Single-particle spectroscopy is a powerful tool for the mechanistic investigations of chemical and biological dynamics because unsynchronized processes can be directly observed. However, the traditional reliance upon fluorescence for single-particle measurements limits such investigations to systems where the target is fluorescent. Ultrahigh-Q optical microresonators offer a way of eliminating the need for fluorescence by enabling additional sensitive means of interaction with individual particles. Frequently, the interaction, either resonant or non-resonant, between an adsorbed analyte species and the propagating mode of the resonator can allow sensitive single-particle detection.We present a two-beam experimental geometry, where the goal is observation of spectral dynamics of a single known target particle. Our experiment relies on ultrahigh-Q toroidal optical microresonators as platforms for photothermal spectroscopy. Transitions are optically driven in the particle of interest, while the thermalization of the excitation energy is detected by the resonator. We show that single carbon nanotubes deposited on the rim of the microresonator, Fig 1, can be photothermally imaged, a critical proof of concept. The relevant heat flows are explored with numerical simulations. Future augmentation will allow spectroscopy on individual non-fluorescent nano-objects.

Optical microresonators as platforms for single-particle photothermal spectroscopy

248th National Meeting (2014)

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