Pub Date : 2025-06-27DOI: 10.1109/TTHZ.2025.3583912
Daniel Headland;Guillermo Carpintero
We address critical physical fragility issues associated with terahertz integrated all-silicon substrateless devices. This is necessary because, although the current state-of-the-art offers excellent electromagnetic performance, real-world deployment is currently held back by structural weaknesses. One such example is the input coupler, which has previously taken the form of an exposed taper that reduces core dimensions over several wavelengths, and is vulnerable to breakage. This is replaced with a compact subwavelength slot-waveguide coupler, which exploits reflection-cancellation as opposed to a progressive transition. The other key structural weakness is the in-plane integrated support that physically suspends the substrateless waveguide's core, and this is addressed with multimode effects that localize a field null to the point of contact with a solid supporting beam. The resultant robust waveguide platform exhibits a working relative bandwidth of $sim$31%, which is sufficient for terahertz communications in standard allocated bands. Multimode effects are also exploited to realize an integrated photonic 2 × 2 splitter, which is incidentally the first demonstration of an integrated dielectric multimode interferometer splitter in the terahertz range.
{"title":"Robust Unclad Terahertz Waveguides and Integrated Components Enabled by Multimode Effects and Matched Slot Couplers","authors":"Daniel Headland;Guillermo Carpintero","doi":"10.1109/TTHZ.2025.3583912","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3583912","url":null,"abstract":"We address critical physical fragility issues associated with terahertz integrated all-silicon substrateless devices. This is necessary because, although the current state-of-the-art offers excellent electromagnetic performance, real-world deployment is currently held back by structural weaknesses. One such example is the input coupler, which has previously taken the form of an exposed taper that reduces core dimensions over several wavelengths, and is vulnerable to breakage. This is replaced with a compact subwavelength slot-waveguide coupler, which exploits reflection-cancellation as opposed to a progressive transition. The other key structural weakness is the in-plane integrated support that physically suspends the substrateless waveguide's core, and this is addressed with multimode effects that localize a field null to the point of contact with a solid supporting beam. The resultant robust waveguide platform exhibits a working relative bandwidth of <inline-formula><tex-math>$sim$</tex-math></inline-formula>31%, which is sufficient for terahertz communications in standard allocated bands. Multimode effects are also exploited to realize an integrated photonic 2 × 2 splitter, which is incidentally the first demonstration of an integrated dielectric multimode interferometer splitter in the terahertz range.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 5","pages":"885-893"},"PeriodicalIF":3.9,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11054290","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-16DOI: 10.1109/TTHZ.2025.3580257
Ehsan Hafezi;Kamal Sarabandi
This article presents a device capable of generating different or hybrid orbital angular momentum (OAM) modes at 225 GHz using a mechanically tunable configuration. The device is composed of two 10 cm-diameter reflectionless plates, each 0.6 mm thick, designed to work together such that their combined phase response produces specific OAM modes, once properly aligned. These plates are patterned with metallic traces on thin glass substrates to form a miniaturized-element frequency selective surface structure. These traces are microfabricated with high precision to achieve accurate transmission phase modulation across the wafer. The mechanism enabling mode flexibility relies on discretizing the plates into finite number of angular sectors, each with a unique phase response. When the plates are properly aligned, the combined phase from corresponding sectors can generate a desired OAM mode. By rotating one plate relative to the other, new alignments between sectors produce different combined phase profiles, allowing for the generation of a different mode. The reflectionless nature of the plates ensures that the overall performance is largely insensitive to the distance between the two plates. Transmission phase measurements of individual and combined plates are validated via near-field measurement and the resulting phase profiles confirmed the generation of distinct OAM modes in agreement with simulation predictions. This device demonstrates an innovative approach to OAM mode generation, with potential applications in near-field communication and high-resolution radar imaging systems.
