Pub Date : 2025-03-28DOI: 10.1109/TTHZ.2025.3555599
Tobias Doeker;Lorenz H. W. Loeser;Thomas Kürner
For wireless communication systems, beam tracking is crucial if the transmitter and/or the receiver is nonstatic. Specifically, for a communication system in the low terahertz frequency range, beam tracking becomes mandatory due to the necessity for highly directive antennas with narrow beams. Therefore, a beam tracking algorithm for horn antennas specified for 300 GHz has been developed. The proposed algorithm uses changes in antenna gain due to the movement of the transmitter and/or receiver. The received power and information about the antenna radiation pattern allow for the prediction of the angle of departure and angle of arrival. Basic verification of the algorithm has already been conducted through simulation and should now be verified under real conditions through measurements. This article presents a measurement campaign conducted with a channel sounding system around 300 GHz. According to the description of the algorithm provided at the beginning of this article, the measurement results are evaluated for both line-of-sight and non-line-of-sight scenarios. The measurement data are used as input for the algorithm to investigate the possibilities of beam tracking in a real system. It is shown that the algorithm can reliably predict angular changes in both line-of-sight and non-line-of-sight cases. With an accuracy of $pm$ 1$^{circ }$, angular changes of up to 20$^{circ }$ can be tracked using information from four different transmitter and receiver antenna combinations. Even higher angular ranges, up to 70$^{circ }$ in the line-of-sight case and 45$^{circ }$ in the non-line-of-sight case, can be tracked if the accuracy value is increased to $pm$ 4$^{circ }$. The proposed algorithm has, thus, been verified both through simulation and real measurements.
{"title":"Measurements and Verification of an Antenna Pattern-Based Tracking Algorithm at 300 GHz","authors":"Tobias Doeker;Lorenz H. W. Loeser;Thomas Kürner","doi":"10.1109/TTHZ.2025.3555599","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3555599","url":null,"abstract":"For wireless communication systems, beam tracking is crucial if the transmitter and/or the receiver is nonstatic. Specifically, for a communication system in the low terahertz frequency range, beam tracking becomes mandatory due to the necessity for highly directive antennas with narrow beams. Therefore, a beam tracking algorithm for horn antennas specified for 300 GHz has been developed. The proposed algorithm uses changes in antenna gain due to the movement of the transmitter and/or receiver. The received power and information about the antenna radiation pattern allow for the prediction of the angle of departure and angle of arrival. Basic verification of the algorithm has already been conducted through simulation and should now be verified under real conditions through measurements. This article presents a measurement campaign conducted with a channel sounding system around 300 GHz. According to the description of the algorithm provided at the beginning of this article, the measurement results are evaluated for both line-of-sight and non-line-of-sight scenarios. The measurement data are used as input for the algorithm to investigate the possibilities of beam tracking in a real system. It is shown that the algorithm can reliably predict angular changes in both line-of-sight and non-line-of-sight cases. With an accuracy of <inline-formula><tex-math>$pm$</tex-math></inline-formula> 1<inline-formula><tex-math>$^{circ }$</tex-math></inline-formula>, angular changes of up to 20<inline-formula><tex-math>$^{circ }$</tex-math></inline-formula> can be tracked using information from four different transmitter and receiver antenna combinations. Even higher angular ranges, up to 70<inline-formula><tex-math>$^{circ }$</tex-math></inline-formula> in the line-of-sight case and 45<inline-formula><tex-math>$^{circ }$</tex-math></inline-formula> in the non-line-of-sight case, can be tracked if the accuracy value is increased to <inline-formula><tex-math>$pm$</tex-math></inline-formula> 4<inline-formula><tex-math>$^{circ }$</tex-math></inline-formula>. The proposed algorithm has, thus, been verified both through simulation and real measurements.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 3","pages":"359-369"},"PeriodicalIF":3.9,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143904627","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 : 2025-03-27DOI: 10.1109/TTHZ.2025.3555418
