Sunday, 22 December 2013

TPS spectra 3000 used in topological insulators research at Nanyang Technological University, Singapore


Terahertz conductivity of topological surface states in Bi1.5Sb0.5Te1.8Se1.2


Chi Sin Tang, Bin Xia, Xingquan Zou, Shi Chen, Hong-Wei Ou, Lan Wang, A. Rusydi, Jian-Xin Zhu& Elbert E. M. Chia

Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore,
NUSNNI-NanoCore, Department of Physics, National University of Singapore, 117542, Singapore,
Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos NM87545, USA.

Scientific Reports 3, 3513 doi:10.1038/srep03513


Abstract
Topological insulators are electronic materials with an insulating bulk and conducting surface. However, due to free carriers in the bulk, the properties of the metallic surface are difficult to detect and characterize in most topological insulator materials. Recently, a new topological insulator Bi1.5Sb0.5Te1.7Se1.3 (BSTS) was found, showing high bulk resistivities of 1–10 Ω.cm and greater contrast between the bulk and surface resistivities compared to other Bi-based topological insulators. Using Terahertz Time-Domain Spectroscopy (THz-TDS), we present complex conductivity of BSTS single crystals, disentangling the surface and bulk contributions. We find that the Drude spectral weight is 1–2 orders of magnitude smaller than in other Bi-based topological insulators, and similar to that of Bi2Se3 thin films, suggesting a significant contribution of the topological surface states to the conductivity of the BSTS sample. Moreover, an impurity band is present about 30 meV below the Fermi level, and the surface and bulk carrier densities agree with those obtained from transport data. Furthermore, from the surface Drude contribution, we obtain a ~98% transmission through one surface layer — this is consistent with the transmission through single-layer or bilayer graphene, which shares a common Dirac-cone feature in the band structure.



THz-TDS
THz transmission of the BSTS single crystal was measured using a conventional THz-TDS system (TeraView Spectra 3000) incorporated with a Janis ST-100-FTIR cryostat. The THz signal was generated and detected by photoconductive antennae fabricated on low temperature-grown GaAs films. The aperture diameter is 3.5 mm, allowing for an accurate measurement of the THz signal down to ~0.4 THz. The time-domain electric field of the THz pulse signal is transmitted through the BSTS sample  , while the reference signal  is transmitted through vacuum. 1800 THz traces were taken in 60 seconds for each reference or sample run. The sample holder was moved back and forth between the sample and reference positions by means of a vertical motorized stage with a resolution of 2.5 μm. Fast Fourier Transform (FFT) was then performed on the time-domain THz signal to obtain the amplitude and phase of the THz spectra. Since the THz-TDS detects both the amplitude and phase of the THz signal, there is no need to use the Kramers-Kronig transformation to extract the real and imaginary components of the material optical parameters.
For more information about TeraView and its products visit TeraView or contact us at ian.grundy@teraview.com for more information.

Thursday, 19 December 2013

Continuous tuning of a narrow-band terahertz wave in periodically poled stoichiometric LiTaO3 crystal with a fan-out grating structure

Nan Ei Yu1, Myoung-Kyu Oh1, Hoonsoo Kang1, Changsoo Jung1, Bok Hyeon Kim1, Kyu-Sup Lee2, Do-Kyeong Ko2, Shunji Takekawa3 and Kenji Kitamura3

Abstract


Continuous tuning of terahertz waves was demonstrated with seamless change in grating period in a periodically poled stoichiometric lithium tantalite (SLT) crystal. The periodically poled fan-out structure allows wide tunability such as 610 GHz with the bandwidth as narrow as 17 GHz at a carrier frequency of 1.00 THz. Temperature-dependent measurements show a gradual intensity increase of the THz pulses as the temperature decreases. Furthermore, absorption and refractive index of SLT in the THz range were estimated and compared with those of LiNbO3 (LN). The absorption coefficient of the LT crystal at ordinary wave was almost half of that in the LN crystal. SLT could be one of the powerful crystals for high-power THz generation with large optical aperture because of the fewer defects inside the crystal.




