Nanomechanical three dimensional force photonic crystal sensor using shoulder-coupled resonant cavity with an inserted pillar

• A photonic crystal stress sensor with high sensitivity in three orthogonal directions is proposed.
• We designed a shoulder-coupled resonant cavity with an inserted pillar.
• The structure of the nanocavity has been optimized and the quality factor of it is high enough to sensing tiny force in the three-dimensional space.

A nanomechanical three-dimensional force photonic crystal (PhC) sensor is proposed in this paper by using a shoulder-coupled aslant resonant nanocavity with a single inserted Si pillar and the sensing characteristics are theoretically analyzed and demonstrated. This sensor can be used to detect nanomechanical force in three orthogonal directions independently by measuring the shift of resonant wavelength. The aslant resonant cavity with high quality factor of 7800 ensures high force sensing sensitivity in every dimension as the sensitivity can be enhanced by optimizing the cavity. The shoulder-coupled PhC structure and mobile Si pillar ensure the sensor can detect force from every direction. By applying finite element method (FEM) and finite difference time domain (FDTD) simulations, sensing sensitivity of 8.2, 12.5 and 10.9 nm/μN have been achieved in three dimensions and limitation of the smallest detectable force is 24, 16 and 18 nN in three dimensions, respectively.