Saturday, June 23, 2018
Abstract-Equilibrium and non-equilibrium free carrier dynamics in two-dimensional Ti3C2Tx MXenes: THz spectroscopy study
Guangjiang Li, Kateryna Kushnir, Yongchang Dong, Sergii Chertopalov, Apparao M Rao, Vadym Mochalin, Ramakrishna Podila, Lyubov Titova
MXenes is an emerging class of two-dimensional transition metal carbides, nitrides and carbonitrides which exhibit large conductivity, ultrahigh volumetric capacitance, high threshold for light induced damage and nonlinear optical transmittance, making them attractive candidates for a variety of optoelectronic and electrochemical applications. Here, we report on equilibrium and non equilibrium free carrier dynamics of Ti3C2Tx gleaned from THz spectroscopic studies for the first time. Ti3C2TX showed high (~ 2x1021 cm-3) intrinsic charge carrier density and relatively high (~34 cm2/Vs) mobility of carriers with an exceptionally large, ~ 46,000 cm-1 absorption in the THz range, which suggests that Ti3C2Tx is well suited for THz detection. We also demonstrate that Ti3C2Tx conductivity and THz transmission can be manipulated by photoexcitation, as absorption of near-infrared, 800 nm pulses is found to cause transient suppression of the conductivity that recovers over hundreds of picoseconds. The possibility of control over THz transmission and conductivity by photoexcitation suggests the promise for application of Ti3C2Tx Mxenes in THz modulation devices and variable electromagnetic shielding.
Hyunseung Jung, Jaemok Koo, Eunah Heo, Boeun Cho, Chihun In, Wonwoo Lee, Hyunwoo Jo, Jeong Ho Cho, Hyunyong Choi, Moon Sung Kang, Hojin Lee,
Active control of metamaterial properties is critical for advanced terahertz (THz) applications. However, the tunability of THz properties, such as the resonance frequency and phase of the wave, remains challenging. Here, a new device design is provided for extensively tuning the resonance properties of THz metamaterials. Unlike previous approaches, the design is intended to control the electrical interconnections between the metallic unit structures of metamaterials. This strategy is referred to as the molecularization of the meta‐atoms and is accomplished by placing graphene bridges between the metallic unit structures whose conductivity is modulated by an electrolyte gating. Because of the scalable nature of the molecularization, the resonance frequency of the terahertz metamaterials can be tuned as a function of the number of meta‐atoms constituting a unit metamolecule. At the same time, the voltage‐controlled molecularization allows delicate control over the phase shift of the transmitted THz, without changing the high transmission of the materials significantly.
Abstract-Metasurfaces for broadband terahertz linear polarization rotation and linear-to-circular polarization conversion
Abstract-High-Speed Terahertz Waveform Measurement for Intense Terahertz Light Using 100-kHz Yb-Doped Fiber Laser
Masaaki Tsubouchi, Keisuke Nagashima,
We demonstrate a high-speed terahertz (THz) waveform measurement system for intense THz light with a scan rate of 100 Hz. To realize the high scan rate, a loudspeaker vibrating at 50 Hz is employed to scan the delay time between THz light and electro-optic sampling light. Because the fast scan system requires a high data sampling rate, we develop an Yb-doped fiber laser with a repetition rate of 100 kHz optimized for effective THz light generation with the output electric field of 1 kV/cm. The present system drastically reduces the measurement time of the THz waveform from several minutes to 10 ms.
Friday, June 22, 2018
|Project Title||Single Channel Terahertz Endoscopic Systems|
A technique to image intrinsic contrast between abnormal and normal tissue based on the terahertz reflectivity values acquired using a continuous-wave terahertz polarization sensitive endoscope.
|Tags||diagnostic imaging, endoscope, noise reduction, large dynamic range|
|Posted Date||Jun 20, 2018 9:38 AM|
Endoscopy is a minimally invasive diagnostic medical procedure that uses an endoscope, a medical device that consists of a long thin flexible tube, to examine the interior surfaces of an organ or tissue without surgery. Besides conventional endoscopy, computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) are current diagnostic imaging modalities for the detection of local and distant relapse of cancers. All currently existing solutions have a number of limitations including the limited detection of small tumors, high costs, and poor resolution of tumors that are not metabolically active. A terahertz (THz) endoscope system, developed by UML researchers, can alleviate many of these limitations for the examination and detection of cancerous or precancerous regions of biological tissue.
Dr. Robert Giles and team have developed a technique to image intrinsic contrast between abnormal and normal tissue based on the terahertz reflectivity values acquired using a continuous-wave terahertz polarization sensitive endoscope.
The THz endoscope is comprised of three parts; a terahertz transceiver system to generate and detect the signal using a coherent detection technique, system optics to guide the beam as per coupling requirements, and a flexible low-loss hollow metal coated waveguide for propagating the THz beam. A single channel will transmit and collect the back reflected intrinsic THz signal from the sample, which will enable lower system costs, simpler data analysis, and fast data acquisition rates. The invention also minimizes non-sample signals and system noise from the generated images.
- Low costs
- Low maintenance
- Room temperature operation
- High system signal-to-noise (SNR) ratio
- Fully polarimetric coherent system with large dynamic range (~120-150 dB)
The global endoscopy equipment market was valued at $24.32 billion in 2016 and is projected to reach $34.82 billion by 2022, at a CAGR of 6.4% during the forecasted period.
About the inventor
Robert Giles serves as Chairman of the Physics Department at UMass Lowell and Principal Investigator of the university’s Submillimeter-Wave Technology Laboratory (STL). STL is a leader of terahertz transmitter and receiver technologies and was recently granted a five-year, $27 million renewal grant from the U.S. Army’s National Ground Intelligence Center. Giles research interests include terahertz spectroscopic imaging, material science, and biomedical imaging instrumentation.
Abstract-Terahertz Time-Domain Imaging to Guide a Conservation Intervention on a Stratified Easel Painting
Corinna L. Koch Dandolo, Gilda María Pasco, Saldaña, Mirta Asunción, Insaurralde Caballero, Monserrat Alma Gómez Sepúlveda, Arturo Ignacio Hernández-Serrano, Alejandro Mesa Orozco, Joselyn Alvarado Calderón, Melba Samara Calderón Zárate, Karen Luna González, Eunice Corazón Peralta de Dios, Gerardo Hernández Rosales, Enrique Castro-Camus
Very few real easel paintings have been scanned by means of terahertz time-domain imaging (THz-TDI) up to now. In this study, four different areas of an eighteenth century easel painting have been scanned by THz-TDI with the aim of proving useful information to the conservators for its imminent restoration treatment, owing to the complexity of its structure. Despite the unevenness of the layers composing the painting (lining canvas, original canvas, patching materials, and paint layers), the recorded THz dataset has been processed so that the THz images of the single layers composing the multilayered object have been clearly obtained. Relevant information about the painting structure, the presence of structural defects, overpainting, and the existence and extension of the original remains could have been determined. Infrared photography and X-ray radiography have been used for integrating the collected THz data and comparing the different outputs.