Terahertz Sensors for Industrial Automation

Saturday, August 30, 2014

Pyrocam IV images laser beams to terahertz range



Ophir-Spiricon's pyroelectric or thermal-electric Pyrocam cameras have allowed laser users working with ultraviolet (UV), infrared (IR), and terahertz (THz) wavelengths to image and characterize laser sources for more than 30 years. But the new, fourth-generation Pyrocam IV (see video at http://bcove.me/iq5gsjqt) adds greater sensitivity, better resolution, a larger active area, and more compact packaging to address next-generation laser source requirements.
Better sensitivity of the Pyrocam IV's imager allows profiling of lasers with lower power density levels than the Pyrocam III. While the Pyrocam III specified a sensitivity level of 2.2 mW/cm2 at a 24 Hz chop rate, the Pyrocam IV specifies 1.0 mW/cm2 at its equivalent chop rate. Pyrocam IV also has a 36% higher saturation level of 3.0 W/cm2 compared to the Pyrocam III's 2.2 W/cm2 (at equivalent chop rates), giving the Pyrocam IV the greatest range of usable power densities to date.  Military labs and those working with low-level THz sources (usually working in tens of microwatts to single-digit milliwatt ranges) benefit from this increased sensitivity. Recently, one of the Naval Research Lab’s laser scientists was thrilled to be able to see his terahertz beam for the very first time.
The 20% smaller pixel pitch from the Pyrocam III's 100 µm to the Pyrocam IV's 80 µm pitch enables more flexibility, both in beam sizes being profiled and the amount of data being collected. DoE and DoD research facilities and others working with relatively small beams have commented that they are now able to collect more reliable data with more pixels illuminated. Used in conjunction with Spiricon's newly-released LBS-400 beam attenuation system, laser users can accurately image focused spots up to 500 W of average power and down to about 1.5 mm in diameter. This allows for the characterization of high-powered industrial lasers being used in manufacturing environments.
The Pyrocam IV uses an active area of 25.6 mm square that is more than twice that of the Pyrocam III’s 12.4 mm square active area. Couple this with the smaller pixels and the result is Pyrocam IV's 320 x 320 resolution compared to Pyrocam III's 124 x 124 resolution. Recently, a fiber manufacturer purchased a Pyrocam IV on the spot after experiencing the beam divergence measurements from his highly-divergent light. The large active area allowed them to take measurements that ultimately led to qualification of their products that they had not previously been able to accomplish.
Technological advancements have allowed for more compact packaging in the Pyrocam IV. While the predecessor Pyrocam III has a thickness of just over 3 inches, the Pyrocam IV is 2.18 inches thick. And while the overall width and height dimensions are similar between the two cameras, the Pyrocam IV has progressed past a rectangular shape to allow the laser user more flexibility in its placement. The Pyrocam IV case also has different interfaces, such as an SMA connection instead of a BNC connection for triggering the camera to allow for more efficient cable management.
Because Ophir-Spiricon realizes that the new case design could cause problems for customers who would like to use the new Pyrocam IV but have system designs around the Pyrocam III form factor, the company is introducing the Pyrocam III-HR which has the new Pyrocam features packaged in the Pyrocam III case.
Some additional Pyrocam IV upgrades are that Ophir-Spiricon has moved away from the legacy FireWire interface to a Gigabit Ethernet interface. Also, in conjunction with the introduction of the Pyrocam IV, the company's BeamGage beam analysis software has also gone through some updates. The most recent release of v6.3 (a free upgrade to those using BeamGage v5.0 or later), allows for a more user-friendly interface to the Pyrocam camera, as well as several front-end and back-end software enhancements.
For more detailed information on Pyrocam IV, please contact Ophir-Spiricon product specialist John McCauley at John.mccauley@us.ophiropt.com.
IMAGE: The Pyrocam IV thermal-electric camera can image and characterize laser beams with high resolution over a broad range of emission frequencies. (Image credit: Ophir-Spiricon)
SOURCE: Ophir-Spiricon; http://www.laserfocusworld.com/articles/2014/04/ophir-photonics-to-showcase-pyroelectric-camera-for-2d-3d-laser-diagnostics-at-spie-dss-2014.html

Abstract-Magnetization and phase transition induced by circularly polarized laser in quantum magnets


