Fig. 1. Structures of the electro-optic modulator. The length of the modulator is 20 μm, the width and height of the substrate are 200 nm and 2 μm, respectively. The refractive index of SiO₂, Si, Al₂O₃ are 1.444, 3.42, and 1.595, respectively (a) single plasma structure, (b) double plasma structures, (c) three plasma structures, (d) four plasma structures

Fig. 2. Modulation performances of modulator for different heights of plasma structure (a) transmission spectra, (b) 3-dB bandwidth

Fig. 3. Modulation performances of modulator for different gap widths between the two plasma structures (a) Transmission spectra, (b) 3-dB bandwidth

Fig. 4. Modulation performances of modulator for different gap widths between adjacent plasma structures. The plasma structure is divided into three equal parts and the two gaps are of equal width (a) transmission spectra, (b) 3-dB bandwidth

Fig. 5. Modulation performances of modulator for different gap widths between adjacent plasma structures. The plasma structure is divided into four equal parts and the three gaps are of equal width (a) transmission spectra,: (b) 3-dB bandwidth

Fig. 6. Transmission spectra as a function of the wavelength corresponding to different bias voltages (a) single-plasma based modulator structure, (b) double- plasma based modulator structure

Fig. 7. 3-dB bandwidths of single- and double-plasma modulators under different bias voltages