Fabien Defrance;Cecile Jung-Kubiak;John Gill;Sofia Rahiminejad;Theodore Macioce;Jack Sayers;Goutam Chattopadhyay;Sunil R. Golwala
In this article, we present the design, fabrication, and characterization of a 100 mm diameter, flat, gradient-index (GRIN) lens fabricated with high-resistivity silicon, combined with a three-layer antireflection (AR) structure optimized for 160–355 GHz. Multidepth, deep reactive-ion etching enables patterning of silicon wafers with subwavelength structures (posts or holes) to locally change the effective refractive index and, thus, create AR layers and a radial index gradient. The structures are nonresonant and, for sufficiently long wavelengths, achromatic. Hexagonal holes varying in size with distance from the optical axis create a parabolic index profile decreasing from 3.15 at the center of the lens to 1.87 at the edge. The AR structure consists of square holes and cross-shaped posts. We have fabricated a lens consisting of a stack of five 525 μm thick GRIN wafers and one AR wafer on each face. We have characterized the lens over the frequency range 220–330 GHz, obtaining behavior consistent with Gaussian optics down to −14 dB and transmittance of 99$pm$3%.
{"title":"Flat Silicon Gradient Index Lens With Deep Reactive-Ion-Etched Three-Layer Antireflection Structure for Millimeter and Submillimeter Wavelengths","authors":"Fabien Defrance;Cecile Jung-Kubiak;John Gill;Sofia Rahiminejad;Theodore Macioce;Jack Sayers;Goutam Chattopadhyay;Sunil R. Golwala","doi":"10.1109/TTHZ.2025.3555418","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3555418","url":null,"abstract":"In this article, we present the design, fabrication, and characterization of a 100 mm diameter, flat, gradient-index (GRIN) lens fabricated with high-resistivity silicon, combined with a three-layer antireflection (AR) structure optimized for 160–355 GHz. Multidepth, deep reactive-ion etching enables patterning of silicon wafers with subwavelength structures (posts or holes) to locally change the effective refractive index and, thus, create AR layers and a radial index gradient. The structures are nonresonant and, for sufficiently long wavelengths, achromatic. Hexagonal holes varying in size with distance from the optical axis create a parabolic index profile decreasing from 3.15 at the center of the lens to 1.87 at the edge. The AR structure consists of square holes and cross-shaped posts. We have fabricated a lens consisting of a stack of five 525 μm thick GRIN wafers and one AR wafer on each face. We have characterized the lens over the frequency range 220–330 GHz, obtaining behavior consistent with Gaussian optics down to −14 dB and transmittance of 99<inline-formula><tex-math>$pm$</tex-math></inline-formula>3%.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"679-693"},"PeriodicalIF":3.9,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550389","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 : 2025-03-26DOI: 10.1109/TTHZ.2025.3573859
Huanxin Li;Xiang Gao;Ziru Chen;Dan Qiao;Xiangyuan Bu;Jianping An
This article presents a dual-port leaky-wave array antenna integrated beam-steerable Schottky heterodyne receiver that may be attractive for terahertz (THz) sensing applications. The receiver chip features a low-cost wideband quasi-optical design that utilizes one frequency-scanning leaky-wave array and one fixed-beam monopole integrated lens antenna for efficiently coupling the radio-frequency (RF) and local-oscillator (LO) signals, respectively. Operating in the subharmonic mixing mode, a dual-channel beam-steerable Schottky heterodyne receiver circuit was designed for performance maximization via both passive and active modeling. A prototype of the THz beam-steerable receiver module was manufactured and experimentally demonstrated. By flexibly switching between seven fixed LO frequencies among 99.5–114.5 GHz, the receiver can reconfigurably detect the RF signal at one of seven equally-divided sub-bands from 200 to 235 GHz, with an intermediate-frequency bandwidth up to 5 GHz. In particular, the receiver can detect the RF beam from unfixed incident direction over a wide steering coverage range of 80°. The measured average single-sideband conversion gain and noise figure are around −9.1 and 9.4 dB, respectively. The results have validated good receiver performance and its potential for sensing applications.
