6 research outputs found
Nonlinear photoluminescence in gold thin films
Promising applications in photonics are driven by the ability to fabricate
crystal-quality metal thin films of controlled thickness down to a few
nanometers. In particular, these materials exhibit a highly nonlinear response
to optical fields owing to the induced ultrafast electron dynamics, which is
however poorly understood on such mesoscopic length scales. Here, we reveal a
new mechanism that controls the nonlinear optical response of thin metallic
films, dominated by ultrafast electronic heat transport when the thickness is
sufficiently small. By experimentally and theoretically studying electronic
transport in such materials, we explain the observed temporal evolution of
photoluminescence in pump-probe measurements that we report for crystalline
gold flakes. Incorporating a first-principles description of the electronic
band structures, we model electronic transport and find that ultrafast thermal
dynamics plays a pivotal role in determining the strength and time-dependent
characteristics of the nonlinear photoluminescence signal, which is largely
influenced by the distribution of hot electrons and holes, subject to diffusion
across the film as well as relaxation to lattice modes. Our findings introduce
conceptually novel elements triggering the nonlinear optical response of
nanoscale materials while suggesting additional ways to control and leverage
hot carrier distributions in metallic films.Comment: 20 pages, 6 figures, 64 reference
Interference in edge-scattering from monocrystalline gold flakes
We observe strongly dissimilar scattering from two types of edges in hexagonal quasi-monocrystalline gold flakes with thicknesses around 1 micron. We identify as the origin the interference between a direct, quasi-specular scattering and an indirect scattering process involving an intermediate surface-plasmon state. The dissimilarity between the two types of edges is a direct consequence of the three-fold symmetry around the [111]-axis and the intrinsic chirality of a face-centered cubic lattice. We propose that this effect can be used to estimate flake thickness, crystal morphology, and surface contamination
Ultrabright single-photon emission from germanium-vacancy zero-phonon lines: deterministic emitter-waveguide interfacing at plasmonic hot spots
Striving for nanometer-sized solid-state single-photon sources, we investigate atom-like quantum emitters based on single germanium-vacancy (GeV) centers isolated in crystalline nanodiamonds (NDs). Cryogenic characterization indicated symmetry-protected and bright (>106 counts/s with off-resonance excitation) zero-phonon optical transitions with up to 6-fold enhancement in energy splitting of their ground states as compared to that found for GeV centers in bulk diamonds (i.e. up to 870 GHz in highly strained NDs vs. 150 GHz in bulk). Utilizing lithographic alignment techniques, we demonstrate an integrated nanophotonic platform for deterministic interfacing plasmonic waveguides with isolated GeV centers in NDs, which enables 10-fold enhancement of single-photon decay rates along with the emission direction control by judiciously designing and positioning a Bragg reflector. This approach allows one to realize the unidirectional emission from single-photon dipolar sources, thereby opening new perspectives for the realization of quantum optical integrated circuits