Pub Date : 2024-07-30DOI: 10.1109/TTHZ.2024.3430013
Jose V. Siles;Alain Eric Maestrini;Choonsup Lee;Robert Lin;Imran Mehdi
In this article, we introduce a groundbreaking 2-THz front end suitable for space use, operating at room temperature. Our objective is to measure high-altitude 3-D winds for precise Sun–earth energy coupling analysis. Employing Schottky-diode-based mixers and multipliers, we have developed a solid-state receiver with double-sideband sensitivity below 8000 K. This sensitivity enables the measurement of atomic oxygen in the approximate 100–200-km altitude range. Our approach encompasses design, fabrication, and sensitivity assessment of the receiver front end.
{"title":"First Demonstration of an All-Solid-State Room Temperature 2-THz Front End Viable for Space Applications","authors":"Jose V. Siles;Alain Eric Maestrini;Choonsup Lee;Robert Lin;Imran Mehdi","doi":"10.1109/TTHZ.2024.3430013","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3430013","url":null,"abstract":"In this article, we introduce a groundbreaking 2-THz front end suitable for space use, operating at room temperature. Our objective is to measure high-altitude 3-D winds for precise Sun–earth energy coupling analysis. Employing Schottky-diode-based mixers and multipliers, we have developed a solid-state receiver with double-sideband sensitivity below 8000 K. This sensitivity enables the measurement of atomic oxygen in the approximate 100–200-km altitude range. Our approach encompasses design, fabrication, and sensitivity assessment of the receiver front end.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"607-612"},"PeriodicalIF":3.9,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142159821","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}
In this article, we present optimization results for the symmetrical-slot-antenna resonant-tunnelling-diode (RTD) oscillators with account of relevant antenna losses and RTD parasitics. The results are in good agreement with available experimental data. The frequency roll-off of the output power has a complicated dependence on the oscillator parameters and does not exhibit a distinct dominant mechanism responsible for it. However, the roll-off is much steeper for lower-current-density RTDs, with much better performance of high-current-density RTDs not only at terahertz (THz) but also at sub-THz frequencies. The required minimum RTD-mesa area for optimized oscillators remains in an acceptable range for common fabrication technology: $approx 0.1text{--}0.2,mutext {m}^{2}$ .
{"title":"Generalized Analysis of Output-Power Limitations of Resonant-Tunnelling-Diode Oscillators With Symmetrical Slot Antennas","authors":"Gabriele Picco;Petr Ourednik;Dinh Tuan Nguyen;Michael Feiginov","doi":"10.1109/TTHZ.2024.3435464","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3435464","url":null,"abstract":"In this article, we present optimization results for the symmetrical-slot-antenna resonant-tunnelling-diode (RTD) oscillators with account of relevant antenna losses and RTD parasitics. The results are in good agreement with available experimental data. The frequency roll-off of the output power has a complicated dependence on the oscillator parameters and does not exhibit a distinct dominant mechanism responsible for it. However, the roll-off is much steeper for lower-current-density RTDs, with much better performance of high-current-density RTDs not only at terahertz (THz) but also at sub-THz frequencies. The required minimum RTD-mesa area for optimized oscillators remains in an acceptable range for common fabrication technology: \u0000<inline-formula><tex-math>$approx 0.1text{--}0.2,mutext {m}^{2}$</tex-math></inline-formula>\u0000.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"621-631"},"PeriodicalIF":3.9,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10614880","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142160007","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 : 2024-07-30DOI: 10.1109/TTHZ.2024.3435461
Zhen Yang;Fanyi Meng;Bing Liu;Kaixue Ma
In this letter, a two-way 170-GHz cascode frequency doubler with a delayed odd-harmonic cancellation line (DOHCL) for second-harmonic power and efficiency boosting fabricated in 130-nm SiGe BiCMOS technology is presented. The harmonic load pull is adopted to optimize the fundamental and second-harmonic impedances of the doubler core. The DOHCL converts the fundamental impedance from zero to optimum and temporarily holds the voltage swing at the load side at the cascode cores. Finally, the frequency doubler achieves a 3-dB bandwidth from 156 to 178 GHz and a bandwidth from 140 to 188 GHz for output power ( P OUT ) ≥ 11 dBm. The maximum P OUT and efficiency are 15.6 dBm and 12.1%, respectively, at 164 GHz. The chip area is 0.37 mm 2 including pads. To the best of our knowledge, the proposed cascode frequency doubler achieves the highest P OUT and power density in G -band Si-based frequency doublers.
