Interface engineered germanium for infrared THz modulation

Abstract All optical THz wave modulation based on semiconductor is a convenient modulation method for real application, which is superior with wideband, large modulation depth and low insertion loss. In some scenario, it is required to use infrared light rather than visible light as the excitation signal where germanium is a better candidate than silicon. Here monolayer gold nanorods and graphene was used to modify the surface of germanium to enhance the THz wave modulation depth by the 1550 nm laser irradiation. Higher modulation depth was achieved by surface modification, which achieve the highest modulation depth of ~90% at 3.5 W/cm2. And the modulation rate is higher than 35 kHz.