We demonstrate controlled squeezing of visible light waves into nanometer-sized optical cavities. The light is perpendicularly confined in a few-nanometer-thick SiO2 film sandwiched between Au claddings in the form of surface plasmon polaritons and exhibits Fabry-Perot resonances in a longitudinal direction. As the thickness of the dielectric core is reduced, the plasmon wavelength becomes shorter; then a smaller cavity is realized. A dispersion relation down to a surface plasmon wavelength of 51 nm for a red light, which is less than 8% of the free-space wavelength, was experimentally observed. Any obvious breakdowns of the macroscopic electromagnetics based on continuous dielectric media were not disclosed for 3-nm-thick cores.
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"The dark dashed lines indicate the respective cut-off photon energy given by ¯ hω = |eV b |. off continuously towards shorter wavelengths. In the absence of slots, as is the case for the reference device, inelastically tunneling electrons predominantly interact with surface plasmon polaritons (SPPs) associated with the metal-insulator-metal (MIM) configuration  . The dispersion relation of these modes can be calculated analytically (see Supplementary Information). "
[Show abstract][Hide abstract] ABSTRACT: The ultrafast conversion of electrical to optical signals at the nanoscale is
of fundamental interest for data processing, telecommunication and optical
interconnects. However, the modulation bandwidths of semiconductor LEDs are
limited by the spontaneous recombination rate of electron-hole pairs and the
footprint of electrically-driven ultrafast lasers is too large for practical
on-chip integration. A metal-insulator-metal (MIM) tunnel junction approaches
the ultimate size limit of electronic devices and its operating speed is
fundamentally limited only by the tunneling time. Here we study the conversion
of electron energy - localized in vertical gold-h-BN-gold tunnel junctions -
into free space photons, mediated by resonant slot antennas. Optical antennas
efficiently bridge the size-mismatch between nanoscale volumes and far-field
radiation and strongly enhance the electron-photon conversion efficiency. We
achieve polarized, directional and resonantly enhanced light emission from
inelastic electron tunneling and establish a novel platform for studying the
interaction of electrons with strong electromagnetic fields. Our results pave
the way for the further development of nanoscopic sources of light enabled by
the combination of nanophotonic design principles and nanoelectronics.
Full-text · Article · Mar 2015 · Nature Nanotechnology
"Since the extraordinary optical transmission (EOT) phenomenon through arrays of nano-holes  milled in a metallic film has been first reported by Ebbesen et al., many nanoscale metallic structures, including single aperture   , circular aperture arrays      and annular aperture arrays   , have been widely studied on their physical mechanisms and applications in EOT. It is well known that surface plasmon polaritons (SPPs) excited at the interface between metal and dielectric material play a crucial role in EOT phenomenon. "
[Show abstract][Hide abstract] ABSTRACT: A novel plasmonic structure, composed of a dipole source and an annular nano-cavity over a nano-slit, is proposed as a surface plasmon polaritons source to enhance the extraordinary optical transmission (EOT) simulated using a finite-difference time-domain (FDTD) method. We find that the annular nano-cavity has an obvious advantage to couple more energy from a dipole source compared with previous EOT configuration. Based on the fact of non-uniform electric field distribution of a dipole source, the transmission through nano-slit is effectively improved by selecting optimized structure parameters. In addition, the transmission spectrum can be well-tuned by adjusting the central angle of the annular nano-cavity, as such, the design holds great promise for its application in EOT-based optoelectronic devices.
"А structure where a dielectric core is sandwiched between two metal layers is very promising as it can provide even smaller dimensions and higher field localization  . A metal–insulator–metal (MIM) waveguide does not exhibit cutoff even at very small core thickness and thus allows unprecedented thin layouts of tens of nanometers   . Planar MIM plasmonic waveguides with thin metal claddings were studied and optimized for various purposes     . "
[Show abstract][Hide abstract] ABSTRACT: We focus on plasmonic modulators with a gain core to be implemented as
active nanodevices in photonic integrated circuits. In particular, we
analyze metal-semiconductor-metal (MSM) waveguides with InGaAsP-based
active material layers. A MSM waveguide enables high field localization
and therefore high modulation speed. The modulation is achieved by
changing the gain of the core that results in different transmittance
through the waveguide. Dependences on the waveguide core size and gain
values of various active materials are studied. The effective
propagation constants in the MSM waveguides are calculated numerically.
We optimize the structure by considering thin metal layers. A thin
single metal layer supports an asymmetric mode with a high propagation
constant. Implementing such layers as the waveguide claddings allows to
achieve several times higher effective indices than in the case of a
waveguide with thick (>50 nm) metal layers. In turn, the high
effective index leads to enhanced modulation speed. We show that a MSM
waveguide with the electrical current control of the gain incorporates
compactness and deep modulation along with a reasonable level of
Full-text · Article · Mar 2013 · Proceedings of SPIE - The International Society for Optical Engineering