Binary THz modulator based on silicon Schottky-metasurface

Saeedeh Ahadi; Mohammad Neshat; Mohammad Kazem Moravvej-Farshi

doi:10.1038/s41598-022-23534-w

Binary THz modulator based on silicon Schottky-metasurface

Sci Rep. 2022 Nov 7;12(1):18871. doi: 10.1038/s41598-022-23534-w.

Authors

Saeedeh Ahadi¹, Mohammad Neshat², Mohammad Kazem Moravvej-Farshi³

Affiliations

¹ Nano Plasmo-Photonic Research Group, Faculty of Electrical and Computer Engineering, Tarbiat Modares University, P. O. Box 14115-194, Tehran, 1411713116, Iran.
² School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, 1439957131, Iran.
³ Nano Plasmo-Photonic Research Group, Faculty of Electrical and Computer Engineering, Tarbiat Modares University, P. O. Box 14115-194, Tehran, 1411713116, Iran. moravvej@modares.ac.ir.

Abstract

We propose a metasurface THz modulator based on split-ring resonators (SRRs) formed by four interconnected horizontal Si-Au Schottky diodes. The equivalent junction capacitance of each SRR in the proposed modulator is much smaller than that of the previously reported metasurface counterparts with vertical Schottky junctions, leading to a higher modulation speed. To modulate a THz incident signal by the proposed metasurface, we vary the bias voltage externally applied to the Schottky junctions. Applying a reverse bias of V_A = - 5 V to the Au gate, two LC resonances at 0.48 THz, and 0.95 THz are excited in the metasurface. Switching the applied voltage to V_A = + 0.49 V, we diminish the oscillator strengths of the LC resonances, creating one dipole resonance at 0.73 THz in the transmission spectrum of the metasurface modulator. The modulation depths at these resonances are more than 45%, reaching 87% at 0.95 THz. The phase modulation for this THz modulator is about 1.12 rad at 0.86 THz. Furthermore, due to the particular design of the meta-atoms, the modulation speed of this device is estimated up to approximately several hundred GHz, which makes this device an appropriate candidate for high-speed applications in wireless communications systems based on external modulators.