{"title":"Reconfigurable Orbital Angular Momentum Mode Generation at 225 GHz Using Cascaded Reflectionless Miniaturized-Element Frequency Selective Surface Phase Plates","authors":"Ehsan Hafezi;Kamal Sarabandi","doi":"10.1109/TTHZ.2025.3580257","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3580257","url":null,"abstract":"This article presents a device capable of generating different or hybrid orbital angular momentum (OAM) modes at 225 GHz using a mechanically tunable configuration. The device is composed of two 10 cm-diameter reflectionless plates, each 0.6 mm thick, designed to work together such that their combined phase response produces specific OAM modes, once properly aligned. These plates are patterned with metallic traces on thin glass substrates to form a miniaturized-element frequency selective surface structure. These traces are microfabricated with high precision to achieve accurate transmission phase modulation across the wafer. The mechanism enabling mode flexibility relies on discretizing the plates into finite number of angular sectors, each with a unique phase response. When the plates are properly aligned, the combined phase from corresponding sectors can generate a desired OAM mode. By rotating one plate relative to the other, new alignments between sectors produce different combined phase profiles, allowing for the generation of a different mode. The reflectionless nature of the plates ensures that the overall performance is largely insensitive to the distance between the two plates. Transmission phase measurements of individual and combined plates are validated via near-field measurement and the resulting phase profiles confirmed the generation of distinct OAM modes in agreement with simulation predictions. This device demonstrates an innovative approach to OAM mode generation, with potential applications in near-field communication and high-resolution radar imaging systems.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 5","pages":"821-830"},"PeriodicalIF":3.9,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-12DOI: 10.1109/TTHZ.2025.3579299
Pouyan Rezapoor;Aleksi Tamminen;Juha Ala-Laurinaho;Dan Ruan;Zachary Taylor
Terahertz (THz) imaging has emerged as a promising technology in medical diagnostics, thanks to nonionizing radiation and the high sensitivity of THz waves to water content. However, in vivo, THz imaging system designs face challenges, such as slow mechanical scanning, limited field-of-view, and variable incidence angle due to poor telecentricity. To address these limitations, we present the telecentric offset reflective imaging system, a novel dual-mirror scanning design optimized for high-speed, distortion-free imaging. Utilizing a telecentric $f-theta$ lens and ray-tracing and physical optics simulations, the system achieves uniform resolution across a 50 × 50 mm$^{2}$ field of view. System capability is demonstrated through broadband spectral imaging of a USAF resolution test target across WR-2.2 (325–500 GHz) and WR-1.5 (500–700 GHz) rectangular waveguide frequency bands, achieving consistent beam focus and minimal distortion, with maximum deviation of 2.7$^{circ }$ from normal incidence and beam waist of 2.1 $lambda$ at the edge of the field of view. Hydration sensitivity is validated by imaging wet tissue paper, illustrating its sensitivity to temporal changes in water content. Further, in vivo, imaging of human skin after capsaicin patch application reveals localized hydration variations influenced by biochemical responses and adhesive patch removal.