{"title":"A 170-GHz Cascode Frequency Doubler With 15.6-dBm POUT in 130-nm SiGe BiCMOS","authors":"Zhen Yang;Fanyi Meng;Bing Liu;Kaixue Ma","doi":"10.1109/TTHZ.2024.3435461","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3435461","url":null,"abstract":"In this letter, a two-way 170-GHz cascode frequency doubler with a delayed odd-harmonic cancellation line (DOHCL) for second-harmonic power and efficiency boosting fabricated in 130-nm SiGe BiCMOS technology is presented. The harmonic load pull is adopted to optimize the fundamental and second-harmonic impedances of the doubler core. The DOHCL converts the fundamental impedance from zero to optimum and temporarily holds the voltage swing at the load side at the cascode cores. Finally, the frequency doubler achieves a 3-dB bandwidth from 156 to 178 GHz and a bandwidth from 140 to 188 GHz for output power (\u0000<italic>P</i>\u0000<sub>OUT</sub>\u0000) ≥ 11 dBm. The maximum \u0000<italic>P</i>\u0000<sub>OUT</sub>\u0000 and efficiency are 15.6 dBm and 12.1%, respectively, at 164 GHz. The chip area is 0.37 mm\u0000<sup>2</sup>\u0000 including pads. To the best of our knowledge, the proposed cascode frequency doubler achieves the highest \u0000<italic>P</i>\u0000<sub>OUT</sub>\u0000 and power density in \u0000<italic>G</i>\u0000-band Si-based frequency doublers.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"774-778"},"PeriodicalIF":3.9,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142160011","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 : 2024-07-23DOI: 10.1109/TTHZ.2024.3432619
Marcel Andree;Janusz Grzyb;Holger Rücker;Ullrich R. Pfeiffer
This work focuses on a systematic analysis of the potential and limitations of modern SiGe HBT devices for broadband passive room-temperature detection in the lower THz range. Multiple necessary conditions need to be fulfilled to facilitate broadband passive imaging with a sufficiently low in-band NEP, which refer to various technology-driven device operation aspects, including the THz rectification process and low-frequency analysis. To properly understand and model the devices' internal parasitics in combination with antenna-detector co-design aspects, a simplified nonlinear high-frequency detector model was applied for the devices operating in the forward-active and saturation region (cold operation). The complete detector was implemented in a modern high-speed 130 nm SiGe HBT technology with $f_{t}/f_{text{max}}$ of 470/650 GHz. It comprises two orthogonal polarization paths within a single dual-polarization lens-coupled on-chip antenna to operate with unpolarized passive illumination. Due to an efficient antenna-circuit co-design, a close-to-optimum detector performance in a near-THz fractional bandwidth was achieved, as experimentally verified in free-space measurements with frequency-tunable coherent CW sources. The detector optical NEP for each polarization path was measured across 200–1000 GHz reporting state-of-the-art values of 2.3–23 pW/ $mathrm{sqrt{Hz}}$ (forward-active) and 4.3–45 pW/ $mathrm{sqrt{Hz}}$ (saturation). This, combined with the de-embedded equivalent noise bandwidth of 512 GHz around 430 GHz, allowed to demonstrate a 1-Hz defined NETD of 0.86 K and 2 K with a focussed cavity black-body standard chopped mechanically at 1.5 kHz. By dual-channel operation, the NETD scaled down to 0.64 K, indicating near-zero noise correlation between both polarization paths.
