In this study,we introduce and experimentally validate,to our knowledge,a new type of terahertz(THz)fiber waveguide.The waveguide features a core made from petroleum jelly(commonly known as Vaseline)and a cladding mad...In this study,we introduce and experimentally validate,to our knowledge,a new type of terahertz(THz)fiber waveguide.The waveguide features a core made from petroleum jelly(commonly known as Vaseline)and a cladding made of holey polytetrafluoroethylene(PTFE),also known as Teflon.Since the core is biocompatible and the cladding is safe for human use,this design has promising applications for biocompatible probes in the THz range.We rigorously analyzed the transmission properties of the waveguide using the finite element method(FEM)and followed up with experimental validation using a THz time-domain spectroscopy(THz-TDS)system.The fiber supports single-mode operation for frequencies below 0.9 THz and demonstrates low-loss transmission of THz waves,even when tightly bent.For instance,with a bending radius as small as 1.61 cm,the fiber exhibited minimal losses of 0.23 dB/cm at 0.2 THz and 0.27 dB/cm at 0.5 THz,surpassing previous technical limitations.Another key advantage is the strong confinement of the THz waves within the petroleum jelly core,which helps maintain low dispersion and ensures stable pulse transmission,even under tight bends.The exceptional stability and flexibility of this biocompatible THz fiber make it highly suitable for sensing and imaging applications in confined,flexible environments,including potential uses within the human body.展开更多
Bound states in the continuum(BICs)and Fano resonances in planar photonic lattices,including metasurfaces and photonic-crystal slabs,have been studied extensively in recent years.Typically,the BICs and Fano resonances...Bound states in the continuum(BICs)and Fano resonances in planar photonic lattices,including metasurfaces and photonic-crystal slabs,have been studied extensively in recent years.Typically,the BICs and Fano resonances are associated with the second stop bands open at the second-order Γ point.This paper addresses the fundamental properties of the fourth stop band accompanied by BICs at the third-order Γ point in one-dimensional leakymode photonic lattices.At the fourth stop band,one band edge mode suffers radiation loss,thereby generating a Fano resonance,while the other band edge mode becomes a nonleaky BIC.The fourth stop band is controlled primarily by the Bragg processes associated with the first,second,and fourth Fourier harmonic components of the periodic dielectric constant modulation.The interplay between these three major processes closes the fourth band gap and induces a band flip whereby the leaky and BIC edges transit across the fourth band gap.At the fourth stop band,an accidental BIC is formed owing to the destructive interplay between the first and second Fourier harmonics.When the fourth band gap closes with strongly enhanced radiative Q factors,Dirac cone dispersions can appear at the third-order Γ point.展开更多
基金Institute of Information Communications Technology Planning Evaluation(2022-0-01029,RS-2022-II221044)National Research Foundation(2023R1A2C1007165)。
文摘In this study,we introduce and experimentally validate,to our knowledge,a new type of terahertz(THz)fiber waveguide.The waveguide features a core made from petroleum jelly(commonly known as Vaseline)and a cladding made of holey polytetrafluoroethylene(PTFE),also known as Teflon.Since the core is biocompatible and the cladding is safe for human use,this design has promising applications for biocompatible probes in the THz range.We rigorously analyzed the transmission properties of the waveguide using the finite element method(FEM)and followed up with experimental validation using a THz time-domain spectroscopy(THz-TDS)system.The fiber supports single-mode operation for frequencies below 0.9 THz and demonstrates low-loss transmission of THz waves,even when tightly bent.For instance,with a bending radius as small as 1.61 cm,the fiber exhibited minimal losses of 0.23 dB/cm at 0.2 THz and 0.27 dB/cm at 0.5 THz,surpassing previous technical limitations.Another key advantage is the strong confinement of the THz waves within the petroleum jelly core,which helps maintain low dispersion and ensures stable pulse transmission,even under tight bends.The exceptional stability and flexibility of this biocompatible THz fiber make it highly suitable for sensing and imaging applications in confined,flexible environments,including potential uses within the human body.
基金National Research Foundation of Korea(2020R1F1A1050227,2020R1I1A1A01073945)Gwangju Institute of Science and Technology(GRI in 2021).
文摘Bound states in the continuum(BICs)and Fano resonances in planar photonic lattices,including metasurfaces and photonic-crystal slabs,have been studied extensively in recent years.Typically,the BICs and Fano resonances are associated with the second stop bands open at the second-order Γ point.This paper addresses the fundamental properties of the fourth stop band accompanied by BICs at the third-order Γ point in one-dimensional leakymode photonic lattices.At the fourth stop band,one band edge mode suffers radiation loss,thereby generating a Fano resonance,while the other band edge mode becomes a nonleaky BIC.The fourth stop band is controlled primarily by the Bragg processes associated with the first,second,and fourth Fourier harmonic components of the periodic dielectric constant modulation.The interplay between these three major processes closes the fourth band gap and induces a band flip whereby the leaky and BIC edges transit across the fourth band gap.At the fourth stop band,an accidental BIC is formed owing to the destructive interplay between the first and second Fourier harmonics.When the fourth band gap closes with strongly enhanced radiative Q factors,Dirac cone dispersions can appear at the third-order Γ point.
