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Wang D, Ning R, Li G, Zhao J, Wang Y, Rong L. 3D image reconstruction of terahertz computed tomography at sparse angles by total variation minimization. APPLIED OPTICS 2022; 61:B1-B7. [PMID: 35201119 DOI: 10.1364/ao.440847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/09/2021] [Indexed: 06/14/2023]
Abstract
Continuous-wave terahertz computed tomography (THz-CT) is an important three-dimensional imaging method for probing the profile and inner properties of a sample's structure. We applied the total variation (TV) minimization iterative algorithm to squeeze 75% data acquisition time of THz-CT without the loss of reconstruction fidelity. The imaging system is built based on a 278.6 GHz avalanche diode source. A zero-order Bessel beam is generated by an axicon, for which the intensity profile remains essentially propagation invariant within the non-diffracting zone. The effectiveness of the proposed method is verified by using three optically opaque objects. The reconstruction results show that the TV-minimization algorithm can effectively suppress noise, artefacts, and shape distortion created in sparse angle reconstruction.
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2
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Li X, Yin W, Khamas S. An Efficient Photomixer Based Slot Fed Terahertz Dielectric Resonator Antenna. SENSORS 2021; 21:s21030876. [PMID: 33525561 PMCID: PMC7866193 DOI: 10.3390/s21030876] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 01/21/2021] [Accepted: 01/25/2021] [Indexed: 02/01/2023]
Abstract
A slot fed terahertz dielectric resonator antenna driven by an optimized photomixer is proposed, and the interaction of the laser and photomixer is studied. It is demonstrated that in a continuous wave terahertz photomixing scheme, the generated THz power is proportional to the 4th power of the surface electric field of photocondutive layer. Consequently, the optical to THz conversion efficiency of the proposed photomixer has an enhancement factor of 487. This is due to the fact that the surface electric field of the proposed photomixer with a 2D-Photonic Crystal (PhC) superstrate has been improved from 2.1 to 9.9 V/m, which represents a substantial improvement. Moreover, the electrically thick Gallium-Arsenide (GaAs) supporting substrate of the device has been truncated to create a dielectric resonator antenna (DRA) that offers a typical radiation efficiency of more than 90%. By employing a traditional coplanar strip (CPS) biasing network, the matching efficiency has been improved to 24.4%. Therefore, the total efficiency has been considerably improved due to the enhancements in the laser-to-THz conversion, as well as radiation and matching efficiencies. Further, the antenna gain has been improved to 9dBi at the presence of GaAs superstrate. Numerical comparisons show that the proposed antenna can achieve a high gain with relatively smaller dimensions compared with traditional THz antenna with Si lens.
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Affiliation(s)
- Xiaohang Li
- Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S10 2TN, UK;
- Correspondence:
| | - Wenfei Yin
- School of Computer Science and Information Engineering, Hefei University of Technology, Hefei 230009, China;
| | - Salam Khamas
- Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S10 2TN, UK;
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3
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The Gyrotrons as Promising Radiation Sources for THz Sensing and Imaging. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10030980] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The gyrotrons are powerful sources of coherent radiation that can operate in both pulsed and CW (continuous wave) regimes. Their recent advancement toward higher frequencies reached the terahertz (THz) region and opened the road to many new applications in the broad fields of high-power terahertz science and technologies. Among them are advanced spectroscopic techniques, most notably NMR-DNP (nuclear magnetic resonance with signal enhancement through dynamic nuclear polarization, ESR (electron spin resonance) spectroscopy, precise spectroscopy for measuring the HFS (hyperfine splitting) of positronium, etc. Other prominent applications include materials processing (e.g., thermal treatment as well as the sintering of advanced ceramics), remote detection of concealed radioactive materials, radars, and biological and medical research, just to name a few. Among prospective and emerging applications that utilize the gyrotrons as radiation sources are imaging and sensing for inspection and control in various technological processes (for example, food production, security, etc). In this paper, we overview the current status of the research in this field and show that the gyrotrons are promising radiation sources for THz sensing and imaging based on both the existent and anticipated novel techniques and methods.