{"title":"A Telecentric Offset Reflective Imaging System (TORIS) for Terahertz Imaging and Spectroscopy","authors":"Pouyan Rezapoor;Aleksi Tamminen;Juha Ala-Laurinaho;Dan Ruan;Zachary Taylor","doi":"10.1109/TTHZ.2025.3579299","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3579299","url":null,"abstract":"Terahertz (THz) imaging has emerged as a promising technology in medical diagnostics, thanks to nonionizing radiation and the high sensitivity of THz waves to water content. However, in vivo, THz imaging system designs face challenges, such as slow mechanical scanning, limited field-of-view, and variable incidence angle due to poor telecentricity. To address these limitations, we present the telecentric offset reflective imaging system, a novel dual-mirror scanning design optimized for high-speed, distortion-free imaging. Utilizing a telecentric <inline-formula><tex-math>$f-theta$</tex-math></inline-formula> lens and ray-tracing and physical optics simulations, the system achieves uniform resolution across a 50 × 50 mm<inline-formula><tex-math>$^{2}$</tex-math></inline-formula> field of view. System capability is demonstrated through broadband spectral imaging of a USAF resolution test target across WR-2.2 (325–500 GHz) and WR-1.5 (500–700 GHz) rectangular waveguide frequency bands, achieving consistent beam focus and minimal distortion, with maximum deviation of 2.7<inline-formula><tex-math>$^{circ }$</tex-math></inline-formula> from normal incidence and beam waist of 2.1 <inline-formula><tex-math>$lambda$</tex-math></inline-formula> at the edge of the field of view. Hydration sensitivity is validated by imaging wet tissue paper, illustrating its sensitivity to temporal changes in water content. Further, in vivo, imaging of human skin after capsaicin patch application reveals localized hydration variations influenced by biochemical responses and adhesive patch removal.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 5","pages":"787-799"},"PeriodicalIF":3.9,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11031208","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145011334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-12DOI: 10.1109/TTHZ.2025.3579298
Philip Dindo;Alessandro Navarrini;Joseph G. Lambert;Anthony R. Kerr;Shing-Kuo Pan;Marian Pospieszalski;Claudio Jarufe;John E. Effland;Kamaljeet Saini
A new method is presented for measuring the intermediate frequency (IF) output impedance (ZIF) of a superconducting tunnel junction (SIS) mixer at cryogenic temperatures. As an example, the impedance ZIF of an atacama large millimeter/submillimeter array band 6 (211–275 GHz) SIS mixer chip was measured at the IF bonding pad. The setup uses a commercial vector network analyzer (VNA) with sensitivity enhancements to increase the dynamic range and allow low-power-one-port reflection coefficient (Γ if) measurements. A coupler inside the VNA is bypassed and replaced with an equivalent cold coupler inside the cryostat. The bias to the mixer is provided through the IF isolator. A cryogenic low-noise amplifier in the return path to the VNA increases its dynamic range. One-port calibration standards (short, open, and 50 Ω) are used, and the impedance is de-embedded from the calibration reference plane to the IF bonding pad of the mixer chip using the proprietary automatic fixture removal capability of the Keysight Technologies VNA. This approach allows direct measurement of the amplitude and phase of ΓIF and hence ZIF, from 2 to 16 GHz with very low power levels at the device under test. The measured results are compared with the predictions made from combining Tucker's quantum mixer theory with electromagnetic model of the mixer.
{"title":"VNA Measurement of the IF Output Impedance of an SIS Mixer","authors":"Philip Dindo;Alessandro Navarrini;Joseph G. Lambert;Anthony R. Kerr;Shing-Kuo Pan;Marian Pospieszalski;Claudio Jarufe;John E. Effland;Kamaljeet Saini","doi":"10.1109/TTHZ.2025.3579298","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3579298","url":null,"abstract":"A new method is presented for measuring the intermediate frequency (IF) output impedance (Z<sub>IF</sub>) of a superconducting tunnel junction (SIS) mixer at cryogenic temperatures. As an example, the impedance Z<sub>IF</sub> of an atacama large millimeter/submillimeter array band 6 (211–275 GHz) SIS mixer chip was measured at the IF bonding pad. The setup uses a commercial vector network analyzer (VNA) with sensitivity enhancements to increase the dynamic range and allow low-power-one-port reflection coefficient (Γ<sub> <small>if</small></sub>) measurements. A coupler inside the VNA is bypassed and replaced with an equivalent cold coupler inside the cryostat. The bias to the mixer is provided through the IF isolator. A cryogenic low-noise amplifier in the return path to the VNA increases its dynamic range. One-port calibration standards (short, open, and 50 Ω) are used, and the impedance is de-embedded from the calibration reference plane to the IF bonding pad of the mixer chip using the proprietary automatic fixture removal capability of the Keysight Technologies VNA. This approach allows direct measurement of the amplitude and phase of Γ<sub>IF</sub> and hence Z<sub>IF</sub>, from 2 to 16 GHz with very low power levels at the device under test. The measured results are compared with the predictions made from combining Tucker's quantum mixer theory with electromagnetic model of the mixer.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 5","pages":"894-902"},"PeriodicalIF":3.9,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work presents a filtenna concept based on cascaded singlet filters, which inherits independent controllability of attenuation poles from the filter design and has high stopband performance. Two fourth-order filters with a center frequency of 270 GHz, a 14 GHz bandwidth, and in-band return losses of 15 and 18 dB, respectively, are manufactured and measured to verify the proposed concept. The filtennas with a single-slot configuration and a double-slot configuration are fabricated by the silicon deep reactive ion etching technology and have the size of 3.65 × 2.6 mm2. Detailed explanations of the synthesis procedure, which was validated through electromagnetic simulation, and measurement results are provided. The measured single-slot and double-slot filtennas exhibit broadside radiation gains of approximately 4.5 and 6.5 dBi at 270 GHz, respectively. Moreover, the challenges and details of silicon micromachining in fabricating the two filtering antennas are discussed.
