ABSTRACT
Following optical excitations' life span from creation to decay into photons is crucial in understanding materials photophysics. Macroscopically, this is studied using optical techniques, such as photoluminescence excitation spectroscopy. However, excitation and emission pathways can vary at nanometer scales, preventing direct access, as no characterization technique has the relevant spatial, spectral, and time resolution. Here, using combined electron spectroscopies, we explore excitations' creation and decay in two representative optical materials: plasmonic nanoparticles and luminescent two-dimensional layers. The analysis of the energy lost by an exciting electron that is coincident in time with a visible-ultraviolet photon unveils the decay pathways from excitation toward light emission. This is demonstrated for phase-locked (coherent) interactions (localized surface plasmons) and non-phase-locked ones (point defect excited states). The developed cathodoluminescence excitation spectroscopy images energy transfer pathways at the nanometer scale, widening the available toolset to explore nanoscale materials.
ABSTRACT
The wavefront quality of white-light supercontinuum is crucial for applications like waveform synthesis or imaging. It has been here generated by 1030 nm centered sub-picosecond pulses in YAG and characterized with a Shack-Hartmann wavefront sensor across different parts of the spectrum. It shows a good wavefront quality of λ/11 and little dependence on the wavelength of the supercontinuum. The wavefront deformations are transferred from the driver laser wavefront to the supercontinuum independently of the wavelength.
ABSTRACT
The synthesis, sorting, and characterization of monodisperse gold nanorods with dimensions around 10 nm in length and below 6 nm in diameter is reported. They display tunable plasmon resonance in the near infrared, a region where cellular absorption is reduced. A dual color photothermal microscope is developed to demonstrate that they are promising single molecule probes for bioimaging.
ABSTRACT
We report on dual-color control of femtosecond direct laser writing (DLW) in a noncommercial silver-containing zinc phosphate glass, thanks to an additional illumination with a cw (continuous wave) UV laser, either after the femtosecond irradiation or simultaneously. By tuning the cw UV power, we demonstrate the tunable control and inhibition of the production efficiency of laser-induced fluorescent silver clusters, leading up to 100% inhibition for simultaneous co-illumination when the laser writing is performed close enough to the permanent structuring threshold. The role of the cw UV illumination is discussed in terms of inhibition of the silver cluster precursors or of dissolution of the laser-induced silver clusters. These results show the ability of laser writing inhibition in our photosensitive silver-containing phosphate glass, which is a necessary step to further develop super-resolution laser writing approaches, such as STED-like DLW, either of fluorescent silver clusters or of silver metallic nanoparticles with plasmonic properties.
ABSTRACT
The paper presents our results on laser micro- and nanostructuring of sodium aluminosilicate glass for the permanent storage purposes and photonics applications. Surface structuring is realized by fs laser irradiation followed by the subsequent etching in a potassium hydroxide (10M@80 °C) for 1 to 10 minutes. As the energy deposited is lower than the damage and/or ablation threshold, the chemical etching permits to produce small craters in the laser modified region. The laser parameters dependent interaction regimes are revealed by microscopic analysis (SEM and AFM). The influence of etching time on craters formation is investigated under different incident energies, number of pulses and polarization states.
