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Article List
2021, 19(5):769-777.
DOI: 10.11805/TKYDA2021246
Abstract:
Terahertz waves with unique spectrum characteristics have provided important applications in cross frontier fields of astronomical observation, interstellar communication and defense security. As one of the key components in the terahertz detection/communication systems, the filter can extract characteristic signals and suppress interference frequencies to improve the target detection performance of the system. In recent years, thanks to the development of the high-precision manufacturing process, some breakthrough results have been achieved in terahertz waveguide filters. And the filters based on different types, structures and processes have been studied. In this review paper, the development status and common problems of terahertz waveguide filters are expounded based on the different processes. The advantages and disadvantages of filters developed by mainstream technologies are also summarized, which can provide a reference for the further development of terahertz waveguide filters with high performance.
Terahertz waves with unique spectrum characteristics have provided important applications in cross frontier fields of astronomical observation, interstellar communication and defense security. As one of the key components in the terahertz detection/communication systems, the filter can extract characteristic signals and suppress interference frequencies to improve the target detection performance of the system. In recent years, thanks to the development of the high-precision manufacturing process, some breakthrough results have been achieved in terahertz waveguide filters. And the filters based on different types, structures and processes have been studied. In this review paper, the development status and common problems of terahertz waveguide filters are expounded based on the different processes. The advantages and disadvantages of filters developed by mainstream technologies are also summarized, which can provide a reference for the further development of terahertz waveguide filters with high performance.
2021, 19(5):778-783.
DOI: 10.11805/TKYDA2021131
Abstract:
Terahertz(THz) imaging has shown wide application prospects in many fields such as human body security inspection, non-destructive inspection, quality monitoring, biomedicine, and semiconductor characterization. In this article, various two-dimensional THz imaging techniques are reviewed, including scanning imaging, single-pixel imaging, electro-optic modulation imaging, direct imaging with THz camera, and so on. The research backgrounds of various imaging technologies are summarized, the specific imaging methods and imaging results are analyzed. The advantages and disadvantages of different terahertz imaging technologies are concluded, and the future development trends of terahertz imaging technologies are forecasted.
Terahertz(THz) imaging has shown wide application prospects in many fields such as human body security inspection, non-destructive inspection, quality monitoring, biomedicine, and semiconductor characterization. In this article, various two-dimensional THz imaging techniques are reviewed, including scanning imaging, single-pixel imaging, electro-optic modulation imaging, direct imaging with THz camera, and so on. The research backgrounds of various imaging technologies are summarized, the specific imaging methods and imaging results are analyzed. The advantages and disadvantages of different terahertz imaging technologies are concluded, and the future development trends of terahertz imaging technologies are forecasted.
2021, 19(5):804-807.
DOI: 10.11805/TKYDA2021245
Abstract:
In radio astronomy field, the development of terahertz superconducting coherent receivers with ultra-wideband performance is required to achieve the simultaneous observation of multi-spectral lines in much wider frequency band. In response to the application requirements of the next-generation terahertz ultra-wideband receivers, an ultra-wideband ridge waveguide duplexer with a frequency band covering 180-420 GHz (the fractional bandwidth up to 87%) is developed. The main contents include the design and conversion of broadband ridge waveguide filters in 180-300 GHz and 320-420 GHz band, as well as the optimization of terahertz multi-stage coupled ridge waveguide duplexer. The simulation results show that this structure can be in duplex operation in the 180-300 GHz and 320-420 GHz bands with an overall return loss better than 15 dB and the isolation more than 20 dB.
In radio astronomy field, the development of terahertz superconducting coherent receivers with ultra-wideband performance is required to achieve the simultaneous observation of multi-spectral lines in much wider frequency band. In response to the application requirements of the next-generation terahertz ultra-wideband receivers, an ultra-wideband ridge waveguide duplexer with a frequency band covering 180-420 GHz (the fractional bandwidth up to 87%) is developed. The main contents include the design and conversion of broadband ridge waveguide filters in 180-300 GHz and 320-420 GHz band, as well as the optimization of terahertz multi-stage coupled ridge waveguide duplexer. The simulation results show that this structure can be in duplex operation in the 180-300 GHz and 320-420 GHz bands with an overall return loss better than 15 dB and the isolation more than 20 dB.
2021, 19(5):808-813.