{"title":"Towards Passive Imaging With Uncooled, Low-NEP SiGe HBT Terahertz Direct Detectors","authors":"Marcel Andree;Janusz Grzyb;Holger Rücker;Ullrich R. Pfeiffer","doi":"10.1109/TTHZ.2024.3432619","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3432619","url":null,"abstract":"This work focuses on a systematic analysis of the potential and limitations of modern SiGe HBT devices for broadband passive room-temperature detection in the lower THz range. Multiple necessary conditions need to be fulfilled to facilitate broadband passive imaging with a sufficiently low in-band NEP, which refer to various technology-driven device operation aspects, including the THz rectification process and low-frequency analysis. To properly understand and model the devices' internal parasitics in combination with antenna-detector co-design aspects, a simplified nonlinear high-frequency detector model was applied for the devices operating in the forward-active and saturation region (cold operation). The complete detector was implemented in a modern high-speed 130 nm SiGe HBT technology with \u0000<inline-formula><tex-math>$f_{t}/f_{text{max}}$</tex-math></inline-formula>\u0000 of 470/650 GHz. It comprises two orthogonal polarization paths within a single dual-polarization lens-coupled on-chip antenna to operate with unpolarized passive illumination. Due to an efficient antenna-circuit co-design, a close-to-optimum detector performance in a near-THz fractional bandwidth was achieved, as experimentally verified in free-space measurements with frequency-tunable coherent CW sources. The detector optical NEP for each polarization path was measured across 200–1000 GHz reporting state-of-the-art values of 2.3–23 pW/\u0000<inline-formula><tex-math>$mathrm{sqrt{Hz}}$</tex-math></inline-formula>\u0000 (forward-active) and 4.3–45 pW/\u0000<inline-formula><tex-math>$mathrm{sqrt{Hz}}$</tex-math></inline-formula>\u0000 (saturation). This, combined with the de-embedded equivalent noise bandwidth of 512 GHz around 430 GHz, allowed to demonstrate a 1-Hz defined NETD of 0.86 K and 2 K with a focussed cavity black-body standard chopped mechanically at 1.5 kHz. By dual-channel operation, the NETD scaled down to 0.64 K, indicating near-zero noise correlation between both polarization paths.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"632-651"},"PeriodicalIF":3.9,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10607950","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142159803","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 : 2024-07-19DOI: 10.1109/TTHZ.2024.3431190
Rob D. Jones;Jerome Cheron;Benjamin F. Jamroz;William R. Deal;Miguel Urteaga;Dylan F. Williams;Ari D. Feldman;Peter H. Aaen;Christian J. Long;Nathan D. Orloff
In this article, we extract the capacitance of shunt and series metal-insulator-metal capacitors from on-wafer S-parameter measurements in the WR1.0 (0.75–1.1 THz) waveguide band. These capacitors were fabricated in two different state-of-the-art terahertz semiconductor processes and measured with two different designs of via-stitched grounded coplanar waveguide calibration kits. We investigate the measurement uncertainty of extracting a shunt capacitance in the presence of probe positioning uncertainty, calibration kit process variation, and vector network analyzer electrical repeatability. We find that these uncertainty sources result in a large prediction interval that is 30.2% of the capacitor's value (14.9 ± 4.5 fF) at 900 GHz with the uncertainty from probe positioning as the largest contributor. This is the first time that an extensive uncertainty analysis has been performed on characterizing on-wafer devices at 1 THz. We quantify the precision of current calibration techniques and measurement equipment.
{"title":"On-Wafer Capacitor Characterization Including Uncertainty Estimates Up to 1.0 THz","authors":"Rob D. Jones;Jerome Cheron;Benjamin F. Jamroz;William R. Deal;Miguel Urteaga;Dylan F. Williams;Ari D. Feldman;Peter H. Aaen;Christian J. Long;Nathan D. Orloff","doi":"10.1109/TTHZ.2024.3431190","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3431190","url":null,"abstract":"In this article, we extract the capacitance of shunt and series metal-insulator-metal capacitors from on-wafer S-parameter measurements in the WR1.0 (0.75–1.1 THz) waveguide band. These capacitors were fabricated in two different state-of-the-art terahertz semiconductor processes and measured with two different designs of via-stitched grounded coplanar waveguide calibration kits. We investigate the measurement uncertainty of extracting a shunt capacitance in the presence of probe positioning uncertainty, calibration kit process variation, and vector network analyzer electrical repeatability. We find that these uncertainty sources result in a large prediction interval that is 30.2% of the capacitor's value (14.9 ± 4.5 fF) at 900 GHz with the uncertainty from probe positioning as the largest contributor. This is the first time that an extensive uncertainty analysis has been performed on characterizing on-wafer devices at 1 THz. We quantify the precision of current calibration techniques and measurement equipment.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"734-744"},"PeriodicalIF":3.9,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142160013","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}
Wepresent a robust method, as well as a new metric, for the comparison of permittivity models in terahertz time-domain spectroscopy (THz-TDS). In this article, we show that the signal is perturbed by a deterministic part that has to be either modeled or removed. Therefore, we perform an extensive perturbation/noise analysis of a THz-TDS system, remove and model the unwanted deterministic perturbation/noises and implement them into our fitting process. This new method has now been implemented in our open-source software, Fit@TDS. This article is the first step toward the derivation of uncertainties, and therefore the use of error bars. We hope that this will lead to performing analytical analysis with THz-TDS, as results obtained from different setups will be comparable. Finally, we apply this protocol to the study of a $alpha$ -lactose monohydrate pellet in order to give more insight on the molecular dynamics behind the absorption peaks. The comparison with simulation results is made easier thanks to the probabilities derived from the metric.
