Acousto-optic modulation based on an AlScN microring resonator for microwave-to-optical conversion

TL;DR

This paper demonstrates an on-chip acousto-optic modulator using a thin-film AlScN microring resonator with integrated interdigital transducer, enabling efficient microwave-to-optical conversion suitable for microwave photonics.

Contribution

It introduces a novel AlScN microring resonator with integrated transducer for efficient on-chip acousto-optic modulation compatible with CMOS fabrication.

Findings

Achieved an optical loaded Q factor of 1.8×10^4.

Low half-wave voltage Vpi of 1.21 V and VpiL of 0.0242 Vcm.

Optomechanical coupling strength g0 of 0.43 kHz.

Abstract

Acoustic-optic (AO) modulation is critical for microwave and optical signal processing, computing and networking. Challenges remain to integrate AO devices on-chip using fabrication process compatible with complementary metal-oxide-semiconductor (CMOS) technology. This work presents the demonstration of an AO modulator exploiting a microring resonator (MRR) based on thin-film aluminum scandium nitride (AlScN) photonic platform. Leveraging the high piezoelectric properties of AlScN, an MRR is employed with interdigital transducer (IDT) inside to couple microwave signals into acoustic resonant modes, enabling efficient by-directional optical modulation in the MRR. The fabricated MRR exhibits an optical loaded quality factor (Q) of 1.8*e4 at the optical L-band for the TE00 mode. A low effective half-wave voltage Vpi of 1.21 V is achieved, corresponding to a VpiL of 0.0242 Vcm, along with an optomechanical single-photon coupling strength g0 of 0.43 kHz between the 2.11 GHz acoustic mode and the TE00 optical mode. The device shows potential for applications in microwave photonics.