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Chen C, Song W, Chen JW, Wang JH, Chen YH, Xu B, Chen MK, Li H, Fang B, Chen J, Kuo HY, Wang S, Tsai DP, Zhu S, Li T. Spectral tomographic imaging with aplanatic metalens. LIGHT, SCIENCE & APPLICATIONS 2019; 8:99. [PMID: 31728191 PMCID: PMC6834576 DOI: 10.1038/s41377-019-0208-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 09/30/2019] [Accepted: 10/03/2019] [Indexed: 05/23/2023]
Abstract
Tomography is an informative imaging modality that is usually implemented by mechanical scanning, owing to the limited depth-of-field (DOF) in conventional systems. However, recent imaging systems are working towards more compact and stable architectures; therefore, developing nonmotion tomography is highly desirable. Here, we propose a metalens-based spectral imaging system with an aplanatic GaN metalens (NA = 0.78), in which large chromatic dispersion is used to access spectral focus tuning and optical zooming in the visible spectrum. After the function of wavelength-switched tomography was confirmed on cascaded samples, this aplanatic metalens is utilized to image microscopic frog egg cells and shows excellent tomographic images with distinct DOF features of the cell membrane and nucleus. Our approach makes good use of the large diffractive dispersion of the metalens and develops a new imaging technique that advances recent informative optical devices.
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Affiliation(s)
- Chen Chen
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
| | - Wange Song
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
| | - Jia-Wern Chen
- Research Center for Applied Sciences, Taipei, 11529 Taiwan, China
- Department of Physics, Taiwan University, Taipei, 10617 Taiwan, China
| | - Jung-Hsi Wang
- Graduate Institute of Electronics Engineering, Taiwan University, Taipei, 10617 Taiwan, China
| | - Yu Han Chen
- Research Center for Applied Sciences, Taipei, 11529 Taiwan, China
- Department of Physics, Taiwan University, Taipei, 10617 Taiwan, China
| | - Beibei Xu
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
| | - Mu-Ku Chen
- Research Center for Applied Sciences, Taipei, 11529 Taiwan, China
- Department of Physics, Taiwan University, Taipei, 10617 Taiwan, China
| | - Hanmeng Li
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
| | - Bin Fang
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
| | - Ji Chen
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
| | - Hsin Yu Kuo
- Research Center for Applied Sciences, Taipei, 11529 Taiwan, China
- Department of Physics, Taiwan University, Taipei, 10617 Taiwan, China
| | - Shuming Wang
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
| | - Din Ping Tsai
- Research Center for Applied Sciences, Taipei, 11529 Taiwan, China
- Department of Physics, Taiwan University, Taipei, 10617 Taiwan, China
| | - Shining Zhu
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
| | - Tao Li
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093 China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
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5
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Jokubauskis D, Minkevičius L, Karaliūnas M, Indrišiūnas S, Kašalynas I, Račiukaitis G, Valušis G. Fibonacci terahertz imaging by silicon diffractive optics. OPTICS LETTERS 2018; 43:2795-2798. [PMID: 29905691 DOI: 10.1364/ol.43.002795] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 05/11/2018] [Indexed: 06/08/2023]
Abstract
Fibonacci or bifocal terahertz (THz) imaging is demonstrated experimentally employing a silicon diffractive zone plate in continuous wave mode. Images simultaneously recorded in two different planes are exhibited at 0.6 THz frequency with the spatial resolution of wavelength. Multifocus imaging operation of the Fibonacci lens is compared with a performance of the conventional silicon phase zone plate. Spatial profiles and focal depth features are discussed varying the frequency from 0.3 to 0.6 THz. Good agreement between experimental results and simulation data is revealed.