{"title":"A Silicon Micromachined Cascaded Singlet Filtenna At 270 GHz","authors":"Arash Arsanjani;Mohammad Mehrabi Gohari;Behrooz Rezaee;Alireza Madannejad;Oleksandr Glubokov;Reinhard Teschl;Joachim Oberhammer;Wolfgang Bösch","doi":"10.1109/TTHZ.2025.3578844","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3578844","url":null,"abstract":"This work presents a filtenna concept based on cascaded singlet filters, which inherits independent controllability of attenuation poles from the filter design and has high stopband performance. Two fourth-order filters with a center frequency of 270 GHz, a 14 GHz bandwidth, and in-band return losses of 15 and 18 dB, respectively, are manufactured and measured to verify the proposed concept. The filtennas with a single-slot configuration and a double-slot configuration are fabricated by the silicon deep reactive ion etching technology and have the size of 3.65 × 2.6 mm<sup>2</sup>. Detailed explanations of the synthesis procedure, which was validated through electromagnetic simulation, and measurement results are provided. The measured single-slot and double-slot filtennas exhibit broadside radiation gains of approximately 4.5 and 6.5 dBi at 270 GHz, respectively. Moreover, the challenges and details of silicon micromachining in fabricating the two filtering antennas are discussed.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 5","pages":"877-884"},"PeriodicalIF":3.9,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11030324","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article investigates sub-THz computational imaging using compact, wideband, cavity-backed frequency-diverse antennas fabricated through silicon micromachining techniques. This article presents a forward model based on pseudorandom frequency-diverse patterns using a Mills-Cross transmitter and receiver pair, which provides high-resolution imaging capabilities in the 220–330 GHz frequency range. The model is coupled with advanced compressed sensing algorithms, specifically compressive sampling matching pursuit (CoSaMP) and fast iterative shrinkage-thresholding algorithm (FISTA), to enhance imaging performance under limited data acquisition. Through emulated simulation and experimental data, it is demonstrated that the system's ability to achieve range resolutions down to 1.4 mm and angular resolutions of 0.35°, even in the presence of noise, and analyze the tradeoff between computational complexity and imaging accuracy. Sparsity investigations in spatial antenna population and frequency samples are comprehensively explored in this article. The results show that using only 6.7% of the data, the CoSaMP algorithm can reconstruct a discernable image of the “KTH” logo. Results show that CoSaMP provides lower reconstruction error for sparse target distributions, while FISTA achieves superior noise resilience. The study highlights the practical implications of using frequency-diverse antennas in security screening and industrial inspection, where high-resolution imaging at sub-THz frequencies is demanded.
