Near-field Nano-optics and Plasmonics
The limit of optical resolution in a conventional microscope, the so-called diffraction limit, is on the order of the wavelength of the light source. Therefore, in the visible range the smallest resolvable features are several hundreds of nanometers, and it will increase to be several micrometers in the infrared range. Near-filed scanning optical microscopy (NSOM), is a microscopy technique for nanostructure investigation that breaks the far field resolution limit by exploiting the properties of evanescent waves. In brief, it is a combination of laser and atomic force microscope (AFM), where light is focused onto the apex of a metal-coated AFM tip. The near-field at the apex is strongly enhanced by the tapped tip, leading to a strong local interaction of light with material that underneath the tip. Optical image with resolution of 20nm at infrared range can be achieved, providing the capability to explore optical physics at nanometer scale, such as plasmonics, nano antenna, local field enhancement and local optical response.
Surface plasmons, collective oscillations of conduction electrons, hold great promise for nanoscale integration of photonics and electronics because plasmons allow for sub-wavelength localization of electromagnetic energies. However, nanophotonic circuit based on plasmons has been significantly hampered by the difficulty in achieving broadband plasmonic waveguides that exhibit simultaneously strong spatial confinement, high quality factor, and low dispersion in conventional metal nanostructures. Quantum plasmons, where quantum mechanical effects of electrons play a dominant role, such as plasmons in very small metal nanoparticles and plasmons affected by tunneling effects, can lead to novel plasmonic phenomena in nanostructures. We showed, for the first time, that the Luttinger liquid of one-dimensional Dirac electrons in carbon nanotubes exhibit quantum plasmons that behave qualitatively different from classical plasmon excitations: the Luttinger-liquid plasmon in carbon nanotubes propagates at “quantized” velocities that are independent of carrier concentration or excitation wavelength, and they exhibit extraordinary spatial confinement and high quality factor simultaneously. Such Luttinger-liquid plasmons could enable novel low-loss plasmonic circuits for sub-wavelength manipulation of light.
The limit of optical resolution in a conventional microscope, the so-called diffraction limit, is on the order of the wavelength of the light source. Therefore, in the visible range the smallest resolvable features are several hundreds of nanometers, and it will increase to be several micrometers in the infrared range. Near-filed scanning optical microscopy (NSOM), is a microscopy technique for nanostructure investigation that breaks the far field resolution limit by exploiting the properties of evanescent waves. In brief, it is a combination of laser and atomic force microscope (AFM), where light is focused onto the apex of a metal-coated AFM tip. The near-field at the apex is strongly enhanced by the tapped tip, leading to a strong local interaction of light with material that underneath the tip. Optical image with resolution of 20nm at infrared range can be achieved, providing the capability to explore optical physics at nanometer scale, such as plasmonics, nano antenna, local field enhancement and local optical response.
Surface plasmons, collective oscillations of conduction electrons, hold great promise for nanoscale integration of photonics and electronics because plasmons allow for sub-wavelength localization of electromagnetic energies. However, nanophotonic circuit based on plasmons has been significantly hampered by the difficulty in achieving broadband plasmonic waveguides that exhibit simultaneously strong spatial confinement, high quality factor, and low dispersion in conventional metal nanostructures. Quantum plasmons, where quantum mechanical effects of electrons play a dominant role, such as plasmons in very small metal nanoparticles and plasmons affected by tunneling effects, can lead to novel plasmonic phenomena in nanostructures. We showed, for the first time, that the Luttinger liquid of one-dimensional Dirac electrons in carbon nanotubes exhibit quantum plasmons that behave qualitatively different from classical plasmon excitations: the Luttinger-liquid plasmon in carbon nanotubes propagates at “quantized” velocities that are independent of carrier concentration or excitation wavelength, and they exhibit extraordinary spatial confinement and high quality factor simultaneously. Such Luttinger-liquid plasmons could enable novel low-loss plasmonic circuits for sub-wavelength manipulation of light.
Related publications:
- Quantum plasmon of Luttinger-liquid in single-walled carbon nanotubes,
Highlights from Lawrence Berkeley National Lab.
- Amplitude- and phase-resolved nano-spectral imaging of phonon polaritons in hexagonal boron nitride. ACS Photonics, 2(7), 790-796 (2015).
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