Pub Date : 2024-04-25DOI: 10.1109/TTHZ.2024.3393627
Nils B. Refvik;Charles E. Jensen;David N. Purschke;Wenwu Pan;Howe R. J. Simpson;Wen Lei;Renjie Gu;Jarek Antoszewski;Gilberto A. Umana-Membreno;Lorenzo Faraone;Frank A. Hegmann
We use terahertz time-domain spectroscopy to measure the complex dielectric function of long-wave infrared Hg 1-x Cd x Te films ( x = 0.18, 0.20, 0.22) as a function of temperature in a noncontact manner. Using a Drude–Lorentz model fit to the measured complex transmission function combined with a Kane model description of the band structure, we obtain the temperature-dependent conduction band carrier density, effective mass, scattering time, and carrier mobility for all three Hg 1−x Cd x Te films. The optical properties of a bare substrate of Cd 0.96 Zn 0.04 Te were also measured in the terahertz region. The high quality of the Hg 1−x Cd x Te films is demonstrated by ultrahigh mobilities exceeding 10 5 cm 2 V −1 s −1 and ionized donor densities less than 3 × 10 15 cm −3 at temperatures below 100 K.
{"title":"Noncontact Characterization of Carrier Mobility in Long-Wave Infrared HgCdTe Films With Terahertz Time-Domain Spectroscopy","authors":"Nils B. Refvik;Charles E. Jensen;David N. Purschke;Wenwu Pan;Howe R. J. Simpson;Wen Lei;Renjie Gu;Jarek Antoszewski;Gilberto A. Umana-Membreno;Lorenzo Faraone;Frank A. Hegmann","doi":"10.1109/TTHZ.2024.3393627","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3393627","url":null,"abstract":"We use terahertz time-domain spectroscopy to measure the complex dielectric function of long-wave infrared Hg\u0000<sub>1-</sub>\u0000<italic><sub>x</sub></i>\u0000Cd\u0000<italic><sub>x</sub></i>\u0000Te films (\u0000<italic>x</i>\u0000 = 0.18, 0.20, 0.22) as a function of temperature in a noncontact manner. Using a Drude–Lorentz model fit to the measured complex transmission function combined with a Kane model description of the band structure, we obtain the temperature-dependent conduction band carrier density, effective mass, scattering time, and carrier mobility for all three Hg\u0000<sub>1−</sub>\u0000<italic><sub>x</sub></i>\u0000Cd\u0000<italic><sub>x</sub></i>\u0000Te films. The optical properties of a bare substrate of Cd\u0000<sub>0.96</sub>\u0000Zn\u0000<sub>0.04</sub>\u0000Te were also measured in the terahertz region. The high quality of the Hg\u0000<sub>1−</sub>\u0000<italic><sub>x</sub></i>\u0000Cd\u0000<italic><sub>x</sub></i>\u0000Te films is demonstrated by ultrahigh mobilities exceeding 10\u0000<sup>5</sup>\u0000 cm\u0000<sup>2</sup>\u0000V\u0000<sup>−1</sup>\u0000s\u0000<sup>−1</sup>\u0000 and ionized donor densities less than 3 × 10\u0000<sup>15</sup>\u0000 cm\u0000<sup>−3</sup>\u0000 at temperatures below 100 K.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"466-475"},"PeriodicalIF":3.9,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495306","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}
We demonstrate spoof surface plasmon coupling of a terahertz wave propagating in free space into a planar silicon waveguide through a bull's eye structure with a subwavelength aperture. Spoof surface plasmon polaritons induced by the bull's eye structure on the backside of the substrate propagate to the frontside through the aperture and couple into the waveguide. Electromagnetic field simulations revealed that the spoof surface plasmon polaritons propagating to the frontside show directivity along the incident polarization direction, and that the phase can be controlled by placing a Y -branched silicon waveguide beside the aperture. A prototype device was fabricated by bonding a copper-plated substrate with a bull's eye aperture and a waveguide fabricated by silicon micromachining. A monochromatic wave of 0.42–0.49 THz from a backward terahertz-wave parametric oscillator was injected into the bull's eye structure, and the intensity of the emitted wave from the end of the waveguide was measured. Directional coupling into the waveguide was confirmed from the intensity change depending on the incident polarization direction when using a straight waveguide. In addition, the phase difference between the two ends of the Y -branched waveguide was confirmed by the intensity change showing constructive or destructive interference depending on the polarization direction. These results indicate that it is possible to couple an incident wave into a planar waveguide perpendicular to it by controlling the phase via spoof surface plasmon coupling, suggesting its applicability to new experimental and practical systems in the terahertz band, such as beyond 5G/6G communications.
