Low-loss modes in hollow metallic terahertz waveguides with dielectric coatings

Bowden, Bradley F.; Harrington, James A.; Mitrofanov, Oleg

doi:10.1063/1.3013585

Cited by 93 publications

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“…However, the TE 01 mode with a doughnut shape electric field profile can be the dominant mode if the dielectric layer is thin ͑0-3 m͒. 4 Mode-specific dispersion characteristics in these waveguides have not been measured yet because several modes are often mixed in transmission experiments. 3,10 In the experimental setup a horizontally polarized broadband terahertz pulse ͑1-2.5 THz͒ is coupled as a slightly diverging wave ͑ϳ2°half-angle͒ into a 133.5 mm long waveguide with 1.7 mm bore diameter and the inner coatings of silver ͑1 m͒ and polystyrene ͑14 m͒.…”

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confidence: 99%

“…In this letter, we discuss the application of terahertz near-field probe microscopy to determine the mode structure and composition in dielectric-lined hollow cylindrical metallic waveguides. [3][4][5] We consider a typical case of multimode propagation of a short terahertz pulse, when the output waveform becomes a superposition of all excited modes. By detecting the spatial distribution of the terahertz pulse field at the waveguide output, we attempt to determine profiles and relative weight of all excited modes experimentally.…”

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confidence: 99%

“…4 The dominant mode is determined by the waveguide design ͑specifically, the dielectric layer thickness and the bore diameter͒. 6-9 The hybrid HE 11 mode is expected to be the lowest loss mode at ϳ1 -3 THz for a waveguide with a relatively thick ͑ϳ10 m͒ dielectric layer.…”

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Waveguide mode imaging and dispersion analysis with terahertz near-field microscopy

Mitrofanov

Tan

Mark

et al. 2009

Applied Physics Letters

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Propagation of terahertz waves in hollow metallic waveguides depends on the waveguide mode. Near-field scanning probe terahertz microscopy is applied to identify the mode structure and composition in dielectric-lined hollow metallic waveguides. Spatial profiles, relative amplitudes, and group velocities of three main waveguide modes are experimentally measured and matched to the HE 11 , HE 12 , and TE 11 modes. The combination of near-field microscopy with terahertz time-resolved spectroscopy opens the possibility of waveguide mode characterization in the terahertz band. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3126053͔Terahertz technology moves toward the component integration and it has become essential to develop terahertz waveguides with low transmission loss and small group velocity dispersion. Terahertz time-domain spectroscopy ͑terahertz-TDS͒ is potentially ideal for waveguide characterization. However, waveguide transmission spectra measured by terahertz TDS often contain periodic patterns, which are caused by the waveguide mode interference. 1 The loss and dispersion analysis in this case is difficult without knowledge of the waveguide mode composition.The mode structure and composition can be determined by imaging the output terahertz wave at the waveguide end. In particular, recently developed collection mode terahertz near-field microscopy has the potential to detect the output wave spatial profile. 2 The near-field technique is preferred because it gives the mode structure directly, contrary to the far-field imaging. In this letter, we discuss the application of terahertz near-field probe microscopy to determine the mode structure and composition in dielectric-lined hollow cylindrical metallic waveguides. [3][4][5] We consider a typical case of multimode propagation of a short terahertz pulse, when the output waveform becomes a superposition of all excited modes. By detecting the spatial distribution of the terahertz pulse field at the waveguide output, we attempt to determine profiles and relative weight of all excited modes experimentally. This knowledge is essential for the loss and dispersion characterization of individual modes and for waveguide design optimization.Identification of modes in the dielectric-lined hollow cylindrical metallic waveguides is of a particular interest because two modes have low-loss characteristics ͑1-3 dB/m at 2.5 THz͒. 4 The dominant mode is determined by the waveguide design ͑specifically, the dielectric layer thickness and the bore diameter͒. 6-9 The hybrid HE 11 mode is expected to be the lowest loss mode at ϳ1 -3 THz for a waveguide with a relatively thick ͑ϳ10 m͒ dielectric layer. However, the TE 01 mode with a doughnut shape electric field profile can be the dominant mode if the dielectric layer is thin ͑0-3 m͒. 4 Mode-specific dispersion characteristics in these waveguides have not been measured yet because several modes are often mixed in transmission experiments. 3,10 In the experimental setup a horizontally polarized broadband terahertz pulse ...