{"title":"A Dual-Port Leaky-Wave Array Antenna Integrated Beam-Steerable Schottky Heterodyne Receiver for Terahertz-Band Applications","authors":"Huanxin Li;Xiang Gao;Ziru Chen;Dan Qiao;Xiangyuan Bu;Jianping An","doi":"10.1109/TTHZ.2025.3573859","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3573859","url":null,"abstract":"This article presents a dual-port leaky-wave array antenna integrated beam-steerable Schottky heterodyne receiver that may be attractive for terahertz (THz) sensing applications. The receiver chip features a low-cost wideband quasi-optical design that utilizes one frequency-scanning leaky-wave array and one fixed-beam monopole integrated lens antenna for efficiently coupling the radio-frequency (RF) and local-oscillator (LO) signals, respectively. Operating in the subharmonic mixing mode, a dual-channel beam-steerable Schottky heterodyne receiver circuit was designed for performance maximization via both passive and active modeling. A prototype of the THz beam-steerable receiver module was manufactured and experimentally demonstrated. By flexibly switching between seven fixed LO frequencies among 99.5–114.5 GHz, the receiver can reconfigurably detect the RF signal at one of seven equally-divided sub-bands from 200 to 235 GHz, with an intermediate-frequency bandwidth up to 5 GHz. In particular, the receiver can detect the RF beam from unfixed incident direction over a wide steering coverage range of 80°. The measured average single-sideband conversion gain and noise figure are around −9.1 and 9.4 dB, respectively. The results have validated good receiver performance and its potential for sensing applications.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 5","pages":"914-926"},"PeriodicalIF":3.9,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998337","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 : 2025-03-26DOI: 10.1109/TTHZ.2025.3573847
James Skinner;Daniel Koller;Hans-Ulrich Nickel;Nick M. Ridler;Stepan Lucyszyn
The IEC 60153-2 and IEEE 1785.1 international standards for rectangular metallic waveguides are currently undergoing revision. Textbook derivations of the associated equations for the metal-pipe rectangular waveguide attenuation constant to be given in the revised standards are presented. These derivations provide important mathematical traceability for these equations, which has previously not been proven in the open literature for these standards. Furthermore, the historical approximations used in the original equations are identified and now corrected here. Results using the newly derived equations are demonstrated, with comparison to experimental results in the WM-380 (500 GHz to 750 GHz) band.
{"title":"Derivation of Rectangular Metallic Waveguide Attenuation Constant for IEC 60153-2 and IEEE 1785.1 International Standards","authors":"James Skinner;Daniel Koller;Hans-Ulrich Nickel;Nick M. Ridler;Stepan Lucyszyn","doi":"10.1109/TTHZ.2025.3573847","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3573847","url":null,"abstract":"The IEC 60153-2 and IEEE 1785.1 international standards for rectangular metallic waveguides are currently undergoing revision. Textbook derivations of the associated equations for the metal-pipe rectangular waveguide attenuation constant to be given in the revised standards are presented. These derivations provide important mathematical traceability for these equations, which has previously not been proven in the open literature for these standards. Furthermore, the historical approximations used in the original equations are identified and now corrected here. Results using the newly derived equations are demonstrated, with comparison to experimental results in the WM-380 (500 GHz to 750 GHz) band.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"734-737"},"PeriodicalIF":3.9,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550483","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 article highlights two 8×1 transmitter and receiver front-ends, which are individually composed of two inparallel assembled four-channel submillimeter-wave monolithic integrated circuits (S-MMICs) operating at 400 GHz. These S-MMICs integrate frequency multipliers, mixers, and amplifiers as well as on-chip antennas. They are manufactured on a 35 nm metamorphic high-electron-mobility transistor technology. The included to-the-broadside radiating on-chip antennas allowed for simplified assembly on a printed circuit board upon which two 4×1 transmitter or receiver S-MMICs are placed in parallel. Furthermore, a separate multiplier-by-four is integrated allowing for a low-frequency input drive in the range of 22.50 to 26.25 GHz. The operational frequency range of the front-ends is from 360 to 420 GHz. Both on-wafer and front-end level measurements are shown, including the farfield pattern characterization of the respective metastructure-based on-chip antennas. With all eight channels of the transmitter front-end active, a radiated output power of at least 10 mW is achieved for the frequency range from 390 to 420 GHz setting the state-of-the-art.
