Abstract-Flexible terahertz modulators based on graphene FET with organic high-k dielectric layer

Yu-Lian He, Jing-Bo Liu, Tian-Long Wen, Qing-Hui Yang, Zheng Feng, Wei Tan, Xue-Song Li, Qi-Ye Wen, Huai-Wu Zhang

https://iopscience.iop.org/article/10.1088/2053-1591/aadeca

Graphene field-effect-transistor (GFET) based terahertz (THz) modulators usually possess an unfulfilling modulation depth (MD) of 15% ~ 20%. In this work we developed a flexible GFET based THz modulator, where the graphene monolayer is coated with an organic high-K dielectric as the screening layer and an ion-gel layer as the gate. With this exquisite composite modulating structure, the new device possesses a significantly enhanced modulation depth (MD) up to 70% over a broad frequency band, an extremely low insert loss (IL) of 1.3 dB, and unexpected good structural and properties stability. The large intrinsic MD, low IL, as well as its flexibility, render this performance enhanced modulator versatile in fabrication of novel THz devices, such as multi-level modulator, for nonplanar or wearable applications.

Abstract-Terahertz Modulators Based on Silicon Nanotip Array

Zhong-Wei Shi,Xing-Xing Cao,Qi-Ye Wen, Tian-Long Wen, Qing-Hui Yang, Zhi Chen, Wen-Sheng Shi, Huai-Wu Zhang.

http://onlinelibrary.wiley.com/doi/10.1002/adom.201700620/full

As an attractive applications of terahertz (THz) radiation, imaging with THz technique stands at the focus of current interest. THz spatial modulators are key issue for fast imaging with a single detector. Here, for the first time, the silicon nanotip (SiNT) arrays are reported that can be utilized as antireflection layers for the THz wave to achieve a low-loss and spectrally broadband optical-driven THz modulator. Compared with the modulator fabricated with bare silicon, a 2–3-time larger modulation depth is achieved in SiNT modulator. Moreover, it is found that the intrinsic THz transmission of SiNT is as high as 90%, which is much higher than that of bare silicon. The theoretical simulation results reveal that a strong antireflection effect induced from SiNT layer plays a crucial role in enhancing the properties of modulator. The SiNT-based optical-driven THz modulator with low loss and high modulation depth is promising for potential application to THz imaging.

Abstract-High-speed and broadband terahertz wave modulators based on large-area graphene field-effect transistors

Qi Mao, Qi-Ye Wen, Wei Tian, Tian-Long Wen, Zhi Chen, Qing-Hui Yang, and Huai-Wu Zhang  »View Authors http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-19-5649 Optics Letters, Vol. 39, Issue 19, pp. 5649-5652 (2014) http://dx.doi.org/10.1364/OL.39.005649

We present a broadband terahertz wave modulator with improved modulation depth and switch speed by cautiously selecting the gate dielectric materials in a large-area graphene-based field-effect transistor (GFET). An ultrathin Al2O3film (∼60  nm) is deposited by an atomic-layer-deposition technique as a high-k gate dielectric layer, which reduces the Coulomb impurity scattering and cavity effect, and thus greatly improves the modulation performance. Our modulator has achieved a modulation depth of 22% and modulation speed of 170 kHz in a frequency range from 0.4 to 1.5 THz, which is a large improvement in comparison to its predecessor of SiO2-based GFET.

© 2014 Optical Society of America

Abstract-High-speed and broadband terahertz wave modulators based on large-area graphene field-effect transistors

Qi Mao, Qi-Ye Wen, Wei Tian, Tian-Long Wen, Zhi Chen, Qing-Hui Yang, and Huai-Wu Zhang  »View Author Affiliations

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-19-5649

Optics Letters, Vol. 39, Issue 19, pp. 5649-5652 (2014)

We present a broadband terahertz wave modulator with improved modulation depth and switch speed by cautiously selecting the gate dielectric materials in a large-area graphene-based field-effect transistor (GFET). An ultrathin Al2O3film (∼60  nm) is deposited by an atomic-layer-deposition technique as a high-k gate dielectric layer, which reduces the Coulomb impurity scattering and cavity effect, and thus greatly improves the modulation performance. Our modulator has achieved a modulation depth of 22% and modulation speed of 170 kHz in a frequency range from 0.4 to 1.5 THz, which is a large improvement in comparison to its predecessor of SiO2-based GFET.

© 2014 Optical Society of America