我们展示了在自由空间传播的太赫兹波通过带有亚波长孔径的牛眼结构进入平面硅波导的欺骗性表面等离子体耦合。由衬底背面牛眼结构诱导的欺骗性表面等离子体极化子通过孔径传播到正面，并耦合到波导中。电磁场模拟显示，传播到正面的欺骗性表面等离子体极化子沿入射极化方向具有指向性，而且相位可以通过在开孔旁边放置一个 Y 形分支硅波导来控制。通过将带有牛眼孔径的镀铜基板与硅微加工制造的波导粘合在一起，制造出了一个原型装置。将来自后向太赫兹波参量振荡器的 0.42-0.49 太赫兹单色波注入牛眼结构，并测量波导末端的发射波强度。使用直波导时，根据入射偏振方向的强度变化，可以确认波导的定向耦合。此外，Y 形分支波导两端的相位差也通过强度变化得到了证实，根据极化方向的不同，Y 形分支波导两端显示出建设性或破坏性干涉。这些结果表明，可以通过欺骗性表面等离子体耦合控制相位，将入射波耦合到垂直于它的平面波导中，这表明它适用于太赫兹波段的新实验和实用系统，例如超越 5G/6G 的通信。
{"title":"Phase-Controllable Spoof Surface Plasmon Coupling From Bull's Eye Aperture to Planar Silicon Waveguide in the Terahertz Band","authors":"Taiyu Okatani;Kaoru Imai;Yuma Takida;Seigo Ohno;Hiroaki Minamide;Yoshiaki Kanamori","doi":"10.1109/TTHZ.2024.3392157","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3392157","url":null,"abstract":"We demonstrate spoof surface plasmon coupling of a terahertz wave propagating in free space into a planar silicon waveguide through a bull's eye structure with a subwavelength aperture. Spoof surface plasmon polaritons induced by the bull's eye structure on the backside of the substrate propagate to the frontside through the aperture and couple into the waveguide. Electromagnetic field simulations revealed that the spoof surface plasmon polaritons propagating to the frontside show directivity along the incident polarization direction, and that the phase can be controlled by placing a \u0000<italic>Y</i>\u0000-branched silicon waveguide beside the aperture. A prototype device was fabricated by bonding a copper-plated substrate with a bull's eye aperture and a waveguide fabricated by silicon micromachining. A monochromatic wave of 0.42–0.49 THz from a backward terahertz-wave parametric oscillator was injected into the bull's eye structure, and the intensity of the emitted wave from the end of the waveguide was measured. Directional coupling into the waveguide was confirmed from the intensity change depending on the incident polarization direction when using a straight waveguide. In addition, the phase difference between the two ends of the \u0000<italic>Y</i>\u0000-branched waveguide was confirmed by the intensity change showing constructive or destructive interference depending on the polarization direction. These results indicate that it is possible to couple an incident wave into a planar waveguide perpendicular to it by controlling the phase via spoof surface plasmon coupling, suggesting its applicability to new experimental and practical systems in the terahertz band, such as beyond 5G/6G communications.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"519-530"},"PeriodicalIF":3.9,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10506676","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495055","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 : 2024-04-18DOI: 10.1109/TTHZ.2024.3390550
Maxim L. Kulygin;Evgeny A. Novikov;Maxim V. Kamensky;Vladimir I. Belousov;Ilya A. Litovsky;Andrey P. Fokin;Andrey A. Ananichev;Alexei A. Orlovsky;Vladimir V. Parshin;Evgeny A. Serov;Mikhail D. Proyavin;Olga A. Malshakova;Andrey V. Afanasiev;Andrey A. Sorokin
We study variations in the dielectric properties of a semi-insulating Gallium arsenide (GaAs) wafer under millisecond pulses of extreme subterahertz power density of up to 180 kW/mm2 at 263 GHz. Increasing the duration and power of the pulse, we have obtained sequential down- and upshifts within the range of more than two orders in the effective loss tangent of the wafer in experiments. We have observed the existence of an optimal regime of subterahertz irradiation, in which the accurate, simple and selective annealing of the wafer from the 300 nanometer-thick surface layer of oxides is achieved, even in plain air, without a damage to pure GaAs. An finite-difference time-domain-based numerical simulation explains such selectivity with a difference in tangent losses of about 25 times between pure GaAs and its impurities in the subterahertz band.