Full Article: http://iopscience.iop.org/1882-0786/7/1/012101



Wednesday, 18 December 2013

Characterisation of Crystalline-Amorphous Blends of Sucrose with Terahertz-Pulsed Spectroscopy: the Development of a Prediction Technique for Estimating the Degree of Crystallinity with Partial Least Squares Regression









Abstract


The control of the amorphous and crystalline states of drugs and excipients is important in many instances of product formulation, manufacture, and packaging, such as the formulation of certain (freeze-dried) fast melt tablets. This study examines the use of terahertz-pulsed spectroscopy (TPS) coupled with two different data analytical methods as an off-line tool (in the first instance) for assessing the degree of crystallinity in a binary mixture of amorphous and polycrystalline sucrose. The terahertz spectrum of sucrose was recorded in the wave number range between 3 and 100 cm−1 for both the pure crystalline form and for a mixture of the crystalline and amorphous (freeze-dried) form. The THz spectra of crystalline sucrose showed distinct absorption bands at ∼48, ∼55, and ∼60 cm−1 while all these features were absent in the amorphous sucrose. Calibration models were constructed based on (1) peak area analysis and (2) partial least square regression analysis, with the latter giving the best LOD and LOQ of 0.76% and 2.3%, respectively. The potential for using THz spectroscopy, as a quantitative in-line tool for percent crystallinity in a range of complex systems such as conventional tablets and freeze-dried formulations, is suggested in this study.

This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://link.springer.com/article/10.1208/s12249-013-0042-2

Tuesday, 17 December 2013

Quantitative analysis of visible surface defect risk in tablets during film coating using terahertz pulsed imaging

  • Masahiro Niwa, 
  • Yasuhiro Hiraishi






  • Abstract

    Tablets are the most common form of solid oral dosage produced by pharmaceutical industries. There are several challenges to successful and consistent tablet manufacturing. One well-known quality issue is visible surface defects, which generally occur due to insufficient physical strength, causing breakage or abrasion during processing, packaging, or shipping. Techniques that allow quantitative evaluation of surface strength and the risk of surface defect would greatly aid in quality control. Here terahertz pulsed imaging (TPI) was employed to evaluate the surface properties of core tablets with visible surface defects of varying severity after film coating. Other analytical methods, such as tensile strength measurements, friability testing, and scanning electron microscopy (SEM), were used to validate TPI results. Tensile strength and friability provided no information on visible surface defect risk, whereas the TPI-derived unique parameter terahertz electric field peak strength (TEFPS) provided spatial distribution of surface density/roughness information on core tablets, which helped in estimating tablet abrasion risk prior to film coating and predicting the location of the defects. TPI also revealed the relationship between surface strength and blending condition and is a nondestructive, quantitative approach to aid formulation development and quality control that can reduce visible surface defect risk in tablets.

  • Thursday, 12 December 2013

    TeraView at Photonics West: TeraView will be one of the companies in the UK cluster

    TeraView will be one of the companies within the UK Cluster at Photonics West 2014.



    Exhibit at SPIE Photonics West, 4 - 6 February 2014, the annual flagship event for the lasers and photonics industry. 

    Friday, 6 December 2013

    Identification of concealed materials, including explosives, by terahertz reflection spectroscopy


    Norbert Palka

    Military University of Technology








    Abstract

    We report on a method for extracting the characteristic features of covered materials, including hexogen, in the range from 0.5 to 1.8 THz. This time-domain spectroscopy-based technique takes into account only part of the signal reflected from a covered sample and analyzes it by using the Fourier transform. The obtained power spectrum has distinctive peaks that correspond to peaks measured in the transmission configuration and can be used for further identification of the materials.

    This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

    Full Article: http://opticalengineering.spiedigitallibrary.org/article.aspx?articleid=1787555

    Thursday, 5 December 2013

    CLEO: 2014 - Laser Science to Photonic Applications

    The submission deadline for CLEO: 2014 (8-13 June 2014 in San Jose, California, USA) will be on the 22nd of January 2014, 17:00 GMT.

    CLEO: 2014 is well known for its high quality, peer-reviewed research, and bridges fundamental science all the way through to technology development and uses of technology and applications. Submissions are being accepted in:

    CLEO: QELS- Fundamental Science
    CLEO: Science & Innovations
    CLEO: Applications & Technology 

    Visit the website for topic categories and descriptions.

    More information about CLEO: 2014 can be found on the website at www.cleoconference.org.

    Wednesday, 27 November 2013

    Business & Innovation Network (BIN) - Ribeirão Preto, Brazil - November 12 – 14th 2013

    TeraView's Ian Grundy was recently at the Business & Innovation Network (BIN) event in Ribeirão Preto, Brazil

    Here's what Ian had to say on the event:

    What a great event!

