xuewei Ju, Ying Chen, Shuncong Zhong, and Xiangfeng Wang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-21-25125

We report on the fabrication and transmission properties of free-standing single-layer and double-layer THz bandpass filters. These filters are fabricated on aluminum foils using femtosecond laser micro-machining. The aluminum foils are periodically patterned with cross apertures with a total area of 1.75×1.75 cm2, also known as frequency-selective surfaces. Their terahertz transmission properties were simulated using the FDTD method and measured using a time-domain terahertz spectroscopy system. The simulation results agree with the measurements results very well. The performance of single-layer bandpass filters is as good as the commercial equivalents on the market. The double-layer filters show extraordinary transmission peaks with changing spacing between the two layers. We show the contour map of the electric field distribution across the apertures, and ascribe the new transmission peaks to the interference and coupling of surface plasmon polaritons between the two layers.

© 2017 Optical Society of America

Abstract-Multiple resonant excitations of surface plasmons in a graphene stratified slab by Otto configuration and their independent tuning

Jin Yao, Ying Chen, Longfang Ye, Na Liu, Guoxiong Cai, and Qing Huo Liu

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-5-4-377&origin=search

Multiple resonant excitations of surface plasmons in a graphene stratified slab are realized by Otto configuration at terahertz frequencies. The proposed graphene stratified slab consists of alternating dielectric layers and graphene sheets, and is sandwiched between a prism and another semi-infinite medium. Optical response and field distribution are determined by the transfer matrix method with the surface current density boundary condition. Multiple resonant excitations appear on the angular reflection spectrum, and are analyzed theoretically via the phase-matching condition. Furthermore, the effects of the system parameters are investigated. Among them, the Fermi levels can tune the corresponding resonances independently. The proposed concept can be engineered for promising applications, including angular selective or multiplex filters, multiple channel sensors, and directional delivery of energy.

© 2017 Chinese Laser Press