Wednesday, December 13, 2017

Abstract-Comparison of digital beamforming algorithms for 3-D terahertz imaging with sparse multistatic line arrays


Bessem Baccouche, Patrick Agostini, Falco Schneider, Wolfgang Sauer-Greff, Ralph Urbansky,  Fabian Friederich

https://www.adv-radio-sci.net/15/283/2017/

In this contribution we compare the back-projection algorithm with our recently developed modified range migration algorithm for 3-D terahertz imaging using sparse multistatic line arrays. A 2-D planar sampling scheme is generated using the array's aperture in combination with an orthogonal synthetic aperture obtained through linear movement of the object under test. A stepped frequency continuous wave signal modulation is used for range focusing. Comparisons of the focusing quality show that results using the modified range migration algorithm reflect these of the back-projection algorithm except for some degradation along the array's axis due to the operation in the array's near-field. Nevertheless the highest computational efficiency is obtained from the modified range migration algorithm, which is better than the numerically optimized version of the back-projection algorithm. Measurements have been performed by using an imaging system operating in the W frequency band to verify the theoretical results.

Abstract-Terahertz integrated device: high-Q silicon dielectric resonators



Jingya Xie, Xi Zhu, Xiaofei Zang, Qingqing Cheng, Lin Chen, and Yiming Zhu

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-8-1-50

We design, fabricate, and characterize the terahertz integrated resonators on the silicon platform. Based on mode analysis and selection, the high-Q feature of resonators made of low-loss high-resistivity Si material is achieved due to the excitation of the whispering gallery mode on waveguide-coupled single-mode racetrack rings and disk cavities. The experimental results demonstrate that the Q-factor can reach up to 2839 at 218.345 GHz, which is significantly improved compared with conventional THz cavities. These high Q-factor integrated resonators can be used as on-chip terahertz ultrasensitive sensors and as terahertz functional integrated circuits.
© 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Tuesday, December 12, 2017