{"title":"A New Metric for the Comparison of Permittivity Models in Terahertz Time-Domain Spectroscopy","authors":"Melanie Lavancier;Nabil Vindas-Yassine;Juliette Vlieghe;Theo Hannotte;Jean-François Lampin;François Orieux;Romain Peretti","doi":"10.1109/TTHZ.2024.3431202","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3431202","url":null,"abstract":"Wepresent a robust method, as well as a new metric, for the comparison of permittivity models in terahertz time-domain spectroscopy (THz-TDS). In this article, we show that the signal is perturbed by a deterministic part that has to be either modeled or removed. Therefore, we perform an extensive perturbation/noise analysis of a THz-TDS system, remove and model the unwanted deterministic perturbation/noises and implement them into our fitting process. This new method has now been implemented in our open-source software, Fit@TDS. This article is the first step toward the derivation of uncertainties, and therefore the use of error bars. We hope that this will lead to performing analytical analysis with THz-TDS, as results obtained from different setups will be comparable. Finally, we apply this protocol to the study of a \u0000<inline-formula><tex-math>$alpha$</tex-math></inline-formula>\u0000-lactose monohydrate pellet in order to give more insight on the molecular dynamics behind the absorption peaks. The comparison with simulation results is made easier thanks to the probabilities derived from the metric.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"725-733"},"PeriodicalIF":3.9,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142160070","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 presents a concurrent dual-band power amplifier (PA) in 130-nm SiGe BiCMOS process. A three-stage stacked BJT amplifier configuration is employed to enhance both the power gain and the output power. To achieve dual-band low-loss matching, the subquarter-wavelength-based baluns are adopted to construct the input and output matching networks. In addition, multiorder LC networks are introduced to achieve excellent dual-band interstage impedance matching. The proposed three-stage dual-band PA exhibits maximum small signal gains of 25.4 dB at 135 GHz and 21.6 dB at 210 GHz, with 3-dB bandwidths of 28 and 25 GHz, respectively. The measured results show a saturated power (Psat) of more than 13.1 dBm and 9.6 dBm and a power-added efficiency (PAE) of more than 6.75% and 3.1% over ranges of 126–154 GHz and 200–225 GHz, respectively. To the best of the authors’ knowledge, the proposed PA achieves the higher Psat and PAE value than other dual-band PA operating at frequencies greater than 100 GHz with silicon-based process.
{"title":"A 140- and 220-GHz Dual-Band Amplifier in 130-nm SiGe BiCMOS Process","authors":"Letian Guo;Shuyang Li;Wenhua Chen;Shunli Ma;Junyan Ren","doi":"10.1109/TTHZ.2024.3430064","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3430064","url":null,"abstract":"This article presents a concurrent dual-band power amplifier (PA) in 130-nm SiGe BiCMOS process. A three-stage stacked BJT amplifier configuration is employed to enhance both the power gain and the output power. To achieve dual-band low-loss matching, the subquarter-wavelength-based baluns are adopted to construct the input and output matching networks. In addition, multiorder \u0000<italic>LC</i>\u0000 networks are introduced to achieve excellent dual-band interstage impedance matching. The proposed three-stage dual-band PA exhibits maximum small signal gains of 25.4 dB at 135 GHz and 21.6 dB at 210 GHz, with 3-dB bandwidths of 28 and 25 GHz, respectively. The measured results show a saturated power (Psat) of more than 13.1 dBm and 9.6 dBm and a power-added efficiency (PAE) of more than 6.75% and 3.1% over ranges of 126–154 GHz and 200–225 GHz, respectively. To the best of the authors’ knowledge, the proposed PA achieves the higher Psat and PAE value than other dual-band PA operating at frequencies greater than 100 GHz with silicon-based process.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"768-773"},"PeriodicalIF":3.9,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142160012","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 : 2024-07-17DOI: 10.1109/TTHZ.2024.3430107
Nick Rothbart;Alexandra Glück;Heinz-Wilhelm Hübers
The characteristics of the terahertz (THz) frequency range are very favorable for gas spectroscopy due to the presence of rotational fingerprint spectra of many molecules. Since advanced silicon-based technology can offer a cost-efficient access to these frequencies, the technology is promising to be used for everyday applications in the near future. In this article, we will present THz systems and their performances for applications in medicine and metrology, namely for the analysis of exhaled human breath and for frequency standards. We will discuss technical backgrounds and summarize our current developments in this field.