{"title":"400 GHz 8×1 Transmitter and Receiver Front-Ends With Metastructured On-Chip Antennas","authors":"Bersant Gashi;Sandrine Wagner;Lucas Tetzel;Michael Kuri;Rainer Weber;Philipp Neininger;Axel Tessmann;Arnulf Leuther;Marius Kretschmann;Steffen Wälde;Rüdiger Quay","doi":"10.1109/TTHZ.2025.3554724","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3554724","url":null,"abstract":"This article highlights two 8×1 transmitter and receiver front-ends, which are individually composed of two inparallel assembled four-channel submillimeter-wave monolithic integrated circuits (S-MMICs) operating at 400 GHz. These S-MMICs integrate frequency multipliers, mixers, and amplifiers as well as on-chip antennas. They are manufactured on a 35 nm metamorphic high-electron-mobility transistor technology. The included to-the-broadside radiating on-chip antennas allowed for simplified assembly on a printed circuit board upon which two 4×1 transmitter or receiver S-MMICs are placed in parallel. Furthermore, a separate multiplier-by-four is integrated allowing for a low-frequency input drive in the range of 22.50 to 26.25 GHz. The operational frequency range of the front-ends is from 360 to 420 GHz. Both on-wafer and front-end level measurements are shown, including the farfield pattern characterization of the respective metastructure-based on-chip antennas. With all eight channels of the transmitter front-end active, a radiated output power of at least 10 mW is achieved for the frequency range from 390 to 420 GHz setting the state-of-the-art.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"660-671"},"PeriodicalIF":3.9,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10938385","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550490","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 presents a 220–260 GHz fully integrated phased-array wireless system featuring direct conversion RF beam-forming. The system is constructed using fully integrated transmitter (Tx) and receiver (Rx) chips with on-chip antenna array. A four-channel Tx and Rx are designed and fabricated in a 130-nm SiGe BiCMOS process with f$_{mathbf{T}}$/f$_{mathbf{max}}$ = 300/500 GHz. A modular design approach enables the chips as building units for 2×N phased arrays and multiple-input multiple-output systems. A comprehensive design approach for the Tx and Rx chips focusing on key design decisions is presented in this work. The transmitter is equipped with a local oscillator (LO) multiplication chain, IQ up $-$ conversion mixer, active RF splitting network, vector modulator phase shifter (VMPS), temperature sensors, and high output power amplifiers (PA). The PA with power $-$ combining boost the effective isotropic radiated power (EIRP) and reduces the need for external lenses. The receiver is equipped with an LO chain, IQ down $-$ conversion mixer, active RF combining network, VMPS, and low noise amplifiers (LNA). In both Tx and Rx the antenna array is composed of four differential double-folded dipole antennas with local backside etching. The Tx and Rx chips consume 4.4 W and 1.84 W of power, respectively, from a 3.5 V supply with each occupying 25 mm$^{text{2}}$ of silicon area. With a measured Tx array EIRP of 24 dBm, a beamforming wireless link is demonstrated supporting up to 50 Gbps of data rates across 85 cm of link distance with no need for focusing lenses and $pm 30^circ$ of scanning capability. With these capabilities, the presented modular chips enable future scaling for 2× N antenna arrays for sensing and communication applications.
