Photothermal absorption spectroscopy provides a route to measure the absorption spectrum of individual nanoscale objects. Here I discuss recent collaborative efforts between my group at U. Washington and Prof. Randall Goldsmith's group at U. Wisconsin to build a photothermal absorption spectrometer using an optical whispering-gallery-mode (WGM) microresonator cavity as ultrasensitive thermometer of individual plasmonic nanoparticle absorption. Suprisingly, the resulting absorption spectrum is littered by a progression of Fano antiresonances due to the interactions between the nanoparticle's dipole plasmon resonance and the dense set of WGMs of the resonator. The spectral position and linewidth of each antiresonance is diagnostic of the degree of hybridization between plasmon and WGM, and I will show how we controllably optimize this hybridization by thermal annealing of the composite system.

Optimizing the hybridization between localized surface plasmons and photonic cavity modes in a photothermal absorption spectrometer

256th National Meeting (2018)

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