{"title":"Investigating Sub-THz Computational Imaging Using Silicon Micromachined Frequency-Diverse Antennas","authors":"Mohammad-Reza Seidi;Mohammad Mehrabi Gohari;Joachim Oberhammer","doi":"10.1109/TTHZ.2025.3575636","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3575636","url":null,"abstract":"This article investigates sub-THz computational imaging using compact, wideband, cavity-backed frequency-diverse antennas fabricated through silicon micromachining techniques. This article presents a forward model based on pseudorandom frequency-diverse patterns using a Mills-Cross transmitter and receiver pair, which provides high-resolution imaging capabilities in the 220–330 GHz frequency range. The model is coupled with advanced compressed sensing algorithms, specifically compressive sampling matching pursuit (CoSaMP) and fast iterative shrinkage-thresholding algorithm (FISTA), to enhance imaging performance under limited data acquisition. Through emulated simulation and experimental data, it is demonstrated that the system's ability to achieve range resolutions down to 1.4 mm and angular resolutions of 0.35°, even in the presence of noise, and analyze the tradeoff between computational complexity and imaging accuracy. Sparsity investigations in spatial antenna population and frequency samples are comprehensively explored in this article. The results show that using only 6.7% of the data, the CoSaMP algorithm can reconstruct a discernable image of the “KTH” logo. Results show that CoSaMP provides lower reconstruction error for sparse target distributions, while FISTA achieves superior noise resilience. The study highlights the practical implications of using frequency-diverse antennas in security screening and industrial inspection, where high-resolution imaging at sub-THz frequencies is demanded.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 5","pages":"843-851"},"PeriodicalIF":3.9,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11020717","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrically large modulated metasurface antennas (MMAs) possess the advantages of simple feeding and absence of beam forming network, while achieving a high radiation gain. However, they suffer from limitation in the gain-bandwidth product. This article introduces a technique to expand the bandwidth of gain by utilizing a polarization selective surface (PSS). The PSS can generate a more uniform phase distribution and almost identical polarized directions above the MMA to improve its radiation performance, including the realized gain, gain bandwidth, sidelobe level, and cross-polarization level. Detailed analysis is presented and discussed. For experimental verification, a D-band metallic MMA loaded with a PSS is fabricated and measured. The proposed metallic MMA is manufactured by a high-precision 3-D-printed technique and metalized using the magnetron-sputtering gold coating. The measured maximum realized gain is 30.5 dBi at 131 GHz with a measured 3-dB gain bandwidth of 9%, which approaches the theoretical limit found for such antennas. The proposed MMA shows potential superiorities for developing high-gain and low-profile THz antennas, even with an operating frequency over 300 GHz.
{"title":"A High-Gain Terahertz Metallic Modulated Metasurface Antenna With a Wide Gain Bandwidth","authors":"Jia-Hui Zhao;Chen-Yu Ding;Zhuo-Wei Miao;Stefano Maci;Zhang-Cheng Hao","doi":"10.1109/TTHZ.2025.3565204","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3565204","url":null,"abstract":"Electrically large modulated metasurface antennas (MMAs) possess the advantages of simple feeding and absence of beam forming network, while achieving a high radiation gain. However, they suffer from limitation in the gain-bandwidth product. This article introduces a technique to expand the bandwidth of gain by utilizing a polarization selective surface (PSS). The PSS can generate a more uniform phase distribution and almost identical polarized directions above the MMA to improve its radiation performance, including the realized gain, gain bandwidth, sidelobe level, and cross-polarization level. Detailed analysis is presented and discussed. For experimental verification, a <italic>D</i>-band metallic MMA loaded with a PSS is fabricated and measured. The proposed metallic MMA is manufactured by a high-precision 3-D-printed technique and metalized using the magnetron-sputtering gold coating. The measured maximum realized gain is 30.5 dBi at 131 GHz with a measured 3-dB gain bandwidth of 9%, which approaches the theoretical limit found for such antennas. The proposed MMA shows potential superiorities for developing high-gain and low-profile THz antennas, even with an operating frequency over 300 GHz.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"694-703"},"PeriodicalIF":3.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The performance of high-repetition-rate (e.g., MHz) 1030-nm-pumped lithium niobate (LiNbO3) terahertz (THz) source is significantly influenced by pulse duration, intensity, and pump wavelength. In this study, we present the application of single-stage multipass cell (MPC) compression technology to compress 1030 nm laser pulses from 200 to 49 fs and investigate its impact on THz emission using the tilted pulse front method. The results show that the compressed 49 fs pulses significantly broaden the THz spectral bandwidth, shifting the center frequency from 0.5 to 0.84 THz and extending the cutoff frequency to 4.1 THz. Although shorter pulses have lower conversion efficiency compared with longer pulses (e.g., 200 fs), they generate a broader THz spectrum. This bandwidth improvement addresses the critical limitations of narrow bandwidth and low temporal resolution in current LiNbO3-based THz scanning tunneling microscopy (THz-STM) systems. By increasing the THz bandwidth, we provide an efficient approach to achieve better temporal resolution and more affluent spectral information in THz-STM systems. This study demonstrates the potential of MPC compression technology to significantly enhance THz bandwidth in LiNbO3 crystals, paving the way for more accurate material analysis, imaging, and characterization using THz-STM.