DOI: 10.11805/TKYDA2021244
Abstract:
A multi-channel terahertz waveguide filter based on multimode resonance is studied. By introducing defects in terahertz periodic structure waveguide, the passband can be formed in the forbidden band range, so as to realize narrow-band filtering. The characteristics of multi-channel filter are studied by numerical simulation. The results show that the multi-channel filtering function with adjustable number of channels can be realized by changing the defect length. The number of channels can reach 10-12, and the transmittance is more than 98%. In addition, by changing the number of cycles of the waveguide structure, the passband bandwidth can be adjusted, and the narrowest bandwidth can reach 0.01 GHz. The waveguide filter has excellent performance and has the advantages of compact structure, easy integration, high transmittance, multi-channel and narrow bandwidth. It provides an important technical reference for the development of functional devices in terahertz band.
A multi-channel terahertz waveguide filter based on multimode resonance is studied. By introducing defects in terahertz periodic structure waveguide, the passband can be formed in the forbidden band range, so as to realize narrow-band filtering. The characteristics of multi-channel filter are studied by numerical simulation. The results show that the multi-channel filtering function with adjustable number of channels can be realized by changing the defect length. The number of channels can reach 10-12, and the transmittance is more than 98%. In addition, by changing the number of cycles of the waveguide structure, the passband bandwidth can be adjusted, and the narrowest bandwidth can reach 0.01 GHz. The waveguide filter has excellent performance and has the advantages of compact structure, easy integration, high transmittance, multi-channel and narrow bandwidth. It provides an important technical reference for the development of functional devices in terahertz band.
2021, 19(5):814-818.
DOI: 10.11805/TKYDA2021201
Abstract:
The terahertz polarization manipulation technology based on electromagnetic metasurface is studied. Specifically, a reflective-type terahertz 90o linear polarization converter is designed by using the metal-dielectric-metal sandwiched structure, and the polarization conversion characteristics are investigated both numerically and experimentally. It is shown that the reflective-type metasurface designed in this work achieves a high polarization conversion efficiency(above 75%) at the operating frequency of 0.5 THz as well as a broad working band(the polarization conversion efficiency is more than 50% over the frequency range of 0.35-0.65 THz). In addition, the ultrathin glass substrate produces the excellent overall performances of the metasurface linear polarization converter, including small thickness, light weight, and good heat resistance.
The terahertz polarization manipulation technology based on electromagnetic metasurface is studied. Specifically, a reflective-type terahertz 90o linear polarization converter is designed by using the metal-dielectric-metal sandwiched structure, and the polarization conversion characteristics are investigated both numerically and experimentally. It is shown that the reflective-type metasurface designed in this work achieves a high polarization conversion efficiency(above 75%) at the operating frequency of 0.5 THz as well as a broad working band(the polarization conversion efficiency is more than 50% over the frequency range of 0.35-0.65 THz). In addition, the ultrathin glass substrate produces the excellent overall performances of the metasurface linear polarization converter, including small thickness, light weight, and good heat resistance.
2021, 19(5):826-830.
DOI: 10.11805/TKYDA2021129
Abstract:
A negative tapered-double-sinusoidal grooves structure is proposed in order to form a coaxial Bragg reflector with narrow bandwidth, high quality factor Q and good selectivity. According to the coupling mode theory, on the basis of the ordinary sinusoidal groove structure, the auxiliary sinusoidal distribution with smaller etching period is superimposed, and the negative taper is added on the inner and outer walls of the conductor to form the negative tapered-double-sinusoidal grooves coaxial Bragg structure. Through FORTRAN software programming, compared with that of the ordinary sinusoidal grooves, the bandwidth of the working mode and the competing mode of the negative tapered-double-sinusoidal grooves coaxial Bragg structure gets narrower, the quality factor Q gets greater, and the residual side lobe phenomenon is suppressed. At the same time, the center resonant frequency point of the competition mode is far away from that of the working mode, the band gap overlap is further separated, and the frequency selectivity is improved. The structure design is simple and reasonable, which can better separate the working mode and the competition mode, and is favorable to construct a single high-order mode resonator with high quality factor Q and high power.