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Waveguide mode imaging and dispersion analysis with terahertz near-field microscopy

Mitrofanov

Tan

Mark

et al. 2009

Applied Physics Letters

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“…1.5-5.0 THz [1][2][3][4][5], where propagation in free-space [6] or in open waveguides [7,8] is highly restricted due to water vapor absorption [9].…”

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“…By introducing a dielectric coating on the inner metallic walls of an oversized waveguide (as a rule of thumb,~λ 0 /4 thick), the waveguide dominant mode becomes the linearly polarized hybrid HE 11 mode [1][2][3][4][5][11][12][13][14][15][16]. This HE 11 mode is advantageous because it suffers low losses and it couples efficiently to freespace linearly polarized Gaussian beams [11,17].…”

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Silver-Coated Teflon Tubes for Waveguiding at 1–2 THz

Navarro‐Cía

Melzer

Harrington

et al. 2015

J Infrared Milli Terahz Waves

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Realization of single-mode low-loss waveguides for 1.0-2.0 THz remains a challenging problem due to large absorption in most dielectrics and ohmic losses in metals. To address this problem, we investigate dielectric-lined hollow metallic waveguides fabricated by coating 1-mm diameter 38-μm-thick polytetrafluoroethylene tubes with silver. These waveguides support a hybrid HE 11 mode, which exhibits low attenuation and low dispersion. Quasisingle-mode propagation is achieved in the band of 1.0-1.6 THz, in which the hybrid HE 11 mode is supported by the waveguide. In this band, the experimentally measured loss is 20 dB/m (~0.046 cm −1 ), whereas the numerically computed loss is~7 dB/m (~0.016 cm). The difference is attributed to additional losses in the dielectric layer, which can be reduced by using alternative polymers.

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Sapphire Photonic Crystal Waveguides for Terahertz Sensing in Aggressive Environments

Katyba

Zaytsev

Chernomyrdin

et al. 2018

Advanced Optical Materials

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IntroductionOver the last decade, THz spectroscopy has been used with success in a variety of fundamental and practical applications, [1,2] which among others include: spectroscopy of condensed matter [3][4][5] and gases, [6] medical diagnosis [7,8] and therapy, [9] Terahertz (THz) frequency range opens significant opportunities in various fundamental and applied fields including condensed matter physics and chemistry, biology and medicine, public security and nondestructive testing. Despite significant advances in THz instrumentation, the problem of THz sensing in harsh environments, particularly at high temperatures and pressures, remains acute due to the lack of THz materials and optical components capable for operation under the extreme conditions. To address this problem, the THz hollow-core photonic crystal sapphire waveguides that are fabricated using shaped crystal growth technique are developed. Numerical analysis and experimental study show that the proposed waveguides operate in a fewmode regime and allow for the broadband transmission of THz pulses with small dispersions and low propagation losses. Thanks to the unique physical properties of sapphire, the proposed waveguides are capable of operating in a variety of aggressive environments. As an example, the developed waveguides are used to conduct the intra-waveguide interferometric sensing of phase transitions in sodium nitrite films at high temperatures. It is believed that the proposed sapphire-based material's platform has strong potential for developing THz guided optics for applications in intra-waveguide spectroscopy, interferometry, and remote sensing in aggressive environments. Sapphire Terahertz Waveguides

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Low-loss modes in hollow metallic terahertz waveguides with dielectric coatings

Cited by 93 publications

References 13 publications

Waveguide mode imaging and dispersion analysis with terahertz near-field microscopy

Waveguide mode imaging and dispersion analysis with terahertz near-field microscopy

Silver-Coated Teflon Tubes for Waveguiding at 1–2 THz

Sapphire Photonic Crystal Waveguides for Terahertz Sensing in Aggressive Environments

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