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Kocybik M, Bauer M, Friederich F. Parasitic mixing in photomixers as continuous wave terahertz sources. Sci Rep 2024; 14:5534. [PMID: 38448503 PMCID: PMC10917803 DOI: 10.1038/s41598-024-55661-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 02/26/2024] [Indexed: 03/08/2024] Open
Abstract
We present observations of parasitic frequency components in the emission spectrum of typical photomixer sources for continuous wave (CW) terahertz generation. Broadband tunable photomixer systems are often used in combination with direct power detectors, e.g., for source and/or detector characterization. Here, spectral components besides the intended terahertz emission at the difference frequency of the two excitation lasers can significantly distort the measurement results. In this work, the appearance of parasitic mixing signals is observed in broadband measurements with a broadband antenna-coupled field-effect transistor as terahertz detector (TeraFET). The measurements reveal weaker spectral absorption features than expected and also a signal plateau towards higher frequencies, both strongly indicating a background in the detection signals. The photomixer emission is investigated in detail with a terahertz Fourier-transform infrared spectrometer (FTIR). We relate the observed parasitic frequency components with good quantitative agreement with the mode spectra of the semiconductor lasers. We also present one possible approach to overcome some of the issues, and we emphasize the importance of our findings to avoid distorted measurement results. To our knowledge, the essential aspect of parasitic mixing has so far been largely ignored in the literature where terahertz CW photomixer emitters are widely used for spectrally resolved measurements.
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Affiliation(s)
- Michael Kocybik
- Department of Materials Characterization and Testing, Fraunhofer Institute for Industrial Mathematics ITWM, 67663, Kaiserslautern, Germany.
- Department of Physics and Research Center OPTIMAS, RPTU Kaiserslautern-Landau, 67663, Kaiserslautern, Germany.
| | - Maris Bauer
- Department of Materials Characterization and Testing, Fraunhofer Institute for Industrial Mathematics ITWM, 67663, Kaiserslautern, Germany
| | - Fabian Friederich
- Department of Materials Characterization and Testing, Fraunhofer Institute for Industrial Mathematics ITWM, 67663, Kaiserslautern, Germany
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2
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Fang X, Huang H, Zhang H, Yang Z, Lyu Z, Yang H, Li N, Zhao T, Yu X, Zhang L. High resolution terahertz ATR frequency-domain spectroscopy for monitoring spinal cord injury in rats. BIOMEDICAL OPTICS EXPRESS 2024; 15:479-490. [PMID: 38223171 PMCID: PMC10783913 DOI: 10.1364/boe.507852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 11/09/2023] [Accepted: 12/17/2023] [Indexed: 01/16/2024]
Abstract
Traumatic spinal cord injury (SCI) can lead to permanent neurological impairment, underscoring the urgency of regular therapeutic intervention and monitoring. In this study, we propose a new strategy for monitoring spinal cord injury through serum based on high-resolution THz attenuated total reflection frequency domain spectroscopy (THz-ATR-FDS). We demonstrated serum spectral differences at different time points after experimental SCI in rats. We also studied the relationship between serum lipid concentration and the time of SCI, which revealed the potential of lipid molecules as biomarkers of SCI. In addition, based on the principal component analysis (PCA) and least squares regression (LSR) models, the quantitative relationship between the refractive index spectrum and lipid concentration in serum was automatically analyzed. This work highlights terahertz spectroscopy as a promising tool for label-free, periodic, and efficient monitoring of SCI.