Shintaro Takayoshi, Hideo Aoki, and Takashi Oka
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.90.085150#abstract

We theoretically predict a nonequilibrium phase transition in quantum spin systems induced by a laser, which provides a purely quantum-mechanical way of coherently controlling magnetization. Namely, when a circularly polarized laser is applied to a spin system, the magnetic component of a laser is shown to induce a magnetization normal to the plane of polarization, leading to an ultrafast phase transition. We first demonstrate this phenomenon numerically for an S=1 antiferromagnetic Heisenberg spin chain, where a new state emerges with magnetization perpendicular to the polarization plane of the laser in place of the topologically ordered Haldane state. We then elucidate its physical mechanism by mapping the system to an effective static model. The theory also indicates that the phenomenon should occur in general quantum spin systems with a magnetic anisotropy. The required laser frequency is in the terahertz range, with the required intensity being within a prospective experimental feasibility.
DOI: http://dx.doi.org/10.1103/PhysRevB.90.085150
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Teraview- Terahertz intraoperative breast cancer probe


http://euroscan.org.uk/technologies/technology/view/2768

Source agency:
NIHR-HSC
Date of Submission:
29/08/2014
Date of Printing:
30/08/2014
Disclaimer:
This report is work in progress and should not be used for external distribution without permission from the originating agency. Users should be aware that reports are based on information available at the time of research and often on a limited literature search.

Technology, Company & Licensing

Technology name:
Terahertz
Technology - description:
An intraoperative imaging probe based on terahertz (THz) light has been developed by TeraView Ltd to aid identification and excision of cancerous tissue during breast cancer surgery.

The probe is intended to be used on women aged 18-90 years who are undergoing wide local excision, re-excision or sentinel node biopsy for breast cancer. It has been designed to help surgeons identify and differentiate between malignant and benign breast and lymph node tissue and can be used at the site of the surgical incision or on excised tissue. The company claim the probe will assist surgeons to achieve complete surgical excision of tumours, including margins of cancerous tissue.

Based on Terahertz Pulsed Imaging (TPI™) core technology, the hand held Terahertz probe scans the tissue and produces and detects pulses of THz. Information from the reflected light is analysed by a custom algorithm to assess the spectral fingerprint of the tissue and differentiate malignant from benign tissue. This information is processed into 3D images by TeraView’s TPI™ software.
Company or developer:
TeraView Ltd
Reason for database entry:
Existing methods used to assess tumour margins intraoperatively, include specimen x-ray mammography and palpation. These methods can however, be unreliable, requiring the surgeon to guess if the tumour has been entirely removed. Histopathological examination of the excised tumour, although more reliable, can only be performed post-operatively and is a time consuming process, requiring 5-7 days for analysis.
Technology - stage in early warning process:
Assessment complete
Technology - stage of development:
Nearly established
Licensing, reimbursement and other approval:
The company anticipate launch for private and NHS clinical use following CE marking in 2015.
Technology - type(s):
Diagnostics, Device
Technology - use(s):
Diagnostic

Patient Indication & Setting

Patient indications:
Breast cancer surgery
Disease description and associated mortality and morbidity:
Number of Patients:
Technology - specialities(s):
Radiology, imaging & nuclear medicine, Oncology & radiotherapy
Technology - setting(s):
General hospital and ambulatory care, Specialist hospital
Setting - further information:

Impact

Alternative and/or complementary technology:
Additive and substitution
Current Technology:
Existing methods used to assess tumour margins intraoperatively, include specimen x-ray mammography and palpation. These methods can however, be unreliable, requiring the surgeon to guess if the tumour has been entirely removed. Histopathological examination of the excised tumour, although more reliable, can only be performed post-operatively and is a time consuming process, requiring 5-7 days for analysis.
Health Impact:
The company state the ability of the probe to identify and differentiate sorts of tissues is based on the sensitivity of Terahertz light to variations in tissue water content. They also claim the probe offers a less invasive and low energy option for high resolution breast cancer imaging. The company claim a key innovative feature of the probe is its ability to assist with the identification of cancerous tissue in real-time. The company state the probe will allow the surgeon to check for cancerous tissue at the site of incision and in the excised tissue, during surgery. Being able to do this in real time may reduce incidence and associated costs of re-excision and additional follow-up surgery, as claimed by the company. As a consequence, this may also reduce waiting times for first-time surgery.

