Wednesday, March 21, 2018

Abstract-High-power sub-terahertz source with a record frequency stability at up to 1 Hz

Alexander Tsvetkov  Gregory Denisov, Andrey Fokin, Boris Movschevich, German Golubiatnikov, Lev Lubyako, Mikhail Glyavin, Mikhail Morozkin,

Many state-of-the-art fundamental and industrial projects need the use of terahertz radiation with high power and small linewidth. Gyrotrons as radiation sources provide the desired level of power in the sub-THz and THz frequency range, but have substantial free-running frequency fluctuations of the order of 10−4. Here, we demonstrate that the precise frequency stability of a high-power sub-THz gyrotron can be achieved by a phase-lock loop in the anode voltage control. The relative width of the frequency spectrum and the frequency stability obtained for a 0.263 THz/100 W gyrotron are 4 × 10−12 and 10−10, respectively, and these parameters are better than those demonstrated so far with high-power sources by almost three orders of magnitude. This approach confirms its potential for ultra-high precision spectroscopy, the development of sources with large-scale radiating apertures, and other new projects.

Abstract-Classification and identification of molecules through factor analysis method based on terahertz spectroscopy

Jianglou Huanga, Jinsong Liua, Kejia Wanga, Zhengang Yanga, Xiaming Liub

By means of factor analysis approach, a method of molecule classification is built based on the measured terahertz absorption spectra of the molecules. A data matrix can be obtained by sampling the absorption spectra at different frequency points. The data matrix is then decomposed into the product of two matrices: a weight matrix and a characteristic matrix. By using the K-means clustering to deal with the weight matrix, these molecules can be classified. A group of samples (spirobenzopyran, indole, styrene derivatives and inorganic salts) has been prepared, and measured via a terahertz time-domain spectrometer. These samples are classified with 75% accuracy compared to that directly classified via their molecular formulas.

Abstract-Ultraviolet light-induced terahertz modulation of an indium oxide film

Hongyu Ji, Bo Zhang, Wei Wang, Longfeng Lv, and Jingling Shen

Active ultraviolet light-induced terahertz modulation of an indium oxide film is investigated. A large absorption modulation of ~66% is achieved upon illumination with a low intensity UV laser (11 mW/cm2). The interaction between indium oxide and a flexible metamaterial structure is investigated owing to the large UV-induced enhancement of photo carriers observed in an indium oxide film. We are able to realize absorption peak shifts of 37 GHz by changing the UV excitation light intensity. We also propose a multi-frequency switch by building a circular metallic split ring resonator whose gaps are filled with silicon, germanium, and indium oxide. In future, a photo-excited tunable multi-frequency metamaterial switch can be realized by irradiating the structure with multi-wavelength laser beam.
© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Design Considerations for Integration of Terahertz Time-Domain Spectroscopy in Microfluidic Platforms

Rasha Al-Hujazy, Christopher M. Collier,

Microfluidic platforms have received much attention in recent years. In particular, there is interest in combining spectroscopy with microfluidic platforms. This work investigates the integration of microfluidic platforms and terahertz time-domain spectroscopy (THz-TDS) systems. A semiclassical computational model is used to simulate the emission of THz radiation from a GaAs photoconductive THz emitter. This model incorporates white noise with increasing noise amplitude (corresponding to decreasing dynamic range values). White noise is selected over other noise due to its contributions in THz-TDS systems. The results from this semiclassical computational model, in combination with defined sample thicknesses, can provide the maximum measurable absorption coefficient for a microfluidic-based THz-TDS system. The maximum measurable frequencies for such systems can be extracted through the relationship between the maximum measurable absorption coefficient and the absorption coefficient for representative biofluids. The sample thickness of the microfluidic platform and the dynamic range of the THz-TDS system play a role in defining the maximum measurable frequency for microfluidic-based THz-TDS systems. The results of this work serve as a design tool for the development of such system

Tuesday, March 20, 2018

Abstract-Probabilistically Shaped 16QAM Signal Transmission in a Photonics-aided Wireless Terahertz-Wave System

Kaihui Wang, Xinying Li, Miao Kong, Pengqi Gou, Wen Zhou, and Jianjun Yu

The 16QAM signal adopting probabilistic shaping (PS) technology is transmitted in a photonics-aided wireless Terahertz-wave system. The experimental results show an improvement of BER performance compared to the uniform distribution.
© 2018 OSA

Abstract-600-GHz-Wave Beam Steering by Terahertz-Wave Combiner

Yang Zhou, Goki Sakano, Yusuke Yamanaka, Hiroshi Ito, Tadao Ishibashi, and Kazutoshi Kato

We achieved 600-GHz-wave power combination with directional gain by optically phase tuning of arrayed photomixers. Using this phase control technique for phase shift, we also demonstrated the beam steering within an angle of 35 degrees.
© 2018 OSA