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Valzania L, Zolliker P, Hack E. Topography of hidden objects using THz digital holography with multi-beam interferences. OPTICS EXPRESS 2017; 25:11038-11047. [PMID: 28788789 DOI: 10.1364/oe.25.011038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We present a method for the separation of the signal scattered from an object hidden behind a THz-transparent sample in the framework of THz digital holography in reflection. It combines three images of different interference patterns to retrieve the amplitude and phase distribution of the object beam. Comparison of simulated with experimental images obtained from a metallic resolution target behind a Teflon plate demonstrates that the interference patterns can be described in the simple form of three-beam interference. Holographic reconstructions after the application of the method show a considerable improvement compared to standard reconstructions exclusively based on Fourier transform phase retrieval.
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7
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Yin XX, Zhang Y, Cao J, Wu JL, Hadjiloucas S. Exploring the complementarity of THz pulse imaging and DCE-MRIs: Toward a unified multi-channel classification and a deep learning framework. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2016; 137:87-114. [PMID: 28110743 DOI: 10.1016/j.cmpb.2016.08.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 07/23/2016] [Accepted: 08/31/2016] [Indexed: 06/06/2023]
Abstract
We provide a comprehensive account of recent advances in biomedical image analysis and classification from two complementary imaging modalities: terahertz (THz) pulse imaging and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). The work aims to highlight underlining commonalities in both data structures so that a common multi-channel data fusion framework can be developed. Signal pre-processing in both datasets is discussed briefly taking into consideration advances in multi-resolution analysis and model based fractional order calculus system identification. Developments in statistical signal processing using principal component and independent component analysis are also considered. These algorithms have been developed independently by the THz-pulse imaging and DCE-MRI communities, and there is scope to place them in a common multi-channel framework to provide better software standardization at the pre-processing de-noising stage. A comprehensive discussion of feature selection strategies is also provided and the importance of preserving textural information is highlighted. Feature extraction and classification methods taking into consideration recent advances in support vector machine (SVM) and extreme learning machine (ELM) classifiers and their complex extensions are presented. An outlook on Clifford algebra classifiers and deep learning techniques suitable to both types of datasets is also provided. The work points toward the direction of developing a new unified multi-channel signal processing framework for biomedical image analysis that will explore synergies from both sensing modalities for inferring disease proliferation.
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Affiliation(s)
- X-X Yin
- Centre of Applied Informatics, College of Engineering and Science, Victoria University, Melbourne, VIC 8001, Australia.
| | - Y Zhang
- Centre of Applied Informatics, College of Engineering and Science, Victoria University, Melbourne, VIC 8001, Australia; School of Computer Science, Fudan University, Shanghai, China.
| | - J Cao
- Nanjing University of Finance and Economics school of Computer Science, Nanjing, China
| | - J-L Wu
- Department of Radiology, Affiliated Zhongshan Hospital of Dalian University, Dalian, Liaoning, China.
| | - S Hadjiloucas
- School of Biological Sciences and Department of Bioengineering, University of Reading, Reading RG6 6AY, UK.
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8
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Zhai ZH, Zhong SC, Li J, Zhu LG, Meng K, Li J, Liu Q, Peng QX, Li ZR, Zhao JH. Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:095101. [PMID: 27782602 DOI: 10.1063/1.4961494] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ∼400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.
