Fabrication and Characterization of an 8 × 8 Terahertz Photoconductive Antenna Array for Spatially Resolved Time Domain Spectroscopy and Imaging Applications

ABSTRACT: Terahertz (THz) technology is promising in several applications such as imaging, spectroscopy and communications. Among several methods in the generation and detection of THz waves, a THz timedomain system that is developed using photoconductive antennas (PCA) as emitter and detector presents several advantages such as simple alignment, low cost, high performance etc. In this work, we report the design, fabrication and characterization of a 2-D PCA array that is capable of detecting both the amplitude and phase of the THz pulse. The PCA array is fabricated using LT-GaAs and has 8 channels with 64 pixels (8 × 8). A novel approach using a spatial light modulator (SLM) to steer and focus the infrared probe beam towards pixels of the PCA array is presented. Each channel records the photocurrent generated by the THz signal (amplitude and phase) separately and frequencies up to 1.4 THz can be detected. Furthermore, the parameters such as directional time delay of the THz pulse, crosstalk between the channels etc., were characterized. Finally, we show that the proposed 2D PCA array design is flexible and can be used for accelerated THz spectral image acquisition

Analysis of causes of gas-oil ratio growth at late stages of oil fields exploration

Relevance of the discussed issue is caused by the need to describe and predict gas/oil ratio growth on highly watered oil fields at late stages of exploration. The aim of the research is to justify the phenomenon of trade gas-oil ratio increase during exploration of fields at late stages on the basis of studying oil gas dissolution effect in passing extracted water and the analysis of separation conditions on oil preparation facilities. Methods. For modeling easy hydrocarbonic components of oil dissolution in water the authors have used the modified Soave-Redliсh-Kwong equation of state taking into account water mineralization and the program complex Aspen HYSYS for assessing ablation of easy oil components in gas phase during separation at booster pump stations and the central oil gathering station depending on the termobaric conditions of separation. Results. On the basis of simulation it is shown that the growth of trade gas-oil ratio occurs at increase of water content of oil wells at the oilfields, which are operated by maintaining the reservoir pressure by water injection at pressures higher than the saturation pressure of oil. This growth is induced on the one hand by extraction of light hydrocarbon fractions from the passing extracted water, on the other hand by increase of oil separation temperature at the surface objects (booster pump stations, preliminary water discharge installations, central collection points). The contribution of gas dissolved in the passing extracted water is the main reason: at water content over 90-95 % the trade gas-oil ratio can multiply grow in comparison with gas content of reservoir oil. The increase of temperature of oil separation by 5-10 °C results in padding increase of gas-oil ratio by 5-10 % because of transition of a part of fluid hydrocarbons to gas-eous state

Special section guest editorial: advances in terahertz and infrared optoelectronics

This special section presents recent results in the field of infrared (IR) and terahertz (THz) optoelectronics, which have been developing rapidly over the past decades. The progress of IR and THz technologies affects a variety of fundamental problems in material science, astrophysics, chemistry and biology, medical diagnosis, and high-resolution and multispectral imaging modalities