Differential refractive index sensor based on photonic molecules and defect cavities.

Area of Science:

• Photonics
• Materials Science
• Sensing Technology

Background:

• Photonic molecules (PM) offer unique light-confining properties.
• Differential refractive index sensing requires high sensitivity and stability.
• Existing sensors may lack tunability or broad applicability.

Purpose of the Study:

• To introduce a novel differential refractive index sensor prototype.
• To investigate the sensing capabilities of a photonic molecule matrix with defect cavities.
• To demonstrate the sensor's linear response and potential for extrapolation to other frequency ranges.

Main Methods:

• Fabrication of a photonic molecule matrix using soda-lime glass cylinders.
• Integration of two defect cavities within the photonic molecule structure.
• Microwave spectroscopy (8-12 GHz) for spectral analysis and simulation.
• Analysis of the localized states and their sensitivity to material permittivity.

Main Results:

• A wide photonic stop band with two localized states (reference and sensing) was observed.
• The sensing state, localized in the defect cavities, exhibited high sensitivity to material permittivity.
• The reference state within the photonic molecule matrix remained unperturbed.
• A linear response of the sensor was confirmed through measurements and simulations.

Conclusions:

• The developed photonic molecule sensor prototype demonstrates effective differential refractive index sensing.
• The sensor's design offers a stable reference and a highly sensitive sensing element.
• The principle's scalability, due to Maxwell's equations' scale invariance, suggests applicability across different frequency ranges, including the visible spectrum.