OT-LUNA Blog-Luna Innovations Introduces New Multichannel ODiSI 6100


Expands Luna’s high-definition fiber optic sensing into manufacturing and multi-channel applications
(ROANOKE, VA, December 12, 2017)  As the automotive and aerospace industries demand advanced measurement systems to enable lightweight designs, Luna Innovations Incorporated (NASDAQ: LUNA) launches its enhanced ODiSI 6100 proprietary strain and temperature measurement technology for integration into these industrial environments that place strict requirements on scalability, usability, interoperability, and overall system stability.
Unlike traditional electrical strain gages and thermocouples, the ODiSI 6100 Platform (Optical Distributed Sensor Interrogator) employs next generation fiber optic technology for distributed, multi-point, ultrahigh-definition profiling of strain and temperature.  ODiSI fiber optic sensors are small, lightweight and economical, enabling greatly reduced cost of sensor installation and the ability to embed sensors directly within materials and structures.
The enhancements included with the ODiSI 6100 strain and temperature measurement platform include minimized per-sensor cost, increased multi-channel capability, increased sensor length, increased speed of output, and real time 3-D data visualization software for computer model calibration.
“Automotive and aerospace R&D and manufacturing teams are incorporating composite and other lightweight materials into new designs at an increasing rate, requiring higher measurement performance in less time,” said Scott Graeff, president and chief executive officer of Luna Innovations. “Luna’s game-changing technology targets this need and addresses the major challenges faced by the aerospace and automotive industries as they incorporate new materials into modern designs.”
The customer feedback-driven ODiSI 6100 Platform now includes integrated, multi-channel capability up to 8 channels, millimeter resolution with up to 38,000 measurement points per channel, sensor length ranges from 2.5 m to 50 m per channel, a new, completely redesigned user interface with intuitive user controls operating on the LinuxTM operating system, and real-time data output at rates up to 250 Hz.  Optional 3-D Visualization Software allows strain and temperature data to be integrated seamlessly with CAD models and plotted and manipulated in three dimensions for the ultimate in computer-aided design. 
“ODiSI 6100 greatly enhances the engineer’s ability to maximize the performance of critical processes and next generation designs,” Graeff added. “ODiSI fiber optic sensors are small, nearly weightless and carry no electricity so they can go where electrical sensors cannot. With its high channel count, ODiSI 6100 replaces cumbersome and expensive strain gage data acquisition systems with a single, continuous, small form-factor sensor per channel. Because fiber optic sensors can also measure temperature, the ODiSI 6100 is also ideal for continuous, high-definition temperature profiling for industrial processes that rely on precise temperature control.”
Luna will be demonstrating the ODiSI 6100 at the CAMX tradeshow in Orlando, Florida this week in booth G79.  More information on the ODiSI 6100 including application case studies and product literature can be found here: http://lunainc.com/product/sensing-solutions/odisi-6100/
About Luna:
Luna Innovations Incorporated (www.lunainc.com) is a leader in optical technology, providing unique capabilities in high speed optoelectronics and high performance fiber optic test products for the telecommunications industry and distributed fiber optic sensing for the aerospace and automotive industries.  Luna is organized into two business segments, which work closely together to turn ideas into products: a Technology Development segment and a Products and Licensing segment. Luna’s business model is designed to accelerate the process of bringing new and innovative technologies to market.
Forward-Looking Statements:
The statements in this release that are not historical facts constitute “forward-looking statements” made pursuant to the safe harbor provision of the Private Securities Litigation Reform Act of 1995 that involve risks and uncertainties. These statements include the company’s expectations regarding the greater performance and new capabilities of the enhanced ODiSI platform, as well as Luna’s strategy to become the leading supplier of sensor testing for testing composites and other advanced materials. Management cautions the reader that these forward-looking statements are only predictions and are subject to a number of both known and unknown risks and uncertainties, and actual results may differ materially from those expressed or implied by these forward-looking statements as a result of a number of factors. These factors include, without limitation, failure of demand for the company’s products and services to meet expectations, technological challenges and those risks and uncertainties set forth in the company’s periodic reports and other filings with the Securities and Exchange Commission (“SEC”). Such filings are available on the SEC’s website at www.sec.gov and on the company’s website at www.lunainc.com. The statements made in this release are based on information available to the company as of the date of this release and Luna undertakes no obligation to update any of the forward-looking statements after the date of this release.
Investor Contact:
Dale Messick, CFO
Luna Innovations Incorporated
Phone: 1.540.769.8400
Email: IR@lunainc.com


Abstract-Observation of Terahertz Radiation via the Two-Color Laser Scheme with Uncommon Frequency Ratios


Liang-Liang Zhang, Wei-Min Wang, Tong Wu, Rui Zhang, Shi-Jing Zhang, Cun-Lin Zhang, Yan Zhang, Zheng-Ming Sheng, and Xi-Cheng Zhang


In the widely studied two-color laser scheme for terahertz (THz) radiation from a gas, the frequency ratio of the two lasers is usually fixed at ω2/ω1=1:2. We investigate THz generation with uncommon frequency ratios. Our experiments show, for the first time, efficient THz generation with new ratios of ω2/ω1=1:4 and 23. We observe that the THz polarization can be adjusted by rotating the longer-wavelength laser polarization and the polarization adjustment becomes inefficient by rotating the other laser polarization; the THz energy shows similar scaling laws with different frequency ratios. These observations are inconsistent with multiwave mixing theory, but support the gas-ionization or plasma-current model. This study pushes the development of the two-color scheme and provides a new dimension to explore the long-standing problem of the THz generation mechanism.
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Abstract-Tunable terahertz optical properties of graphene in dc electric fields


H.M.Dong, F.Huang, W.Xu


https://www.sciencedirect.com/science/article/pii/S1386947717312031

We develop a simple theoretical approach to investigate terahertz (THz) optical properties of monolayer graphene in the presence of an external dc electric field. The analytical results for optical coefficients such as the absorptance and reflectivity are obtained self-consistently on the basis of a diagrammatic self-consistent field theory and a Boltzmann equilibrium equation. It is found that the optical refractive index, reflectivity and conductivity can be effectively tuned by not only a gate voltage but also a driving dc electric field. This study is relevant to the applications of graphene as advanced THz optoelectronic devices.