{"title":"Up-and-Down Adjustment of the GaAs Loss Tangent Using Extreme Power Densities in a Subterahertz Cavity","authors":"Maxim L. Kulygin;Evgeny A. Novikov;Maxim V. Kamensky;Vladimir I. Belousov;Ilya A. Litovsky;Andrey P. Fokin;Andrey A. Ananichev;Alexei A. Orlovsky;Vladimir V. Parshin;Evgeny A. Serov;Mikhail D. Proyavin;Olga A. Malshakova;Andrey V. Afanasiev;Andrey A. Sorokin","doi":"10.1109/TTHZ.2024.3390550","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3390550","url":null,"abstract":"We study variations in the dielectric properties of a semi-insulating Gallium arsenide (GaAs) wafer under millisecond pulses of extreme subterahertz power density of up to 180 kW/mm2 at 263 GHz. Increasing the duration and power of the pulse, we have obtained sequential down- and upshifts within the range of more than two orders in the effective loss tangent of the wafer in experiments. We have observed the existence of an optimal regime of subterahertz irradiation, in which the accurate, simple and selective annealing of the wafer from the 300 nanometer-thick surface layer of oxides is achieved, even in plain air, without a damage to pure GaAs. An finite-difference time-domain-based numerical simulation explains such selectivity with a difference in tangent losses of about 25 times between pure GaAs and its impurities in the subterahertz band.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"537-542"},"PeriodicalIF":3.9,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495054","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 : 2024-04-12DOI: 10.1109/TTHZ.2024.3388254
Florian Ludwig;Jakob Holstein;Anastasiya Krysl;Alvydas Lisauskas;Hartmut G. Roskos
We report on the modeling and experimental characterization of Si complementary metal-oxide-silicon (CMOS) detectors of terahertz radiation based on antenna-coupled field-effect transistors (TeraFETs). The detectors are manufactured using Taiwan semiconductor manufacturing company (TSMC's) 65-nm technology. We apply two models—the TSMC RF foundry model and our own advanced design system (ADS)-hydrodynamic transport model (HDM)—to simulate the Si CMOS TeraFET performance and compare their predictions with respective experimental data. Both models are implemented in the commercial circuit simulation software keysight ADS. We find that the compact model TSMC RF is capable to predict the detector responsivity and its dependence on frequency and gate voltage with good accuracy up to the highest frequency of 1.2 THz covered in this study. This frequency is well beyond the tool's intended operation range for 5G communications and 110-GHz millimeter wave applications. We demonstrate that our self-developed physics-based ADS-HDM tool, which relies on an extended 1-D HDM and can be adapted readily to other material technologies, has high predictive qualities comparable to those of the foundry model. We use the ADS-HDM to discuss the contribution of diffusive and plasmonic effects to the THz response of Si CMOS TeraFETs, finding that these effects, while becoming more significant with rising frequency, are never dominant. Finally, we estimate that the electrical noise-equivalent power (perfect power coupling conditions) is on the order of 5 pW/ $sqrt{mathrm{Hz}}$ at room-temperature.
