A 1D Optomechanical crystal with a complete phononic band gap

TL;DR

This paper presents a 1D optomechanical crystal engineered to have a complete phononic bandgap at 4 GHz, enabling high-Q acoustic modes with minimal leakage and robustness to fabrication imperfections.

Contribution

The design of a 1D optomechanical crystal with a full phononic bandgap at GHz frequencies, achieving high mechanical Q factors and fabrication robustness.

Findings

Achieved a complete phononic bandgap at 4 GHz.

Mechanical Q factors above 10^8 within the bandgap.

Modes are robust to fabrication imperfections.

Abstract

Recent years have witnessed the boom of cavity optomechanics, which exploits the confinement and coupling of optical and mechanical waves at the nanoscale. Amongst their physical implementations, optomechanical (OM) crystals built on semiconductor slabs enable the integration and manipulation of multiple OM elements in a single chip and provide GHz phonons suitable for coherent phonon manipulation. Different demonstrations of coupling of infrared photons and GHz phonons in cavities created by inserting defects on OM crystals have been performed. However, the considered structures do not show a complete phononic bandgap, which should allow longer dephasing time, since acoustic leakage is minimized. We demonstrate the excitation of acoustic modes in a 1D OM crystal properly designed to display a full phononic bandgap for acoustic modes at 4 GHz. The modes inside the complete bandgap are designed to have mechanical Q factors above 10e8 and invariant to fabrication imperfections.