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Affiliation(s)
- Xing Fang
- College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Hanxu Huang
- Department of Orthopedic Surgery, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310009, China
| | - Hongqi Zhang
- College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Zuomin Yang
- College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Zhidong Lyu
- College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Hang Yang
- College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Nan Li
- College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Tengfei Zhao
- Department of Orthopedic Surgery, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310009, China
| | - Xianbin Yu
- College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
| | - Lu Zhang
- College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
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3
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Iwamatsu S, Ali M, Estévez JLF, Grzeslo M, Makhlouf S, Rivera A, Carpintero G, Stöhr A. Terahertz photodiode integration with multi-octave-bandwidth dielectric rod waveguide probe. OPTICS LETTERS 2023; 48:6275-6278. [PMID: 38039245 DOI: 10.1364/ol.504354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 10/24/2023] [Indexed: 12/03/2023]
Abstract
Photonic integrated circuits play a vital role in enabling terahertz (THz) applications that require multi-octave bandwidth. Prior research has been limited in bandwidth due to rectangular waveguide (WRs) interconnects, which can only support single octave at low loss. To overcome this fundamental limitation, we exploit the ultra-wideband (UWB) near-field coupling between planar waveguides and silicon (Si)-based subwavelength dielectric rod waveguides (DRWs) to interconnect THz bandwidth uni-traveling-carrier photodiodes (UTC-PDs) at 0.08-1.03 THz. In a proof-of-concept experiment, the on-chip integrated UTC-PDs demonstrate a UWB operation from 0.1 THz to 0.4 THz. Furthermore, by employing Si DRWs as probes, multi-octave device-under-test characterization of UTC-PDs integrated with UWB transition is enabled with only one DRW probe. The proposed UWB interconnect technology is distinct from previously used WR-based ground-signal-ground probes or quasi-optical free-space coupling since it can provide multi-octave bandwidth and enable on-chip THz circuit integration.
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4
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Hoog Antink C, Schulz R, Rohr M, Wenzel K, Liebermeister L, Kohlhaas R, Preu S. Estimating Thoracic Movement with High-Sampling Rate THz Technology. SENSORS (BASEL, SWITZERLAND) 2023; 23:s23115233. [PMID: 37299961 DOI: 10.3390/s23115233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 05/25/2023] [Accepted: 05/26/2023] [Indexed: 06/12/2023]
Abstract
We use a high-sampling rate terahertz (THz) homodyne spectroscopy system to estimate thoracic movement from healthy subjects performing breathing at different frequencies. The THz system provides both the amplitude and phase of the THz wave. From the raw phase information, a motion signal is estimated. An electrocardiogram (ECG) signal is recorded with a polar chest strap to obtain ECG-derived respiration information. While the ECG showed sub-optimal performance for the purpose and only provided usable information for some subjects, the signal derived from the THz system showed good agreement with the measurement protocol. Over all the subjects, a root mean square estimation error of 1.40 BPM is obtained.
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Affiliation(s)
- Christoph Hoog Antink
- KIS*MED (AI Systems in Medicine Lab), Technische Universität Darmstadt, 64283 Darmstadt, Germany
| | - Romina Schulz
- Terahertz Devices and Systems, Technische Universität Darmstadt, 64283 Darmstadt, Germany
| | - Maurice Rohr
- KIS*MED (AI Systems in Medicine Lab), Technische Universität Darmstadt, 64283 Darmstadt, Germany
| | - Konstantin Wenzel
- Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, 10587 Berlin, Germany
| | - Lars Liebermeister
- Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, 10587 Berlin, Germany
| | - Robert Kohlhaas
- Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, 10587 Berlin, Germany
| | - Sascha Preu
- Terahertz Devices and Systems, Technische Universität Darmstadt, 64283 Darmstadt, Germany
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5
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Lu PK, Jarrahi M. Frequency-domain terahertz spectroscopy using long-carrier-lifetime photoconductive antennas. OPTICS EXPRESS 2023; 31:9319-9329. [PMID: 37157504 DOI: 10.1364/oe.483746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We present a telecommunication-compatible frequency-domain terahertz spectroscopy system realized by novel photoconductive antennas without using short-carrier-lifetime photoconductors. Built on a high-mobility InGaAs photoactive layer, these photoconductive antennas are designed with plasmonics-enhanced contact electrodes to achieve highly confined optical generation near the metal/semiconductor surface, which offers ultrafast photocarrier transport and, hence, efficient continuous-wave terahertz operation including both generation and detection. Consequently, using two plasmonic photoconductive antennas as a terahertz source and a terahertz detector, we successfully demonstrate frequency-domain spectroscopy with a dynamic range more than 95 dB and an operation bandwidth of 2.5 THz. Moreover, this novel approach to terahertz antenna design opens up a wide range of new possibilities for many different semiconductors and optical excitation wavelengths to be utilized, therefore bypassing short-carrier-lifetime photoconductors with limited availability.