我们报告了基于天线耦合场效应晶体管（TeraFET）的 Si CMOS 太赫兹辐射探测器的建模和实验特性。探测器采用台积电 65 纳米技术制造。我们采用两种模型--台积电射频代工模型和我们自己的 ADS-HDM 模型--来模拟 Si CMOS TeraFET 的性能，并将它们的预测结果与各自的实验数据进行比较。这两个模型都是在商业电路仿真软件 Keysight Advanced Design System (ADS) 中实现的。我们发现，紧凑型模型 TSMC RF 能够准确预测探测器的响应率及其与频率和栅极电压的关系，最高频率可达 1.2 THz。这一频率远远超出了该工具在 5G 通信和 110 GHz 毫米波应用中的预期工作范围。我们证明，我们自主开发的基于物理学的 ADS-HDM 工具依赖于扩展的一维流体力学传输模型，并可随时适应其他材料技术，具有与代工模型相当的高预测质量。我们使用 ADS-HDM 讨论了扩散效应和等离子效应对 Si CMOS TeraFET 太赫兹响应的贡献，发现这些效应虽然随着频率的上升而变得更加显著，但却从未占据主导地位。最后，我们估计室温下的电 NEP（完美功率耦合条件）约为 5 pW/$sqrt{rm{Hz}}$。
{"title":"Modeling of Antenna-Coupled Si MOSFETs in the Terahertz Frequency Range","authors":"Florian Ludwig;Jakob Holstein;Anastasiya Krysl;Alvydas Lisauskas;Hartmut G. Roskos","doi":"10.1109/TTHZ.2024.3388254","DOIUrl":"10.1109/TTHZ.2024.3388254","url":null,"abstract":"We report on the modeling and experimental characterization of Si complementary metal-oxide-silicon (CMOS) detectors of terahertz radiation based on antenna-coupled field-effect transistors (TeraFETs). The detectors are manufactured using Taiwan semiconductor manufacturing company (TSMC's) 65-nm technology. We apply two models—the TSMC RF foundry model and our own advanced design system (ADS)-hydrodynamic transport model (HDM)—to simulate the Si CMOS TeraFET performance and compare their predictions with respective experimental data. Both models are implemented in the commercial circuit simulation software keysight ADS. We find that the compact model TSMC RF is capable to predict the detector responsivity and its dependence on frequency and gate voltage with good accuracy up to the highest frequency of 1.2 THz covered in this study. This frequency is well beyond the tool's intended operation range for 5G communications and 110-GHz millimeter wave applications. We demonstrate that our self-developed physics-based ADS-HDM tool, which relies on an extended 1-D HDM and can be adapted readily to other material technologies, has high predictive qualities comparable to those of the foundry model. We use the ADS-HDM to discuss the contribution of diffusive and plasmonic effects to the THz response of Si CMOS TeraFETs, finding that these effects, while becoming more significant with rising frequency, are never dominant. Finally, we estimate that the electrical noise-equivalent power (perfect power coupling conditions) is on the order of 5 pW/\u0000<inline-formula><tex-math>$sqrt{mathrm{Hz}}$</tex-math></inline-formula>\u0000 at room-temperature.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 3","pages":"414-423"},"PeriodicalIF":3.2,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10497872","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140717652","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 : 2024-04-11DOI: 10.1109/TTHZ.2024.3387650
Martijn Hoogelander;Robbin van Dijk;Marco Spirito;Nuria Llombart;Maria Alonso-delPino
This letter demonstrates the near diffraction-limited imaging capabilities of an ultra-broadband terahertz camera based on a tightly sampled chessboard focal plane array (FPA) with integrated direct detectors, operating from 200 to 600 GHz. The terahertz camera is implemented in a 22-nm CMOS process and cointegrated with a hyperhemispherical silicon lens. To provide an efficient illumination of the subject without affecting the resolution of the camera, a quasi-optical imaging system was developed for operation in the WR2.2 band. The imaging system was designed to achieve a dynamic range of 25 dB and an imaging resolution of 2.1 mm at 400 GHz. The crossover level between adjacent beams from the CMOS camera is preserved in the imaging plane and yields 1.4 dB at 400 GHz. Compared with similar works where no mechanical scanning is used for resolution enhancement, the terahertz images created using the chessboard FPA demonstrate the highest resolution up to date.
