Integrated optical force sensors using focusing photonic crystal arrays

Area of Science:

• Optomechanics
• Nanophotonics
• Materials Science

Background:

• Mechanical oscillators are crucial for sensors, with optical probing of silicon nitride resonators offering high force sensitivity.
• Current optical read-out methods for these sensors are complex and impractical due to bulky experimental setups.
• High-stress silicon nitride films enable sensitive and reflective mechanical oscillators.

Purpose of the Study:

• To propose and simulate a novel, fully integrated all-optical force sensor.
• To overcome limitations in stability and complexity of existing optical sensors.
• To demonstrate a simplified sensor design using silicon nitride mechanical resonators with photonic crystal reflectors.

Main Methods:

• Simulating a suspended focusing photonic crystal made entirely of silicon nitride.
• Designing an integrated Fabry-Pérot cavity within a single block of silicon nitride.
• Investigating a mechanically suspended flat membrane with subwavelength thickness as a focusing mirror.

Main Results:

• Successful simulation of a novel integrated all-optical force sensor design.
• Demonstration of a silicon nitride photonic crystal reflector for enhanced optical detection.
• Validation of a single-block sensor design integrating a Fabry-Pérot cavity without assembly.
• Achieved subwavelength thickness for the mechanically suspended focusing mirror.

Conclusions:

• The proposed design offers a radical simplification for high-Q silicon nitride membrane-based sensors.
• This work presents the first simulations of a focusing mirror from a suspended subwavelength-thickness membrane.
• The integrated all-optical force sensor design is practical for real-world applications, circumventing assembly and alignment issues.