    At the invitation of the organizing committee Ian Grundy, SVP sales at TeraView was pleased to attend the above event to talk about TeraViews technology and the process/experience of spinning technology companies out from universities.

    The event was attended by a mix of academics and spin out companies from Europe and N. and S. America. The aim was simply to build networks and to do some business!

    The weather was hot and the people great.

    A number of conversations are now under-way and TeraView would like to thank everyone for their hospitality and help. Next year the event will be held in the UK, in Sheffield, and we look forward to attending.

    Thursday, 21 November 2013

    Detailed non-destructive evaluation of UHMWPE composites in the terahertz range


    Optical and Quantum ElectronicsDOI 10.1007/s11082-013-9836-4

    N. Palka, D. Miedzinska



    Abstract

    We report on the terahertz analysis of an internal structure of an ultra-high molecular weight polyethylene (UHMWPE) composite material, which is based on the HB10-tape from Dyneema®. This type of composite is very hard and resistant and therefore it is often used to manufacture personal armors such as bulletproof vests and helmets. The multilayer structure of the UHMWPE composite was investigated by means of a raster scanning time domain spectroscopy technique in a reflection configuration. The mechanism of the formation of many shifted in time THz pulses (reflected from the internal layers of the sample) originates from the periodic modulation of the refractive index along the propagation of the radiation. This modulation is connected with alternate layers of fibers, each having different direction (perpendicular to each other). As a result we obtained the detailed three dimensional profile of the 3.3-mm thick sample with all 74 layers clearly visible. Thicknesses of all layers, having around 45 μm each, were determined. Moreover, it is also possible to identify internal defects i.e. delaminations in the internal structure of this composite material.

    Friday, 15 November 2013

    Professor Sir Michael Pepper FRS, will be awarded the Dirac Medal and give the 2013 Dirac Public Lecture.

    Semiconductor Nanostructures and Quantum Phenomena


    Sir Michael Pepper
    Industry innovation has developed a combination of electron beam lithography and advanced semiconductor growth. This has stimulated interest in discovering more about the basic properties of semiconductor nanostructures.

    Professor Pepper will give the Dirac Lecture on advanced semiconductor growth technology. The Lecture will show how this technology, which was developed for the information technology industry, has allowed the creation of new types of structures for investigating the quantum aspects of electron transport. It will also show how the dimensionality which is experienced by the electrons can be reduced from 3 to 2 to 1 and then to 0.

    History of the Dirac Lecture:


    The Dirac Medal for the Advancement of Theoretical Physics is awarded by the UNSW and the Australian Institute of Physics. The Lecture and the Medal commemorate the visit to the university in 1975 of Professor Dirac, who gave five lectures. The lectures were subsequently published as a book Directions of Physics. Professor Dirac donated the royalties from this book to the University for the establishment of the Dirac Lecture and Prize. The prize includes a silver medal and honorarium. It was first awarded in 1979.



    Professor Pepper will also be awarded an Honorary Degree on the evening. Please join us in congratulating Professor Pepper.

    For more information read the full article at the TeraView website.

    http://www.ee.ucl.ac.uk/research/2013-dirac-medal-awarded
    http://www.science.unsw.edu.au/events/dirac-lecture-medal-presentation

    Friday, 8 November 2013

    Influence of high-pressure treatment on charge carrier transport in PbS colloidal quantum dot solids


    Seung Jin Heo,   Seokhyun Yoon,   Sang Hoon Oh,   Doo Hyun Yoon and    Hyun Jae Kim -Nanoscale, 2013




    Abstract 

    We investigated the effects of high-pressure treatment on charge carrier transport in PbS colloidal quantum dot (CQD) solids. We applied high pressure to PbS CQD solids using nitrogen gas to reduce the inter-dot distance. Using this simple process, we obtained conductive PbS CQD solids. Terahertz time-domain spectroscopy was used to study charge carrier transport as a function of pressure. We found that the minimum pressure needed to increase the dielectric constant, conductivity, and carrier mobility was 4 MPa. All properties dramatically improved at 5 MPa; for example, mobility increased from 0.13 cm2 V-1 s-1 at 0.1 MPa to 0.91 cm2 V-1 s-1 at 5 MPa. We propose this simple process as a nondestructive approach for making conductive PbS CQD solids that are free of chemical and physical defects.






