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Zhu H, Wang G, Wang K, Liu G, Zhou Y, Xie S, Di Y, Xu J, Zhou H, Mou J, Ding C. Grid composite meta-surface absorber with thermal isolation structure for terahertz detection. OPTICS EXPRESS 2024; 32:205-216. [PMID: 38175049 DOI: 10.1364/oe.509580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 12/04/2023] [Indexed: 01/05/2024]
Abstract
This paper specifically focuses on the absorber, the critical component responsible for the detector's response performance. The meta-surface absorber combines two resonant structures and achieves over 80% absorptance around 210 GHz, resulting in a broad operating frequency range. FR-4 is selected as the dielectric layer to be compatible with standard printed circuit board (PCB) technology, which reduces the overall fabrication time and cost. The absorbing unit and array layout are symmetrically designed, providing stable absorptance performance even under incident waves of different polarization angles. The polarization-insensitive absorptance characteristic further enhances the compatibility between the absorber and the detector in the application scenario. Furthermore, the thermal insulation performance of the absorber is ensured by introducing thermal insulation gaps. After completing fabrication through PCB technology, testing revealed that the absorber maintained excellent absorptance performance within its primary operating frequency range. This performance consistency closely matched the simulation results.
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Tamaki R, Suzuki M, Kusaba S, Takeda J, Katayama I. Ultrafast pump-probe spectroscopy via chirped-pulse up-conversion with dispersion compensation. OPTICS EXPRESS 2023; 31:40142-40150. [PMID: 38041321 DOI: 10.1364/oe.504429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 10/31/2023] [Indexed: 12/03/2023]
Abstract
In this study, ultrafast transient signals were detected on a single-shot basis using chirped-pulse up-conversion spectroscopy with dispersion compensation. Unlike in the conventional time-encoding technique using chirped pulses, distortion of the ultrafast waveform was reduced by applying dispersion compensation to the chirped probe pulses and using sum-frequency generation with the chirped readout pulses. The method was applied to terahertz time-domain spectroscopy and near-infrared pump-probe spectroscopy, providing ultrafast observations with an improved temporal resolution comparable to the transform-limited pulse durations. Terahertz waveforms, Kerr rotation signals, and phonon-polariton oscillations were measured accurately with no significant waveform distortion, thereby showing the proposed scheme to be promising for single-shot pump-probe spectroscopy in a wide range of spectroscopic applications.
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Wu X, Kong D, Hao S, Zeng Y, Yu X, Zhang B, Dai M, Liu S, Wang J, Ren Z, Chen S, Sang J, Wang K, Zhang D, Liu Z, Gui J, Yang X, Xu Y, Leng Y, Li Y, Song L, Tian Y, Li R. Generation of 13.9-mJ Terahertz Radiation from Lithium Niobate Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2208947. [PMID: 36932897 DOI: 10.1002/adma.202208947] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 03/12/2023] [Indexed: 06/09/2023]
Abstract
Extremely strong-field terahertz (THz) radiation in free space has compelling applications in nonequilibrium condensed matter state regulation, all-optical THz electron acceleration and manipulation, THz biological effects, etc. However, these practical applications are constrained by the absence of high-intensity, high-efficiency, high-beam-quality, and stable solid-state THz light sources. Here, the generation of single-cycle 13.9-mJ extreme THz pulses from cryogenically cooled lithium niobate crystals and a 1.2% energy conversion efficiency from 800 nm to THz are demonstrated experimentally using the tilted pulse-front technique driven by a home-built 30-fs, 1.2-Joule Ti:sapphire laser amplifier. The focused peak electric field strength is estimated to be 7.5 MV cm-1 . A record of 1.1-mJ THz single-pulse energy at a 450 mJ pump at room temperature is produced and observed that the self-phase modulation of the optical pump can induce THz saturation behavior from the crystals in the substantially nonlinear pump regime. This study lays the foundation for the generation of sub-Joule THz radiation from lithium niobate crystals and will inspire more innovations in extreme THz science and applications.
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Affiliation(s)
- Xiaojun Wu
- School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
- Zhangjiang Laboratory, 100 Haike Road, Shanghai, 201210, China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Deyin Kong
- School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
- Zhangjiang Laboratory, 100 Haike Road, Shanghai, 201210, China
| | - Sibo Hao
- School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Yushan Zeng
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Xieqiu Yu
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Baolong Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Mingcong Dai
- School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Shaojie Liu
- School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Jiaqi Wang
- School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Zejun Ren
- School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Sai Chen
- School of Electronic and Information Engineering, and School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Jianhua Sang
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Kang Wang
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Dongdong Zhang
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Zhongkai Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai, 201210, China
| | - Jiayan Gui
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Xiaojun Yang
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Yi Xu
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Yuxin Leng
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Yutong Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Liwei Song
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Ye Tian
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Ruxin Li
- State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China
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4
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Xu J, Zhang Z, Yang P, Dong L, Zhao Y. Nondestructive testing and 3D imaging of PE pipes using terahertz frequency-modulated continuous wave. APPLIED OPTICS 2022; 61:10230-10239. [PMID: 36606787 DOI: 10.1364/ao.468851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 10/17/2022] [Indexed: 06/17/2023]
Abstract
Polyethylene (PE) pipes are widely used as the main carrier for the transportation of natural gas, so nondestructive testing techniques for PE pipes are essential for the safety of natural gas transportation. In order to compensate for the shortcomings of conventional inspection methods, a terahertz (THz) three-dimensional imaging system for nondestructive inspection of PE pipes is designed. The system is based on frequency-modulated continuous-wave (FMCW) technology, with a THz source bandwidth of 0.225-0.330 THz and an output power of over 5 mW, which can achieve submillimeter spatial resolution in three dimensions. The system is used to scan PE pipes in three dimensions in a laboratory environment, and the results show that the system could achieve nondestructive testing and three-dimensional imaging of different defects in PE pipes. In addition, combined with the deep-learning-based THz transformer network, the intelligent identification of different defects is realized, and the accuracy rate can reach up to 88%. The above results provide technical guidance for the application of THz FMCW systems in the actual detection of PE pipes, and provide supplements and improvements for traditional detection methods.
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Tamaki R, Kasai T, Asai G, Hata D, Kubo H, Takigawa Y, Takeda J, Katayama I. Pulse-to-pulse detection of terahertz radiation emitted from the femtosecond laser ablation process. OPTICS EXPRESS 2022; 30:23622-23630. [PMID: 36225038 DOI: 10.1364/oe.459588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 06/06/2022] [Indexed: 06/16/2023]
Abstract
Determining the dynamics of electrons and ions emitted from a target material during laser ablation is crucial for desirable control of laser processing. However, these dynamics are still challenging to understand because of a lack of ubiquitous spectroscopic tools to observe tangled-up dynamics appearing at ultrafast timescales. Here by harnessing highly sensitive single-shot terahertz time-domain spectroscopy using an echelon mirror, we investigate pulse-to-pulse temporal profile of terahertz radiation generated from the material surface. We clearly found that the carrier-envelope phase and the electric field amplitude of the terahertz waveform systematically vary between the pre- and post-ablation depending on the laser fluence and irradiated pulse numbers. Our results provide a stepping-stone towards perception of Coulomb explosion occurring throughout the laser ablation process, which is indispensable for future laser processing applications.
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Isgandarov E, Ropagnol X, Singh M, Ozaki T. Intense terahertz generation from photoconductive antennas. FRONTIERS OF OPTOELECTRONICS 2021; 14:64-93. [PMID: 36637784 PMCID: PMC9743868 DOI: 10.1007/s12200-020-1081-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 10/16/2020] [Indexed: 06/14/2023]
Abstract
In this paper, we review the past and recent works on generating intense terahertz (THz) pulses from photoconductive antennas (PCAs). We will focus on two types of large-aperture photoconductive antenna (LAPCA) that can generate high-intensity THz pulses (a) those with large-aperture dipoles and (b) those with interdigitated electrodes. We will first describe the principles of THz generation from PCAs. The critical parameters for improving the peak intensity of THz radiation from LAPCAs are summarized. We will then describe the saturation and limitation process of LAPCAs along with the advantages and disadvantages of working with wide-bandgap semiconductor substrates. Then, we will explain the evolution of LAPCA with interdigitated electrodes, which allows one to reduce the photoconductive gap size, and thus obtain higher bias fields while applying lower voltages. We will also describe recent achievements in intense THz pulses generated by interdigitated LAPCAs based on wide-bandgap semiconductors driven by amplified lasers. Finally, we will discuss the future perspectives of THz pulse generation using LAPCAs.
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Affiliation(s)
- Elchin Isgandarov
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux Télécommunications (INRS-EMT), Varennes, Québec, J3X 1S2, Canada
| | - Xavier Ropagnol
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux Télécommunications (INRS-EMT), Varennes, Québec, J3X 1S2, Canada
- Département de Génie Électrique, École de Technologie Supérieure (ETS), Montréal, Québec, H3C 1K3, Canada
| | - Mangaljit Singh
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux Télécommunications (INRS-EMT), Varennes, Québec, J3X 1S2, Canada
| | - Tsuneyuki Ozaki
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux Télécommunications (INRS-EMT), Varennes, Québec, J3X 1S2, Canada.
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Baydin A, Makihara T, Peraca NM, Kono J. Time-domain terahertz spectroscopy in high magnetic fields. FRONTIERS OF OPTOELECTRONICS 2021; 14:110-129. [PMID: 36637783 PMCID: PMC9743882 DOI: 10.1007/s12200-020-1101-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 10/29/2020] [Indexed: 06/14/2023]
Abstract
There are a variety of elementary and collective terahertz-frequency excitations in condensed matter whose magnetic field dependence contains significant insight into the states and dynamics of the electrons involved. Often, determining the frequency, temperature, and magnetic field dependence of the optical conductivity tensor, especially in high magnetic fields, can clarify the microscopic physics behind complex many-body behaviors of solids. While there are advanced terahertz spectroscopy techniques as well as high magnetic field generation techniques available, a combination of the two has only been realized relatively recently. Here, we review the current state of terahertz time-domain spectroscopy (THz-TDS) experiments in high magnetic fields. We start with an overview of time-domain terahertz detection schemes with a special focus on how they have been incorporated into optically accessible high-field magnets. Advantages and disadvantages of different types of magnets in performing THz-TDS experiments are also discussed. Finally, we highlight some of the new fascinating physical phenomena that have been revealed by THz-TDS in high magnetic fields.
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Affiliation(s)
- Andrey Baydin
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 70005, USA.
| | - Takuma Makihara
- Department of Physics and Astronomy, Rice University, Houston, Texas, 77005, USA
| | | | - Junichiro Kono
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 70005, USA.
- Department of Physics and Astronomy, Rice University, Houston, Texas, 77005, USA.
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas, 77005, USA.
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8
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Asai G, Hata D, Harada S, Kasai T, Arashida Y, Katayama I. High-throughput terahertz spectral line imaging using an echelon mirror. OPTICS EXPRESS 2021; 29:3515-3523. [PMID: 33770948 DOI: 10.1364/oe.413802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 12/28/2020] [Indexed: 06/12/2023]
Abstract
This work demonstrates terahertz (THz) line imaging that acquires broadband spectral information by combining echelon-based single-shot THz spectroscopy with high-sensitivity phase-offset electrooptic detection. An approximately 40 dB signal-to-noise ratio is obtained for a THz spectrum from a single line of the camera, with a detection bandwidth up to 2 THz at the peak electric-field strength of 1.2 kV/cm. The spatial resolution of the image is confirmed to be diffraction limited for each spectral component of the THz wave. We use the system to image sugar tablets by quickly scanning the sample, which illustrates the capacity of the proposed spectral line imaging system for high-throughput applications.
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9
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Non-Contact, Non-Destructive Testing in Various Industrial Sectors with Terahertz Technology. SENSORS 2020; 20:s20030712. [PMID: 32012901 PMCID: PMC7039230 DOI: 10.3390/s20030712] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 01/09/2020] [Accepted: 01/24/2020] [Indexed: 12/21/2022]
Abstract
In this article, we survey various non-contact, non-destructive testing methods by way of terahertz (THz) spectroscopy and imaging designed for use in various industrial sectors. A brief overview of the working principles of THz spectroscopy and imaging is provided, followed by a survey of selected applications from three industries—the building and construction industry, the energy and power industry, and the manufacturing industry. Material characterization, thickness measurement, and defect/corrosion assessment are demonstrated through the examples presented. The article concludes with a discussion of novel spectroscopy and imaging devices and techniques that are expected to accelerate industry adoption of THz systems.
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10
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Kobayashi M, Arashida Y, Yamashita G, Matsubara E, Ashida M, Johnson JA, Katayama I. Fast-frame single-shot pump-probe spectroscopy with chirped-fiber Bragg gratings. OPTICS LETTERS 2019; 44:163-166. [PMID: 30645575 DOI: 10.1364/ol.44.000163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 11/30/2018] [Indexed: 06/09/2023]
Abstract
To acquire single-shot pump-probe waveforms for each laser pulse at a high repetition rate and high signal-to-noise ratio, we combined the photonic time-stretch technique and time-encoding method using a chirped-fiber Bragg grating (CFBG) and a grating-pair pulse compressor. By changing the pre-chirping of the probe pulse, a variable time window of the pump-probe traces from 1.4 to 17 ps was demonstrated. The use of a CFBG improved the signal-to-noise ratio of the waveforms by minimizing the loss of probe pulses due to the transmission through a long fiber. These techniques are promising, for example, in applications in multi-timescale pump-probe spectroscopy of irreversible phenomena.
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11
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Ushakov AA, Chizhov PA, Andreeva VA, Panov NA, Shipilo DE, Matoba M, Nemoto N, Kanda N, Konishi K, Bukin VV, Kuwata-Gonokami M, Kosareva OG, Garnov SV, Savel'ev AB. Ring and unimodal angular-frequency distribution of THz emission from two-color femtosecond plasma spark. OPTICS EXPRESS 2018; 26:18202-18213. [PMID: 30114100 DOI: 10.1364/oe.26.018202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 06/25/2018] [Indexed: 06/08/2023]
Abstract
We study angular and frequency-angular distributions of the terahertz (THz) emission of the low-frequency region (0.3-3 THz) from a two-color femtosecond plasma spark experimentally and in three-dimensional numerical simulations. We investigate the dependence of the angular shapes of the THz radiation on focusing conditions and pulse durations by using two laser facilities (pulse durations 35 and 150 fs) for different focusing geometries. Our experiments and simulations show that decrease in the numerical aperture from NA ≈0.2 to NA ≈0.02 results simultaneously in (I) squeezing of the THz angular distribution and (II) formation of the bright conical emission in the THz range. The moderate focusing NA ≈0.05, which forms the relatively narrow unimodal THz angular distribution, is identified as optimal in terms of angular divergence. Numerical simulations with carrier wave resolved show that bright THz ring structures appear at the frequencies ≥2 THz for longer focuses (NA ≈0.02), while for optimal focusing conditions NA ≈0.05 the conical emission develops at THz frequencies higher than 10 THz.
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12
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Rovere A, Jeong YG, Piccoli R, Lee SH, Lee SC, Kwon OP, Jazbinsek M, Morandotti R, Razzari L. Generation of high-field terahertz pulses in an HMQ-TMS organic crystal pumped by an ytterbium laser at 1030 nm. OPTICS EXPRESS 2018; 26:2509-2516. [PMID: 29401789 DOI: 10.1364/oe.26.002509] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 01/13/2018] [Indexed: 06/07/2023]
Abstract
We present the generation of high-peak-electric-field terahertz pulses via collinear optical rectification in a 2-(4-hydroxy-3-methoxystyryl)-1-methilquinolinium-2,4,6-trimethylbenzenesulfonate (HMQ-TMS) organic crystal. The crystal is pumped by an amplified ytterbium laser system, emitting 170-fs-long pulses centered at 1030 nm. A terahertz peak electric field greater than 200 kV/cm is obtained for 420 µJ of optical pump energy, with an energy conversion efficiency of 0.26% - about two orders of magnitude higher than in common inorganic crystals collinearly pumped by amplified femtosecond lasers. An open-aperture Z-scan measurement performed on an n-doped InGaAs thin film using such terahertz source shows a nonlinear increase in the terahertz transmission of about 2.2 times. Our findings demonstrate the potential of this terahertz generation scheme, based on ytterbium laser technology, as a simple and efficient alternative to the existing intense table-top terahertz sources. In particular, we show that it can be readily used to explore nonlinear effects at terahertz frequencies.
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Russell BK, Ofori-Okai BK, Chen Z, Hoffmann MC, Tsui YY, Glenzer SH. Self-referenced single-shot THz detection. OPTICS EXPRESS 2017; 25:16140-16150. [PMID: 28789123 DOI: 10.1364/oe.25.016140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 06/23/2017] [Indexed: 05/23/2023]
Abstract
We demonstrate a self-referencing method to reduce noise in a single-shot terahertz detection scheme. By splitting a single terahertz pulse and using a reflective echelon, both the signal and reference terahertz time-domain waveforms were measured using one laser pulse. Simultaneous acquisition of these waveforms significantly reduces noise originating from shot-to-shot fluctuations. We show that correlation function based referencing, which is not limited to polarization dependent measurements, can achieve a noise floor that is comparable to state-of-the-art polarization-gated balanced detection. Lastly, we extract the DC conductivity of a 30 nm free-standing gold film using a single THz pulse. The measured value of σ0 = 1.3 ± 0.4 × 107 S m-1 is in good agreement with the value measured by four-point probe, indicating the viability of this method for measuring dynamical changes and small signals.
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Kobayashi M, Minami Y, Johnson CL, Salmans PD, Ellsworth NR, Takeda J, Johnson JA, Katayama I. High-Acquisition-Rate Single-Shot Pump-Probe Measurements Using Time-Stretching Method. Sci Rep 2016; 6:37614. [PMID: 27876881 PMCID: PMC5120281 DOI: 10.1038/srep37614] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 11/01/2016] [Indexed: 11/09/2022] Open
Abstract
Recent advances of ultrafast spectroscopy allow the capture of an entire ultrafast signal waveform in a single probe shot, which greatly reduces the measurement time and opens the door for the spectroscopy of unrepeatable phenomena. However, most single-shot detection schemes rely on two-dimensional detectors, which limit the repetition rate of the measurement and can hinder real-time visualization and manipulation of signal waveforms. Here, we demonstrate a new method to circumvent these difficulties and to greatly simplify the detection setup by using a long, single-mode optical fiber and a fast photodiode. Initially, a probe pulse is linearly chirped (the optical frequency varies linearly across the pulse in time), and the temporal profile of an ultrafast signal is then encoded in the probe spectrum. The probe pulse and encoded temporal dynamics are further chirped to nanosecond time scales using the dispersion in the optical fiber, thus, slowing down the ultrafast signal to time scales easily recorded with fast detectors and high-bandwidth electronics. We apply this method to three distinct ultrafast experiments: investigating the power dependence of the Kerr signal in LiNbO3, observing an irreversible transmission change of a phase change material, and capturing terahertz waveforms.
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Affiliation(s)
- Masataka Kobayashi
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501 Japan
| | - Yasuo Minami
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501 Japan
| | - Courtney L Johnson
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, 84602, USA
| | - Parker D Salmans
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, 84602, USA
| | - Nicholas R Ellsworth
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, 84602, USA
| | - Jun Takeda
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501 Japan
| | - Jeremy A Johnson
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501 Japan.,Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, 84602, USA
| | - Ikufumi Katayama
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501 Japan
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15
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Suzuki T, Isa F, Fujii L, Hirosawa K, Nakagawa K, Goda K, Sakuma I, Kannari F. Sequentially timed all-optical mapping photography (STAMP) utilizing spectral filtering. OPTICS EXPRESS 2015; 23:30512-30522. [PMID: 26698529 DOI: 10.1364/oe.23.030512] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We propose and experimentally demonstrate a new method called SF-STAMP for sequentially timed all-optical mapping photography (STAMP) that utilizes spectral filtering. SF-STAMP is composed of a diffractive optical element (DOE), a band-pass filter, and two Fourier transform lenses. Using a linearly frequency-chirped pulse and converting the wavelength to the time axis, we realize single-shot ultrafast burst imaging. As an experimental demonstration of SF-STAMP, we monitor the dynamics of a laser ablation using a linearly frequency-chirped broadband pulse (>100 nm) that is temporally stretched up to ~40 ps. This imaging method is expected to be effective for investigating ultrafast dynamics in a diverse range of fields, such as photochemistry, plasma physics, and fluidics.
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16
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Pogson EM, McNamara J, Metcalfe P, Lewis RA. Comparing and evaluating the efficacy of the TOR18FG Leeds test X-ray phantom for T-rays. Quant Imaging Med Surg 2013; 3:18-27. [PMID: 23483115 PMCID: PMC3591503 DOI: 10.3978/j.issn.2223-4292.2013.02.05] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Accepted: 02/27/2013] [Indexed: 11/14/2022]
Abstract
The commercially available X-ray fluoroscopy quality assurance phantom, the Leeds test object TOR18FG, was found to be suitable to assess T-ray image quality in the range (0.1-0.4) THz at a depth of 0.5 cm. Previous to this only custom made phantoms, made especially for the T-ray region, assessed T-ray spatial resolution. However, if sub-wavelength techniques are used, the Leeds test phantom may be implemented to measure the T-ray systems spatial resolution, allowing us to directly compare X-ray and T-ray spatial resolution. The systems compared include a Gulmay Orthovoltage machine (X-ray), the On Board Imager (OBI) of a Varian linear accelerator (X-ray), a two-colour system (T-ray) and Terahertz Time Domain Spectroscopy (THz-TDS) system. X-rays were found to have a spatial resolution of 1.25 lp/mm using the On Board Imager of a Varian Linear Accelerator whilst T-rays imaged using a broadband source imaged through a spatial pinhole had a spatial resolution of 0.56 lp/mm. The TOR18FG background material was found to block, 90% and 99% of the broadband T-rays emitted from a THz-TDS photo-conductive emitter, at 0.4 THz and 0.53 THz respectively. Contrast sensitivity was found to be 3% for 25 cm × 25 cm X-ray field at 65 kV, whilst this value could not be established for T-rays using the TOR18FG. All contrast circles were found to be the same for T-rays i.e. all 40% at 0.1 THz. Images of the same leaf were taken with diagnostic X-rays and both broadband and continuous wave (CW) T-ray systems. T-rays proved superior in providing image contrast, for a hydrated leaf, over X-rays.
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Affiliation(s)
- Elise Maree Pogson
- Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Joanne McNamara
- Department of Medical Physics, Illawarra Cancer Care Centre, Locked Bag 8808, South Coast Mail Centre, Wollongong, NSW 2521, Australia
| | - Peter Metcalfe
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Roger A Lewis
- Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia
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Abstract
We demonstrate two algorithms used forreconstructing the target's structure basedon the diffracted pulses and additionallyshow that a three-dimensional target can bereconstructed using the broadband pulsesand a Fresnel lens by virtue of itsfrequency dependent focal length. Oneadvantage of T-ray imaging is the abilityto measure the far-infrared spectralresponse of the target. To highlight theimportance of this spectral information, wedemonstrate T-ray classification imagingwith different biological samples using asimple classification algorithm and twodimensional T-ray spectroscopic images.
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Affiliation(s)
- S Wang
- Center for Subsurface Sensing and Imaging Systems, Rensselaer Polytechnic Institute, Troy, NY 12180-3590 USA
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18
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Sharma G, Singh K, Al-Naib I, Morandotti R, Ozaki T. Terahertz detection using spectral domain interferometry. OPTICS LETTERS 2012; 37:4338-40. [PMID: 23073455 DOI: 10.1364/ol.37.004338] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this work, we present a novel method based on spectral domain interferometry for the electro-optic (EO) sampling of terahertz (THz) electric fields. This technique allows the use of thick crystals without the drawback of the over-rotation that may occur with intense THz sources, allowing longer temporal scans and thus, better spectral resolution. Using this technique, a phase difference of approximately 8898π can be measured, which is 18,000 times larger than the phase difference that could be measured using EO sampling.
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Affiliation(s)
- Gargi Sharma
- Advanced Laser Light Source, Institut National de la Recherche Scientifique, Énergie, Matériaux et Télécommunications, 1650 Boul. Lionel-Boulet, Varennes, Québec J3X 1S2, Canada
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19
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Abstract
Terahertz (THz) radiation occupies part of the electromagnetic spectrum between the infrared and microwave bands. Until recently, technology at THz frequencies was under-developed compared to the rest of the electromagnetic spectrum, leaving a gap between millimeter waves and the far-infrared (FIR). In the past decade, interest in the THz gap has been increased by the development of ultrafast laser-based T-ray systems and their demonstration of diffraction-limited spatial resolution, picosecond temporal resolution, DC-THz spectral bandwidth and signal-to-noise ratios above 104. This chapter reviews the development, the state of the art and the applications of T-ray spectrometers. Continuous-wave (CW) THz-frequency sources and detectors are briefly introduced in comparison to ultrafast pulsed THz systems. An emphasis is placed on experimental applications of T-rays to sensing and imaging, with a view to the continuing advance of technologies and applications in the THz band.
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Affiliation(s)
- S. P. Mickan
- Department of Physics, Applied Physics & Astronomy, and Department of Electrical, Computer & System Engineering, Rensselaer Polytechnic Institute, Troy NY 12180, USA
| | - X.-C. Zhang
- Department of Physics, Applied Physics & Astronomy, and Department of Electrical, Computer & System Engineering, Rensselaer Polytechnic Institute, Troy NY 12180, USA
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21
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van Tilborg J, Bakker DJ, Matlis NH, Leemans WP. Spectral sidebands on a narrow-bandwidth optical probe as a broad-bandwidth THz pulse diagnostic. OPTICS EXPRESS 2011; 19:26634-26644. [PMID: 22274247 DOI: 10.1364/oe.19.026634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Broad-bandwidth THz-domain electro-magnetic pulses are typically diagnosed through temporal electro-optic (EO) cross-correlation with an optical probe pulse. Single-shot time-domain measurements of the THz waveform involve complex setups at a bandwidth coverage limited by the probe bandwidth. Here we present an EO-based diagnostic directly in the spectral domain, relying on THz-induced optical sidebands on a narrow-bandwidth optical probe. Experiments are conducted with a 0.11-THz-bandwidth optical probe and a broadband source (0-8 THz detection bandwidth) rich in spectral features. The validity of the sideband diagnostic concept, its spectral resolution, sideband amplitude, and the effects of probe timing are studied. For probe pulses longer than the THz pulse, the sideband technique proves an accurate single-shot spectral diagnostic, with advantages in setup simplicity and bandwidth coverage no longer limited by the laser bandwidth.
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Affiliation(s)
- J van Tilborg
- Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA.
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22
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Li C, Zhou ML, Ding WJ, Du F, Liu F, Li YT, Wang WM, Sheng ZM, Ma JL, Chen LM, Lu X, Dong QL, Wang ZH, Lou Z, Shi SC, Wei ZY, Zhang J. Effects of laser-plasma interactions on terahertz radiation from solid targets irradiated by ultrashort intense laser pulses. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:036405. [PMID: 22060511 DOI: 10.1103/physreve.84.036405] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 05/16/2011] [Indexed: 05/31/2023]
Abstract
Interactions of 100-fs laser pulses with solid targets at intensities of 10(18) W/cm(2) and resultant terahertz (THz) radiation are studied under different laser contrast ratio conditions. THz emission is measured in the specular reflection direction, which appears to decrease as the laser contrast ratio varies from 10(-8) to 10(-6). Correspondingly, the frequency spectra of the reflected light are observed changing from second harmonic dominant, three-halves harmonic dominant, to vanishing of both harmonics. Two-dimensional particle-in-cell simulation also suggests that this observation is correlated with the plasma density scale length change. The results demonstrate that the THz emission is closely related to the laser-plasma interaction processes. The emission is strong when resonance absorption is a key feature of the interaction, and becomes much weaker when parametric instabilities dominate.
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Affiliation(s)
- Chun Li
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190, China
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23
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Li L, Wang X, Zhai H. Single-shot diagnostic for the three-dimensional field distribution of a terahertz pulse based on pulsed digital holography. OPTICS LETTERS 2011; 36:2737-2739. [PMID: 21765526 DOI: 10.1364/ol.36.002737] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this Letter, a pulsed digital holographic approach for detecting the three-dimensional (3D) field distribution of a freely propagating single terahertz (THz) pulse based on an electro-optic (E-O) sampling technique is proposed, by which the 3D field distribution of a single THz pulse sampled at different time points can be recorded in real-time on a series of subholograms and will be finally reconstructed as a series of two-dimensional spatial electric field distributions in a time series with a time resolution of femtosecond order. Simulation is carried out to demonstrate the process of the implementation, which confirmed the feasibility of the proposal.
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Affiliation(s)
- Lujie Li
- Institute of Modern Optics, Nankai University, Tianjin 300071, China
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24
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Zhang R, Cui Y, Sun W, Zhang Y. Polarization information for terahertz imaging. APPLIED OPTICS 2008; 47:6422-6427. [PMID: 19037370 DOI: 10.1364/ao.47.006422] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A method to analyze the change in the polarization state of a terahertz (THz) wave by using a typical electro-optic sampling setup with a ?110? zinc-blende crystal as a sensor is presented. To illustrate knowledge of the polarization of the THz pulse, the THz detection function in a ZnTe crystal is presented. Two kinds of Jones matrix for the birefringence device and the polarizer device are used to analyze the polarization change in the THz electric field caused by the sample. It is found that THz polarization imaging is sensitive to the edge of the sample.
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Affiliation(s)
- Ranxi Zhang
- Beijing Key Lab for THz Spectroscopy and Imaging, Key Laboratory of THz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing, 100037 China
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25
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Bandyopadhyay A, Stepanov A, Schulkin B, Federici MD, Sengupta A, Gary D, Federici JF, Barat R, Michalopoulou ZH, Zimdars D. Terahertz interferometric and synthetic aperture imaging. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2006; 23:1168-78. [PMID: 16642196 DOI: 10.1364/josaa.23.001168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The stand-off imaging properties of a terahertz (THz) interferometric array are examined. For this application, the imaged object is in the near-field region limit of the imaging array. In this region, spherical and circular array architectures can compensate for near-field distortions and increase the field of view and depth of focus. Imaging of THz point sources is emphasized to demonstrate the imaging method and to compare theoretical predictions to experimental performance.
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26
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Affiliation(s)
- Charles A Schmuttenmaer
- Department of Chemistry, Yale University, 225 Prospect Street, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA
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27
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Zhang XC. Three-dimensional terahertz wave imaging. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2004; 362:283-299. [PMID: 15306520 DOI: 10.1098/rsta.2003.1317] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Pulsed terahertz (THz) wave sensing and imaging is a coherent measurement technology. Like radar, based on the phase and amplitude of the THz pulse at each frequency, THz waves provide temporal and spectroscopic information that allows us to develop various three-dimensional (3D) terahertz tomographic imaging modalities. The 3D THz tomographic imaging methods we investigated include THz time-of-flight tomography, THz computed tomography (CT) and THz binary lens tomography. THz time-of-flight uses the THz pulses as a probe beam to temporally mark the target, and then constructs a 3D image of the target using the THz waves scattered by the target. THz CT is based on geometrical optics and inspired from X-ray CT. THz binary lens tomography uses the frequency-dependent focal-length property of binary lenses to obtain tomographic images of an object. Three-dimensional THz imaging has potential in such applications as non-destructive inspection. The interaction between a coherent THz pulse and an object provides rich information about the object under study; therefore, 3D THz imaging can be used to inspect or characterize dielectric and semiconductor objects. For example, 3D THz imaging has been used to detect and identify the defects inside a Space Shuttle insulation tile.
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Affiliation(s)
- X-C Zhang
- Center for Terahertz Research, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180, USA.
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28
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Jamison SP, Shen J, MacLeod AM, Gillespie WA, Jaroszynski DA. High-temporal-resolution, single-shot characterization of terahertz pulses. OPTICS LETTERS 2003; 28:1710-1712. [PMID: 13677545 DOI: 10.1364/ol.28.001710] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A technique for noncollinear cross correlation of electro-optic modulated optical pulses is presented for the single-shot characterization of terahertz waveforms and is compared to established electro-optic terahertz characterization methods. This technique is free from the limitations on time resolution and faithful reproduction of previously demonstrated single-shot amplitude modulation spectral encoding.
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Affiliation(s)
- Steven P Jamison
- School of Computing and Advanced Technologies, University of Abertay Dundee, Bell Street, Dundee DD1 1HG, UK.
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29
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Galvão R, Hadjiloucas S, Bowen J, Coelho C. Optimal discrimination and classification of THz spectra in the wavelet domain. OPTICS EXPRESS 2003; 11:1462-1473. [PMID: 19466018 DOI: 10.1364/oe.11.001462] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In rapid scan Fourier transform spectrometry, we show that the noise in the wavelet coefficients resulting from the filter bank decomposition of the complex insertion loss function is linearly related to the noise power in the sample interferogram by a noise amplification factor. By maximizing an objective function composed of the power of the wavelet coefficients divided by the noise amplification factor, optimal feature extraction in the wavelet domain is performed. The performance of a classifier based on the output of a filter bank is shown to be considerably better than that of an Euclidean distance classifier in the original spectral domain. An optimization procedure results in a further improvement of the wavelet classifier. The procedure is suitable for enhancing the contrast or classifying spectra acquired by either continuous wave or THz transient spectrometers as well as for increasing the dynamic range of THz imaging systems.
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30
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Woodward RM, Wallace VP, Pye RJ, Cole BE, Arnone DD, Linfield EH, Pepper M. Terahertz pulse imaging of ex vivo basal cell carcinoma. J Invest Dermatol 2003; 120:72-8. [PMID: 12535200 DOI: 10.1046/j.1523-1747.2003.12013.x] [Citation(s) in RCA: 320] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Terahertz pulse imaging has been used for the first time to study basal cell carcinoma ex vivo, the most common form of skin cancer. This noninvasive technique uses part of the electromagnetic spectrum in the frequency range 0.1-2.7 THz. A total of 21 samples were imaged; the study was performed blind and results were compared to histology. Each image consisted of possible diseased tissue and normal tissue from the same patient. The diseased tissue showed an increase in absorption compared to normal tissue, which is attributed to either an increase in the interstitial water within the diseased tissue or a change in the vibrational modes of water molecules with other functional groups. Seventeen of the images showed a significant difference between the normal and the diseased tissue. These were confirmed by histology to be basal cell carcinomas. Of the remaining four cases, three showed no contrast and were confirmed as blind controls of normal tissue; the fourth case was a suspected basal cell carcinoma but showed no contrast, and histology showed no tumor. Cross-sections of the terahertz images, showing the terahertz absorption, were compared to histology. Regions of increased terahertz absorption agreed well with the location of the tumor sites. Resolutions at 1 THz of 350 microm laterally and 40 microm axially in skin were attainable with our system. These results demonstrate the ability of terahertz pulse imaging to distinguish basal cell carcinoma from normal tissue, and this macroscopic technique may, in the future, help plan surgery.
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31
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Hadjiloucas S, Galvão RKH, Bowen JW. Analysis of spectroscopic measurements of leaf water content at terahertz frequencies using linear transforms. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2002; 19:2495-509. [PMID: 12469746 DOI: 10.1364/josaa.19.002495] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We provide a unified framework for a range of linear transforms that can be used for the analysis of terahertz spectroscopic data, with particular emphasis on their application to the measurement of leaf water content. The use of linear transforms for filtering, regression, and classification is discussed. For illustration, a classification problem involving leaves at three stages of drought and a prediction problem involving simulated spectra are presented. Issues resulting from scaling the data set are discussed. Using Lagrange multipliers, we arrive at the transform that yields the maximum separation between the spectra and show that this optimal transform is equivalent to computing the Euclidean distance between the samples. The optimal linear transform is compared with the average for all the spectra as well as with the Karhunen-Loève transform to discriminate a wet leaf from a dry leaf. We show that taking several principal components into account is equivalent to defining new axes in which data are to be analyzed. The procedure shows that the coefficients of the Karhunen-Loève transform are well suited to the process of classification of spectra. This is in line with expectations, as these coefficients are built from the statistical properties of the data set analyzed.
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Affiliation(s)
- Sillas Hadjiloucas
- Department of Cybernetics, The University of Reading, PO Box 225, Whiteknights, Reading, RG6 6AY UK.
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32
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Abstract
We review the recent development of T-ray computed tomography, a terahertz imaging technique that allows the reconstruction of the three-dimensional refractive index profile of weakly scattering objects. Terahertz pulse imaging is used to obtain images of the target at multiple projection angles and the filtered backprojection algorithm enables the reconstruction of the object's frequency-dependent refractive index. The application of this technique to a biological bone sample and a plastic test structure is demonstrated. The structure of each target is accurately resolved and the frequency-dependent refractive index is determined. The frequency-dependent information may potentially be used to extract functional information from the target, to uniquely identify different materials or to diagnose medical conditions.
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Abstract
Terahertz (THz) science will profoundly impact biotechnology. It has tremendous potential for applications in imaging, medical diagnosis, health monitoring, environmental control and chemical and biological identification. THz research will become one of the most promising research areas in the 21st century for transformational advances in imaging, as well as in other interdisciplinary fields. However, terahertz wave (T-ray) imaging is still in its infancy. This paper discusses the uniqueness and limitations of T-ray imaging, identifies the major challenges impeding T-ray imaging and proposes solutions and opportunities in this field. It also concentrates on the generation, propagation and detection of T-rays by the use of femtosecond optics.
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Affiliation(s)
- X C Zhang
- Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA.
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34
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Beard MC, Turner GM, Schmuttenmaer CA. Progress towards two-dimensional biomedical imaging with THz spectroscopy. Phys Med Biol 2002; 47:3841-6. [PMID: 12452575 DOI: 10.1088/0031-9155/47/21/323] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Terahertz spectroscopy represents a frontier in the field of biomedical imaging. It is possible to image complex objects that are opaque to visible and infrared light. In this paper, we have used THz imaging to reveal the structure inside a sunflower seed. We compare images based on time- and frequency-domain representations of the THz scans, and conclude that for this type of specimen the time-domain THz scans provide more detailed information than their frequency-domain counterparts.
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Affiliation(s)
- Matthew C Beard
- Department of Chemistry, Yale University, 225 Prospect Street, PO Box 208107, New Haven, CT 06520-8107, USA
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35
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Stoyanov NS, Ward DW, Feurer T, Nelson KA. Terahertz polariton propagation in patterned materials. NATURE MATERIALS 2002; 1:95-98. [PMID: 12618821 DOI: 10.1038/nmat725] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2002] [Accepted: 08/12/2002] [Indexed: 05/24/2023]
Abstract
Generation and control of pulsed terahertz-frequency radiation have received extensive attention, with applications in terahertz spectroscopy, imaging and ultrahigh-bandwidth electro-optic signal processing. Terahertz 'polaritonics', in which terahertz lattice waves called phonon-polaritons are generated, manipulated and visualized with femtosecond optical pulses, offers prospects for an integrated solid-state platform for terahertz signal generation and guidance. Here, we extend terahertz polaritonics methods to patterned structures. We demonstrate femtosecond laser fabrication of polaritonic waveguide structures in lithium tantalate and lithium niobate crystals, and illustrate polariton focusing into, and propagation within, the fabricated waveguide structures. We also demonstrate a 90 degrees turn within a structure consisting of two waveguides and a reflecting face, as well as a structure consisting of splitting and recombining elements that can be used as a terahertz Mach-Zehnder interferometer. The structures permit integrated terahertz signal generation, propagation through waveguide-based devices, and readout within a single solid-state platform.
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Affiliation(s)
- Nikolay S Stoyanov
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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36
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37
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Galvão RKH, Hadjiloucas S, Bowen JW. Use of the statistical properties of the wavelet-transform coefficients for optimization of integration time in Fourier transform spectrometry. OPTICS LETTERS 2002; 27:643-645. [PMID: 18007889 DOI: 10.1364/ol.27.000643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We show that an analysis of the mean and variance of discrete wavelet coefficients of coaveraged time-domain interferograms can be used as a specification for determining when to stop coaveraging. We also show that, if a prediction model built in the wavelet domain is used to determine the composition of unknown samples, a stopping criterion for the coaveraging process can be developed with respect to the uncertainty tolerated in the prediction.
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38
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Abstract
We demonstrate quasi-optical, diffraction-limited two-dimensional image production by means of reflected pulses of terahertz (THz) radiation. A spherical mirror is used to form a real one-to-one THz image of two 1-mm-diameter steel spheres, which is then scanned over a THz receiver. Diffraction-limited spatial (cross-range) resolution and THz pulse range resolution are simultaneously observed.
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39
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Feng S, Winful HG. Higher-order transverse modes of ultrashort isodiffracting pulses. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 63:046602. [PMID: 11308963 DOI: 10.1103/physreve.63.046602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2000] [Revised: 11/10/2000] [Indexed: 05/23/2023]
Abstract
We present a family of space-time nonseparable analytic solutions describing spatiotemporal dynamics of isodiffracting single-cycle and few-cycle pulses with Hermite-Gaussian and Laguerre-Gaussian transverse profiles. These solutions are space-time localized wave packets propagating in free space. The transverse field profile acts as a spatially dependent filter, modifying the pulse spectrum and removing certain frequencies. The consequences of those effects in the time domain are the distortions of pulse envelope and temporal wave form and the creation of "dark pulses" at certain transverse positions. In addition, due to the space-time coupling, the instantaneous transverse field pattern changes inside the pulse, as well as with propagation distance. These higher-order mode solutions can be used to analyze reflected or scattered terahertz pulses, and to understand the wave-form distortions of terahertz signals in applications. They are also capable of modeling pulsed fields of phase locking of both transverse and longitudinal modes in total mode-locked lasers.
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Affiliation(s)
- S Feng
- EECS Department, University of Michigan, 1301 Beal Avenue, Ann Arbor, MI 48109-2122, USA.
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