Ultrafast Meets Ultrasmall: Controlling Nanoantennas and Molecules

Abstract

We present a review on the advances of pulse control and ultrafast coherent excitation of both plasmonic nanoantennas and individual molecular systems, primarily based on the achievements in our group. Essential concepts from coherent control of ultrashort broadband laser pulses are combined with nanoscale diffraction limited detection and imaging of single photon emitters, i.e. the central area of this work is where ultrafast meets ultrasmall. First, the critical role of dedicated pulse shaping and phase control is discussed, which is crucial to realize free of spatio-temporal coupling Fourier limited pulses inside a high numerical aperture microscope at the diffraction limited spot. Next we apply this scheme to plasmonic antennas, exploiting broadband two-photon excitation, to determine amplitude and phase of plasmonic resonances, to achieve ultrafast switching of nanoscale hotspots, and multicolor second harmonic detection for imaging applications. Subsequently we address single molecules with phase-shaped pulses to control the electronic state population and retrieve single molecule vibrational dynamics response. We compare the response of a molecule to phase-locked with free phase multipulse excitation. Furthermore, we discuss phase control of excited state energy transfer in photosynthetic molecular complexes. Finally we combine nanoscale plasmonics with single molecule detection, to attain strong enhancement of both excitation and emission, with fluorescence lifetime shortening to the ps range. In conclusion, we anticipate that this review on ultrafast plasmonics and single emitter control will provide a useful view of the status of ultrafast nanophotonics and its application potential.

Exciton Transport in Molecular Aggregates – From Natural Antennas to Synthetic Chromophore Systems

“…A particularly important question in this regime concerns the impact of unavoidable electronic and structural disorder from complex to complex [138] on the coherent transport. As such heterogeneity cannot be resolved by conventional time-resolved spectroscopy, ultrafast singlemolecule spectroscopy [105,139] was applied on individual complexes at room temperature to address this issue. [109] To probe coherence in this B800-B850 transfer step in single LH2, a two-color experiment was employed in which a first pulse is resonant with the B800 absorption and a second timedelayed and phase-controlled pulse is resonant with the optically allowed bottom B850 exciton states (Figure 8a).…”

Non-Markovian dynamics in plasmon-induced spontaneous emission interference

“…This strong field localization leads to an enhancement of the light-matter interaction in the vicinity of the MNP, featuring some very interesting physics in a broad range of contexts such as optical antennas 1,2 , surface-enhanced Raman scattering 3 , photovoltaics 4 , energy transfer in light-harvesting 5 and biosensing 6 . The presence of LSPs in metal-dielectric interfaces strongly modifies the density of the EM modes in the surroundings, leading to strong modification of the lifetime of quantum emitters (QE) placed close to the MNP.…”

Investigation of optical fiber-tip probes for common and ultrafast SERS

“…At the same time, we expected a larger difference in field amplitudes along Line 1 for different configurations due to the gap inside the chain waveguide if a nanoparticle was removed. This large gap leads to an increased b to a ratio [42], where b is the center-to-center (of NPs) distance and a is the radius of the NP. In other words, this large gap acts as the termination of the NP chain waveguide and lead to the propagating plasmon wave reflecting from it, which increased the amplitude of the previous hot spot.…”

“…In our simulation, to excite the structures under consideration, we used an ultrashort Gaussianshaped pulse centered at a wavelength in vacuum of 785 nm ( f 0 =382.2 THz) with an FWHM duration time Δt of 2.11 fs (see figure 2). Such ultrashort pulse was considered due to the fact that optical pulses of such duration possess high potential in ultrafast nanophotonics [42], as ultrafast science is rapidly moving toward increasingly complex systems [43], such as multiphoton microscopy in membranes and cells, quantum networks in diamond, or excitonic coherence in photosynthesis. Despite the fact that in some cases [44] pulses with duration of>1 fs undergo barely noticeable degradation during propagation to the optical fiber extremities, pulse elongation in a fiber is strongly dependent on the fiber structure.…”