{"title":"Demonstration of Near Diffraction-Limited Terahertz Images Using a CMOS-Integrated Chessboard Array","authors":"Martijn Hoogelander;Robbin van Dijk;Marco Spirito;Nuria Llombart;Maria Alonso-delPino","doi":"10.1109/TTHZ.2024.3387650","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3387650","url":null,"abstract":"This letter demonstrates the near diffraction-limited imaging capabilities of an ultra-broadband terahertz camera based on a tightly sampled chessboard focal plane array (FPA) with integrated direct detectors, operating from 200 to 600 GHz. The terahertz camera is implemented in a 22-nm CMOS process and cointegrated with a hyperhemispherical silicon lens. To provide an efficient illumination of the subject without affecting the resolution of the camera, a quasi-optical imaging system was developed for operation in the WR2.2 band. The imaging system was designed to achieve a dynamic range of 25 dB and an imaging resolution of 2.1 mm at 400 GHz. The crossover level between adjacent beams from the CMOS camera is preserved in the imaging plane and yields 1.4 dB at 400 GHz. Compared with similar works where no mechanical scanning is used for resolution enhancement, the terahertz images created using the chessboard FPA demonstrate the highest resolution up to date.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"531-536"},"PeriodicalIF":3.9,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141494983","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 terahertz systems, polarization conversion is usually carried out using conventional waveplates. However, limitations in these waveplates arise from inadequate material accessibility, relatively narrow bandwidth, low efficiency, and bulkiness. To overcome these limitations, a transmissive terahertz metasurface with mechanically reconfigurable polarization conversion is proposed. The separation between two identical metasurface plates is varied to switch between quarter-wave plate and half-wave plate functionalities. Measurement results verify that with no separation, the device can perform as a quarter-wave plate providing better than 3-dB axial ratio and an efficiency of over 75% from 246 to 320 GHz. With a separation of 150 $bm {mu }$ m between the two units, the transmission output becomes a cross-polarized wave with a 18-dB extinction ratio and an efficiency of over 74% across the same band. Altogether, the proposed polarization conversion device provides the advantage of reconfigurability and can be simply installed into existing terahertz systems to achieve multiple functionalities.
{"title":"Mechanically Reconfigurable Polarization Converter for Terahertz Waves","authors":"Sakib Quader;Rajour Tanyi Ako;Sharath Sriram;Christophe Fumeaux;Withawat Withayachumnankul","doi":"10.1109/TTHZ.2024.3387654","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3387654","url":null,"abstract":"In terahertz systems, polarization conversion is usually carried out using conventional waveplates. However, limitations in these waveplates arise from inadequate material accessibility, relatively narrow bandwidth, low efficiency, and bulkiness. To overcome these limitations, a transmissive terahertz metasurface with mechanically reconfigurable polarization conversion is proposed. The separation between two identical metasurface plates is varied to switch between quarter-wave plate and half-wave plate functionalities. Measurement results verify that with no separation, the device can perform as a quarter-wave plate providing better than 3-dB axial ratio and an efficiency of over 75% from 246 to 320 GHz. With a separation of 150 \u0000<inline-formula><tex-math>$bm {mu }$</tex-math></inline-formula>\u0000m between the two units, the transmission output becomes a cross-polarized wave with a 18-dB extinction ratio and an efficiency of over 74% across the same band. Altogether, the proposed polarization conversion device provides the advantage of reconfigurability and can be simply installed into existing terahertz systems to achieve multiple functionalities.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"502-509"},"PeriodicalIF":3.9,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141494982","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 : 2024-04-11DOI: 10.1109/TTHZ.2024.3387719
Seth N. Lowry;James M. Flood;Glitta R. Cheeran;Matthew E. Reid;Christopher M. Collier
Terahertz (THz) technology has been developed to meet advancements in spatial light modulation of frequencies in the THz regime, where fast modulation techniques designed for optical wavelengths perform poorly. Applications of THz frequencies in nondestructive imaging and quality testing have been thoroughly explored—specifically, polarization-resolved measurements can be scanned to image fiber anisotropy and birefringence in wood products and 3-D printed materials and strains in plastics. There is a need to explore faster image acquisition techniques, such as single-pixel imaging via spatial light modulation, to realize fast polarization-resolved THz imagers. Such spatial light modulators are vital for patterning the THz imaging beam before interacting with the sample to reconstruct the response of the sample with a single detector via compressive sensing algorithms. In this work, a spatial polarization modulation scheme is employed using wire grid polarizer (WGP) mask patterns to acquire polarization-resolved images of polarizing samples at 0.1 THz. A laser ablation technique is used to fabricate 8 × 8 WGP masks with randomly vertical and horizontal wire grids to pattern the imaging beam and enable orthogonal polarization images. With various sampling amounts, 8 × 8 polarization images are successfully reconstructed for polarizing samples of low and high spatial frequencies.
