Mid-infrared modulators integrating silicon and black phosphorus photonics

Vast applications of mid-infrared await the realisation of integrated photonic systems for this unique spectrum. Despite its potential as a universal platform for diverse active functions in mid-infrared, black phosphorus (BP) photonics still lacks integrated modulators for completion. Here we realize a hybrid integration of mid-infrared BP modulator on silicon photonics waveguide. Through gating effect, the anisotropic absorption in armchair BP can be tuned for enabling efficient optical modulation spanning ∼3.85–4.1 μm. The integrated waveguide design further promotes light–BP interaction that achieves a modulation depth of ∼5 dB at a low bias of −4 V. Additionally, the active footprint of 225 μm2 and the switching energy of ∼2.6 pJ are remarkably smaller compared to traditional counterparts. Function diversity of such a platform is further verified by integrating BP photodetector and modulator. The combination of two-dimensional materials and silicon photonics manifests a versatile platform to realise high-performance optoelectronic devices for compact on-chip mid-infrared system.