Polarization-independent terahertz wave modulator based on graphene-silicon hybrid structure

Abstract

In this study, we propose and demonstrate a broadband polarization-independent terahertz modulator based on graphene/silicon hybrid structure through a combination of continuous wave optical illumination and electrical gating. Under a pump power of 400 mW and the voltages ranging from –1.8 V to 1.4 V, modulation depths in a range of –23%–62% are achieved in a frequency range from 0.25 THz to 0.65 THz. The modulator is also found to have a transition from unidirectional modulation to bidirectional modulation with the increase of pump power. Combining the Raman spectra and Schottky current–voltage characteristics of the device, it is found that the large amplitude modulation is ascribed to the electric-field controlled carrier concentration in silicon with assistance of the graphene electrode and Schottky junction.

Dynamic modulation in graphene-integrated silicon photonic crystal nanocavity*

“…Graphene, [5][6][7][8] a two-dimensional (2D) material with linear dispersion at the Dirac point, is an attractive candidate because of its excellent properties, such as tunable chemical potential and high carrier mobility, achieved by applying an electric field. Owing to these advantages, graphene can be used in integrated photonics based on silicon, [9][10][11][12][13][14][15][16][17] which is a promising candidate for on-chip data transmission. Through covering silicon devices with monolayer or multilayer graphene, tunable electro-optic modulators can be realized by the electrical gating of graphene by the use of an electrolyte.…”

Recent progress in graphene terahertz modulators*

“…[14,15] In recent years, graphene has also been used to modulate the properties of the THz wave. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Compared to other materials, graphene has many unique advantages: (i) ultrahigh carrier mobility on the order of 10 6 cm 2 /(V•s). [36] (ii) The carrier concentration of graphene and thus its optical properties in the THz regime can be extensively modified by external stimulants, such as gate voltage [37] and optical pump.…”

Active metasurfaces for manipulatable terahertz technology*

“…Besides, by utilizing active materials sensitive to external stimuli, [22][23][24] such as temperature, electrical bias, illumination, magnetic effects, etc., the desired dynamic manipulations of THz waves can be realized. A variety of materials including doped semiconductors, [25][26][27][28] graphene, [29][30][31][32] vanadium dioxide films, [33][34][35][36][37] superconductors, [38,39] etc. have been demonstrated to be promising candidates for the generation of the active THz metasurfaces.…”