Abstract-Detection of Living Cervical Cancer Cells by Transient Terahertz Spectroscopy

Wei Shi, Yuezheng Wang, Lei Hou, Cheng Ma, Lei Yang, Chengang Dong, Zhiquan Wang, Haiqing Wang, Juan Guo, Shenglong Xu  Jing Li,

https://onlinelibrary.wiley.com/doi/abs/10.1002/jbio.202000237

The photonic energy of terahertz wave is in the same order of magnitude as the rotational and vibrational energy levels of organic and biological macro‐molecules, so it has unique advantages in detecting cells and biological macro‐molecules. However, in the life environment, the dynamic time scale of cell‐environment interaction and structural conformation change of biological macro‐molecules are within picosecond to millisecond, and water has strong absorption to terahertz wave, which has become the bottleneck problem for the detection of cells and biological macro‐molecules by terahertz technology. In this paper, we developed a set of terahertz single measurement system based on the tilt wave front of grating pulse technique. The system was employed for the terahertz detection of trace living cervical cancer cells. We achieved transient detection of the terahertz pulse time domain waveform of the living HeLa cells. The characteristic absorption peaks were identified by Lambert‐Beer law, respectively at 0.49 THz, 0.71 THz, 1.04 THz, 1.07 THz, 1.26 THz and1.37 THz. The absorbance is proportional to the cell concentration.

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Abstract-Investigation of aging characteristics in explosive using terahertz time-domain spectroscopy

Wei Shi, Chengang Dong, Lei Hou, Zhiyang Xing, Qian Sun,  Lihao Zhang

https://www.worldscientific.com/doi/abs/10.1142/S0217979219502722

The terahertz absorption spectrum of the five aging explosive samples (PETN, RDX, HMX, LLM-105 and TATB) was measured and calculated by Terahertz time-domain spectroscopy system (THz-TDS) and air-biased coherent detection system (ZAP-ABCD), respectively. In this paper, compared with the unaging explosive, each aging explosive sample’s terahertz time-domain spectra were obtained and the terahertz absorption spectra were calculated by using Fourier transform and Lambert’s law. The results show that there are several terahertz absorption peaks which were called “fingerprint spectra” for different aging explosive samples in the range of 0.3–6.0 THz spectrum. Meanwhile, the results also show that the locations of the characteristic absorption peaks are not the same. Moreover, the unaging and aging explosive samples have obviously different terahertz absorption spectra.

Abstract-Low-threshold terahertz-wave generation based on a cavity phase-matched parametric process in a Fabry–Perot microresonator

Pengxiang Liu, Feng Qi, Weifan Li, Yelong Wang, Zhaoyang Liu, Hongming Wu, Wei Ning, Wei Shi, and Jianquan Yao

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-35-1-68&origin=search

A configuration for an optical pumped monochromatic terahertz (THz) source operating in a high repetition rate is developed and based on a resonant parametric process within a Fabry–Perot microcavity. Comprehensive analysis of the spectral selection, cavity phase matching, energy-conversion dynamic, and input–output characteristics is provided. Calculations are performed on a Tm3+${\mathrm{Tm}}^{3+}$-doped fiber laser pumped GaAs sheet. It is indicated that a pump threshold can be scaled down by injection seeding of the signal wave. Efficient THz wave generation (mW level average power) under relatively low pump peak power (65 kW) is predicted.

© 2017 Optical Society of America

Abstract-Compact and stable high-repetition-rate terahertz generation based on an efficient coaxially pumped dual-wavelength laser

Yang Liu, Kai Zhong, Jialin Mei, Chu Liu, Jie Shi, Xin Ding, Degang Xu, Wei Shi, Jianquan Yao

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-25-31988

A compact and stable terahertz (THz) source is demonstrated based on difference frequency generation (DFG) pumped by an efficient dual-wavelength acousto-optic (AO) Q-switched solid-state Nd:YLF laser with composite gain media (a-cut and c-cut) in the coaxial pumping configuration. Optimal power ratio and pulse synchronization of the orthogonal polarized 1047/1053 nm dual-wavelength laser could be realized by varying the pump focusing depth and/or pump wavelength. The total power of 2.92 W was obtained at 5 kHz pumped by 10-W laser-diode power at 803 nm. Such an efficient dual-wavelength laser demonstrated good stability and inconspicuous timing jitter benefiting from the suppressed gain competition between two resonating wavelengths. An 8-mm-long GaSe crystal was employed to generate THz waves at 1.64 THz by DFG and the maximum THz average output power was about 0.93 μW. This compact coaxial pumping method can be extended to all kinds of neodymium (Nd) doped laser crystals to produce different dual-wavelength lasers for various THz wavelength generation, which have good prospects for portable and costless applications like imaging, non-destructive inspection, etc.

