Search

We proposed a novel multi-frequency-band terahertz modulator working for free-space terahertz radiation. The unit cell of the metamaterial/perovskite hybrid structure, which consists of split-ring resonator, is patterned on silica with a dielectric constant of e = 3 . 75 , a loss tangent of tan δ = 0 . 01 and concentric double rings are fabricated on the bottom of the silica with the thickness of 200 nm. The split gaps of split-ring resonators are filled with perovskite quantum dots thin film. The terahertz wave modulation mechanism of our structure is numerically investigated by using CST Microwave Studio. We have also employed an equivalent circuit model (ECM) to validate our numerically simulated observations. The results exhibit four different frequency carrier wave signal modulation at 0.42THz, 0.83THz, 1.18THz and 1.62THz with modulation depth ( > 99%) and megahertz modulation speed. This work demonstrates a new approach for realizing multi-band terahertz amplitude shift keying (ASK) modulator for terahertz wavelength division multiplex (WDM) communication.

Owing to the eigenstates of orbital angular momentum (OAM) are infinite and orthogonal to each other, OAM can improve communication capacity infinitely. In this paper, we propose a terahertz vortex beam generator on transmissive metasurfaces. When the y-polarized terahertz wave illuminates vertically to the metasurface along the -z direction, the proposed metasurface generates terahertz vortex beams with topological charges l = ±1, l = ±2 and l = ±3 at the frequency ranging from 0.3 THz to 0.9 THz. We study the far-field radiation, electric field phase, amplitude characteristics, and mode purity with different topological charges. The simulation results are in good agreements with the theoretical predictions.

Diverse applications of terahertz technology depend on the efficient manipulation of terahertz beam. Terahertz switch with transmitting electromagnetic intensity tunability is essential for effective control of terahertz wave. Existing approaches are a lack of simple structure able to achieve superior switching performance. Here we experimentally demonstrate a new approach to manipulate terahertz wave transmittance controlled by Calcium and Titanium Precipitate (CTP) electro-rheological (ER) fluid, and develop a novel CTP ER-fluid switch at terahertz frequencies based on this mechanism. In this way, we achieve perfect terahertz wave intensity switching through actively adjusting the external applied electric field. This operating principle ensures that our presented device can operate in terahertz frequency range.

Lately, programmable metasurfaces have been proposed by adding a PIN diode between two metallic patches in microwave region. However, the pin-diode switches can only operate at relatively lower frequencies (i 60 GHz), the conventional electronic method of device design used in the microwave band cannot easily be extended to the terahertz frequency regime. Here, we describe a new design principle for the actively tunable terahertz wave coding metasurfaces using vanadium dioxide embedded metallic patch. The radar cross section (RCS) reduction and radiation patterns of our new coding scheme can be altered using the metal–insulator transition of vanadium dioxide at around 68 °C. To the best of our knowledge, this is the first time that an active control of programmable coding metasurfaces was demonstrated at terahertz regime.

We design an electrically controllable terahertz wave attenuator by using graphene. We show that terahertz wave can be confined and propagate on S-shaped graphene waveguide with little radiation losses, and the confined terahertz wave is further manipulated and controlled via external applied voltage bias. The simulated results show that, when chemical potential changes from 0.03 into 0.05 eV, the extinction ratio of the terahertz wave attenuator can be tuned from 1.28 to 39.42 dB. Besides the simplicity, this novel terahertz wave attenuator has advantages of small size (24 × 30 μm2), a low insertion loss, and good controllability. It has a potential application for forthcoming planar terahertz wave integrated circuit fields.

The combination of terahertz technology and photonic crystal provides a new approach to realize compact terahertz wave devices. Relying on a conventional photonic crystal waveguide and photonic crystal surface-mode waveguides, a tunable multi-channel terahertz-wave power splitter is proposed. The mechanism of such a power splitter is further theoretically analyzed and numerically investigated with the aid of the plane-wave-expansion method and the finite-difference time-domain method. With an appropriate design, the proposed device can split the input terahertz wave energy equally into six output ports at the frequency of 0.6 THz. When changing the external magnetic field, the input terahertz wave can be equally divided into four output ports with the aid of a magnetic-sensitive material. Furthermore, the present device is very compact and the total size is of 4.4×6.0 mm 2 .

