In this abstract, I will discuss our efforts in realizing ultra-sharp nanoantennas with radius of curvature of 1 nm and 5 nm nanogap for extreme photon squeezing applications. Firstly, we propose an unconventional nanolithography technique called cascade domino lithography (CDL) to realize such sharp tip structures. By controlling collapse of micro/nanopillar photoresist structures, diverse plasmonic nanogap structures or single-digit nanometer scale structures can be realized, which are not obtainable with conventional nanofabrications. Secondly, we analyze the optical characteristics of sharp bowtie nanoantennas by using numerical simulations and near/far-field experiments. For instances, an extreme field localization and enhancement are verified by finite-difference time-domain (FDTD) simulations along with near-field scanning optical microscopy (NSOM) measurement, nonlinear spectroscopy and surface-enhanced Raman spectroscopy (SERS).
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