Single molecule absorption spectroscopy using nanophotonic devices for non-fluorescent molecules

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This research aims at development of sensitive single molecule absorption spectroscopy of non-fluorescent molecules by increasing molecular absorption cross-section dramatically with nanophotonic devices. The main results of this project were following three. (1) We demonstrated that single colloidal quantum dots can couple with optical nanofiber with a coupling efficiency of 7.4%. This coupling efficiency estimates 0.1% of optical absorption by single molecules on optical nanofiber even at room temperature. (2) We investigated the coupling of the optical nanofibers with various nanophotonic structures using numerical simulations and found best possible nanophotonic waveguide structures where the maximum absorption of single molecules can be obtained. (3) We have demonstrated the fabrication of free-standing silicon nitride waveguides for this absorption spectroscopy.