© 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-High-average-power, high-repetition-rate tunable terahertz difference frequency generation with GaSe crystal pumped by 2 μm dual-wavelength intracavity KTP optical parametric oscillator

Dexian Yan, Yuye Wang, Degang Xu, Pengxiang Liu, Chao Yan, Jia Shi, Hongxiang Liu, Yixin He, Longhuang Tang, Jianchen Feng, Jianqin Guo, Wei Shi, Kai Zhong, Yuen H. Tsang, and Jianquan Yao

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-5-2-82&origin=search

We have demonstrated a high-average-power, high-repetition-rate optical terahertz (THz) source based on difference frequency generation (DFG) in the GaSe crystal by using a near-degenerate 2 μm intracavity KTP optical parametric oscillator as the pump source. The power of the 2 μm dual-wavelength laser was up to 12.33 W with continuous tuning ranges of 1988.0–2196.2 nm/2278.4–2065.6 nm for two waves. Different GaSe cystal lengths have been experimentally investigated for the DFG THz source in order to optimize the THz output power, which was in good agreement with the theoretical analysis. Based on an 8 mm long GaSe crystal, the THz wave was continuously tuned from 0.21 to 3 THz. The maximum THz average power of 1.66 μW was obtained at repetition rate of 10 kHz under 1.48 THz. The single pulse energy amounted to 166 pJ and the conversion efficiency from 2 μm laser to THz output was 1.68×10−6$1.68\times {10}^{-6}$. The signal-to-noise ratio of the detected THz voltage was 23 dB. The acceptance angle of DFG in the GaSe crystal was measured to be 0.16°.

© 2017 Chinese Laser Press

Abstract-Terahertz Real-Time Off-Axis Digital Holography with Zoom Function

Lei Hou (侯磊)1,2, Xiao-Wei Han (韩小卫)1,3, Lei Yang (杨磊)1 and Wei Shi (施卫)1,2

http://iopscience.iop.org/article/10.1088/0256-307X/34/5/054207/meta;jsessionid=3E8C126700C724792F9F7ED8AAB28723.c1.iopscience.cld.iop.org

We present a terahertz (THz) real-time digital holographic system with zoom function worked at 0.17 THz. The magnification factor ranges from 1 to 2. In the imaging experiment, the resolution is 2 mm with the magnification factor of 1.2. A metal sheet with F-shaped hollow is used as a sample, and its THz holograms are reconstructed by our developed algorithm based on the angular spectrum theorem, and the qualities of the THz images under different conditions are compared.

Abstract-High-average-power, high-repetition-rate tunable terahertz difference frequency generation with GaSe crystal pumped by 2 μm dual-wavelength intracavity KTP optical parametric oscillator

Dexian Yan, Yuye Wang, Degang Xu, Pengxiang Liu, Chao Yan, Jia Shi, Hongxiang Liu, Yixin He, Longhuang Tang, Jianchen Feng, Jianqin Guo, Wei Shi, Kai Zhong, Yuen H. Tsang, and Jianquan Yao

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-5-2-82

We have demonstrated a high-average-power, high-repetition-rate optical terahertz (THz) source based on difference frequency generation (DFG) in the GaSe crystal by using a near-degenerate 2 μm intracavity KTP optical parametric oscillator as the pump source. The power of the 2 μm dual-wavelength laser was up to 12.33 W with continuous tuning ranges of 1988.0–2196.2 nm/2278.4–2065.6 nm for two waves. Different GaSe cystal lengths have been experimentally investigated for the DFG THz source in order to optimize the THz output power, which was in good agreement with the theoretical analysis. Based on an 8 mm long GaSe crystal, the THz wave was continuously tuned from 0.21 to 3 THz. The maximum THz average power of 1.66 μW was obtained at repetition rate of 10 kHz under 1.48 THz. The single pulse energy amounted to 166 pJ and the conversion efficiency from 2 μm laser to THz output was 1.68×10−6$1.68\times {10}^{-6}$. The signal-to-noise ratio of the detected THz voltage was 23 dB. The acceptance angle of DFG in the GaSe crystal was measured to be 0.16°.