{"title":"Application of Multipass Cell Compression to Achieve High Repetition Rate Lithium Niobate Terahertz Sources With Broadened Bandwidth","authors":"Lu-Zhen Chen;Hong-Bo Li;Dong-Liang Xie;Kai Zhang;Jing-Yin Xu;Hao-Ran Song;Hong Li;Tian-Wu Wang;Yi Qu","doi":"10.1109/TTHZ.2025.3564709","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3564709","url":null,"abstract":"The performance of high-repetition-rate (e.g., MHz) 1030-nm-pumped lithium niobate (LiNbO<sub>3</sub>) terahertz (THz) source is significantly influenced by pulse duration, intensity, and pump wavelength. In this study, we present the application of single-stage multipass cell (MPC) compression technology to compress 1030 nm laser pulses from 200 to 49 fs and investigate its impact on THz emission using the tilted pulse front method. The results show that the compressed 49 fs pulses significantly broaden the THz spectral bandwidth, shifting the center frequency from 0.5 to 0.84 THz and extending the cutoff frequency to 4.1 THz. Although shorter pulses have lower conversion efficiency compared with longer pulses (e.g., 200 fs), they generate a broader THz spectrum. This bandwidth improvement addresses the critical limitations of narrow bandwidth and low temporal resolution in current LiNbO<sub>3</sub>-based THz scanning tunneling microscopy (THz-STM) systems. By increasing the THz bandwidth, we provide an efficient approach to achieve better temporal resolution and more affluent spectral information in THz-STM systems. This study demonstrates the potential of MPC compression technology to significantly enhance THz bandwidth in LiNbO<sub>3</sub> crystals, paving the way for more accurate material analysis, imaging, and characterization using THz-STM.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"642-649"},"PeriodicalIF":3.9,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10978068","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-28DOI: 10.1109/TTHZ.2025.3564771
Marius Kretschmann;Thomas Zwick;Akanksha Bhutani
This article presents an antenna measurement setup for characterizing the radiation behavior of antennas in the WM-570 frequency band (330 GHz to 500 GHz) and WM-380 frequency band (500 GHz to 750 GHz) in the far field. The measurement setup can be used to measure planar antenna prototypes quasi-in-air by contacting them with a WM-570 or WM-380 probe on a cantilever arm protruding into the free space as well as waveguide-based antennas and antennas of fully integrated transmitter modules. The electrical and mechanical design of the antenna measurement setup is described. In addition, the system dynamic range is discussed, from which the measurement range for the minimum and maximum gain of the antenna under test is derived. The parasitic radiation of the THz probe limits the lower limit of the antenna gain that can be measured with this setup. For this reason, the radiation behavior of FormFactor T-Wave probes is investigated in the frequency bands listed above. In radiation pattern measurements, ripples are caused by reflections from the waveguide components used on the receiver side of the measurement setup. These ripples are minimized by using plastic shields with elastomer absorbers, whose influence is investigated by measurements in this work.