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Affiliation(s)
- Zhao-Hui Zhai
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Sen-Cheng Zhong
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Jun Li
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Li-Guo Zhu
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Kun Meng
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Jiang Li
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Qiao Liu
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Qi-Xian Peng
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Ze-Ren Li
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
| | - Jian-Heng Zhao
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China
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9
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Ibrahim A, Férachou D, Sharma G, Singh K, Kirouac-Turmel M, Ozaki T. Ultra-high dynamic range electro-optic sampling for detecting millimeter and sub-millimeter radiation. Sci Rep 2016; 6:23107. [PMID: 26976363 PMCID: PMC4791559 DOI: 10.1038/srep23107] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 02/29/2016] [Indexed: 11/25/2022] Open
Abstract
Time-domain spectroscopy using coherent millimeter and sub-millimeter radiation (also known as terahertz radiation) is rapidly expanding its application, owing greatly to the remarkable advances in generating and detecting such radiation. However, many current techniques for coherent terahertz detection have limited dynamic range, thus making it difficult to perform some basic experiments that need to directly compare strong and weak terahertz signals. Here, we propose and demonstrate a novel technique based on cross-polarized spectral-domain interferometry to achieve ultra-high dynamic range electro-optic sampling measurement of coherent millimeter and sub-millimeter radiation. In our scheme, we exploit the birefringence in a single-mode polarization maintaining fiber in order to measure the phase change induced by the electric field of terahertz radiation in the detection crystal. With our new technique, we have achieved a dynamic range of 7 × 106, which is 4 orders of magnitude higher than conventional electro-optic sampling techniques, while maintaining comparable signal-to-noise ratio. The present technique is foreseen to have great impact on experiments such as linear terahertz spectroscopy of optically thick materials (such as aqueous samples) and nonlinear terahertz spectroscopy, where the higher dynamic range is crucial for proper interpretation of experimentally obtained results.
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Affiliation(s)
- Akram Ibrahim
- INRS-EMT, Advanced Laser Light Source, Université du Québec, 1650 boul. Lionel- Boulet, Varennes J3X 1S2, Québec, Canada
| | - Denis Férachou
- INRS-EMT, Advanced Laser Light Source, Université du Québec, 1650 boul. Lionel- Boulet, Varennes J3X 1S2, Québec, Canada
| | - Gargi Sharma
- University of Massachusetts Lowell, 1 University Avenue, Lowell, 01854, Massachusetts, USA
| | - Kanwarpal Singh
- Harvard Medical School, Massachusetts General Hospital, 40 Blossom Street, Boston, 02114, Massachusetts, USA
| | - Marie Kirouac-Turmel
- INRS-EMT, Advanced Laser Light Source, Université du Québec, 1650 boul. Lionel- Boulet, Varennes J3X 1S2, Québec, Canada
| | - Tsuneyuki Ozaki
- INRS-EMT, Advanced Laser Light Source, Université du Québec, 1650 boul. Lionel- Boulet, Varennes J3X 1S2, Québec, Canada
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10
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THz near-field spectral encoding imaging using a rainbow metasurface. Sci Rep 2015; 5:14403. [PMID: 26400502 PMCID: PMC4585877 DOI: 10.1038/srep14403] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 08/03/2015] [Indexed: 11/22/2022] Open
Abstract
We demonstrate a fast image acquisition technique in the terahertz range via spectral encoding using a metasurface. The metasurface is composed of spatially varying units of mesh filters that exhibit bandpass features. Each mesh filter is arranged such that the centre frequencies of the mesh filters are proportional to their position within the metasurface, similar to a rainbow. For imaging, the object is placed in front of the rainbow metasurface, and the image is reconstructed by measuring the transmitted broadband THz pulses through both the metasurface and the object. The 1D image information regarding the object is linearly mapped into the spectrum of the transmitted wave of the rainbow metasurface. Thus, 2D images can be successfully reconstructed using simple 1D data acquisition processes.
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11
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Recur B, Balacey H, Bou Sleiman J, Perraud JB, Guillet JP, Kingston A, Mounaix P. Ordered subsets convex algorithm for 3D terahertz transmission tomography. OPTICS EXPRESS 2014; 22:23299-23309. [PMID: 25321798 DOI: 10.1364/oe.22.023299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigate in this paper a new reconstruction method in order to perform 3D Terahertz (THz) tomography using a continuous wave acquisition setup in transmission mode. This method is based on the Maximum Likelihood for TRansmission tomography (ML-TR) first developed for X-ray imaging. We optimize the Ordered Subsets Convex (OSC) implementation of the ML-TR by including the Gaussian propagation model of THz waves and take into account the intensity distributions of both blank calibration scan and dark-field measured on THz detectors. THz ML-TR reconstruction quality and accuracy are discussed and compared to other tomographic reconstructions.
