Guided Terahertz Pulse Reflectometry with Double Photoconductive Antenna
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2025
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| author | Pan, Mingming Cassar, Quentin FAUQUET, FREDERIC HUMBERT, Georges Mounaix, patrick Guillet, Jean-Paul |
| author_facet | Pan, Mingming Cassar, Quentin FAUQUET, FREDERIC HUMBERT, Georges Mounaix, patrick Guillet, Jean-Paul |
| contents | <p>We present the development of a guided terahertz pulse reflectometry (GTPR) system utilizing a dual photoconductive antenna (PCA) structure integrated with a silica hollow-core waveguide to create an optics-free terahertz imaging system our goal is to address the increasing demand for terahertz technologies in non-destructive testing spectroscopy imaging and material analysis due to their ability to penetrate opaque structures and identify chemical compositions however conventional terahertz systems rely on quasi-optical components requiring precise alignment introducing bulkiness and making in-situ measurements particularly challenging in confined environments to overcome these limitations we have developed a system integrating two PCAs fabricated on the same low-temperature-grown gallium arsenide (LT-GaAs) substrate allowing both the generation and detection of terahertz pulses without additional coupling optics a 3-mm diameter silica hollow-core waveguide is used to guide the terahertz pulses from the PCA transmitter to the sample and return the reflected signal to the PCA receiver by eliminating the need for lenses or mirrors we significantly reduce system complexity improve compactness and facilitate alignment we characterized the transceiver and waveguide separately before integrating them into a complete system we simulated and experimentally validated the radiation pattern of the PCA antennas demonstrating the effectiveness of quasi-Yagi antenna structures in directing terahertz waves into the waveguide to optimize coupling we designed the PCA dimensions to match the waveguide core ensuring efficient energy transfer our finite-difference time-domain (FDTD) simulations indicate that approximately 22% of the emitted terahertz power is coupled into the waveguide we then experimentally characterized the waveguide using a terahertz time-domain spectroscopy (THz-TDS) system confirming that its guiding mechanism relies on anti-resonant effects enabling broadband low-loss propagation over a frequency range from 400 to 650 GHz after assembling the system we evaluated its imaging performance by scanning a 1951 USAF resolution test target our results show that we achieve an imaging resolution of approximately 0.707 line pairs per millimeter (LP/mm) after 53 mm of waveguide propagation demonstrating the potential of our approach for compact terahertz imaging systems intended for non-destructive testing applications our experimental validation highlights that guided terahertz pulses exhibit a significantly higher signal-to-noise ratio compared to free-space propagation enhancing the sensitivity of reflectivity detection however we observed some signal distortions due to dispersion within the waveguide slightly affecting image quality we discuss potential solutions such as optimizing waveguide design or implementing dispersion compensation techniques in conclusion our work successfully demonstrates a guided terahertz reflectometry approach using an integrated transceiver and waveguide configuration paving the way for compact and efficient terahertz imaging systems for industrial and scientific applications our future work includes further miniaturizing the system improving waveguide transmission efficiency and exploring new applications such as in-situ biomedical diagnostics and non-invasive material inspections</p> |
| format | Recurso digital |
| id | zenodo_https___doi_org_10_1364_AO_381646 |
| institution | Zenodo |
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| publishDate | 2025 |
| publisher | Zenodo |
| record_format | zenodo |
| spellingShingle | Guided Terahertz Pulse Reflectometry with Double Photoconductive Antenna Pan, Mingming Cassar, Quentin FAUQUET, FREDERIC HUMBERT, Georges Mounaix, patrick Guillet, Jean-Paul Terahertz Radiation Terahertz Spectroscopy Terahertz Imaging Terahertz Spectroscopy/classification Terahertz Spectroscopy/history Terahertz Spectroscopy/methods Terahertz Imaging/history Terahertz Imaging/standards Terahertz Imaging/methods Terahertz Imaging/veterinary Terahertz Spectroscopy/instrumentation Terahertz Spectroscopy/standards Terahertz Imaging/classification terahertz <p>We present the development of a guided terahertz pulse reflectometry (GTPR) system utilizing a dual photoconductive antenna (PCA) structure integrated with a silica hollow-core waveguide to create an optics-free terahertz imaging system our goal is to address the increasing demand for terahertz technologies in non-destructive testing spectroscopy imaging and material analysis due to their ability to penetrate opaque structures and identify chemical compositions however conventional terahertz systems rely on quasi-optical components requiring precise alignment introducing bulkiness and making in-situ measurements particularly challenging in confined environments to overcome these limitations we have developed a system integrating two PCAs fabricated on the same low-temperature-grown gallium arsenide (LT-GaAs) substrate allowing both the generation and detection of terahertz pulses without additional coupling optics a 3-mm diameter silica hollow-core waveguide is used to guide the terahertz pulses from the PCA transmitter to the sample and return the reflected signal to the PCA receiver by eliminating the need for lenses or mirrors we significantly reduce system complexity improve compactness and facilitate alignment we characterized the transceiver and waveguide separately before integrating them into a complete system we simulated and experimentally validated the radiation pattern of the PCA antennas demonstrating the effectiveness of quasi-Yagi antenna structures in directing terahertz waves into the waveguide to optimize coupling we designed the PCA dimensions to match the waveguide core ensuring efficient energy transfer our finite-difference time-domain (FDTD) simulations indicate that approximately 22% of the emitted terahertz power is coupled into the waveguide we then experimentally characterized the waveguide using a terahertz time-domain spectroscopy (THz-TDS) system confirming that its guiding mechanism relies on anti-resonant effects enabling broadband low-loss propagation over a frequency range from 400 to 650 GHz after assembling the system we evaluated its imaging performance by scanning a 1951 USAF resolution test target our results show that we achieve an imaging resolution of approximately 0.707 line pairs per millimeter (LP/mm) after 53 mm of waveguide propagation demonstrating the potential of our approach for compact terahertz imaging systems intended for non-destructive testing applications our experimental validation highlights that guided terahertz pulses exhibit a significantly higher signal-to-noise ratio compared to free-space propagation enhancing the sensitivity of reflectivity detection however we observed some signal distortions due to dispersion within the waveguide slightly affecting image quality we discuss potential solutions such as optimizing waveguide design or implementing dispersion compensation techniques in conclusion our work successfully demonstrates a guided terahertz reflectometry approach using an integrated transceiver and waveguide configuration paving the way for compact and efficient terahertz imaging systems for industrial and scientific applications our future work includes further miniaturizing the system improving waveguide transmission efficiency and exploring new applications such as in-situ biomedical diagnostics and non-invasive material inspections</p> |
| title | Guided Terahertz Pulse Reflectometry with Double Photoconductive Antenna |
| topic | Terahertz Radiation Terahertz Spectroscopy Terahertz Imaging Terahertz Spectroscopy/classification Terahertz Spectroscopy/history Terahertz Spectroscopy/methods Terahertz Imaging/history Terahertz Imaging/standards Terahertz Imaging/methods Terahertz Imaging/veterinary Terahertz Spectroscopy/instrumentation Terahertz Spectroscopy/standards Terahertz Imaging/classification terahertz |
| url | https://doi.org/10.1364/AO.381646 |