{"title":"Terahertz Gas Spectroscopy Applied to Medicine and Metrology","authors":"Nick Rothbart;Alexandra Glück;Heinz-Wilhelm Hübers","doi":"10.1109/TTHZ.2024.3430107","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3430107","url":null,"abstract":"The characteristics of the terahertz (THz) frequency range are very favorable for gas spectroscopy due to the presence of rotational fingerprint spectra of many molecules. Since advanced silicon-based technology can offer a cost-efficient access to these frequencies, the technology is promising to be used for everyday applications in the near future. In this article, we will present THz systems and their performances for applications in medicine and metrology, namely for the analysis of exhaled human breath and for frequency standards. We will discuss technical backgrounds and summarize our current developments in this field.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"613-620"},"PeriodicalIF":3.9,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142159802","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 : 2024-07-17DOI: 10.1109/TTHZ.2024.3430040
Maruf Md. Sajjad Hossain;Niru K. Nahar;Kubilay Sertel
We present a novel millimeter-wave and terahertz-band imaging system capable of sensing the full polarization matrix of the signals that are locally reflected by a sample under test. A high-resistivity extended-hemispherical lens further provides 3.4× improved pixel resolution, leading to a powerful fully polarimetric imaging sensor. The generation and sensing of millimeter-wave/terahertz signals are based on commercially available VNA frequency extension modules interfaced with diagonal horn antenna. As such, the transmitted and received signals can be controlled to exhibit pure linear polarization. With a precisely aligned quasi-optical link consisting of 90° off-axis parabolic mirror, a wire-grid polarizer and the high-permittivity lens, the beam can be tightly focused at the sample plane, resulting in an unprecedented resolution as fine as 50 $mu$ m for the WR-1.0 band (750–1100 GHz). To demonstrate the utility of the proposed fully polarimetric THz reflectrometry, copolarized and cross-polarized reflection images of a diverse set of FFPE brain tissue samples are captured and the image quality, as well as statistical properties are discussed. The effectiveness of THz fully polarimetric imaging in capturing the anisotropic features in a sample by discriminating edges based on the polarization is demonstrated. This new approach can find wide application areas in nondestructive imaging, such as crack and delamination detection in multilayered composite materials, and diagnosis of degenerative diseases.
{"title":"Resolution-Enhanced Polarimetric Terahertz Imaging","authors":"Maruf Md. Sajjad Hossain;Niru K. Nahar;Kubilay Sertel","doi":"10.1109/TTHZ.2024.3430040","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3430040","url":null,"abstract":"We present a novel millimeter-wave and terahertz-band imaging system capable of sensing the full polarization matrix of the signals that are locally reflected by a sample under test. A high-resistivity extended-hemispherical lens further provides 3.4× improved pixel resolution, leading to a powerful fully polarimetric imaging sensor. The generation and sensing of millimeter-wave/terahertz signals are based on commercially available VNA frequency extension modules interfaced with diagonal horn antenna. As such, the transmitted and received signals can be controlled to exhibit pure linear polarization. With a precisely aligned quasi-optical link consisting of 90° off-axis parabolic mirror, a wire-grid polarizer and the high-permittivity lens, the beam can be tightly focused at the sample plane, resulting in an unprecedented resolution as fine as 50 \u0000<inline-formula><tex-math>$mu$</tex-math></inline-formula>\u0000m for the WR-1.0 band (750–1100 GHz). To demonstrate the utility of the proposed fully polarimetric THz reflectrometry, copolarized and cross-polarized reflection images of a diverse set of FFPE brain tissue samples are captured and the image quality, as well as statistical properties are discussed. The effectiveness of THz fully polarimetric imaging in capturing the anisotropic features in a sample by discriminating edges based on the polarization is demonstrated. This new approach can find wide application areas in nondestructive imaging, such as crack and delamination detection in multilayered composite materials, and diagnosis of degenerative diseases.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"675-690"},"PeriodicalIF":3.9,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142159972","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 : 2024-07-09DOI: 10.1109/TTHZ.2024.3425059