Electromagnetic polarization conveys valuable information for signal processing. Manipulation of terahertz wavelength demultiplexer exhibits tremendous potential in developing application of terahertz science and technology. We propose an approach to separate efficiently four frequencies terahertz waves based on three cascaded directional coupling two-dimensional photonic crystal waveguides. Both plane wave expansion method and finite-difference time-domain method are used to calculate and analyze the characteristics of the proposed device. The simulation results show that the designed terahertz wavelength demultiplexer can split four different wavelengths of terahertz wave into different propagation directions with high transmittance and low crosstalk. The present device is very compact and the total size is 6.8×10.6 mm 2 . This enables the terahertz wavelength demultiplexer to be used in terahertz wave system and terahertz wave integrated circuit fields.

In order to extend to 3-bit encoding, we propose notched-wheel structures as polarization insensitive coding metasurfaces to control terahertz wave reflection and suppress backward scattering. By using a coding sequence of "00110011…" along x-axis direction and 16 × 16 random coding sequence, we investigate the polarization insensitive properties of the coding metasurfaces. By designing the coding sequences of the basic coding elements, the terahertz wave reflection can be flexibly manipulated. Additionally, radar cross section (RCS) reduction in the backward direction is less than -10dB in a wide band. The present approach can offer application for novel terahertz manipulation devices.

We present a terahertz wave switch utilizing Kretschmann configuration which consists of high-refractive-index prism-liquid crystal-periodically grooved metal grating. The switching mechanism of the terahertz switch is based on spoof surface plasmon polariton (SSPP) excitation in the attenuated total reflection regime by changing the liquid crystal refractive index. The results highlighted the fact that the feasibility to “tune” the attenuated total reflection terahertz wave intensity by using the external applied bias voltage. The extinction ratio of the terahertz switch reaches 31.48dB. The terahertz switch has good control ability and flexibility, and can be used in potential terahertz free space device systems.

A novel terahertz modulator based on graphene split-ring resonator (SRR) is proposed and designed. The device consists of a graphene SRR and two graphene surface plasmon polaritons waveguides. By changing the chemical potential of the graphene SRR, a compact terahertz wave modulator with an extraordinary modulation depth of 98.9% and low insertion loss of 0.83 dB is achieved. The results show that an electrically controlled graphene-integrated SRR terahertz modulator can be realized. The size of the proposed device is of 13 µm × 7 µm. It makes the graphene-based terahertz modulator promising as single-chip solutions for the compact terahertz system.

Background As a significant terahertz functional device, terahertz beam splitters with high performance are highly required to meet the need for terahertz communication, terahertz image, and terahertz sensor systems. Results The proposed 1×6 power splitter becomes 1×4 power splitter with the aid of the localized temperature change at the frequency of 1.0THz. The total output power is equivalent to 97.8% of the input power for the six-channel splitter and 95.4% for the four-channel splitter. The dimension of the device is of 35a×27a. Conclusions A temperature-controlled terahertz power divider based on photonic crystal multimode interference structure and Y-junction photonic crystal waveguides is an efficient mechanism for the power divider of terahertz waves. The proposed device paves a promising way for the realization of terahertz wave integrated device.

Manipulation of terahertz wave polarization state exhibits tremendous potential in developing application of terahertz science and technology. A terahertz polarization beam splitter based on three linear defect photonic crystal waveguides is designed and numerically demonstrated. Both plane wave expansion method and finite-difference time-domain method are used to calculate and analyze the characteristics of the proposed device. The simulation results show that the designed polarization beam splitter can split TE and TM polarized mode into different propagation directions with high efficiency in the frequency range from 1.225THz to 1.260THz. Especially, the extinction ratios for both TE and TM modes are larger than 20dB.

We investigate the giant tunable Goos–Hanchen shifts in prism/graphene structure. It is found that large positive and negative lateral Goos–Hanchen shifts can be easily controlled by adjusting the chemical potential of the graphene, which is modulated by the external applied electric field. By using the stationary-phase method, we theoretically analyze the effect of the external applied electric field on Goos–Hanchen shifts of the proposed prism/graphene structure. Our theoretical study shows that the magnitude of the Goos–Hanchen shift is more than 200 times that of the operating terahertz wavelength. Numerical calculation results further indicate that the present structure has the potential application for the terahertz-wave switch.