© 2017 Chinese Laser Press

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Abstract-Widely-tunable high-repetition-rate terahertz generation in GaSe with a compact dual-wavelength KTP OPO around 2 μm

Jialin Mei, Kai Zhong, Maorong Wang, Yang Liu, Degang Xu, Wei Shi, Yuye Wang, Jianquan Yao, Robert A. Norwood, and Nasser Peyghambarian

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-20-23368

A compact efficient high-repetition-rate doubly-resonant dual-wavelength KTP optical parametric oscillator (OPO), with output power up to 3.65 W and tuning ranges of 2.088-2.133 μm/2.171-2.122 μm for signal/idler waves, was deployed for terahertz (THz) generation in a GaSe crystal. Based on difference frequency generation (DFG), the THz wave was continuously tunable from 730.9 μm (0.41 THz) to 80.8 μm (3.71 THz), believed to be the first report of a compact high-repetition-rate widely-tunable THz source. The maximum THz average power reached 1.2 μW at 1.54 THz and the corresponding DFG efficiency was 7.8 × 10−7, entirely suitable for portable applications. The utility of the THz source was also demonstrated through spectroscopy and imaging experiments.

© 2016 Optical Society of America

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Abstract-Single pixel imaging with tunable terahertz parametric oscillator

Pan Duan, Yuye Wang, Degang Xu, Chao Yan, Zhen Yang, Wentao Xu, Wei Shi, and Jianquan Yao
https://www.osapublishing.org/ao/abstract.cfm?uri=ao-55-13-3670

A method of active terahertz imaging based on compressive sampling is demonstrated. A metal mask structure is designed with all modulation matrices engraved on. The imaging approach based on the mask eliminates the need for imaging object movement in point-wise scanning and shows high sensitivity. A terahertz parametric oscillator with tunability from 0.5 to 2.7 THz was used as the light source. Holes with circular, rectangular, and letter “H” shapes were imaged at 1.75 THz at 20% sampling rate. The influence of sampling rates and averaging times on the image was analyzed. Imaging of the letter “H” at different frequencies from 1.0 to 2.2 THz was tested and evaluated, and recognizable results were obtained in the range of 1.4–2.0 THz.

© 2016 Optical Society of America

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Abstract-Green laser induced terahertz tuning range expanding in KTiOPO4 terahertz parametric oscillator

Chao Yan^1,2, Yuye Wang^1,2,3,a), Degang Xu^1,2,a), Wentao Xu^1,2,Pengxiang Liu^1,2, Dexian Yan^1,2, Pan Duan^1,2, Kai Zhong^1,2, Wei Shi^1,2 and Jianquan Yao^1,2
 HIDE AFFILIATIONS
1 Institute of Laser and Optoelectronics, College of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China
2 Key Laboratory of Optoelectronic Information Science and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China
3 Institute of Neurosurgery, Southwest Hospital, Third Military Medical University, Chongqing 400038, China
a) Authors to whom correspondence should be addressed. Electronic addresses:yuyewang@tju.edu.cn and xudegang@tju.edu.cn.
Appl. Phys. Lett. 108, 011107 (2016); http://dx.doi.org/10.1063/1.4939548
http://scitation.aip.org/content/aip/journal/apl/108/1/10.1063/1.4939548?TRACK=RSS

532 nm green laser is utilized to achieve terahertz tuning range expanding in KTiOPO4 terahertz parametric oscillator. With the theoretical analysis of the stimulated polaritonscattering, an expanded tunability of the KTiOPO4 terahertz parametric oscillator can be realized. A wide terahertz output tuning range from 5.7 to 6.1 THz, from 7.4 to 7.8 THz, from 11.5 to 11.8 THz, and from 13.3 to 13.5 THz was demonstrated in our experiment, and the result well matched the analysis. The maximum terahertz output energy was 1.61 μJ under the pump energy of 140 mJ, corresponding to the maximum THz wave conversion efficiency of 1.3 × 10⁻⁵, and the threshold pump energy is about 30 mJ.