{"title":"Antenna Measurement Setup in the WM-570 and WM-380 Frequency Band","authors":"Marius Kretschmann;Thomas Zwick;Akanksha Bhutani","doi":"10.1109/TTHZ.2025.3564771","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3564771","url":null,"abstract":"This article presents an antenna measurement setup for characterizing the radiation behavior of antennas in the WM-570 frequency band (330 GHz to 500 GHz) and WM-380 frequency band (500 GHz to 750 GHz) in the far field. The measurement setup can be used to measure planar antenna prototypes quasi-in-air by contacting them with a WM-570 or WM-380 probe on a cantilever arm protruding into the free space as well as waveguide-based antennas and antennas of fully integrated transmitter modules. The electrical and mechanical design of the antenna measurement setup is described. In addition, the system dynamic range is discussed, from which the measurement range for the minimum and maximum gain of the antenna under test is derived. The parasitic radiation of the THz probe limits the lower limit of the antenna gain that can be measured with this setup. For this reason, the radiation behavior of FormFactor T-Wave probes is investigated in the frequency bands listed above. In radiation pattern measurements, ripples are caused by reflections from the waveguide components used on the receiver side of the measurement setup. These ripples are minimized by using plastic shields with elastomer absorbers, whose influence is investigated by measurements in this work.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 6","pages":"951-962"},"PeriodicalIF":3.9,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145435688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reconfigurable reflectarray antennas (RRAs) at submillimeter and terahertz frequencies are critical for communications and imaging applications. This article examines, fabricates, and measures an RRA integrated with a gallium nitride (GaN) high electron mobility transistor (HEMT) device, operating at 220 GHz. A reflectarray element on a sapphire substrate, incorporating a GaN HEMT device and a matching circuit, is designed to achieve a 1-bit phase shift of the reflected wave. Detailed analyses of the HEMT device model and the submillimeter element design are conducted. The proposed RRA is fabricated using standard chip processes, resulting in a 16 × 16 element array on an 11.2 × 11.2 × 0.1 mm3 chip. The 1-bit phase-shift performance is validated through two-state reflection coefficient measurements. Due to the fabrication challenges of element control, a column-control biasing network is implemented. The 1-D beam-scanning capability of the RRA prototype is experimentally demonstrated at 220 GHz, achieving a scanning angle of up to 40°. The experimental results demonstrate strong agreement with theoretical predictions.
{"title":"A 220 GHz Reconfigurable Reflectarray Antenna Using GaN HEMT Device","authors":"Xiaotian Pan;Fan Yang;Fengfeng Liu;Chunping Jiang;Shenheng Xu","doi":"10.1109/TTHZ.2025.3563715","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3563715","url":null,"abstract":"Reconfigurable reflectarray antennas (RRAs) at submillimeter and terahertz frequencies are critical for communications and imaging applications. This article examines, fabricates, and measures an RRA integrated with a gallium nitride (GaN) high electron mobility transistor (HEMT) device, operating at 220 GHz. A reflectarray element on a sapphire substrate, incorporating a GaN HEMT device and a matching circuit, is designed to achieve a 1-bit phase shift of the reflected wave. Detailed analyses of the HEMT device model and the submillimeter element design are conducted. The proposed RRA is fabricated using standard chip processes, resulting in a 16 × 16 element array on an 11.2 × 11.2 × 0.1 mm<sup>3</sup> chip. The 1-bit phase-shift performance is validated through two-state reflection coefficient measurements. Due to the fabrication challenges of element control, a column-control biasing network is implemented. The 1-D beam-scanning capability of the RRA prototype is experimentally demonstrated at 220 GHz, achieving a scanning angle of up to 40°. The experimental results demonstrate strong agreement with theoretical predictions.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"704-714"},"PeriodicalIF":3.9,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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