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Terahertz high-data communication creates numerous demands for terahertz wave amplitude modulation. Here, we experimentally demonstrate a high-speed terahertz wave modulator based on 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST)/Si hybrid structure. An externally modulated 808-nm pumping laser is utilized to generate photoexcited free carriers at the DAST medium. With the increase of illumination laser intensity, the modulation depth continues to increase in the frequency range from 0.23 to 0.35 THz. A dynamic amplitude modulation at 0.25-THz carrier wave shows that the our modulator provides a modulation speed of 1.26 MHz with a depth of up to 53% at an external pump laser irradiance of 3.5 W/cm2. Our present DAST/Si hybrid structure provides a practicable route to achieve effective signal modulation for terahertz communication system.

Abstract 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.

We investigate the giant tunable Goos-Hänchen shifts in prism/graphene structure. It is found that large positive and negative lateral Goos-Hänchen 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-Hänchen shifts of the proposed prism/graphene structure. Our theoretical study shows that the magnitude of the Goos-Hänchen 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.

The analysis and design of a small planar multiband antenna operating in the 4G frequency bands are presented. The numerical and experimental results demonstrated that the proposed antenna satisfies the requirement of 6 dB return loss for the impedance bandwidth of the LTE700/LTE2300/LTE2500 and WiMAX3500 bands. The gains at 750 MHz/2.3 GHz/2.6 GHz/3.5 GHz are 2.1 dBi/4.9 dBi/4.7 dBi/4.3 dBi, respectively. The measured radiation patterns verify the suitability of the antenna to be employed in mobile phones. The dimensions of the radiant patch are 49 × 10 mm2. The proposed antenna can be easily fabricated and customized to various 4G mobile phones as a compact internal antenna.