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6
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Nellen S, Qian T, Schwanke G, Lauck S, de Felipe D, Kleinert M, Deumer M, Liebermeister L, Baier M, Globisch B, Keil N, Kohlhaas RB, Schell M. Photonic-enabled beam steering at 300 GHz using a photodiode-based antenna array and a polymer-based optical phased array. OPTICS EXPRESS 2022; 30:44701-44716. [PMID: 36522889 DOI: 10.1364/oe.472507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 11/03/2022] [Indexed: 06/17/2023]
Abstract
For wireless networks beyond 5G, directivity and reconfigurability of antennas are highly relevant. Therefore, we propose a linear antenna array based on photodiodes operating at 300 GHz, and an optical phased array based on polymer waveguides to orchestrate the antennas. Due to its low thermal conductivity and high thermo-optical coefficient, the polymer chip enables highly efficient and crosstalk-free phase shifting. With these, we demonstrate purely photonic-controlled beam steering across 20°. Compared to a single emitter, the 3-dB beam width is reduced by 8.5° to 22.5° and the output power is >10 dB higher. Employing Snell's law for coupling into air, we can precisely predict the radiation patterns.
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7
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Xu J, Zhang Z, Yang P, Dong L, Zhao Y. Nondestructive testing and 3D imaging of PE pipes using terahertz frequency-modulated continuous wave. APPLIED OPTICS 2022; 61:10230-10239. [PMID: 36606787 DOI: 10.1364/ao.468851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 10/17/2022] [Indexed: 06/17/2023]
Abstract
Polyethylene (PE) pipes are widely used as the main carrier for the transportation of natural gas, so nondestructive testing techniques for PE pipes are essential for the safety of natural gas transportation. In order to compensate for the shortcomings of conventional inspection methods, a terahertz (THz) three-dimensional imaging system for nondestructive inspection of PE pipes is designed. The system is based on frequency-modulated continuous-wave (FMCW) technology, with a THz source bandwidth of 0.225-0.330 THz and an output power of over 5 mW, which can achieve submillimeter spatial resolution in three dimensions. The system is used to scan PE pipes in three dimensions in a laboratory environment, and the results show that the system could achieve nondestructive testing and three-dimensional imaging of different defects in PE pipes. In addition, combined with the deep-learning-based THz transformer network, the intelligent identification of different defects is realized, and the accuracy rate can reach up to 88%. The above results provide technical guidance for the application of THz FMCW systems in the actual detection of PE pipes, and provide supplements and improvements for traditional detection methods.
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Belio-Apaolaza I, Seddon J, Moro-Melgar D, Indiran HP, Graham C, Balakier K, Cojocari O, Renaud CC. Photonically-driven Schottky diode based 0.3 THz heterodyne receiver. OPTICS EXPRESS 2022; 30:43223-43236. [PMID: 36523025 DOI: 10.1364/oe.471102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 10/10/2022] [Indexed: 06/17/2023]
Abstract
Photonics-based technologies are key players in a number of emerging applications in the terahertz (THz) field. These solutions exploit the well-known advantages of optical devices, such as ultra-wide tuneability and direct integration with fiber networks. However, THz receivers are mainly implemented by fully electronic solutions, where Schottky barrier diodes (SBD) are the preferred option as detectors and mixers due to their excellent response within the THz range at room temperature, and technological maturity. Here, we demonstrate an SBD-based subharmonic mixer (SHM) at 300 GHz pumped with a photonic local oscillator. The Schottky mixer is a prototype designed and manufactured by ACST GmbH, operating at 270-320 GHz. The local oscillator is generated by photomixing on a high-frequency and high-power uni-travelling-carrier photodiode (UTC-PD), providing enough power to saturate conversion loss. Minimum single-side-band conversion loss of 14.4 dB and a peak dynamic range of 130 dB have been measured. Finally, as a proof of concept we realize an all-photonics-based 5 Gbps wireless bridge, utilizing the optically-pumped SBD mixer. With this work, we prove the feasibility of high-performance hybrid Schottky-photonic THz receivers, incorporating the best of both worlds.