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12
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Bitman A, Goldring S, Moshe I, Zalevsky Z. Computed tomography using broadband Bessel THz beams and phase contrast. OPTICS LETTERS 2014; 39:1925-1928. [PMID: 24686640 DOI: 10.1364/ol.39.001925] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present new results demonstrating the capability of performing computed tomography (CT) using broadband Bessel terahertz (THz) beams. Nondiffractive beams such as these exhibit propagation-invariant lines of focus with an extended depth-of-field compared to conventional Gaussian beams. Using this property, we demonstrate a considerable improvement in the 3D reconstruction image of a synthetic sample through the backprojection algorithm. Only when THz Bessel beams are used, a full reconstruction of the object structure is made. Moreover, we use phase-contrast mechanism which improves the spatial resolution and reconstructed images. Our results highlight the potential in using nondiffractive Bessel beams to significantly improve 3D-image reconstruction of THz CT.
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13
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Bessou M, Chassagne B, Caumes JP, Pradère C, Maire P, Tondusson M, Abraham E. Three-dimensional terahertz computed tomography of human bones. APPLIED OPTICS 2012; 51:6738-44. [PMID: 23033089 DOI: 10.1364/ao.51.006738] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Three-dimensional terahertz computed tomography has been used to investigate dried human bones such as a lumbar vertebra, a coxal bone, and a skull, with a direct comparison with standard radiography. In spite of lower spatial resolution compared with x-ray, terahertz imaging clearly discerns a compact bone from a spongy one, with strong terahertz absorption as shown by additional terahertz time-domain transmission spectroscopy.
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Affiliation(s)
- Maryelle Bessou
- PACEA, Univ. Bordeaux, CNRS, UMR 5199, F-33405 Talence, France
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14
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Morris CM, Aguilar RV, Stier AV, Armitage NP. Polarization modulation time-domain terahertz polarimetry. OPTICS EXPRESS 2012; 20:12303-12317. [PMID: 22714218 DOI: 10.1364/oe.20.012303] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present high precision measurements of polarization rotations in the frequency range from 0.1 to 2.5 THz using a polarization modulation technique. A motorized stage rotates a polarizer at ~ 80 Hz, and the resulting modulation of the polarization is measured by a lock-in technique. We achieve an accuracy of 0.050° (900 μrad) and a precision of 0.02° (350 μrad) for small rotation angles. A detailed mathematical description of the technique is presented, showing its ability to fully characterize elliptical polarizations from 0.1 to 2.5 THz.
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Affiliation(s)
- C M Morris
- Department of Physics and Astronomy, The Johns Hopkins University, 3400 N Charles St, Baltimore, Maryland 21218, USA
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15
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Recur B, Guillet JP, Manek-Hönninger I, Delagnes JC, Benharbone W, Desbarats P, Domenger JP, Canioni L, Mounaix P. Propagation beam consideration for 3D THz computed tomography. OPTICS EXPRESS 2012; 20:5817-5829. [PMID: 22418459 DOI: 10.1364/oe.20.005817] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this paper, a model of the beam propagation is developed according to the physical properties of THz waves used in THz computed tomography (CT) scan imaging. This model is first included in an acquisition simulator to observe and estimate the impact of the Gaussian beam intensity profile on the projection sets. Second, the model is introduced in several inversion methods as a convolution filter to perform efficient tomographic reconstructions of simulated and real acquired objects. Results obtained with three reconstruction methods (BFP, SART and OSEM) are compared to the techniques proposed in this paper. We will demonstrate an increase of the overall quality and accuracy of the 3D reconstructions.
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Affiliation(s)
- B Recur
- LaBRI, Bordeaux 1 University, CNRS UMR 5800, 351 cours de la Liberation, 33405 Talence, France.