{"title":"A Fully Integrated Modular 2×4 220–260 GHz Beam-Forming Transmitter and Receiver With 50 Gbps Wireless Transmission in SiGe:C BiCMOS","authors":"Mohamed Hussein Eissa;Nebojsa Maletic;Matthias Wietstruck;Vladica Sark;Andrea Malignaggi;Wael Abdullah;Corrado Carta;Gerhard Kahmen","doi":"10.1109/TTHZ.2025.3573157","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3573157","url":null,"abstract":"This article presents a 220–260 GHz fully integrated phased-array wireless system featuring direct conversion RF beam-forming. The system is constructed using fully integrated transmitter (Tx) and receiver (Rx) chips with on-chip antenna array. A four-channel Tx and Rx are designed and fabricated in a 130-nm SiGe BiCMOS process with <italic>f</i><inline-formula><tex-math>$_{mathbf{T}}$</tex-math></inline-formula>/<italic>f</i><inline-formula><tex-math>$_{mathbf{max}}$</tex-math></inline-formula> = 300/500 GHz. A modular design approach enables the chips as building units for 2×N phased arrays and multiple-input multiple-output systems. A comprehensive design approach for the Tx and Rx chips focusing on key design decisions is presented in this work. The transmitter is equipped with a local oscillator (LO) multiplication chain, IQ up <inline-formula><tex-math>$-$</tex-math></inline-formula> conversion mixer, active RF splitting network, vector modulator phase shifter (VMPS), temperature sensors, and high output power amplifiers (PA). The PA with power <inline-formula><tex-math>$-$</tex-math></inline-formula> combining boost the effective isotropic radiated power (EIRP) and reduces the need for external lenses. The receiver is equipped with an LO chain, IQ down <inline-formula><tex-math>$-$</tex-math></inline-formula> conversion mixer, active RF combining network, VMPS, and low noise amplifiers (LNA). In both Tx and Rx the antenna array is composed of four differential double-folded dipole antennas with local backside etching. The Tx and Rx chips consume 4.4 W and 1.84 W of power, respectively, from a 3.5 V supply with each occupying 25 mm<inline-formula><tex-math>$^{text{2}}$</tex-math></inline-formula> of silicon area. With a measured Tx array EIRP of 24 dBm, a beamforming wireless link is demonstrated supporting up to 50 Gbps of data rates across 85 cm of link distance with no need for focusing lenses and <inline-formula><tex-math>$pm 30^circ$</tex-math></inline-formula> of scanning capability. With these capabilities, the presented modular chips enable future scaling for 2× N antenna arrays for sensing and communication applications.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 5","pages":"805-820"},"PeriodicalIF":3.9,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998302","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 : 2025-03-21DOI: 10.1109/TTHZ.2025.3572249
Francis Hindle;Alexandra Khabbaz;Anthony Roucou;Jean-François Lampin;Gaël Mouret
We demonstrate the advantages of THz frequency combs (FCs) for high-resolution spectroscopy. This benefits from wide spectral coverage and the exact knowledge of the frequency position of each comb component. Heterodyne detection combined with a fast Fourier spectrometer enables rapid and simultaneous measurement of more than 80 FC modes covering a 7.5 GHz bandwidth. A spectrum is obtained in under 20 min yielding a uniform resolution of 70 kHz. This new setup has been validated by recording more than 150 lines of methanol around 723 GHz, and represents a new solution to exploit THz FCs for high-resolution spectroscopy.