A negative tapered-double-sinusoidal grooves structure is proposed in order to form a coaxial Bragg reflector with narrow bandwidth, high quality factor Q and good selectivity. According to the coupling mode theory, on the basis of the ordinary sinusoidal groove structure, the auxiliary sinusoidal distribution with smaller etching period is superimposed, and the negative taper is added on the inner and outer walls of the conductor to form the negative tapered-double-sinusoidal grooves coaxial Bragg structure. Through FORTRAN software programming, compared with that of the ordinary sinusoidal grooves, the bandwidth of the working mode and the competing mode of the negative tapered-double-sinusoidal grooves coaxial Bragg structure gets narrower, the quality factor Q gets greater, and the residual side lobe phenomenon is suppressed. At the same time, the center resonant frequency point of the competition mode is far away from that of the working mode, the band gap overlap is further separated, and the frequency selectivity is improved. The structure design is simple and reasonable, which can better separate the working mode and the competition mode, and is favorable to construct a single high-order mode resonator with high quality factor Q and high power.
2021, 19(5):753-768.
DOI: 10.11805/TKYDA2021252
Abstract:
Being different from traditional terahertz components, silicon-based terahertz systems have the characteristics of low cost, small size, high integration, great maneuverability, and easier implementation of large arrays for large volume adoption. In the past ten years, with the rapid development of semiconductor technology and the increase of the cut-off frequency of silicon-based process transistors, the field of silicon-based terahertz system chip design has developed rapidly. The current research status and development trends of silicon-based terahertz system chips from four aspects: silicon-based terahertz sources, silicon-based terahertz imaging chips, silicon-based terahertz communication chips, and silicon-based terahertz radar chips are reviewed in this paper.
Being different from traditional terahertz components, silicon-based terahertz systems have the characteristics of low cost, small size, high integration, great maneuverability, and easier implementation of large arrays for large volume adoption. In the past ten years, with the rapid development of semiconductor technology and the increase of the cut-off frequency of silicon-based process transistors, the field of silicon-based terahertz system chip design has developed rapidly. The current research status and development trends of silicon-based terahertz system chips from four aspects: silicon-based terahertz sources, silicon-based terahertz imaging chips, silicon-based terahertz communication chips, and silicon-based terahertz radar chips are reviewed in this paper.
2021, 19(5):800-803.
DOI: 10.11805/TKYDA2021233
Abstract:
It is difficult to excite large chiral optical responses for metasurfaces based on single-layer metal resonators under normal incidence, because they are difficult to excite in-plane magnetic dipole moment that are not orthogonal to the electric dipole moment. The displacement current excited by optical field in the dielectric meta-atoms may induce an in-plane magnetic moment to achieve chiral optical responses. A huge chiral response is achieved in terahertz band based on the lossless all-silicon metasurface. The leaky waveguide mode in the chiral silicon pillar excites the in-plane magnetic dipole moment, which triggers the spin-selected backward electromagnetic radiation, and then realizes the chiral optical response of terahertz wave. A polarization-dependent TDS system is built by using wire grid polarizers，and the peak value of circular dichroism in the transmission spectrum reaches 0.2. This simple-prepared all-silicon metasurface provides a new idea for the design of terahertz chiral metadevices, and it is expected to be applied in the fields of terahertz imaging and spectral detection.
It is difficult to excite large chiral optical responses for metasurfaces based on single-layer metal resonators under normal incidence, because they are difficult to excite in-plane magnetic dipole moment that are not orthogonal to the electric dipole moment. The displacement current excited by optical field in the dielectric meta-atoms may induce an in-plane magnetic moment to achieve chiral optical responses. A huge chiral response is achieved in terahertz band based on the lossless all-silicon metasurface. The leaky waveguide mode in the chiral silicon pillar excites the in-plane magnetic dipole moment, which triggers the spin-selected backward electromagnetic radiation, and then realizes the chiral optical response of terahertz wave. A polarization-dependent TDS system is built by using wire grid polarizers，and the peak value of circular dichroism in the transmission spectrum reaches 0.2. This simple-prepared all-silicon metasurface provides a new idea for the design of terahertz chiral metadevices, and it is expected to be applied in the fields of terahertz imaging and spectral detection.
2021, 19(5):819-825.