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16
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Recur B, Younus A, Salort S, Mounaix P, Chassagne B, Desbarats P, Caumes JP, Abraham E. Investigation on reconstruction methods applied to 3D terahertz computed tomography. OPTICS EXPRESS 2011; 19:5105-5117. [PMID: 21445145 DOI: 10.1364/oe.19.005105] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
3D terahertz computed tomography has been performed using a monochromatic millimeter wave imaging system coupled with an infrared temperature sensor. Three different reconstruction methods (standard back-projection algorithm and two iterative analysis) have been compared in order to reconstruct large size 3D objects. The quality (intensity, contrast and geometric preservation) of reconstructed cross-sectional images has been discussed together with the optimization of the number of projections. Final demonstration to real-life 3D objects has been processed to illustrate the potential of the reconstruction methods for applied terahertz tomography.
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Affiliation(s)
- B Recur
- LOMA, Université de Bordeaux/CNRS, 351 Cours de la Libération, 33405 Talence Cedex, France
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17
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Naderi NA, Grillot F, Yang K, Wright JB, Gin A, Lester LF. Two-color multi-section quantum dot distributed feedback laser. OPTICS EXPRESS 2010; 18:27028-27035. [PMID: 21196979 DOI: 10.1364/oe.18.027028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A dual-wavelength emission source is realized by asymmetrically pumping a two-section quantum-dot distributed feedback laser. It is found that under asymmetric bias conditions, the powers between the ground-state and excited-state modes of the two-section device can be equalized, which is mainly attributed to the unique carrier dynamics of the quantum-dot gain medium. As a result, a two-color emission with an 8-THz frequency difference is realized that has potential as a compact THz source. It is also shown that the combination of significant inhomogeneous broadening and excited-state coupled mode operation allows the manipulation of the quantum-dot states through external optical stabilization.
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Affiliation(s)
- Nader A Naderi
- Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87106, USA.
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Lee K, Jin KH, Ye JC, Ahn J. Coherent optical computing for T-ray imaging. OPTICS LETTERS 2010; 35:508-510. [PMID: 20160800 DOI: 10.1364/ol.35.000508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Single-point imagery of 2D objects is proposed by exploiting the extreme broadband nature of an ultrafast terahertz wave. In the proposed imagery, a collimated terahertz beam is illuminated on an object, and the scattered fields are measured through a hole at the Fourier plane in a conventional terahertz time-domain spectroscope. This arrangement allows conversion of radial spatial frequencies of the object to the temporal spectrum of the pulse. Hence, a 2D image can be readily obtained by rotating a hole around the optical axis. Experimental results confirm that a complicated object can be reliably imaged using only 30 waveform measurements.
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Affiliation(s)
- Kanghee Lee
- Department of Physics, Korean Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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Sunaguchi N, Sasaki Y, Maikusa N, Kawai M, Yuasa T, Otani C. Depth-resolving THz imaging with tomosynthesis. OPTICS EXPRESS 2009; 17:9558-9570. [PMID: 19506604 DOI: 10.1364/oe.17.009558] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We demonstrated a depth-resolved 3D imaging technique based on absorption contrast using tomosynthesis. Tomosynthesis is similar to computed tomography except that the number of projections is much smaller. We constructed a tomosynthesis imaging system, which detects a transmitted continuous THz wave. We applied a backprojection method that was suitable for the constructed detection configuration, to reconstruct an image. Using this system, we imaged a test sample made from paper and reproduced characters written by pencil.
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Jepsen PU, Fischer BM. Dynamic range in terahertz time-domain transmission and reflection spectroscopy. OPTICS LETTERS 2005; 30:29-31. [PMID: 15648627 DOI: 10.1364/ol.30.000029] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present a quantitative method for identification of the dynamic range of the detectable absorption coefficient in the analysis of transmission terahertz (THz) time-domain spectroscopy data. In transmission measurements the largest detectable absorption coefficient is determined by the dynamic range of the THz signals, whereas in reflection measurements the largest detectable absorption coefficient is determined by the scan-to-scan reproducibility of the signal.
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Affiliation(s)
- Peter Uhd Jepsen
- Department of Molecular and Optical Physics, Physikalisches Institut, Universität Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany.
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