We design an ultra-fast absorption type switch operating in the terahertz wave regime. The device consists of dual metallic layers for allowing near-perfect absorption due to electric and magnetic resonances, and a nonlinear Kerr-media layer for actively manipulating device absorption. In this novel design, the center frequency of the absorption peak can be dynamically shifted by adjusting the incident external pump laser intensity. By using the finite-difference time-domain method, the switch properties of terahertz wave absorption in sub-wavelength period structures on the Kerr-media layer under different incident optical intensities have been investigated. The simulation results demonstrate that device absorption can be flexibly tuned from near unity to zero by adjusting the incident optical intensity. It is extremely versatile to control the ultra-fast terahertz switch by varying the incident optical intensity. These results provide a useful guide for the developments of terahertz wave functional components.

We report a perfect absorber based on dual-C metamaterial structure operating in the terahertz regime.The proposed structure is numerically investigated by the CST Microwave Studio. By manipulating the periodic patterned structures as well as the dielectric layer material, significantly high absorption can be obtained at specific resonance frequency. The fabricated device has been characterized using a Fourier transform infrared spectrometer. The experimental results show that the distinct absorption peak at 0.573 THz with absorption magnitudes of 0.996, which is in good agreement with the simulation. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1185–1189, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27468

We theoretically and numerically study the absorption effect of a metamaterial absorber in the terahertz region.An equivalent circuit model is proposed to estimate the absorption characteristics of the metamaterial structures for terahertz wave normally incident on the structure. Theoretical and experimental results show that the absorber has nearly perfect absorption bandwidth of 53.3 GHz and an absorption peak (0.992) at the frequency of 0.734 THz. The good agreement between the measurement results and simulated prediction is observed. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:793–796, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27405

We design a coding metasurface based on Pancharatnam-Berry (PB) phase to manipulate terahertz waves, which is simple and flexible. Compared with the previous design of the coding metasurface, the present coding particles can be obtained by using a same size meta-particle with various orientations instead of designing multiple structures or changing specific size parameters. The PB coding metasurfaces composed of U-shaped particles with pre-designed coding sequences can generate multi-bit coding in the terahertz frequencies and control the reflected terahertz waves to the various directions. Both simulation and theoretical calculation scattering patterns of the designed PB coding metasurfaces demonstrate the expected manipulations. Additionally, the bandwidth of radar cross section (RCS) reduction of approaching −15 dB is 1.05THz (range from 0.9THz to 1.95THz). We believe that the proposed design provides a more flexible way for the manipulation of reflected terahertz waves.

A broadband travelling-wave modulator is proposed based on Si 2 N 2 O substrate with ridge structure. The structure is analyzed using finite element method. At 1.5 μm wavelength the modulator operates with a 3 dB optical bandwidth of 119.37 GHz, a half-wave driving voltage of 3.5 V, and characteristic impedance of 50.32 Ω. The results show that broad bandwidth and low half-wave voltage can be achieved simultaneously.

In this letter, a novel terahertz (THz) wave switch based on metamaterial is proposed and measured.On–off switching is based on a controllable resonance of the metamaterial by applying an external semiconductor laser to illuminate substrate. Experimentally, we demonstrate on–off response time speed and extinction ratio of the proposed THz wave switch is of 1 ms and 19.4 dB at 0.32 THz, respectively. The presented THz wave switch has a potential application to THz wave communication systems. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:276–278, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25751

A novel magnetically tunable left-handed material based on YIG/SRR was designed. Both theoretical analysis and calculation results show that the presented structure achieves a left-handed pass band in the THz frequency range.

A novel terahertz wave absorber is proposed. Theoretical results show that the absorber has a high absorptivity of 99.968% and a minimum reflectivity of 0.032% at frequency of 0.28THz. The absorption bandwidth is of 316.5GHz.

We design the terahertz wave filter based on microstrip structure. The experimental result shows that the terahertz wave filter has dual passband transmittance peak of 66.5% at 2.347THz and 60% at 2.76 THz.

The terahertz time-domain spectra (THz-TDS) of four kinds of vegetable oils were measured in the frequency range extending from 0.2 to 1.5 THz. An iterative algorithm is employed to determine the parameter extraction for terahertz time-domain spectroscopy. The terahertz absorption spectra and refractive indices of four kinds of vegetable oils were analyzed. Compared with the existing data extraction algorithms, the novel iterative algorithm further enhances the accuracy of the parameter extraction for terahertz time-domain spectroscopy.

