Strong Dispersive Propagation of Terahertz Wave: Time‐Domain Self‐Consistent Modeling of Metallic Wall Losses

Gao, Zi‐Chao; Du, Chao‐Hai; Li, Fan‐Hong; Shi, Peng; Zhang, Zi‐Wen; Liu, Pu‐Kun

doi:10.1002/adts.201900218

Cited by 4 publications

(4 citation statements)

References 24 publications

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“…When more than one mode is considered, Equation (B1) turns into the following form, To consider the wall losses, Equation (A2) is extended to the time domain using the algorithms mentioned in ref. [30]. The theories mentioned above do not use Gaussian or sinusoidal functions to approximate the longitudinal distribution of the wave, and the system will spontaneously converge to a self-consistent state (either the first or second axial mode) according to the behavior of the electrons.…”

Section: Appendix B: Multimode Time-domain Simulationmentioning

confidence: 99%

Instability Entanglement in the Electron Cyclotron Maser

Gao

et al. 2023

Annalen der Physik

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Investigation of absolute instability (AI) and convective instability (CI) of the electron cyclotron maser has independently led to the birth of gyrotron oscillators and amplifiers. Here, it is demonstrated that these instabilities can form a cooperative relationship owing to the nonlinear behavior of the stimulated electron beam. The CI can be induced in a zero‐drive system with the assistance of AI, and the ohmic losses of all the excited waves inside the system are greatly reduced, which is called “instability entanglement” here. According to the theoretical and experimental study of a 167/330 GHz gyrotron, when instability entanglement occurs, the ohmic dissipation decreases to one‐ninth of the AI‐only condition, and the output power is enhanced by 20%. This discovery is promising for surpassing the ceiling of output power and frequency of gyrodevices placed by ohmic losses.

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Section: Appendix B: Multimode Time-domain Simulationmentioning

confidence: 99%

Instability Entanglement in the Electron Cyclotron Maser

Gao

et al. 2023

Annalen der Physik

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“…In this case σeff equals 1.45×10 7 S/m (~0.25σ0). By substituting the evaluation of H-B formula into the impedance wall, it is convenient to combine the surface roughness with the analytical models including the steady-state frequency-domain theory [28], [29], [30] and the multimode time-domain theory [31], [32].…”

Section: Model For Surface Roughnessmentioning

confidence: 99%

“…9. The output and ohmic loss power are calculated based on the time-domain multi-mode theory [30], [32]. The electron gun is modeled and simulated in MAGIC.…”

Section: B Output Characteristics In Multi-mode Step-tuningmentioning

confidence: 99%

Design of a 1-THz Fourth-Harmonic Gyrotron Driven by Axis-Encircling Electron Beam

Zhang

et al. 2022

IEEE Trans. Electron Devices

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In this paper, the design of a 4 th -harmonic gyrotron with 1-kW-level output power at 1 terahertz (THz) is presented. A unique advantage of this design is that, with a well-optimized magnetic-cusp large-orbit electron gun, the designed gyrotron can operate from 1 st harmonic to 4 th harmonic in multiple discrete bands by varying the operating voltage. By carefully balancing the competing modes, the gyrotron can be tuned to operate at six candidate modes, including TE1,2 for fundamental harmonic, TE2,3 and TE2,4 for 2 nd harmonic, TE3,5 and TE3,6 for 3 rd harmonic, and TE4,8 for 4 th harmonic interactions. As the main operating mode, the TE4,8 can generate a peak output power of 1.68 kW, with an efficiency of about 2.1%, and a magnetically controlled frequency tuning range of about 1.8 GHz around 1 THz. The impact of the longitudinal nonuniformity of the cavity at high-harmonic interaction was also studied. It shows a radial tolerance of several micrometers will significantly elevate the start-oscillation current and deteriorate output performance. This design is towards the development of a synthesizing THz source with ultra-wideband tuning capability ranging from the sub-millimeter-wave to 1-THz bands.Index Terms-high harmonic terahertz gyrotron, multi-mode switching, broad-range magnetic tuning.

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“…A terahertz wave refers to an electromagnetic wave with a frequency between 0.1 and 10 THz. Its special position in the electromagnetic spectrum endows it with unique properties, such as low energy, high permeability, and fingerprint spectrum characteristics [1,2]. Such waves are widely used in communication [3], explosive detection [4], imaging [5], biological information extraction [6], medical diagnosis [6] and other fields.…”

Section: Introductionmentioning

confidence: 99%

Terahertz Sensor With Resonance Enhancement Based on Square Split-Ring Resonators

et al. 2021

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A novel design of a nearly perfect metamaterial absorber based on square split-ring resonators for terahertz sensing applications is proposed and analyzed. The design in this report is simulated and analyzed by using standard numerical simulation software. Magnetic and electric resonant field enhancement in the impedance matched absorber cavity enables stronger interaction with the dielectric analyte. The proposed structure is based on the simultaneous increase in the electromagnetic field and the surface current distribution at the resonance frequency. An absorptivity of 99% is achieved at 0.53 THz with a narrow resonance peak and a Q-factor of 44.17. At a fixed analyte thickness, the resonance frequency is sensitive to the refractive index of the surrounding medium. The influence of the thickness of the covering sample on the sensitivity and absorption coefficient of the absorber is comprehensively analyzed, and the reported design can be used as a refractive index sensor with a high sensitivity of 126.0 GHz/RIU and a figure of merit of 10.5 in the refractive index range from 1.0 to 2.0 at an analyte thickness of 15.0 µm. The results show that the sensor has high sensitivity to the analyte covering it. The sensor not only exhibits good sensitivity to thin analytes but also shows high sensitivity to analytes more than 10 µm thick in the terahertz low frequency band. Specifically, the sensitivity changes rapidly when the thickness of the sample changes in the range of 0-6 µm, but slowly in the range of 6-16 µm. In general, the response of the resonance frequency to changes in the refractive index of the sample becomes more sensitive as the thickness of the sample is increased from 0 to 16 µm . The reported terahertz sensor of a metamaterial absorber has potential applications in biomedical sensing and trace detection of substances.

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Strong Dispersive Propagation of Terahertz Wave: Time‐Domain Self‐Consistent Modeling of Metallic Wall Losses

Cited by 4 publications

References 24 publications

Instability Entanglement in the Electron Cyclotron Maser

Instability Entanglement in the Electron Cyclotron Maser

Design of a 1-THz Fourth-Harmonic Gyrotron Driven by Axis-Encircling Electron Beam

Terahertz Sensor With Resonance Enhancement Based on Square Split-Ring Resonators

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