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9
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Abdulkarim Y, Altintas O, Karim AS, Awl HN, Muhammadsharif FF, Alkurt FÖ, Bakir M, Appasani B, Karaaslan M, Dong J. Highly Sensitive Dual-Band Terahertz Metamaterial Absorber for Biomedical Applications: Simulation and Experiment. ACS OMEGA 2022; 7:38094-38104. [PMID: 36312388 PMCID: PMC9608393 DOI: 10.1021/acsomega.2c06118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 10/05/2022] [Indexed: 06/16/2023]
Abstract
In this paper, a terahertz (THz) metamaterial absorber (MTMA), incorporating surface Pythagorean tree fractal resonators, was designed and experimentally fabricated on the flexible substrate of polyethylene terephthalate. The design presented two peaks with strong absorption of more than 97% at 0.49 and 0.69 THz. The dual-band absorption peaks were seen to be shifted with the change in the refractive index of the surrounding medium, with a corresponding sensitivity of 0.0968 and 0.1182 THz/RIU. The spectral shift of the reflection resonance dip was utilized as an assessment index to evaluate the sensing performance of the new structure, and it was found to be 2.08 and 2.98 for the two resonance peaks, respectively. It was observed that the proposed structure acted as an epsilon negative material at the first resonance and as a mu negative material at the second resonance. Further investigations on the electric field, magnetic field, and surface current distributions were carried out to elaborate on the absorption characteristics at various resonance frequencies. The proposed sensor is a highly sensitive MTMA which can be used to investigate the interaction of matter with THz waves.
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Affiliation(s)
- Yadgar
I. Abdulkarim
- School
of Computer Science and Engineering, Central
South University, Changsha410075, China
- Medical
Physics Department, College of Medicals & Applied Science, Charmo University, Chamchamal, 46023Sulaimania, Iraq
| | - Olcay Altintas
- Department
of Electrical-Electronics Engineering, Iskenderun
Technical University, 31200Hatay, Turkey
| | - Ayoub Sabir Karim
- Physics
Department, College of Education, Salahaddin
University-Erbil, 44002Erbil, Iraq
| | - Halgurd N. Awl
- Department
of Communication Engineering, Sulaimani
Polytechnic University, 46001Sulaimani, Iraq
| | | | - Fatih Özkan Alkurt
- Department
of Electrical-Electronics Engineering, Iskenderun
Technical University, 31200Hatay, Turkey
| | - Mehmet Bakir
- Department
of Computer Engineering, Bozok University, 66200Yozgat, Turkey
| | - Bhargav Appasani
- School
of Electronics Engineering, KIIT University, 751024Bhubaneswar, India
| | - Muharrem Karaaslan
- Department
of Electrical-Electronics Engineering, Iskenderun
Technical University, 31200Hatay, Turkey
| | - Jian Dong
- School
of Computer Science and Engineering, Central
South University, Changsha410075, China
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10
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Haddad T, Biurrun-Quel C, Lu P, Tebart J, Sievert B, Makhlouf S, Grzeslo M, Teniente J, Del-Río C, Stöhr A. Photonic-assisted 2-D terahertz beam steering enabled by a LWA array monolithically integrated with a BFN. OPTICS EXPRESS 2022; 30:38596-38612. [PMID: 36258421 DOI: 10.1364/oe.468200] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 08/26/2022] [Indexed: 06/16/2023]
Abstract
A novel photonic-assisted 2-D Terahertz beam steering chip using only two tuning elements is presented. The chip is based on an array of three leaky wave antennas (LWAs) with a monolithically integrated beamforming network (BFN) on a 50 µm-thick indium phosphide substrate. The THz beam angle in elevation (E-plane) is controlled via optical frequency tuning using a tunable dual-wavelength laser. An optical delay line is used for azimuth (H-plane) beam control. The simulated beam scanning range is 92° in elevation for a frequency sweep from 0.23 THz to 0.33 THz and 69.18° in azimuth for a time delay of 3.6 ps. For the frequency range from 0.26 THz to 0.32 THz, it is confirmed experimentally that the THz beam scans from -12° to +33°, which is in good agreement with the numerical simulations. The beam direction in azimuth scans with a total angle of 39° when applying a delay difference of 1.68 ps. A good agreement is found between theoretically predicted and experimentally determined THz beam angles with a maximum angle deviation below 5°. The experimental scanning angles are limited due to the mechanical constraints of the on-wafer probes, the on-chip integrated transition and the bandwidth of the THz receiver LNA. The mechanical limitation will be overcome when using a packaged chip.
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11
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Chen WC, Chang CW, Yang SH. Group IV THz large area emitter based on GeSn alloy. OPTICS LETTERS 2022; 47:4411-4414. [PMID: 36048666 DOI: 10.1364/ol.464541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/31/2022] [Indexed: 06/15/2023]
Abstract
THz photoconductive emitters based on III-V materials have demonstrated excellent THz radiation properties, enabling many unique applications. However, the incompatibility with the complementary-metal-oxide-semiconductor (CMOS) foundry fabrication process and the challenging growth condition hampers THz photoconductive emitters from large-scale production. To address this limitation, we proposed the GeSn alloy as the photoconductive material candidate through the CMOS-compatible epitaxy instrument. The GeSn photoconductor features a 518 cm2/V-s mobility and a 7187 cm-1 absorption coefficient at the wavelength of 1560 nm, resulting in sufficiently ultrafast photocurrent generation for THz radiation. As a result, the GeSn THz emitter provides over a bandwidth of 2 THz and a 40 dB signal-to-noise ratio, which shows its potential in realizing mass-producible, cost-effective THz integrated systems with CMOS technology.
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12
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Tang L, Li L, Li J, Chen M. Hybrid integrated ultralow-linewidth and fast-chirped laser for FMCW LiDAR. OPTICS EXPRESS 2022; 30:30420-30429. [PMID: 36242146 DOI: 10.1364/oe.465858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 07/19/2022] [Indexed: 06/16/2023]
Abstract
Narrow linewidth and fast-chirped frequency are essential in frequency-modulated continuous-wave lasers. We introduce a laser that meets these requirements by coupling a distributed feedback laser with an external high-Q microring resonator, where a bulky stacked piezoelectric chip is attached to the resonator for fast tuning. The laser demonstrates an ultranarrow intrinsic linewidth of 22 Hz in the self-injection-locked state. Actuated by the bulky piezoelectric chip, the maximum triangular actuation bandwidth can reach 100 kHz. The driving voltage is filtered to avoid a resonant mechanical mode, obtaining the minimum residual linearity error at 10 kHz with a 4.2 GHz tuning range. A light detection and ranging system was set up for a proof-of-concept experiment, demonstrating a high detection precision with standard deviations of 2.7 and 4.0 cm for targets at 15 and 30 m, respectively.
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13
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Nallappan K, Skorobogatiy M. Photonics based frequency hopping spread spectrum system for secure terahertz communications. OPTICS EXPRESS 2022; 30:27028-27047. [PMID: 36236883 DOI: 10.1364/oe.459939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 06/17/2022] [Indexed: 06/16/2023]
Abstract
Terahertz (THz) spectrum (100 GHz-10 THz) is considered the next frontier in the design of high-speed wireless communication systems. While the high-power THz sources have commercially become available, it increases the possibility of developing THz jammers to disrupt the THz communication link. Therefore, the development of novel anti-jamming solutions is the need of the hour. In this work, we present the photonics-based THz communication system and demonstrate the frequency hopping spread spectrum (FHSS) technique which acts against the single/multi-tone jamming attack in the frequency window of 110 GHz-170 GHz. By tuning the output wavelength of the distributed feedback lasers, the THz carrier frequencies are swept back and forth within the scanning window. The frequency tuning range was measured for different scanning rates of the laser which decreases rapidly with the increase in the scanning rate. Next, we demonstrate the THz FHSS technique in a real-time communication system by transmitting a 6 Gbps NRZ signal in both wireless and THz-fiber-based links within the link distance of 1.75 m. We experimentally found that the measured bit error rate in the THz FHSS system is the time average of the measured BER for individual carrier frequencies within the hopping frequency window. By combining with the forward error correction codes and by using the tunable filter in the receiver, we believe that the proposed technique will offer a novel and compact solution against the single/multi-tone jammer for high-bit rate THz communications.
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14
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A Novel System for Quasi-Continuous THz Signal Transmission and Reception. SENSORS 2022; 22:s22124448. [PMID: 35746230 PMCID: PMC9227974 DOI: 10.3390/s22124448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/02/2022] [Accepted: 06/10/2022] [Indexed: 12/10/2022]
Abstract
This paper presents a novel system for generating and receiving quasi-continuous (QC) TeraHertz (THz) waves. A system design and theoretical foundation for QC-THz signal generation are presented. The proposed QC-THz system consists of commercially available photo-conductive antennas used for transmission and reception of THz waves and a custom-designed QC optical signal generator, which is based on a fast optical frequency sweep of a single telecom distributed-feedback laser diode and unbalanced optical fiber Michelson interferometer used for a high-frequency modulation. The theoretical model for the proposed system is presented and experimentally evaluated. The experimental results were compared to the state-of-the-art continuous-wave THz system. The comparison between the continuous-wave THz system and the proposed QC-THz system showed the ability to transmit and receive QC-THz waves up to 300 GHz. The upper-frequency limit is bounded by the length of the used Michelson interferometer. The presented design of THz signal generation has a potential for industrial application because it is cost-efficient and can be built using commercially available components.
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15
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Lee MH, Nellen S, Soares F, Moehrle M, Rehbein W, Baier M, Globisch B, Schell M. Photonic integrated circuit with sampled grating lasers fabricated on a generic foundry platform for broadband terahertz generation. OPTICS EXPRESS 2022; 30:20149-20158. [PMID: 36224766 DOI: 10.1364/oe.454296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 03/24/2022] [Indexed: 06/16/2023]
Abstract
We demonstrate a monolithically integrated photonic integrated circuit (PIC) for terahertz spectroscopy with wide spectral bandwidth. The PIC includes two widely tunable sampled grating DBR (SG DBR) lasers, semiconductor optical amplifiers (SOAs), and passive components to combine signals. The SG DBR lasers cover 22 nm and 24 nm tuning range, respectively, with 4 nm overlap in the C band. The side mode suppression ratio (SMSR) exceeds 37 dB with a linewidth below 4.3 MHz. We used the PIC to generate THz radiation with a state-of-the-art photodiode emitter. The measured THz power spectrum between 0.03 and 1 THz compares well with the spectrum generated with commercial tunable laser sources. This demonstrates the suitability of our PIC for future miniaturized continuous wave (cw) THz systems.
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16
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Li P, Liu S, Chen X, Geng C, Wu X. Spintronic terahertz emission with manipulated polarization (STEMP). FRONTIERS OF OPTOELECTRONICS 2022; 15:12. [PMID: 36637604 PMCID: PMC9756272 DOI: 10.1007/s12200-022-00011-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 01/11/2022] [Indexed: 06/17/2023]
Abstract
Highly efficient generation and arbitrary manipulation of spin-polarized terahertz (THz) radiation will enable chiral lightwave driven quantum nonequilibrium state regulation, induce new electronic structures, consequently provide a powerful experimental tool for investigation of nonlinear THz optics and extreme THz science and applications. THz circular dichromic spectroscopy, ultrafast electron bunch manipulation, as well as THz imaging, sensing, and telecommunication, also need chiral THz waves. Here we review optical generation of circularly-polarized THz radiation but focus on recently emerged polarization tunable spintronic THz emission techniques, which possess many advantages of ultra-broadband, high efficiency, low cost, easy for integration and so on. We believe that chiral THz sources based on the combination of electron spin, ultrafast optical techniques and material structure engineering will accelerate the development of THz science and applications.
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Affiliation(s)
- Peiyan Li
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Shaojie Liu
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Xinhou Chen
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Chunyan Geng
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Xiaojun Wu
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China.
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China.
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China.
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Abstract
In this paper, we report the development of a frequency-shifted (FS) terahertz (THz) wave source for the non-destructive inspection of buildings. Currently, terahertz-time domain spectroscopy (THz-TDS) is the mainstream method for non-destructive inspection using THz waves. However, THz-TDS is limited by its measurement range and difficulties encountered when there is a strong frequency dependence in the absorption characteristics and refractive index of the measurement target. To address these issues, we developed a novel non-destructive approach for inspection applications using frequency-shifted THz waves. Our system uses a frequency-shifted feedback (FSF) laser as the pump light source to generate FS-THz waves; this allowed us to obtain precise distance measurements of objects over a broad range of distances. We tested a prototype FS-THz system and confirmed successful measurement of spatial distances inside a building material.
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Spectral Shaping of a Superluminescent Diode for Terahertz Cross-Correlation Spectroscopy. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12041772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
After 20 years of terahertz cross-correlation spectroscopy (THz-CCS), the performance of the systems has been improved to practical relevance by reaching a bandwidth of ~2 THz. For the development of high-performance THz-CCS systems, it is necessary to get a deeper knowledge of the signal generation from incoherent light sources. In this work, the bandwidth, dynamic range, and peak-to-peak amplitude of a THz-CCS systems using a superluminescent diode as light source and a programmable optical filter for spectral shaping was investigated to obtain a better understanding of the relationship between the optical spectrum and the generated terahertz spectrum. By a periodic structuring of the continuous optical spectrum, an enhancement of the peak dynamic range of more than 10 dB was achieved with a bandwidth of 1.6 THz. The experimental results are confirmed by numerical simulations.
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Visualizing nanometric structures with sub-millimeter waves. Nat Commun 2021; 12:7091. [PMID: 34876583 PMCID: PMC8651651 DOI: 10.1038/s41467-021-27264-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 11/09/2021] [Indexed: 11/08/2022] Open
Abstract
The resolution along the propagation direction of far field imagers can be much smaller than the wavelength by exploiting coherent interference phenomena. We demonstrate a height profile precision as low as 31 nm using wavelengths between 0.375 mm and 0.5 mm (corresponding to 0.6 THz-0.8 THz) by evaluating the Fabry-Pérot oscillations within surface-structured samples. We prove the extreme precision by visualizing structures with a height of only 49 nm, corresponding to 1:7500 to 1:10000 vacuum wavelengths, a height difference usually only accessible to near field measurement techniques at this wavelength range. At the same time, the approach can determine thicknesses in the centimeter range, surpassing the dynamic range of any near field measurement system by orders of magnitude. The measurement technique combined with a Hilbert-transform approach yields the (optical) thickness extracted from the relative phase without any extraordinary wavelength stabilization.
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Akter N, Hasan MM, Pala N. A Review of THz Technologies for Rapid Sensing and Detection of Viruses including SARS-CoV-2. BIOSENSORS 2021; 11:349. [PMID: 34677305 PMCID: PMC8534088 DOI: 10.3390/bios11100349] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/12/2021] [Accepted: 09/18/2021] [Indexed: 12/15/2022]
Abstract
Virus epidemics such as Ebola virus, Zika virus, MERS-coronavirus, and others have wreaked havoc on humanity in the last decade. In addition, a coronavirus (SARS-CoV-2) pandemic and its continuously evolving mutants have become so deadly that they have forced the entire technical advancement of healthcare into peril. Traditional ways of detecting these viruses have been successful to some extent, but they are costly, time-consuming, and require specialized human resources. Terahertz-based biosensors have the potential to lead the way for low-cost, non-invasive, and rapid virus detection. This review explores the latest progresses in terahertz technology-based biosensors for the virus, viral particle, and antigen detection, as well as upcoming research directions in the field.
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Affiliation(s)
| | | | - Nezih Pala
- Department of Electrical and Computer Engineering, Florida International University, Miami, FL 33174, USA; (N.A.); (M.M.H.)
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