Terahertz and Millimeter Wave Sensing and Applications

Bauer, Maris; Friederich, Fabian

doi:10.3390/s22249693

Cited by 7 publications

(5 citation statements)

References 22 publications

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“…Metasurfaces offer unprecedented advantages at subwavelength scales. Composed of single layers of artificial meta-atoms, they enable precise control of incident light's phase, amplitude, and polarization by adjusting the geometry or arrangement of meta-atoms [1]. Due to these characteristics, metasurfaces are considered promising candidates to replace traditional optical elements.…”

Section: Introductionmentioning

confidence: 99%

Tunable and super-wide angle defocusing lens large phase modulator

Xu,

Zhu,

Qin

2024

Phys. Scr.

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Traditional terahertz wavefront modulators exhibit significant limitations in controlling optical wavefronts. In order to address the adjustability issues of terahertz wavefront modulators, we have developed a novel optical device based on the tunability of Fermi energy levels. Structurally, we find the ability to modulate the Fermi energy levels of graphene by modulating the carrier concentration. We can also change the phase of the light, causing the transmission path of the light as it passes through the graphene array to change, affecting the position of the backfocusing focal point, thus realizing a dynamically adjustable backfocusing effect. Theoretically, employing Dirac notation and Matrix analyze, reveals the corresponding relationship between Fermi level and phase shift. Specifically, one group Fermi levels induces a set of modulated phase changes. Experimental results demonstrate that the proposed modulator offers a large phase modulation range, enabling 2 π phase adjustments. Moreover, it accurately focuses on a predefined focal point located at 400 um, with a numerical aperture of 0.882, a resolution of 30.39, and a full-width at half-maximum of 38. The substantial numerical aperture and small full-width at half-maximum imply that the lens can focus more light while maintaining high resolution, enhanced optical efficiency, and concentrated light focusing. At the same time, by adjusting the position of the Fermi energy level, we have succeeded in realizing a wide-angle focusing effect up to 90°. This capability extends the terahertz wave’s focusing within a wide range, expanding the application scope of traditional focusing devices.

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Section: Introductionmentioning

confidence: 99%

Tunable and super-wide angle defocusing lens large phase modulator

Xu,

Zhu,

Qin

2024

Phys. Scr.

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“…Electromagnetic wave with a frequency range of 0.1-10 terahertz (THz) is referred to as terahertz wave [1] . Due to its characteristics of penetration, fingerprint, and non-ionization, THz spectroscopy has demonstrated great potential in non-destructive detection, especially in the fields of food, medicine, environmental protection, and some industrial fields [2] , [3] , [4] , [5] . With THz spectra, Friska et al [6] utilized fast independent component analysis (ICA) and random forest (RF) algorithms to identify adulterated rice.…”

Section: Introductionmentioning

confidence: 99%

Interval-based sparse ensemble multi-class classification algorithm for terahertz data

Zheng,

Zha,

Cai

et al. 2024

Heliyon

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“…Terahertz Technologies have proven suitable for many applications in the fields of, e.g., non-destructive testing, wireless communication, and spectroscopy 1 , 2 . This success is to a large extent based on ongoing research and development of technological devices and systems for this type of electromagnetic radiation, both on the side of terahertz generation as well as detection.…”

Section: Introductionmentioning

confidence: 99%

Parasitic mixing in photomixers as continuous wave terahertz sources

Kocybik,

Bauer,

Friederich

2024

Sci Rep

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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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Terahertz and Millimeter Wave Sensing and Applications

Abstract: The field of terahertz and millimeter wave science and technology has evolved in recent years into an area attracting a lot of attention from all sides of science, industry, and~the public.

Cited by 7 publications

References 22 publications

Tunable and super-wide angle defocusing lens large phase modulator

Tunable and super-wide angle defocusing lens large phase modulator

Interval-based sparse ensemble multi-class classification algorithm for terahertz data

Parasitic mixing in photomixers as continuous wave terahertz sources

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