A high-performance terahertz modulator based on double-layer graphene

Graphene has become an ideal material in terahertz domain due to its linear band-structure and extraordinary carrier transport properties as well as the variable carrier density which can be modified by bias voltage. A high-performance modulator based on double-layer graphene was proposed here which was composed of graphene-silica-silicon-silica-graphene five layers. The equivalent circuit method was used to calculate its 3dB bandwidth, modulation speed, insertion loss and modulation depth. The results show its 3dB bandwidth is approximately 264 KHz, the modulation speed can reach 151 KHz and insertion loss is about 0.3 dB. The modulator was fabricated by chemical vapor deposition method and measured using terahertz-time domain spectroscopy system which was produced by Zomega Terahertz company of America. The experimental results show a best measured modulation depth of 61% can be achieved with a bias voltage of 32 V. The proposed modulator here has many advantages such as fast modulation rate, high modulation depth, wide bandwidth as well as easy to fabricate which provides an effective method to the terahertz communications and imaging systems.