If clinical and cost effectiveness can be demonstrated, the Terahertz intraoperative probe may offer an additional imaging option for selected patients. 
Diffusion:
Cost, infrastructure and economic consequences:
Ethical, social, legal, political and cultural impact:

Evidence & Policy

Clinical evidence and safety:
Economic evaluation:
Ongoing research:
TPI- in vivo study in breast cancer and sentinel lymph nodes: In vivo evaluation of Terahertz Pulse Imaging of breast cancer and sentinel lymph nodes. [Online]
http://public.ukcrn.org.uk/Search/StudyDetail.aspx?StudyID=13598 Accessed 24th July 2014. 
Ongoing or planned HTA:
Web link:
http://www.hsc.nihr.ac.uk/topics/terahertz-intraoperative-breast-cancer-probe/
References and sources:
Ashworth PC, Pickwell-MacPherson E, Provenzano E et al. Terahertz pulsed spectroscopy of freshly excised human breast cancer. Optics Express 2009; 17(15):12444-12454. http://www.ncbi.nlm.nih.gov/pubmed/19654646

Calvin Y, Shuting Fan, Yiwen S et al. The potential of terahertz imaging for cancer diagnosis: A review of investigations to date. Quantitative imaging in medicine and surgery 2012;2(1): 33-45.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3496499/

Fitzgerald AJ, Wallace VP, Jimenez-Linan M et al. Terahertz pulsed imaging of human breast tumours. Radiology 2006;239(2):533-540. http://www.ncbi.nlm.nih.gov/pubmed/16543586

Fitzgerald AJ, Pinder S, Purushotham AD et al. Classification of terahertz-pulsed imaging data from excised breast tissue. Journal of biomedical optics 2012;17(1). http://www.ncbi.nlm.nih.gov/pubmed/22352655

Pickwell-Macherson E and Wallace VP. Terahertz pulsed imaging- A potential medical imaging modality? Photodiagnosis and photodynamic therapy 2009;6(2):128-134. http://www.ncbi.nlm.nih.gov/pubmed/19683214 
Notes:
Another intraoperative imaging probe is the MarginProbe® system, which has been developed by Dune Medical devices. The system became commercially available following CE marking in 2006. MarginProbe® is not currently distributed in the UK.
Other technologies for the identification of cancerous tissue currently in early development include: a heads up goggle display by Washington University, the Artemis fluorescence camera and C-dots system by Quest Medical and Cornell University and the iKnife surgical tool by Medimass and Imperial College London, which can also cut the identified cancerous tissue. 

Friday, August 29, 2014

Abstract-A review of terahertz sources





R A Lewis
Institute for Superconducting and Electronic Materials and School of Physics, University of Wollongong, Wollongong NSW 2522, Australia 
http://iopscience.iop.org/0022-3727/47/37/374001
Bibliometric data set the scene by illustrating the growth of terahertz work and the present interest in terahertz science and technology. After locating terahertz sources within the broader context of terahertz systems, an overview is given of the range of available sources, emphasizing recent developments. The focus then narrows to terahertz sources that rely on surface phenomena. Three are highlighted. Optical rectification, usually thought of as a bulk process, may in addition exhibit a surface contribution, which, in some cases, predominates. Transient surface currents, for convenience often separated into drift and diffusion currents, are well understood according to Monte Carlo modelling. Finally, terahertz surface emission by mechanical means—in the absence of photoexcitation—is described.

Abstract-Terahertz spectroscopy of quantum 2D electron systems


James Lloyd-Hughes

University of Warwick, Department of Physics, Gibbet Hill Road, Coventry, CV4 7AL, UK 

Terahertz time-domain spectroscopy permits the coherent motion of charges to be examined in a diverse range of two-dimensional semiconductor heterostructures. Studies of the THz conductivity and magnetoconductivity of two-dimensional quantum systems are reviewed, including cyclotron resonance spectroscopy and the transverse conductivity in the Hall and quantum Hall regimes. Experiments are described that demonstrate quantum phenomena at THz frequencies, principally coherent control and enhanced light–matter coupling in electromagnetic cavities.