Saturday, July 30, 2016

Abstract-Generating terahertz radiation via optical rectification in nonlinear crystals: Theory and experimental results

  • A.r N. Bugay 
  • S. V. Sazonov

Key principles of terahertz radiation generation via laser pulse optical rectification are reviewed. The development of theoretical concepts is considered in connection with recent experimental results. The usability of resonant effects and metamaterials for the further development of this technique of generation is analyzed.

Friday, July 29, 2016

Abstract-Remote and in situ sensing products in chemical reaction using a flexible terahertz pipe waveguide

The feasibility of remote chemical detection is experimentally demonstrated by using a Teflon pipe as a scanning arm in a continuous-terahertz wave sensing and imaging system. Different tablets with distinct mixed ratios of aluminum and polyethylene powders are well distinguished by measuring the power reflectivities of 0.4 THz wave associated with their distinct terahertz refractive indices. Given its refractive index sensitivity and fast response, the reflective terahertz sensing system can be used to real-time trace and quantitatively analyze the ammonium–chloride aerosols produced by the chemical reaction between hydrochloric acid and ammonia vapors. With a tightly focusing terahertz beam spot, the spatial and concentration distributions of the generated chemical product are successfully mapped out by the 1D scan of the flexible pipe probe. In consideration of the responsitivity, power stability, and focused spot size of the system, its detection limit for the ammonium–chloride aerosol is estimated to be approximately 165 nmol/mm2. The reliable and compact terahertz pipe scan system is potentially suitable for practical applications, such as biomedical or industrial fiber endoscopy.
© 2016 Optical Society of America
Full Article  |  PDF Article

OT LUNA Blog-Introducing the ODiSI-B 5.0

Today we introduced major enhancements to our ODiSI platform that provide valuable new capabilities to better measure strain and temperature. To keep pace with tomorrow, you need advanced technology in order to test advanced technology.
Are you ready?
Advanced materials are creating new challenges in the lab as well as on the production floor. While testing metals is easy, the anisotropic characteristics of composite materials pose new measurement challenges. Additionally, traditional test methods are inadequate for the new fastening processes utilized in composite structures. Furthermore, Finite Element Modeling programs don’t have the accuracy to predict the strain of complex structures made with advanced materials.
So, to be ready for the challenges of tomorrow’s technology, you need the ODiSI-B 5.0 today!
_P1A6582_web New features of the ODiSI-B 5.0:
  • Two Sensing Options – High-Definition and High-Speed CFG*
    • High-Definition offers ultrahigh resolution and a lower priced sensor
    • High-Speed CFG offers greater dynamic sensing capability
  • Robust Sensing with Ruggedized Cable and Connectors
    • Industrial grade stand-off cable and connectors are suitable for harsh environments and rough handling
  • Data_visualizationData Visualization with CAD Integration*
    • Analyze ODiSI data files quickly and visually using the new 3D data visualization with CAD integration
  • Strain Sensors with NIST-Traceable Calibration
    • Strain sensors are calibrated to NIST-traceable standards and come with a certificate of conformance
*High-Speed CFG module and 3D data visualization package sold as options
To learn more about the ODiSI-B 5.0 click here.
Users of the current ODiSI-B should contact Luna to discuss upgrade options to the enhanced system. Call 540.961.5190 or request a quote by clicking here 
Click here to view the ODiSI-B 5.0 one-pager.  The data sheet can be downloaded here.  

Thursday, July 28, 2016

Abstract-Self-polarized terahertz magnon absorption in a single crystal of BiFeO3

Eiichi Matsubara, Takeshi Mochizuki, Masaya Nagai, and Masaaki Ashida

We report the polarization dependence of terahertz magnon absorption in single crystals of BiFeO3 grown by a modified floating zone method. In a (111)\rm pc-oriented crystal, two major magnon absorption signals were observed for all terahertz polarizations, which indicates that magnetic domains were not aligned in one of the three allowed directions. In contrast, the absorption modes in a (001)\rm pc-oriented crystal showed significant polarization dependence, which was unchanged even after annealing the crystal at temperatures far above the N\'{e}el point to demagnetize it. This polarization dependence coincides with that of E mode phonons. Thus, we conclude that magnon and phonon in BiFeO3are strongly coupled and the selection rules for magnon absorption are governed by the activity of E mode phonons, namely, the crystalline anisotropy originating from ferroelectric polarization.

Wednesday, July 27, 2016

Making Terahertz Lasers More Powerful

Scanning electron microscope image of the terahertz quantum cascade laser
Scanning electron microscope image of the terahertz quantum cascade laser.
CREDIT: Wang, et al/AIP Advances

Researchers in China nearly double the continuous output power of a type of terahertz laser, opening up applications in spectroscopy, imaging, remote sensing and more

WASHINGTON, D.C., July 26, 2016 -- Researchers have nearly doubled the continuous output power of a type of laser, called a terahertz quantum cascade laser, with potential applications in medical imaging, airport security and more. Increasing the continuous output power of these lasers is an important step toward increasing the range of practical applications. The researchers report their results in the journal AIP Advances, from AIP Publishing.
Terahertz radiation sits between microwaves and infrared light on the electromagnetic spectrum. It is relatively low-energy and can penetrate materials such as clothing, wood, plastic and ceramics. The unique qualitites of terahertz radiation make it an attractive candidiate for imaging, but the ability to produce and control terahertz waves has lagged behind technology for radio, microwave and visible light.
Recently, scientists have made rapid progress on a technology to produce terahertz light called a quantum cascade laser or QCL. Quantum cascade lasers are made from thin layers of material. The thin layers give the laser the valuble property of tunability, meaning the laser can be designed to emit at a chosen wavelength. The output power of terahertz QCLs is also relatively high compared to other terahertz sources, said Xuemin Wang, a researcher in the China Academy of Engineering Physics and first author on the new paper.
Wang and his colleagues' work focuses on even further increasing the output power of terahertz quantum cascade lasers, especially in the mode in which the laser output power is continuous. "In engineering, biomechanics and medical science, the applications require continuous wave mode," Wang said.
By optimizing the material growth and manufacturing process for terahertz QCLs, Wang and his team made a laser with a record output power of up to 230 milliwatts in continuous wave mode. The previous record was 138 milliwatts.
Wang said the new 230 milliwatt laser could be used in air, a challenge for lower-powered lasers since particles in the air can scatter or absorb the laser light before it reaches its target.
The increase demonstrates that the team's method of precisely controlling the growth of the laser's layers can increase output power, Wang said, and he is hopeful that future improvements could bring the continuous power above 1 watt. The 1 watt level has been reached in terahertz QCLs in pulsed wave mode.
Wang said he thinks scientists and engineers could use the new laser as a flexible source of terahertz radiation for spectroscopy, medicial imaging, remote sensing and other applications.
For More Information:
AIP Media Line
Article title: 
Xuemin Wang, Changle Shen, Tao Jiang, Zhiqiang Zhan, Qinghua Deng, Weihua Li, Weidong Wu, Ning Yang, Weidong Chu and Suqing Duan
Author affiliations: 
China Academy of Engineering Physics in Sichuan, China and the Institute of Applied Physics and Computational Mathematics in Beijing, China