High-performance graphene-on-silicon slot waveguide modulators for the 2 μm waveband

The 2 μm wavelength band communication technology, with its prominent spectral resource advantages, has emerged as a key technological direction to break through the capacity bottleneck of conventional optical communication systems. As a crucial component of optical communication systems, high-performance optical modulators directly determine critical system parameters, including transmission rates, energy efficiency ratios, and integration levels. However, current high-speed modulators operating at the 2 μm wavelength still fail to match the performance of their well-established counterparts at 1.55 μm, posing a fundamental limitation to the practical viability of this emerging spectral window. Here, we designed high-performance modulators at the 2 μm band, based on a graphene-on-silicon slot waveguide. An electro-absorption optical modulator was designed with a voltage-length product of 0.113 V·cm, a low insertion loss of 1.9 dB, a high extinction ratio of 50.7 dB, a 3-dB modulation bandwidth of ∼520 GHz, and an energy consumption of 177.38 fJ/bit. Additionally, we proposed a refractive index modulator based on the platform, theoretically demonstrating four-amplitude shift keying modulation and quaternary phase shift keying modulation by using microring resonators. The study is expected to offer a low insertion loss and highly integrated modulator, advancing the development of 2 μm waveband communications.