{"title":"Terahertz Frequency Comb High-Resolution Heterodyne Spectrometer","authors":"Francis Hindle;Alexandra Khabbaz;Anthony Roucou;Jean-François Lampin;Gaël Mouret","doi":"10.1109/TTHZ.2025.3572249","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3572249","url":null,"abstract":"We demonstrate the advantages of THz frequency combs (FCs) for high-resolution spectroscopy. This benefits from wide spectral coverage and the exact knowledge of the frequency position of each comb component. Heterodyne detection combined with a fast Fourier spectrometer enables rapid and simultaneous measurement of more than 80 FC modes covering a 7.5 GHz bandwidth. A spectrum is obtained in under 20 min yielding a uniform resolution of 70 kHz. This new setup has been validated by recording more than 150 lines of methanol around 723 GHz, and represents a new solution to exploit THz FCs for high-resolution spectroscopy.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"566-572"},"PeriodicalIF":3.9,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550486","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 : 2025-03-19DOI: 10.1109/TTHZ.2025.3553031
Federico Sanjuan;Gwenaël Gaborit
Optical rectification (OR) and second harmonic generation (SHG) are second-order nonlinear optical processes that can occur simultaneously when an intense electromagnetic wave interacts with a noncentrosymmetric material. Specially, OR has been used to generate terahertz (THz) waves and SHG for laser frequency conversion. In both cases, bulk crystals are generally used as nonlinear media. In SHG, however, powder crystals have also been employed. In contrast, this has not been confirmed either experimentally or theoretically for the case of OR. Thus, we propose and present here for the first time, the feasibility of generating THz signals by OR in tablets specifically made from powdered sugar. Experimental results obtained with a THz time domain spectrometer reveal that the polarization of the generated electromagnetic field is linear. They also showed, in the best case, a signal with a spectrum extending up to 3 THz with a dynamic range of 40 dB. These findings were validated by a proposed theoretical model.
{"title":"Terahertz Generation in Nonlinear Crystal Powders","authors":"Federico Sanjuan;Gwenaël Gaborit","doi":"10.1109/TTHZ.2025.3553031","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3553031","url":null,"abstract":"Optical rectification (OR) and second harmonic generation (SHG) are second-order nonlinear optical processes that can occur simultaneously when an intense electromagnetic wave interacts with a noncentrosymmetric material. Specially, OR has been used to generate terahertz (THz) waves and SHG for laser frequency conversion. In both cases, bulk crystals are generally used as nonlinear media. In SHG, however, powder crystals have also been employed. In contrast, this has not been confirmed either experimentally or theoretically for the case of OR. Thus, we propose and present here for the first time, the feasibility of generating THz signals by OR in tablets specifically made from powdered sugar. Experimental results obtained with a THz time domain spectrometer reveal that the polarization of the generated electromagnetic field is linear. They also showed, in the best case, a signal with a spectrum extending up to 3 THz with a dynamic range of 40 dB. These findings were validated by a proposed theoretical model.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"715-719"},"PeriodicalIF":3.9,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550387","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 : 2025-03-16DOI: 10.1109/TTHZ.2025.3571191
Zhao-Yang Liu;Feng Qi;Ye-Long Wang;Peng-Xiang Liu;Wei-Fan Li
This article presents a method for designing a compact wideband on-chip terahertz frequency meter and a power meter. The core of this method lies in leveraging two highly correlated terahertz incoherent detectors to create a frequency-dependent and power-independent output ratio, which allows for the precise extraction of frequency information and effectively cancels out common external interference factors, ensuring strong robustness. At a known frequency, the terahertz power can be calculated using the precharacterized voltage responsivity (Rv) and the detector output voltage. The robustness of the method against process, voltage, and temperature variations was analyzed, confirming its strong reliability and practical applicability. The proposed method was validated using a chip containing eight nested detectors fabricated in a 65-nm CMOS process. Frequency measurements demonstrated an accuracy of 1 GHz within the range of 180–500 GHz, and power measurements showed an average deviation of 8.8% across 180–500 GHz compared to a commercial power meter.
