Abstract-Ultrabroadband photosensitivity from visible to terahertz at room temperature

Dong Wu, Yongchang Ma, Yingying Niu, Qiaomei Liu, Tao Dong, Sijie Zhang, Jiasen Niu, Huibin Zhou, Jian Wei,Yingxin Wang, Ziran Zhao,  Nanlin Wang,

http://advances.sciencemag.org/content/4/8/eaao3057

Charge density wave (CDW) is one of the most fundamental quantum phenomena in solids. Different from ordinary metals in which only single-particle excitations exist, CDW also has collective excitations and can carry electric current in a collective fashion. Manipulating this collective condensation for applications has long been a goal in the condensed matter and materials community. We show that the CDW system of 1T-TaS2 is highly sensitive to light directly from visible down to terahertz, with current responsivities on the order of ~1 AW−1 at room temperature. Our findings open a new avenue for realizing uncooled, ultrabroadband, and sensitive photoelectronics continuously down to the terahertz spectral range.

Abstract-Uncooled EuSbTe3 photodetector highly sensitive from ultraviolet to terahertz frequencies

Biao Wang, Dong Wu, Hai Zhu, Huibin Zhou, Jian Wei, Nan Lin Wang, Jiasen Niu, Ping Zheng, Yingxin Wang, Yingying Niu, Yu Quan Su, Ziran Zhao

http://iopscience.iop.org/article/10.1088/2053-1583/aa939c/pdf

Light probe from Uv to THz is critical in photoelectronics and has great applications ranging from imaging, communication to medicine. However, the room temperature ultrabroadband photodetection across visible down to far-infrared is still challenging. The challenging arises mainly from the lack of suitable photoactive materials. Because that conventional semiconductors, such as silicon, have their photosensitive properties cut off by the bandgap and are transparent to spectrum at long-wavelength infrared side. Comparatively, the dielectrics with very narrow band-gap but maintain the semiconductor-like electrical conduction would have priorities for ultrabroadband photodetection. Here we report on EuSbTe3 is highly sensitive from ultraviolet directly to terahertz (THz) at room temperature. High photoresponsivities 1 ~ 8 A W-1 reached in our prototype EuSbTe3 detectors with low noise equivalent power (NEP) recorded, for instances ~ 150 pW  Hz-1/2 (at λ = 532 nm) and ~0.6 nW  Hz-1/2 (at λ = 118.8 µm) respectively. Our results demonstrate a promising system with direct photosensitivity extending well into THz regime at room temperature, shed new light on exploring more sophisticated multi-band photoelectronics

Abstract-Continuous-terahertz-wave molecular imaging system for biomedical applications

Rui Zhang

Peking University, College of Engineering, No. 8 YiHeYuan Road, Beijing 100871, China

Liangliang Zhang, Tong Wu, Cunlin Zhang

Capital Normal University, Department of Physics, No. 105 XiSanHuan BeiLu, Beijing 100048, China

Ruixue Wang, Shasha Zuo, Dong Wu

Peking University, Academy for Advanced Interdisciplinary Studies, No. 8 YiHeYuan Road, Beijing 100871, China

Jue Zhang, Jing Fang

Peking University, College of Engineering, No. 8 YiHeYuan Road, Beijing 100871, China

Peking University, Academy for Advanced Interdisciplinary Studies, No. 8 YiHeYuan Road, Beijing 100871, China

J. Biomed. Opt. 21(7), 076006 (Jul 12, 2016). doi:10.1117/1.JBO.21.7.076006

http://biomedicaloptics.spiedigitallibrary.org/article.aspx?articleid=2534363

Abstract.  Molecular imaging techniques are becoming increasingly important in biomedical research and potentially in clinical practice. We present a continuous-terahertz (THz)-wave molecular imaging system for biomedical applications, in which an infrared (IR) laser is integrated into a 0.2-THz reflection-mode continuous-THz-wave imaging system to induce surface plasmon polaritons on the nanoparticles and further improve the intensity of the reflected signal from the water around the nanoparticles. A strong and rapid increment of the reflected THz signal in the nanoparticle solution upon the IR laser irradiation is demonstrated, using either gold or silver nanoparticles. This low-cost, simple, and stable continuous-THz-wave molecular imaging system is suitable for miniaturization and practical imaging applications; in particular, it shows great promise for cancer diagnosis and nanoparticle drug-delivery monitoring.

Abstract-Energy scaling of terahertz-wave parametric sources

Energy scaling of terahertz-wave parametric sources Guanqi Tang, Zhenhua Cong, Zengguang Qin, Xingyu Zhang, Weitao Wang, Dong Wu, Ning Li, Qiang Fu, Qingming Lu, and Shaojun Zhang  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-23-4-4144

Optics Express, Vol. 23, Issue 4, pp. 4144-4152 (2015)
http://dx.doi.org/10.1364/OE.23.004144

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Terahertz-wave parametric oscillators (TPOs) have advantages of room temperature operation, wide tunable range, narrow line-width, good coherence. They have also disadvantage of small pulse energy. In this paper, several factors preventing TPOs from generating high-energy THz pulses and the corresponding solutions are analyzed. A scheme to generate high-energy THz pulses by using the combination of a TPO and a Stokes-pulse-injected terahertz-wave parametric generator (spi-TPG) is proposed and demonstrated. A TPO is used as a source to generate a seed pulse for the surface-emitted spi-TPG. The time delay between the pump and Stokes pulses is adjusted to guarantee they have good temporal overlap. The pump pulses have a large pulse energy and a large beam size. The Stokes beam is enlarged to make its size be larger than the pump beam size to have a large effective interaction volume. The experimental results show that the generated THz pulse energy from the spi-TPG is 1.8 times as large as that obtained from the TPO for the same pumping pulse energy density of 0.90 J/cm² and the same pumping beam size of 3.0 mm. When the pumping beam sizes are 5.0 and 7.0 mm, the enhancement times are 3.7 and 7.5, respectively. The spi-TPG here is similar to a difference frequency generator; it can also be used as a Stokes pulse amplifier.

© 2015 Optical Society of America