Bridging the gap between ultrashort pulsed optical waves and terahertz (THz) waves, THz photoconductive antenna (PCA) is a major constituent for emission or detection of by diverse electrical methods. However, PCA still lacks employment advanced breakthrough technologies high-power emission. Here, we report enhancement power incorporating nanoantennas with antenna. The confinement concentration an pump beam on substrate can be efficiently achieved over high-index substrate. Both numerical...

Based on the polarization-sensitive terahertz time-domain spectroscopy, we measured birefringence for Al2O3 and LiNbO3 single crystals, which correspond to trigonal structures that have an uniaxial birefringence, in THz frequency range of 0.25 1.4 THz. For more comprehensive understanding is compared with results ab initio calculations. The shows good agreement calculated value.

Conformal metal reflectarray antennas on the surface of a cylinder are designed for millimetre‐wave applications. All depths grooves in reflectarrays specially manipulated high‐gain conformal antennas. There is good agreement between simulated and experimental radiation performance results two different ‘sagittas’. The proposed can be helpful choice applications requiring curved platforms.

A reflectarray element using a conductor cell with variable height is proposed. It found that the reflection phase can be tuned by adjusting of cells arranged on spatially discretised reflector plane. complete linearised thus achieved when proposed used as unit element. millimetre‐wave antenna has been designed method and it shows 50% aperture efficiency half‐wavelength variation.

A multimode theory of the resonant backward-wave oscillator (BWO) with an electron beam inclined respect to surface a periodic structure—a clinotron—is presented. It is shown that mode interaction provides phase velocity variation in space. The beam–wave power increases at favorable profile along space, which manifests as peaks clinotron zone. In contrast, when it nonfavorable, there drop bandwidth. Developed results are satisfactory agreement BWO reflections and particle-in-cell simulations.

We report a simple method of creating terahertz waves by applying the photo-Dember effect in (100)-oriented InAs film coated onto 45-degree wedged-end facet an optical fiber. The are generated infrared pulses guided through fiber which is nearly contact with sample and then measured conventional photo-conductive antenna detector. Using this alignment-free source, we performed proof-of-principle experiments time-domain spectroscopy near-field microscopy. obtained bandwidth 2 THz 180-microm...

In this paper, we propose an X-band photonic-based pulsed radar architecture with a high range resolution. The proposed is operated as by adding Mach-Zehnder modulator (MZM) operating optical switch to transmitter of conventional frequency-modulated continuous wave (FMCW) radar. addition, balanced photodetector (BPD) employed enhance the amplitude received signal and remove common-mode noise. A prototype implemented operate at center frequency 10 GHz, bandwidth 640 MHz, pulse repetition...

Gouy phase shift is a well-known behavior that occurs when propagating light focused, but its in the sub-wavelength confinement not yet known. Here, we report theoretical and experimental study of aperture-size dependency diffraction regime. In experiments carried out with laser-induced terahertz (THz) wave emission from various semiconductor apertures, demonstrate use Guoy shit for THz microscopy.

We present a polarization shaping technique for few-cycle terahertz (THz) waves. For this, N femtosecond laser pulses are generated from devised diffractive optical system made of as-many glass wedges, which then simultaneously illuminate on various angular positions sub-wavelength circular pattern an indium arsenide thin film, to produce THz wave tailor-made state given as superposition linearly-polarized pulses. By properly arranging the orientation and thickness determine its timing...

The automodulation processes in backward-wave oscillator with an inclined electron beam (the clinotron) operating at low-focusing magnetic fields have been studied. behavior has analyzed the clinotron for different angles of inclination. It shown that low fields, RF transverse electric field may cause significant changes trajectories, and hence beam–wave interaction power leads to automodulation.

We present a method of using one-dimensional dielectric multilayer structures for designing terahertz frequency spreading filters. The interference pulses in these composed alternating weak and strong refractive materials allows design well-separated THz components within modulation-limited spectral envelope. characteristics coarse combs are limited by the saturation effect also deformation pulse time-traveling structure. details designed waveform synthesis from filters verified experiments...

Digitized beam-forming metal reflectarray antennas are designed for the millimeter-wave region. The phase control of has been implemented by reconfiguration rectangular grooves on a plate. antenna 1147 elements arranged in an aluminum depths all manipulated high-gain beam-aimed reflectors. We have demonstrated digitized reconfigurable to steer re-radiated field from reflector two-dimensional scanning plane −20∘ 20∘. far-field patterns show that measured gain 2-bit is only 1 dB lower than...

Terahertz time-domain spectroscopy probes anomalous phase-shift caused by wave diffraction from a subwavelength-scale metal slit or aperture. Carrier frequency phase measurements in the far-field region reveals that nearly 30° advance is induced subwavelength and 180° phase-advance These results indicate conventional 90° of diffracted waves region, known as Gouy shift, not valid for phenomena. The physical origin these anomalies attributed to electric currents magnetic dipole radiation,...

Terahertz pulse shaping technique is used to adaptively design terahertz waveforms of enhanced spectral correlation particular materials among a given set materials. In proof-of-principle experiment performed with two-dimensional image target consisted meta-materials distinctive resonance frequencies, the as-designed are demonstrate substance imaging. It hoped that this material-specific may enable single- or few-shot material classification when being in conjunction power measurement.

The radio frequency (RF) signal generation method using an external modulator is widely used in microwave photonics applications because it has the advantage of being able to generate coherent and stable RF signals with a higher resolution performance compared conventional method. A Mach–Zehnder as due its high electro-optic coefficients low attenuation characteristics but critical problem that electrical are changed by environments such temperature. In this paper, we considered...

We introduce a flexible multilayered THz metamaterial designed by using the Babinet's principle with functionality of narrow band-pass filter. The gives us systematic way to design frequency selective surfaces working on intended frequencies and bandwidths. It shows highly enhanced transmission 80% for normal incident waves due strong coupling two layers complementary each other.

홀 추력기에서 플라즈마 방전의 급작스러운 중단으로 정의되는 방전 중단 현상은 위성 추진 시스템의 개발, 시험 및 운용 과정에서 주요한 관심의 대상이 되고 있다. 본 연구에서는 추력기의 현상을 분석하기 위해 기존의 경험적인 방법을 탈피하여 체계적인 데이터 기반 방법론을 적용하였다. 구체적으로, 퍼뮤테이션 엔트로피와 젠슨-섀년 복잡도를 결합한 복잡도-엔트로피 인과 평면상에서 현상의 발생 특성을 파악할 수 있음을 제시하고, 이를 통해 안정적인 추력기 운전 조건을 도출할 보였다. 연구에 사용된 활용하여 그간 무작위적으로 발생한다고 알려진 중단에 대해 이론적인 분석을 제공하고 상태 조건과의 인과관계를 도출하여 정량화하고자 하였다.

We compare the spectral amplitude of terahertz pulses generated using difference-frequency mixing, via second-order nonlinear process in CdTe and ZnTe, with numerical model calculations Maxwell equation. have found that details from are well explained by considering effects optical absorptions, diffraction, frequency dependence coefficients. This method allows us to design tailored compound materials improved versatility for generating specific pulse shapes.