Giant optical nonlinearity of a single plasmonic nanostructure.

We realize giant optical nonlinearity of a single plasmonic nanostructure which we call a split hole resonator (SHR). The SHR is the marriage of two basic elements of nanoplasmonics, a nanohole and a nanorod. A peak field intensity in the SHR occurs at the single tip of the nanorod inside the nanohole. The peak field is much stronger than those of the nanorod and nanohole, because the SHR field involves contributions from the following two field-enhancement mechanisms: (1) the excitation of surface plasmon resonances and (2) the lightning-rod effect. Here, we demonstrate the use of the SHR as a highly efficient nonlinear optical element for: (i) the generation of the third harmonic from a single SHR; (ii) the excitation of intense multiphoton luminescence from a single SHR.

Subwavelength light localization based on optical nonlinearity and light polarization.

We propose and experimentally realize subwavelength light localization based on the optical nonlinearity of a single nonlinear element in nanoplasmonics-a split hole resonator (SHR). The SHR is composed of two basic elements of nanoplasmonics, a nanohole, and a nanorod. A peak field intensity occurs at the single spot of the SHR nanostructure. We demonstrate the use of the SHR as a highly efficient nonlinear optical element for (i) the construction of a polarization-ultrasensitive nanoelement and, as a practical application, (ii) the building up of an all-optical display.

Single nanohole and photoluminescence: nanolocalized and wavelength tunable light source.

We are first to demonstrate a broadband, nanometer-scale, and background-free light source that is based on photoluminescence of a single nanohole in an Au film. We show that a nanohole with a diameter of as small as 20 nm in a 200-nm thick Au film can be used for this purpose. Further development of the localized source that involves the use of a photon-crystal microcavity with a Q-factor of 100 makes it possible to create a 30-fold enhanced, narrowband tunable light source and with a narrow directivity of the radiation.