    Thursday, 7 November 2013

    TeraView at ISTFA 2013

    TeraView were recently at ISTFA 2013 from the 4th - 7th of November.

    Here is Stephane Barbeau from IBM for his talk:

    ElectroElectro Optical Terahertz Pulse Reflectometry - a Fast and Highly Accurate Non-Destructive Fault Isolation Technique for 3D Flip Chip Packages 

    As well as the TeraView Booth. 
    Stephane Barbeau

    Monday, 4 November 2013

    TeraView At Photonics West 2014

    TeraView Will be attending Photonics West - 2014 

    SPIE Photonics West, 1st - 6th February 2014,
    The Moscone Center,
    San Francisco, 
    California,
    United State


    SPIE Photonics West 2014 - The largest and most influential event for the laser and photonics community in North America: 20,000 attendees, two exhibitions, 1,300 exhibiting companies, a wide range of papers on biomedical optics, biophotonics, translational research, industrial lasers, optoelectronics, microfabrication, optical MEMS, and more.

    TeraView will be at Booth #5311

    If you would like to pre-arrange a meeting, please e-mail Dr. Phil Taday.

    Wednesday, 30 October 2013

    Terahertz Pulsed Imaging and Magnetic Resonance Imaging as Tools to Probe Formulation Stability

    1 Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China2 Department of Chemical Engineering & Biotechnology, University of Cambridge, Cambridge CB2 3RA, UK3 Merck Sharp & Dohme Ltd., Hoddesdon EN11 9BU, UK


    Abstract

    Dissolution stability over the entire shelf life duration is of critical importance to ensure the quality of solid dosage forms. Changes in the drug release profile during storage may affect the bioavailability of drug products. This study investigated the stability of a commercial tablet (Lescolr XL) when stored under accelerated conditions (40 oC/75% r.h.). Terahertz pulsed imaging (TPI) was used to investigate the structure of the tablet coating before and after the accelerated aging process. The results indicate that the coating was reduced in thickness and exhibited a higher density after being stored under accelerated conditions for four weeks. In situ magnetic resonance imaging (MRI) of the water penetration processes during tablet dissolution in a USP-IV dissolution cell equipped with an in-line UV-vis analyzer was carried out to study local differences in water uptake into the tablet matrix between the stressed and unstressed state. The drug release profiles of the Lescolr XL tablet before and after the accelerated storage stability testing were compared using a “difference” factor ∫1 and a “similarity” factor ∫2. The results reveal that even though the physical properties of the coating layers changed significantly during the stress testing, the coating protected the tablet matrix and the densification of the coating polymer had no adverse effect on the drug release performance.



    The TPI studies were performed using TeraView's TPI imaga 2000 system (TeraView, Cambridge, UK
    Original Article:   http://www.mdpi.com/1999-4923/5/4/591

    Tuesday, 15 October 2013

    Position at TeraView - Software Development Specialist (6 month contract)

    TeraView Limited is the world's leader in the design and manufacture of terahertz (THz) products to the pharmaceutical, security, medical and materials characterisation markets. Our products continue to yield many ground-breaking applications such as tablet coating thickness and uniformity, cracks, defect analysis, foreign materials and analysis of solid-state structure to be exploited by our customers. Based in Cambridge UK, we have a global client base and a highly-skilled workforce.

    We are seeking a Software Development Specialist to join our team; an individual who is able to meet the existing operational needs of the company, as well as planning for the future needs of the company as we grow.

    You will have 3 years or more industry experience as a development engineer in scientific or engineering application environments. You will have worked within a formalised Quality System framework, with experience of scientific instrumentation. You must be able to demonstrate a track record of instrumentation or scientific software architecture design. You will be a self-starter with a positive attitude and a proven ability to work in small multi-disciplinary teams.