{"title":"Wideband Terahertz Frequency Meter and Power Meter in CMOS","authors":"Zhao-Yang Liu;Feng Qi;Ye-Long Wang;Peng-Xiang Liu;Wei-Fan Li","doi":"10.1109/TTHZ.2025.3571191","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3571191","url":null,"abstract":"This article presents a method for designing a compact wideband on-chip terahertz frequency meter and a power meter. The core of this method lies in leveraging two highly correlated terahertz incoherent detectors to create a frequency-dependent and power-independent output ratio, which allows for the precise extraction of frequency information and effectively cancels out common external interference factors, ensuring strong robustness. At a known frequency, the terahertz power can be calculated using the precharacterized voltage responsivity (<italic>R<sub>v</sub></i>) and the detector output voltage. The robustness of the method against process, voltage, and temperature variations was analyzed, confirming its strong reliability and practical applicability. The proposed method was validated using a chip containing eight nested detectors fabricated in a 65-nm CMOS process. Frequency measurements demonstrated an accuracy of 1 GHz within the range of 180–500 GHz, and power measurements showed an average deviation of 8.8% across 180–500 GHz compared to a commercial power meter.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 4","pages":"720-727"},"PeriodicalIF":3.9,"publicationDate":"2025-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550489","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 : 2025-03-14DOI: 10.1109/TTHZ.2025.3551619
Roman Grigorev;Faezeh Zarrinkhat;Joel Lamberg;Irina Nefedova;Mohammad Mirmoosa;Juha Ala-Laurinaho;Aleksi Tamminen;Zachary Taylor
This study aims to explore the effect of the Gouy phase shift correction on determining refractive index and physical thickness of concentric spherical shells measured by quasioptical terahertz (THz) spectroscopy. The shells consisted of a loss-free quartz layer sitting on a water core which serves as an aqueous half space similar to the cornea's aqueous humour. The reflection of the water-backed quartz shells were measured with a focused Gaussian beam in the 220–330 GHz range. The optics generated a beam with a frequency-independent confocal distance resulting in equal radius of curvature and thus optimal wavefront matching to the sample curvature across the band. Thickness and refractive index were estimated from the measurements using Fresnel’s equations and a fixed phase velocity. Parameter extraction was performed a second time where the frequency and axial location dependent phase velocity was corrected by incorporating the expected Gouy phase shift. The correction improved both the thickness and refractive index accuracy. The utility of Gouy phase correction was explored on hydrated corneal phantoms and increased the accuracy of thickness, and anterior and posterior water content estimates.
{"title":"Gouy Phase Correction for Quasioptical, Dielectric Spectroscopy of Spherical Shells in a Gaussian Beam for Terahertz Corneal Sensing","authors":"Roman Grigorev;Faezeh Zarrinkhat;Joel Lamberg;Irina Nefedova;Mohammad Mirmoosa;Juha Ala-Laurinaho;Aleksi Tamminen;Zachary Taylor","doi":"10.1109/TTHZ.2025.3551619","DOIUrl":"https://doi.org/10.1109/TTHZ.2025.3551619","url":null,"abstract":"This study aims to explore the effect of the Gouy phase shift correction on determining refractive index and physical thickness of concentric spherical shells measured by quasioptical terahertz (THz) spectroscopy. The shells consisted of a loss-free quartz layer sitting on a water core which serves as an aqueous half space similar to the cornea's aqueous humour. The reflection of the water-backed quartz shells were measured with a focused Gaussian beam in the 220–330 GHz range. The optics generated a beam with a frequency-independent confocal distance resulting in equal radius of curvature and thus optimal wavefront matching to the sample curvature across the band. Thickness and refractive index were estimated from the measurements using Fresnel’s equations and a fixed phase velocity. Parameter extraction was performed a second time where the frequency and axial location dependent phase velocity was corrected by incorporating the expected Gouy phase shift. The correction improved both the thickness and refractive index accuracy. The utility of Gouy phase correction was explored on hydrated corneal phantoms and increased the accuracy of thickness, and anterior and posterior water content estimates.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"15 3","pages":"370-378"},"PeriodicalIF":3.9,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143904666","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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