Full Silicon Pillar-based 1D Optomechanical cavities

TL;DR

This paper introduces a novel full-silicon 1D photonic crystal cavity using nanopillars with enhanced vertical light confinement, enabling efficient optomechanical transduction for force and biosensing applications.

Contribution

The work presents a new nanopillar-based 1D photonic crystal cavity with high Q-factors and integrated optomechanical capabilities, advancing the design of scalable, cost-effective force sensors.

Findings

Achieved Q-factors exceeding 1,000 in silicon nanopillar cavities.

Demonstrated optical transduction of mechanical motion of nanopillars.

Enabled vertical light confinement in pillar-based photonic crystals.

Abstract

Nanomechanical resonators can serve as ultrasensitive, miniaturized force probes. While vertical structures like nanopillars are ideal for this purpose, transducing their motion is challenging. Pillar-based photonic crystals (PhCs) offer a potential solution by integrating optical transduction within the pillars. However, achieving high-quality PhCs is hindered by inefficient vertical light confinement. Here, we present a full-silicon 1D photonic crystal cavity based on nanopillars as a new platform with great potential for applications in force sensing and biosensing areas. Its unit cell consists of a silicon pillar with larger diameter at its top portion than at the bottom, which allows vertical light confinement and an energy bandgap in the near infrared range for transverse-magnetic (TM) polarization. We experimentally demonstrate optical cavities with Q-factors exceeding 1e3 constructed by inserting a defect within a periodic arrangement of this type of pillars. Given the fact that that each nanopillar naturally behaves as a nanomechanical cantilever, the fabricated geometries are excellent optomechanical (OM) photonic crystal cavities in which the mechanical motion of each nanopillar composing the cavity can be optically transduced. These novel geometries display enhanced mechanical properties, cost-effectiveness, integration possibilities, and scalability, and opens and new path in front of the widely used suspended Si beam OM cavities made on silicon-on-insulator.