{"title":"Spatial Polarization Modulation for Terahertz Single-Pixel Imaging","authors":"Seth N. Lowry;James M. Flood;Glitta R. Cheeran;Matthew E. Reid;Christopher M. Collier","doi":"10.1109/TTHZ.2024.3387719","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3387719","url":null,"abstract":"Terahertz (THz) technology has been developed to meet advancements in spatial light modulation of frequencies in the THz regime, where fast modulation techniques designed for optical wavelengths perform poorly. Applications of THz frequencies in nondestructive imaging and quality testing have been thoroughly explored—specifically, polarization-resolved measurements can be scanned to image fiber anisotropy and birefringence in wood products and 3-D printed materials and strains in plastics. There is a need to explore faster image acquisition techniques, such as single-pixel imaging via spatial light modulation, to realize fast polarization-resolved THz imagers. Such spatial light modulators are vital for patterning the THz imaging beam before interacting with the sample to reconstruct the response of the sample with a single detector via compressive sensing algorithms. In this work, a spatial polarization modulation scheme is employed using wire grid polarizer (WGP) mask patterns to acquire polarization-resolved images of polarizing samples at 0.1 THz. A laser ablation technique is used to fabricate 8 × 8 WGP masks with randomly vertical and horizontal wire grids to pattern the imaging beam and enable orthogonal polarization images. With various sampling amounts, 8 × 8 polarization images are successfully reconstructed for polarizing samples of low and high spatial frequencies.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 3","pages":"386-394"},"PeriodicalIF":3.2,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820388","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}
Quantum-cascade lasers (QCLs) are critical components for high-resolution terahertz spectroscopy, especially in heterodyne spectrometers, where they serve as local oscillators. For this purpose, QCLs with stable frequencies and narrow linewidths are essential since their spectral properties limit the spectral resolution. We demonstrate the phase locking of QCLs around 3.5 and 4.7 THz in mechanical cryocoolers. These frequencies are particularly interesting for atmospheric research because they correspond to the hydroxyl radical and the neutral oxygen atom. The phase-locked loop is based on frequency mixing of the QCLs at 3.5 and 4.7 THz with the sixth and eighth harmonic, respectively, generated by an amplifier–multiplier chain operating around 600 GHz, with a Schottky-diode harmonic mixer. At both frequencies, we achieved a linewidth of the intermediate frequency signal of less than 1 Hz. This is about seven orders of magnitude less than the linewidth of the free-running QCL.
{"title":"Phase Locking of Quantum-Cascade Lasers Operating Around 3.5 and 4.7 THz With a Schottky-Diode Harmonic Mixer","authors":"Heiko Richter;Nick Rothbart;Martin Wienold;Xiang Lü;Klaus Biermann;Lutz Schrottke;Divya Jayasankar;Jan Stake;Peter Sobis;Heinz-Wilhelm Hübers","doi":"10.1109/TTHZ.2024.3385379","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3385379","url":null,"abstract":"Quantum-cascade lasers (QCLs) are critical components for high-resolution terahertz spectroscopy, especially in heterodyne spectrometers, where they serve as local oscillators. For this purpose, QCLs with stable frequencies and narrow linewidths are essential since their spectral properties limit the spectral resolution. We demonstrate the phase locking of QCLs around 3.5 and 4.7 THz in mechanical cryocoolers. These frequencies are particularly interesting for atmospheric research because they correspond to the hydroxyl radical and the neutral oxygen atom. The phase-locked loop is based on frequency mixing of the QCLs at 3.5 and 4.7 THz with the sixth and eighth harmonic, respectively, generated by an amplifier–multiplier chain operating around 600 GHz, with a Schottky-diode harmonic mixer. At both frequencies, we achieved a linewidth of the intermediate frequency signal of less than 1 Hz. This is about seven orders of magnitude less than the linewidth of the free-running QCL.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 3","pages":"346-353"},"PeriodicalIF":3.2,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820272","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 : 2024-03-30DOI: 10.1109/TTHZ.2024.3407686
Daniel Headland;Daniel C. Gallego;Guillermo Carpintero
We extend the operation bandwidth of substrateless all-silicon waveguides beyond the single-mode region. This requires a suitably broadband port-access scheme, as well as careful management of undesired higher order modes. It is found that a length of two-conductor waveguide serves both purposes. In this way, we experimentally demonstrate broadband power transfer between dielectric waveguides and numerically investigate suppression of higher order modes. This 3-D solid-metal two-conductor waveguide shows promise as a package-external terahertz port, to address the 40% relative-bandwidth bottleneck that is currently imposed by hollow metallic waveguides. This represents a step toward efficient handheld terahertz systems that fully exploit the broad available spectrum.