By using terahertz time domain spectroscopy (THz-TDS) system, the terahertz dielectric properties of various gallium arsenides were tested in the frequency range extending from 0.2 to 1.5 THz. The power absorption coefficient and refractive index of various resistivity gallium arsenides were measured and compared. The refractive index of the high resistivity and ultra-high resistivity GaAs are equal to be 6.53 and 5.9, respectively. The variation of the refractive index of the GaAs was less than 1%, ranging from 0.2 to 1.5THz, but the absorption coefficient of the ultra-high resistivity GaAs showed very different frequency-dependent behaviors, ranging from 0.02cm−1 to 2.21cm−1, within the investigated frequency range. The results show that the ultra-high resistivity GaAs will be a good candidate material for terahertz transmission waveguide.

A novel compact sub-terahertz wave switch based on photonic crystals is proposed. We have investigated the performance of the proposed sub-terahertz wave switch by using plane wave expansion and finite-difference time-domain method. The numerical results show that an excellent sub-terahertz wave switch at a frequency of 0.1THz is achieved. The proposed sub-terahertz wave switch has a high extinction ratio of -40dB, and small size of 6.811mm. It has a potential application to sub-terahertz wave communication systems.

A novel bandstop filter based on composite right/left-handed (CRLH) transmission line (TL) is proposed and studied. This designed bandstop filter provides low passband insertion loss, very sharp transitions at the edges of the stopband, large attenuation in the stopband, easy fabrication, and low cost. The performances of the proposed filter are demonstrated by simulation results.

A novel narrow-band bandpass filter using metamaterials is proposed. The filter is composed of cascaded four metamaterial unit cells. We study the properties of the device theoretically and experimentally. The measured results are presented and compared with the results simulated by a high-frequency structure simulator. It is observed that the measured results are good agreement with the simulated results. The proposed filter has narrow bandwidth, low insertion loss, compact dimensions, easy fabrication, and low cost.

We design an omnidirectional dielectric mirror that operates over a wide terahertz wavelength range and is based on a periodic bilayer (tellurium and polystyrene) structure. The structure is characterized by using transfer matrix calculations. Results of simulation show that the presented dielectric mirror is highly reflecting for all incidence angles and TE as well as TM polarization in the frequency band between 0.451THz and 0.821THz (wavelength range 365.5?m~665.5?m), when the incidence angle is less than 45?. Tolerance analysis reveals a large tolerance to fabrication errors.

We design terahertz wave reflective polarizer that operates over a wide terahertz wavelength range and is based on a periodic bilayer structure. The structure is characterized by transfer matrix calculations. Results of simulations show that the mirror is highly reflecting for all incidence angles and s as well as p polarization in the frequency band between 319 and 375 GHz. Tolerance analysis reveals a large tolerance to fabrication errors.

Finite element method is employed to analyze terahertz wave transmission characteristic in hexagonal photonic crystal fiber. We compared the terahertz field distribution and attenuation of the proposed photonic crystal fiber for different air-hole diameter. When d/ equals to 0.95, the lowest of transmission loss is 0.0012dB/m. The simulated results show that the performance of the presented photonic crystal fiber meets with the demand of terahertz transmission.

We demonstrated experimentally a terahertz wave modulator based on microstrip resonator structure. The signal modulation mechanism of the presented terahertz wave modulator is based on the resonance characteristic of resonator microstrip structure controlled by without or with light excitation. A modulated semiconductor laser with 808nm wavelength is employed to light the microstrip resonator structure. The experimental results show that the modulation speed and attenuation of the proposed terahertz modulator are of 0.1Kb/s and 25dB at frequency of 0.32THz, respectively

In this paper, two novel planar terahertz semiconductor split-ring resonators are successfully constructed and measured using the commercial software CST Microwave Studio. They exhibit a duel-band and a triple-band transmission property within the frequencies ranging from 0.1THz to 3THz. We have simulated the dual-band planar metamaterial with two distinct electric resonances at 0.81THz and 1.818THz, and triple-band planar metamaterial with three distinct electric resonances at 0.543THz, 1.044THz, and 1.506THz. These developments are further steps towards the development of broadband terahertz devices.