DOI: 10.11805/TKYDA2021240
Abstract:
Saccharides are typical chiral substances, and their chiral spectra in the terahertz band have not been fully studied. The refractive index and absorption spectra of lactose, galactose, and glucose at low temperature and normal temperature are studied respectively, and the chiral spectra of these samples are obtained through terahertz time-domain polarization spectroscopy. The experimental results show that the absorption of saccharides will decrease as the temperature decreases, which is conducive to obtain the chiral characteristics of the sample at low temperature. At 80 K, glucose exhibits strong Circular Dichroism(CD) in 1.3-1.5 THz; the CD peak value reaches 44.97% at 1.39 THz. All three saccharides have specific chiral characteristic peaks, and the CD values all exceed 20% in 1.6-1.8 THz. The research results can provide important reference for further understanding of the chiral spectra of chiral biochemical samples in terahertz band and their internal mechanisms.
Saccharides are typical chiral substances, and their chiral spectra in the terahertz band have not been fully studied. The refractive index and absorption spectra of lactose, galactose, and glucose at low temperature and normal temperature are studied respectively, and the chiral spectra of these samples are obtained through terahertz time-domain polarization spectroscopy. The experimental results show that the absorption of saccharides will decrease as the temperature decreases, which is conducive to obtain the chiral characteristics of the sample at low temperature. At 80 K, glucose exhibits strong Circular Dichroism(CD) in 1.3-1.5 THz; the CD peak value reaches 44.97% at 1.39 THz. All three saccharides have specific chiral characteristic peaks, and the CD values all exceed 20% in 1.6-1.8 THz. The research results can provide important reference for further understanding of the chiral spectra of chiral biochemical samples in terahertz band and their internal mechanisms.
2021, 19(5):784-793.
DOI: 10.11805/TKYDA2021267
Abstract:
Because terahertz(THz) waves have the characteristics of low energy, strong penetration, and broad bandwidth, terahertz imaging technology has been widely used in many fields such as non-destructive testing, biomedicine, and safety testing. How to improve the resolution of terahertz imaging in practical applications is becoming more and more important. Terahertz near-field imaging technology can break through the diffraction limit and obtain high-quality images with submicron or even nanometer resolution, thus high-resolution THz imaging technologies based on near-field methods have been proposed and further applied. This article first describes the basic principles of terahertz near-field imaging; secondly, summarizes its progresses and enhancement methods; and finally prospect the future of terahertz near-field imaging.
Because terahertz(THz) waves have the characteristics of low energy, strong penetration, and broad bandwidth, terahertz imaging technology has been widely used in many fields such as non-destructive testing, biomedicine, and safety testing. How to improve the resolution of terahertz imaging in practical applications is becoming more and more important. Terahertz near-field imaging technology can break through the diffraction limit and obtain high-quality images with submicron or even nanometer resolution, thus high-resolution THz imaging technologies based on near-field methods have been proposed and further applied. This article first describes the basic principles of terahertz near-field imaging; secondly, summarizes its progresses and enhancement methods; and finally prospect the future of terahertz near-field imaging.
2021, 19(5):794-799.
DOI: 10.11805/TKYDA2021243
Abstract:
Terahertz time-domain spectroscopy is used as a new spectroscopic detection tool for the characterization of a wide range of substances including hydrates. Metal sulphates have a variety of different hydrates that exhibit different absorption properties in the terahertz band, and the different hydrates of transition metal sulphates can be effectively characterized by using terahertz spectroscopy. In this paper, magnesium sulphate and its hydrates were characterized by using a terahertz time-domain spectroscopy system. Different magnesium sulphate pyrolysis products were obtained by constant temperature drying of magnesium sulphate heptahydrate and their terahertz absorption spectra were investigated, which shows that different hydrates exhibit significantly different terahertz absorption properties. The research provides a simple, fast and effective means of characterization for the detection of magnesium sulphate and its hydrates, as well as an important reference for a variety of applications of magnesium sulphate.
Terahertz time-domain spectroscopy is used as a new spectroscopic detection tool for the characterization of a wide range of substances including hydrates. Metal sulphates have a variety of different hydrates that exhibit different absorption properties in the terahertz band, and the different hydrates of transition metal sulphates can be effectively characterized by using terahertz spectroscopy. In this paper, magnesium sulphate and its hydrates were characterized by using a terahertz time-domain spectroscopy system. Different magnesium sulphate pyrolysis products were obtained by constant temperature drying of magnesium sulphate heptahydrate and their terahertz absorption spectra were investigated, which shows that different hydrates exhibit significantly different terahertz absorption properties. The research provides a simple, fast and effective means of characterization for the detection of magnesium sulphate and its hydrates, as well as an important reference for a variety of applications of magnesium sulphate.