    Role & Responsibilities:

    Reporting to the Technical Development Team Leader, your responsibilities will include:

        ·         Design and development of software in support of instrumentation related to our terahertz systems, either individually or as part of a wider team

        ·         Hand-on work in prototyping and implementation of proposed solutions

        ·         Product design and related processes within a formal Quality Management System

    Key Skills:

    The successful applicant will have:

        ·         Extensive knowledge in at least one object-oriented development platform (C#, C++, Python or comparable)

        ·         A proven track record in the design of multi-threaded hardware/instrumentation control applications, graphical user-interface and desktop application design

        ·         The flexibility to develop across multiple languages / platforms

        ·         A scientific or engineering background

        ·         Experience of product design and related processes within a formal Quality Management System

        ·         Good interpersonal skills and attention to detail

    Experience and Education:

    Essentials: 

        ·         Computer Science or Engineering degree

        ·         Design and development of scientific measurement equipment, for example spectrometers or imaging systems

        ·         3 years minimum industrial experience in scientific software or instrumentation

        ·         The ability to work alone and on own initiative

        ·         Ability to work in a team

        ·         Flexible approach to work

    Desirables: 

        ·         Agile development methodology

        ·         Experience of using boost and STL

        ·         3D & 2D scientific visualisation

        ·         Hardware interfacing experience

        ·         Signal processing, statistics and other data analysis methods

        ·         Knowledge of Matlab or other numerical analysis packages SQL / Relational-database usage


    If you think you have the skills and qualities we need, please send your CV, with a covering letter, outlining your current role and remuneration to:

    Paddy O’Kelly
    Chief Operating Officer
    TeraView Limited
    Platinum Building
    St John’s Innovation Park 
    Cambridge CB4 0DS
    UK

    No agencies, please.


    TeraView offers an excellent salary and benefits package, along with the opportunity for highly-motivated staff to work together and shape the development of products in one of the newest and most exciting areas of technology. We are an equal opportunities employer and pride ourselves on our diverse workforce. For further information and background on the company, please visit our website on: www.teraview.com

    Tuesday, 8 October 2013

    The Society for Applied Spectroscopy (SAS) UK Regional Section will hold its 3rd Annual Technical Meeting: “Graphene Spectroscopy”

    The Society for Applied Spectroscopy (SAS) UK Regional Section will host its 3rd Annual Technical Meeting Graphene Spectroscopy on Tuesday 29th October 2013. This one day meeting will be held at Trinity Hall in Cambridge and will focus on recent advances in the characterization of graphene and two dimensional crystals by spectroscopic methods.

    Graphene, thanks to its unique structural and electronic properties, has been called the “miracle material” of the 21st Century. Its isolation in 2004 has sparked a considerable scientific activity that has now established a broad international community with interest ranging from fundamental studies to applications in different fields e.g. composite materials, (opto)electronics, energy, etc. Graphene is just the first of a new class of two dimensional (2d) materials, derived from layered bulk crystals.

    Studying and understanding the structure of graphene and 2d crystals is therefore of utmost importance for materials optimization and devices integration. This timely meeting strives to bring together international stakeholders in the field, to give perspectives on the current status of graphene spectroscopy. 


    The speakers will be:


    Prof. Ping-Heng Tan, Chinese Academy of Sciences, Beijing, P.R. China, “Application of ultra-low frequency Raman spectroscopy in two-dimensional layered materials.”
    Prof. Andrea C. Ferrari, Cambridge Graphene Centre, UK, “Raman Spectroscopy in Graphene: State of the Art” 
    Dr. Cinzia Casiraghi, University of Manchester, UK. "Raman spectroscopy of defective graphene: Effect of the excitation energy, type, amount of defects and applied gate voltage."
    Dr. Duhee Yoon Cambridge Graphene Centre, UK, “Raman spectroscopy for characterization of strained 
    graphene.”
    Prof. Günter G. Hoffmann, Eindhoven University of Technology, The Netherlands, “Tip-enhanced Raman Spectroscopy (TERS) and Mapping (TERM) of graphene and related materials”.
    Prof. Giulio Cerullo, Politecnico di Milano, Italy. "Ultrafast electron-electron scattering in graphene.”
    Prof. Euan Hendry, University of Exeter, UK. "Ultrafast optical measurements of graphene."
    Dr. Michael Johnston, University of Oxford, UK. Terahertz spectroscopy of graphene.”
    Dr. Rahul Raveendran-Nair, University of Manchester, UK, Characterisation of graphene and its chemical derivatives by different spectroscopic techniques.”


    [The scientific program for the meeting has been co-organised by Francesco Bonaccorso (CNR-IPCF (Italy) and CGC, Cambridge University) and John Chalmers (SAS UK Regional Section.]

    For registration details for this meeting or for more information, please email: