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Wang Y, Jing W, Gao L, Han F, Meng Q, Yang C, Zhao L, Jiang Z, Chan CH. Split ring hole metamaterial-enhanced pyroelectric detector for efficient multi-narrowband terahertz detection. OPTICS EXPRESS 2024; 32:19779-19791. [PMID: 38859104 DOI: 10.1364/oe.522788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Accepted: 05/04/2024] [Indexed: 06/12/2024]
Abstract
Derived from infrared pyroelectric detection, typical terahertz (THz) pyroelectric detectors have low sensitivity at low-frequency THz bands. Based on the high-efficiency absorption of the metamaterial perfect absorber (MPA), a novel split ring hole metamaterial-enhanced pyroelectric detector is proposed to achieve efficient multi-narrowband THz detection. Using high frequency simulation software (HFSS), the dimensional parameters including ring radius, ring width, connection beam width, array period, and thickness, are optimized to enhance efficient multi-narrowband absorption. The as-optimized metamaterial-enhanced detectors are fabricated via micro-nano manufacturing technology. The voltage responsiveness and noise equivalent power of the metamaterial-enhanced detector are tested by THz focused optical path and compared with those of the typical pyroelectric detector and the simulated MPA absorptivity. The results indicate that the metamaterial-enhanced detector has a multi-narrowband detection capability at 0.245 THz, 0.295 THz, and 0.38 THz, which is close to the simulated MPA absorptivity. Compared to the typical pyroelectric detector, the split ring hole metamaterial-enhanced detector can simultaneously achieve thermal absorption, thermal conduction, and pyroelectricity in the same MPA structure, providing faster response speed above 100 Hz chopper frequency and two times higher detection sensitivity at multi-narrowband THz frequencies. This research can be used for THz sensing, absorption filtering, biological macromolecule detection, and other applications.
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2
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Penketh H, Ergoktas MS, Lawrence CR, Phillips DB, Cunningham JE, Hendry E, Mrnka M. Real-time millimeter wave holography with an arrayed detector. OPTICS EXPRESS 2024; 32:5783-5792. [PMID: 38439296 DOI: 10.1364/oe.513852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 01/17/2024] [Indexed: 03/06/2024]
Abstract
Millimeter and terahertz wave imaging has emerged as a powerful tool for applications such as security screening, biomedical imaging, and material analysis. However, intensity images alone are often insufficient for detecting variations in the dielectric constant of a sample, and extraction of material properties without additional phase information requires extensive prior knowledge of the sample. Digital holography provides a means for intensity-only detectors to reconstruct both amplitude and phase images. Here we utilize a commercially available source and detector array, both operating at room temperature, to perform digital holography in real-time for the first time in the mm-wave band (at 290 GHz). We compare the off-axis and phase-shifting approaches to digital holography and discuss their trade-offs and practical challenges in this regime. Owing to the low pixel count, we find phase-shifting holography to be the most practical and high fidelity approach for such commercial mm-wave cameras even under real-time operational requirements.
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Li X, Li J, Li Y, Ozcan A, Jarrahi M. High-throughput terahertz imaging: progress and challenges. LIGHT, SCIENCE & APPLICATIONS 2023; 12:233. [PMID: 37714865 PMCID: PMC10504281 DOI: 10.1038/s41377-023-01278-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 08/04/2023] [Accepted: 08/28/2023] [Indexed: 09/17/2023]
Abstract
Many exciting terahertz imaging applications, such as non-destructive evaluation, biomedical diagnosis, and security screening, have been historically limited in practical usage due to the raster-scanning requirement of imaging systems, which impose very low imaging speeds. However, recent advancements in terahertz imaging systems have greatly increased the imaging throughput and brought the promising potential of terahertz radiation from research laboratories closer to real-world applications. Here, we review the development of terahertz imaging technologies from both hardware and computational imaging perspectives. We introduce and compare different types of hardware enabling frequency-domain and time-domain imaging using various thermal, photon, and field image sensor arrays. We discuss how different imaging hardware and computational imaging algorithms provide opportunities for capturing time-of-flight, spectroscopic, phase, and intensity image data at high throughputs. Furthermore, the new prospects and challenges for the development of future high-throughput terahertz imaging systems are briefly introduced.
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Affiliation(s)
- Xurong Li
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Jingxi Li
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- Department of Bioengineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Yuhang Li
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- Department of Bioengineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Aydogan Ozcan
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- Department of Bioengineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Mona Jarrahi
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA.
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA.
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Liu JP, Tsai KC, Lin YC, Chen KH. Single-pixel three-dimensional imaging of the terahertz-wave by complex-field synthesis. OPTICS EXPRESS 2023; 31:4357-4366. [PMID: 36785406 DOI: 10.1364/oe.480212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 01/10/2023] [Indexed: 06/18/2023]
Abstract
We propose a novel three-dimensional (3D) imaging technique by terahertz (THz) waves. Specifically, we modulate the THz wave using diffusers to produce three different speckle-like illumination patterns. The object is raster scanned by the three illumination patterns to generate three raw images via the single-pixel detection method. Subsequently, we synthesize a complex field using the three raw images. Finally, the retrieved image is calculated using the phase correlation of the complex point spread function. The proposed imaging system is simple and highly cost-effective. Therefore, it is a promising technique that can be adopted for industrial inspection and security screening.
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Abstract
In the past few decades, the applications of terahertz (THz) spectroscopy and imaging technology have seen significant developments in the fields of biology, medical diagnosis, food safety, and nondestructive testing. Label-free diagnosis of malignant tumours has been obtained and also achieved significant development in THz biomedical imaging. This review mainly presents the research status and prospects of several common continuous-wave (CW) THz medical imaging systems and applications of THz medical imaging in biological tissues. Here, we first introduce the properties of THz waves and how these properties play a role in biomedical imaging. Then, we analyse both the advantages and disadvantages of the CW THz imaging methods and the progress of these methods in THz biomedical imaging in recent ten years. Finally, we summarise the obstacles in the way of the application of THz bio-imaging application technology in clinical detection, which need to be investigated and overcome in the future.
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Wang D, Zhang Y, Rong L, Ma D, Zhao J, Wang Y. Continuous-wave terahertz self-referencing digital holography based on Fresnel's mirrors. OPTICS LETTERS 2020; 45:913-916. [PMID: 32058503 DOI: 10.1364/ol.385943] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 01/16/2020] [Indexed: 06/10/2023]
Abstract
Continuous-wave terahertz digital holography (TDH) is a booming full-field phase-contrast imaging method validated in both in-line and Mach-Zehnder off-axis geometries. In this Letter, a self-referencing TDH approach is proposed based on the Fresnel's mirrors, by which the object wavefront is partitioned and reflected. Two beams interfere with each other to form an off-axis hologram. The proposed recording configuration is immune from a superposed twin image and has higher temporal stability than Mach-Zehnder interferometers. To evaluate the phase-contrast imaging performance, different types of samples are measured.
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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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Turov AT, Kulya MS, Petrov NV, Gorodetsky A. Resolution and contrast in terahertz pulse time-domain holographic reconstruction. APPLIED OPTICS 2019; 58:G231-G240. [PMID: 31873506 DOI: 10.1364/ao.58.00g231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 09/30/2019] [Indexed: 06/10/2023]
Abstract
Here, we present a comprehensive study of the reconstruction quality in terahertz (THz) pulse time-domain holography. We look into single wavelength reconstructions, as well as broadband recovery enabled by the ultrabroadband nature of radiation and coherent detection enabled by electro-optic or photoconductive sensing. We demonstrate the transverse resolution dependence for amplitude and phase objects on the solid angle of the inline recorded time-domain THz hologram, and then turn to the contrast of reconstructed binary amplitude objects, and further to longitudinal resolution of phase objects. We show that transverse resolution can reach values comparable to the wavelength of the radiation used, and longitudinally, phase objects can be resolved with even greater precision. We compare the obtained resolution with theoretical estimates and show that THz pulse time-domain holography is a powerful non-contact imaging tool.
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Valzania L, Zhao Y, Rong L, Wang D, Georges M, Hack E, Zolliker P. THz coherent lensless imaging. APPLIED OPTICS 2019; 58:G256-G275. [PMID: 31873509 DOI: 10.1364/ao.58.00g256] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 09/28/2019] [Indexed: 06/10/2023]
Abstract
Imaging with THz radiation has proved an important tool for both fundamental science and industrial use. Here we review a class of THz imaging implementations, named coherent lensless imaging, that reconstruct the coherent response of arbitrary samples with a minimized experimental setup based only on a coherent source and a camera. After discussing the appropriate sources and detectors to perform them, we detail the fundamental principles and implementations of THz digital holography and phase retrieval. These techniques owe a lot to imaging with different wavelengths, yet innovative concepts are also being developed in the THz range and are ready to be applied in other spectral ranges. This makes our review useful for both the THz and imaging communities, and we hope it will foster their interaction.
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Zhao Y, Vandenrijt JF, Kirkove M, Georges M. Iterative phase-retrieval-assisted off-axis terahertz digital holography. APPLIED OPTICS 2019; 58:9208-9216. [PMID: 31873598 DOI: 10.1364/ao.58.009208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 10/23/2019] [Indexed: 06/10/2023]
Abstract
In terahertz digital holography, the off-axis configuration is the appropriate choice when the investigated object is non-sparse and complex. The limitation of recording distance in the off-axis configuration restricts the imaging quality. Either low-resolution or spectra overlap can potentially occur. We propose an iterative phase-retrieval approach to improve the quality of reconstruction results obtained from an off-axis hologram. One additional capture of object wave intensity is recorded to perform iterative phase retrieval with off-axis reconstruction as the initial guess. Apodization operation can be applied to the object wave intensity capture to suppress undesired border diffraction effects. The image quality using the proposed method has been improved both from simulation and experimental verification.
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Lim YL, Bertling K, Taimre T, Gillespie T, Glenn C, Robinson A, Indjin D, Han Y, Li L, Linfield EH, Davies AG, Dean P, Rakić AD. Coherent imaging using laser feedback interferometry with pulsed-mode terahertz quantum cascade lasers. OPTICS EXPRESS 2019; 27:10221-10233. [PMID: 31045166 DOI: 10.1364/oe.27.010221] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/14/2019] [Indexed: 06/09/2023]
Abstract
We report a coherent terahertz (THz) imaging system that utilises a quantum cascade laser (QCL) operating in pulsed-mode as both the source and detector. The realisation of a short-pulsed THz QCL feedback interferometer permits both high peak powers and improved thermal efficiency, which enables the cryogen-free operation of the system. In this work, we demonstrated pulsed-mode swept-frequency laser feedback interferometry experimentally. Our interferometric detection scheme not only permits the simultaneous creation of both amplitude and phase images, but inherently suppresses unwanted background radiation. We demonstrate that the proposed system utilising microsecond pulses has the potential to achieve 0.25 mega-pixel per second acquisition rates, paving the pathway to video frame rate THz imaging.
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12
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Chen M, Wang Y, Wen J, Chen H, Ma W, Fan F, Huang Y, Zhao Z. Annealing Temperature-Dependent Terahertz Thermal-Electrical Conversion Characteristics of Three-Dimensional Microporous Graphene. ACS APPLIED MATERIALS & INTERFACES 2019; 11:6411-6420. [PMID: 30648383 DOI: 10.1021/acsami.8b20095] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Three-dimensional microporous graphene (3DMG) possesses ultrahigh photon absorptivity and excellent photothermal conversion ability and shows great potential in energy storage and photodetection, especially for the not well-explored terahertz (THz) frequency range. Here, we report on the characterization of the THz thermal-electrical conversion properties of 3DMG with different annealing treatments. We observe distinct behavior of bolometric and photothermoelectric responses varying with annealing temperature. Resistance-temperature characteristics and thermoelectric power measurements reveal that marked charge carrier reversal occurs in 3DMG as the annealing temperature changes between 600 and 800 °C, which can be well explained by Fermi-level tuning associated with oxygen functional group evolution. Benefiting from the large specific surface area of 3DMG, it has an extraordinary capability of reaching thermal equilibrium quickly and exhibits a fast photothermal conversion with a time constant of 23 ms. In addition, 3DMG can serve as an ideal absorber to improve the sensitivity of THz detectors and we demonstrate that the responsivity of a carbon nanotube device could be enhanced by 12 times through 3DMG. Our work provides new insight into the physical characteristics of carrier transport and THz thermal-electrical conversion in 3DMG controlled by annealing temperature and opens an avenue for the development of highly efficient graphene-based THz devices.
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Affiliation(s)
- Meng Chen
- Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Department of Engineering Physics , Tsinghua University , Beijing 100084 , China
| | - Yingxin Wang
- Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Department of Engineering Physics , Tsinghua University , Beijing 100084 , China
| | - Jianguo Wen
- Nuctech Company Limited , Beijing 100084 , China
| | | | | | | | | | - Ziran Zhao
- Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Department of Engineering Physics , Tsinghua University , Beijing 100084 , China
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Rong L, Tang C, Wang D, Li B, Tan F, Wang Y, Shi X. Probe position correction based on overlapped object wavefront cross-correlation for continuous-wave terahertz ptychography. OPTICS EXPRESS 2019; 27:938-950. [PMID: 30696172 DOI: 10.1364/oe.27.000938] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 01/08/2019] [Indexed: 06/09/2023]
Abstract
Continuous-wave terahertz ptychography is a promising large field-of-view lensless terahertz phase imaging method. Inaccurate probe positions would severely degrade the reconstruction quality, as compared to other spectral bands. In this paper, we propose a probe position correction method based on cross-correlation registration on overlapped regions of the object wavefront for terahertz ptychography. The translation errors could be minimized in the order of 0.01 pixels. The simulation results suggest good computational efficiency, correction, and reconstruction accuracy. We perform continuous-wave terahertz ptychography on a cicada's forewing. The subcosta and the first radius vein are distinguished after position correction. The probe position distribution reveals that the tilt angle between the object plane and the recording plane is 0.26°.
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14
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Li Z, Li L, Qin Y, Li G, Wang D, Zhou X. Resolution and quality enhancement in terahertz in-line holography by sub-pixel sampling with double-distance reconstruction. OPTICS EXPRESS 2016; 24:21134-21146. [PMID: 27607716 DOI: 10.1364/oe.24.021134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate the enhancement of resolution and image quality in terahertz (THz) lens-free in-line digital holography by sub-pixel sampling with double-distance reconstruction. Multiple sub-pixel shifted low-resolution (LR) holograms recorded by a pyroelectric array detector (100 μm × 100 μm pixel pitch, 124 × 124 pixels) are aligned precisely to synthesize a high-resolution (HR) hologram. By this method, the lateral resolution is no more limited by the pixel pitch, and lateral resolution of 150 μm is obtained, which corresponds to 1.26λ with respect to the illuminating wavelength of 118.8 μm (2.52 THz). Compared with other published works, to date, this is the highest resolution in THz digital holography when considering the illuminating wavelength. In addition, to suppress the twin-image and zero-order artifacts, the complex amplitude distributions of both object and illuminaing background wave fields are reconstructed simultaneously. This is achieved by iterative phase retrieval between the double HR holograms and background images at two recording planes, which does not require any constraints on object plane or a priori knowledge of the sample.
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15
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Huang H, Rong L, Wang D, Li W, Deng Q, Li B, Wang Y, Zhan Z, Wang X, Wu W. Synthetic aperture in terahertz in-line digital holography for resolution enhancement. APPLIED OPTICS 2016; 55:A43-A48. [PMID: 26835956 DOI: 10.1364/ao.55.000a43] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Terahertz digital holography is a combination of terahertz technology and digital holography. In digital holography, the imaging resolution is the key parameter in determining the detailed quality of a reconstructed wavefront. In this paper, the synthetic aperture method is used in terahertz digital holography and the in-line arrangement is built to perform the detection. The resolved capability of previous terahertz digital holographic systems restricts this technique to meet the requirement of practical detection. In contrast, the experimental resolved power of the present method can reach 125 μm, which is the best resolution of terahertz digital holography to date. Furthermore, the basic detection of a biological specimen is conducted to show the practical application. In all, the results of the proposed method demonstrate the enhancement of experimental imaging resolution and that the amplitude and phase distributions of the fine structure of samples can be reconstructed by using terahertz digital holography.
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Real-time terahertz digital holography with a quantum cascade laser. Sci Rep 2015; 5:13566. [PMID: 26315647 PMCID: PMC4551990 DOI: 10.1038/srep13566] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 07/30/2015] [Indexed: 11/08/2022] Open
Abstract
Coherent imaging in the THz range promises to exploit the peculiar capabilities of these wavelengths to penetrate common materials like plastics, ceramics, paper or clothes with potential breakthroughs in non-destructive inspection and quality control, homeland security and biomedical applications. Up to now, however, THz coherent imaging has been limited by time-consuming raster scanning, point-like detection schemes and by the lack of adequate coherent sources. Here, we demonstrate real-time digital holography (DH) at THz frequencies exploiting the high spectral purity and the mW output power of a quantum cascade laser combined with the high sensitivity and resolution of a microbolometric array. We show that, in a one-shot exposure, phase and amplitude information of whole samples, either in reflection or in transmission, can be recorded. Furthermore, a 200 times reduced sensitivity to mechanical vibrations and a significantly enlarged field of view are observed, as compared to DH in the visible range. These properties of THz DH enable unprecedented holographic recording of real world dynamic scenes.
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Terahertz in-line digital holography of human hepatocellular carcinoma tissue. Sci Rep 2015; 5:8445. [PMID: 25676705 PMCID: PMC4326957 DOI: 10.1038/srep08445] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 01/20/2015] [Indexed: 11/08/2022] Open
Abstract
Terahertz waves provide a better contrast in imaging soft biomedical tissues than X-rays, and unlike X-rays, they cause no ionisation damage, making them a good option for biomedical imaging. Terahertz absorption imaging has conventionally been used for cancer diagnosis. However, the absorption properties of a cancerous sample are influenced by two opposing factors: an increase in absorption due to a higher degree of hydration and a decrease in absorption due to structural changes. It is therefore difficult to diagnose cancer from an absorption image. Phase imaging can thus be critical for diagnostics. We demonstrate imaging of the absorption and phase-shift distributions of 3.2 mm × 2.3 mm × 30-μm-thick human hepatocellular carcinoma tissue by continuous-wave terahertz digital in-line holography. The acquisition time of a few seconds for a single in-line hologram is much shorter than that of other terahertz diagnostic techniques, and future detectors will allow acquisition of meaningful holograms without sample dehydration. The resolution of the reconstructions was enhanced by sub-pixel shifting and extrapolation. Another advantage of this technique is its relaxed minimal sample size limitation. The fibrosis indicated in the phase distribution demonstrates the potential of terahertz holographic imaging to obtain a more objective, early diagnosis of cancer.
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Rong L, Latychevskaia T, Wang D, Zhou X, Huang H, Li Z, Wang Y. Terahertz in-line digital holography of dragonfly hindwing: amplitude and phase reconstruction at enhanced resolution by extrapolation. OPTICS EXPRESS 2014; 22:17236-17245. [PMID: 25090537 DOI: 10.1364/oe.22.017236] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report here on terahertz (THz) digital holography on a biological specimen. A continuous-wave (CW) THz in-line holographic setup was built based on a 2.52 THz CO(2) pumped THz laser and a pyroelectric array detector. We introduced novel statistical method of obtaining true intensity values for the pyroelectric array detector's pixels. Absorption and phase-shifting images of a dragonfly's hindwing were reconstructed simultaneously from single in-line hologram. Furthermore, we applied phase retrieval routines to eliminate twin image and enhanced the resolution of the reconstructions by hologram extrapolation beyond the detector area. The finest observed features are 35 μm width cross veins.
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Hack E, Zolliker P. Terahertz holography for imaging amplitude and phase objects. OPTICS EXPRESS 2014; 22:16079-16086. [PMID: 24977861 DOI: 10.1364/oe.22.016079] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A non-monochromatic THz Quantum Cascade Laser and an uncooled micro-bolometer array detector with VGA resolution are used in a beam-splitter free holographic set-up to measure amplitude and phase objects in transmission. Phase maps of the diffraction pattern are retrieved using the Fourier transform carrier fringe method; while a Fresnel-Kirchhoff back propagation algorithm is used to reconstruct the complex object image. A lateral resolution of 280 µm and a relative phase sensitivity of about 0.5 rad are estimated from reconstructed images of a metallic Siemens star and a polypropylene test structure, respectively. Simulations corroborate the experimental results.
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Geng LJ, Qu YC, Zhao WJ, Du J. Highly efficient and compact cavity oscillator for high-power, optically pumped gas terahertz laser. OPTICS LETTERS 2013; 38:4793-4796. [PMID: 24322134 DOI: 10.1364/ol.38.004793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate a highly efficient and compact terahertz cavity oscillator that is based on z-cut crystal quartz used as the dichroic beam splitter, for the first time to the best of our knowledge. With D(2)O gas as the active medium, pumped with a multitransverse mode TEACO(2) laser, experimental verification was also presented to demonstrate the advantages of this cavity oscillator. With the cavity length of 120 cm, 7.4 mJ pulse energy at pulse repetition frequency of 6 Hz, pulse width of 90 ns, and peak power of 82.2 kW were achieved at a wavelength of 385 μm. Photon conversion efficiency (PCE) of 44% was obtained at the maximum output level from this terahertz cavity oscillator. Furthermore, to our knowledge, this PCE is the highest efficiency ever reported in D(2)O gas, 385 μm terahertz cavity laser systems. The beam quality or M(2) factor was found to be about 1.77.
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Li Q, Xue K, Li YD, Wang Q. Experimental research on terahertz Gabor inline digital holography of concealed objects. APPLIED OPTICS 2012; 51:7052-7058. [PMID: 23052085 DOI: 10.1364/ao.51.007052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 09/07/2012] [Indexed: 06/01/2023]
Abstract
Terahertz (THz) radiation has the characteristics of penetrating nonmetallic and nonpolar materials that are opaque to visible light, which makes THz digital holography have an application potential of imaging concealed objects with certain barriers. A CO(2) pumped continuous THz Gabor inline digital holographic imaging system was utilized to conduct experimental researches on imaging concealed objects. Paper, Teflon, a plastic express envelope, and silicon wafers were used as barriers. High-quality reconstructed images were obtained. Compared with the reconstruction results without any barriers, the results verify the feasibility of THz Gabor inline digital holography in imaging concealed objects.
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Affiliation(s)
- Qi Li
- National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology, Harbin, China.
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22
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Földesy P. Terahertz single-shot quadrature phase-shifting interferometry. OPTICS LETTERS 2012; 37:4044-4046. [PMID: 23027273 DOI: 10.1364/ol.37.004044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A single-shot quadrature phase-shifting interferometry architecture is presented that is applicable to antenna coupled detector technologies. The method is based on orthogonally polarized object and reference beams and on linear and circular polarization sensitive antennas in space-division multiplexing. The technique can be adapted to two-, three-, and four-step and Gabor holography recordings. It is also demonstrated that the space-division multiplexing does not necessarily cause sparse sampling. A sub-THz detector array is presented containing multiple on-chip antennas and FET plasma wave detectors implemented in a 90 nm complementary metal-oxide semiconductor technology. As an example, two-step phase-shifting reconstruction results are given at 360 GHz.
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Affiliation(s)
- Péter Földesy
- Computer and Automation Research Institute, Hungarian Academy of Sciences, Kende utca 13-17, 1111, Budapest, Hungary.
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Xue K, Li Q, Li YD, Wang Q. Continuous-wave terahertz in-line digital holography. OPTICS LETTERS 2012; 37:3228-3230. [PMID: 22859141 DOI: 10.1364/ol.37.003228] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A terahertz (THz) in-line digital holography project has been proposed based on a CO2 pumped 2.52 THz continuous-wave laser and a pyroelectric-array camera used as the detector. The THz Gabor in-line digital holograms have been obtained and then the high resolution reconstruction of THz in-line digital holography was realized. The resolution of an in-line digital holography system has been tested by the use of a series of objects. High-quality and high-resolution reconstructed images have been obtained, and the real lateral resolution is higher than 0.2 mm. It can be inferred from the results that the THz Gabor in-line digital holography system has the abilities of real-time and high-resolution imaging.
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Affiliation(s)
- Kai Xue
- National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology, Harbin, China
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