Overcoming thermo-optical dynamics in broadband nanophotonic sensing

Area of Science:

• Integrated photonics
• Nanophotonics
• Optical sensors

Background:

• High-quality-factor nanophotonic cavities offer ultrahigh sensitivity and bandwidths for optical sensors.
• Localized absorption and heating in micrometer-scale mode volumes distort cavity resonances, limiting sensor sensitivity and broadband measurements.

Purpose of the Study:

• To derive a frequency-dependent photonic sensor transfer function accounting for thermo-optical dynamics.
• To quantitatively describe broadband optomechanical signals from integrated photonic atomic force microscopy probes.
• To enable operation in high optical power, nonlinear regimes for accurate dynamic signal measurement.

Main Methods:

• Derivation of a frequency-dependent photonic sensor transfer function.
• Quantitative analysis of thermo-optical dynamics in nanophotonic cavities.
• Experimental validation using an integrated photonic atomic force microscopy nanomechanical probe.

Main Results:

• The derived transfer function accurately describes optomechanical signals in the nonlinear regime.
• Achieved a sensitivity of 0.7 fm/Hz^1/2 at high frequencies, a 10x improvement.
• Discovered that lower quality-factor optical modes enhance transduction gain and sensitivity for low signal frequencies.

Conclusions:

• The developed transfer function allows photonic sensors to operate effectively in the nonlinear thermo-optical regime.
• This approach significantly improves sensitivity and enables accurate measurement of broadband dynamic signals.
• The transfer function is broadly applicable to various photonic sensors affected by the thermo-optical effect.