{"title":"Two-Conductor Ports Enabling Broadband Operation of Substrateless Microscale Silicon Waveguides","authors":"Daniel Headland;Daniel C. Gallego;Guillermo Carpintero","doi":"10.1109/TTHZ.2024.3407686","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3407686","url":null,"abstract":"We extend the operation bandwidth of substrateless all-silicon waveguides beyond the single-mode region. This requires a suitably broadband port-access scheme, as well as careful management of undesired higher order modes. It is found that a length of two-conductor waveguide serves both purposes. In this way, we experimentally demonstrate broadband power transfer between dielectric waveguides and numerically investigate suppression of higher order modes. This 3-D solid-metal two-conductor waveguide shows promise as a package-external terahertz port, to address the 40% relative-bandwidth bottleneck that is currently imposed by hollow metallic waveguides. This represents a step toward efficient handheld terahertz systems that fully exploit the broad available spectrum.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"543-547"},"PeriodicalIF":3.9,"publicationDate":"2024-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10542437","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495193","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 : 2024-03-24DOI: 10.1109/TTHZ.2024.3405168
Guanqiong Ma;Xue Li;Fangjing Hu;Tao Deng;Linan Li;Chang Gao;Jingye Sun
The manufacturing of 3-D metamaterials remains a major challenge and the narrow-band absorption characteristics limit the practical applications of terahertz (THz) metamaterial absorbers. To this end, we propose to combine the 3-D printing technology with the microfluidics technique to fabricate a THz metamaterial absorber with a relative broadband (∼0.3 THz) under 1 THz. Here, the absorber consists of embedded multilayer disk microfluidics channels stacked vertically within the resin and filled with liquid metal. It has been demonstrated that the experimental results agree well with the simulations, where the absorber exhibits polarization sensitive and incident angle insensitive in the frequency range from 0.25 to 0.6 THz. The proposed method enables the fabrication of THz metamaterial devices with complex structures in a fast, simple, and low-cost way, which is no longer limited to the conventional photolithography processes. This approach effectively stimulates many potential applications in emerging THz technologies, such as sensing, imaging, and wireless communications.
{"title":"A Novel Multilayer Broadband Terahertz Metamaterial Absorber Based on Three- Dimensional Printing and Microfluidics Technologies","authors":"Guanqiong Ma;Xue Li;Fangjing Hu;Tao Deng;Linan Li;Chang Gao;Jingye Sun","doi":"10.1109/TTHZ.2024.3405168","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3405168","url":null,"abstract":"The manufacturing of 3-D metamaterials remains a major challenge and the narrow-band absorption characteristics limit the practical applications of terahertz (THz) metamaterial absorbers. To this end, we propose to combine the 3-D printing technology with the microfluidics technique to fabricate a THz metamaterial absorber with a relative broadband (∼0.3 THz) under 1 THz. Here, the absorber consists of embedded multilayer disk microfluidics channels stacked vertically within the resin and filled with liquid metal. It has been demonstrated that the experimental results agree well with the simulations, where the absorber exhibits polarization sensitive and incident angle insensitive in the frequency range from 0.25 to 0.6 THz. The proposed method enables the fabrication of THz metamaterial devices with complex structures in a fast, simple, and low-cost way, which is no longer limited to the conventional photolithography processes. This approach effectively stimulates many potential applications in emerging THz technologies, such as sensing, imaging, and wireless communications.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"484-494"},"PeriodicalIF":3.9,"publicationDate":"2024-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495057","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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