Part-per-trillion trace gas detection using frequency-locked whispering gallery mode microtoroids

We use a system known as FLOWER (frequency locked optical whispering evanescent resonator) to rapidly detect trace amounts of the chemical warfare agent surrogates DIMP and DMMP. We use sorbent polymer layers covalently bound to the surface of the microtoroid cavity to selectively adsorb target gases. As the target gas diffuses into the polymer layer, a measurable change in the resonance frequency of the toroid occurs. We demonstrate 80 ppt (part per trillion) sensing of DIMP; two orders of magnitude better than what can be achieved using mass spectroscopy.