Scalable photonic-phonoinc integrated circuitry for reconfigurable signal processing

The interaction between photons and phonons plays a crucial role in broad areas ranging from optical sources and modulators to quantum transduction and metrology. The performance can be further improved using integrated photonic-phononic devices, promising enhanced interaction strength and large-scale integration. While the enhanced interaction has been widely demonstrated, it is challenging to realize large-scale integrated photonic-phononic circuits due to material limitations. Here, we resolve this critical issue by using gallium nitride on sapphire for scalable photonicphononic integrated circuits. Both optical and acoustic fields are confined in sub-wavelength scales without suspended structures. This enables us to achieve the efficient launching, flexible routing, and reconfigruable processing of optical and acoustic fields simultaneously. With the controlled photonic-phononic interaction and strong piezoelectric effect, we further demonstrate the reconfigurable conversion between frequency-multiplexed RF and optical signals mediated by acoustics. This work provides an ideal platform for achieving ultimate performance of photonic-phononic hybrid systems with high efficiency, multiple functions, and large scalability.