Alexandra Nabilkova;Azat Ismagilov;Maksim Melnik;Daniil Gushchin;Maria Zhukova;Mikhail Guselnikov;Sergey Kozlov;Anton Tcypkin
The study applies for the first time the eclipse Z-scan technique to measure LiNbO $_{3}$ crystal's nonlinear refractive index coefficient in the THz range. This technique is by one order of magnitude more sensitive than the conventional Z-scan method. The obtained value of LiNbO $_{3}$ nonlinear refractive index coefficient is estimated to be 5 $pm , 2times 10^{-11}$ cm $^{2}$ /W, which is commensurate with the established results. This value correlates with the theoretically calculated nonlinear refractive index coefficient of vibrational nature. The influence of thermal nonlinearity on the experimental results can be neglected, since the estimated refractive index change induced by temperature $Delta n{text{th}}$ equals 2.6 $times, 10^{-5}$ , while the contribution $Delta n_{nl}$ from optical nonlinearity is 2.9 $times, 10^{-3}$ . The demonstrated heightened sensitivity of eclipse Z-scan holds promise for the evaluation of properties of materials with lower nonlinear refractive index coefficients, thus expanding the method applicability in characterizing various nonlinear optical materials.
该研究首次应用日食 Z 扫描技术测量太赫兹范围内 LiNbO$_{3}$ 晶体的非线性折射率系数。该技术的灵敏度比传统的 Z 扫描方法高出一个数量级。所获得的 LiNbO$_{3}$ 非线性折射率系数值估计为 5 $pm ，2times 10^{-11}$ cm$^{2}$/W，这与已有的结果相符。该值与理论计算的振动非线性折射率系数相关。热非线性对实验结果的影响可以忽略不计，因为估计温度引起的折射率变化 $Delta ntext{th}}$ 等于 2.6 $times, 10^{-5}$，而光学非线性的贡献 $Delta n_{nl}$ 是 2.9 $times, 10^{-3}$。日食 Z 扫描所显示的高灵敏度为评估具有较低非线性折射率系数的材料特性带来了希望，从而扩大了该方法在表征各种非线性光学材料方面的适用性。
{"title":"Sensitivity Enhancement of Cubic Nonlinearity Measurement in THz Frequency Range","authors":"Alexandra Nabilkova;Azat Ismagilov;Maksim Melnik;Daniil Gushchin;Maria Zhukova;Mikhail Guselnikov;Sergey Kozlov;Anton Tcypkin","doi":"10.1109/TTHZ.2024.3425059","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3425059","url":null,"abstract":"The study applies for the first time the eclipse Z-scan technique to measure LiNbO\u0000<inline-formula><tex-math>$_{3}$</tex-math></inline-formula>\u0000 crystal's nonlinear refractive index coefficient in the THz range. This technique is by one order of magnitude more sensitive than the conventional Z-scan method. The obtained value of LiNbO\u0000<inline-formula><tex-math>$_{3}$</tex-math></inline-formula>\u0000 nonlinear refractive index coefficient is estimated to be 5 \u0000<inline-formula><tex-math>$pm , 2times 10^{-11}$</tex-math></inline-formula>\u0000 cm\u0000<inline-formula><tex-math>$^{2}$</tex-math></inline-formula>\u0000/W, which is commensurate with the established results. This value correlates with the theoretically calculated nonlinear refractive index coefficient of vibrational nature. The influence of thermal nonlinearity on the experimental results can be neglected, since the estimated refractive index change induced by temperature \u0000<inline-formula><tex-math>$Delta n{text{th}}$</tex-math></inline-formula>\u0000 equals 2.6 \u0000<inline-formula><tex-math>$times, 10^{-5}$</tex-math></inline-formula>\u0000, while the contribution \u0000<inline-formula><tex-math>$Delta n_{nl}$</tex-math></inline-formula>\u0000 from optical nonlinearity is 2.9 \u0000<inline-formula><tex-math>$times, 10^{-3}$</tex-math></inline-formula>\u0000. The demonstrated heightened sensitivity of eclipse Z-scan holds promise for the evaluation of properties of materials with lower nonlinear refractive index coefficients, thus expanding the method applicability in characterizing various nonlinear optical materials.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"718-724"},"PeriodicalIF":3.9,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142159974","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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