Observing the localization of light in space and time by ultrafast second-harmonic microscopy

Near-field-assisted localization: effect of size and filling factor of randomly distributed zinc oxide nanoneedles on multiple scattering and localization of light

“…By using an allreflective objective, dispersion effects limiting the temporal resolution of our microscope are minimized and a time resolution of 6 fs is reached [34]. An early version of this set-up has been used in [23]. We obtain a diffraction-limited spot size of 1.0 and 0.5 µm at the fundamental wavelength and at the SH wavelength, respectively, governing the spatial resolution of our nonlinear experiment.…”

“…The SH radiation generated in the ZnO needle array is collected in reflection geometry by the same Cassegrain objective, separated from the fundamental reflected laser light using a dichroic beam splitter and analysed in a spectrometer. By using a phase-locked pulse pair for excitation, coherent SH emission from the needles can be distinguished from incoherent multiphoton luminescence [23,35].…”

“…These hot spots of light have been studied extensively in the past in metallic nanostructures [14][15][16][17] and more recently also in photonic crystal waveguides [18][19][20][21][22] and dielectric media [23,24].…”

“…Using SH microscopy, we recently observed rather strong fluctuations of the SH intensity in a random array of thin needles with a diameter of only 30 nm [23]. Here, we use this approach to systematically study the correlation between the geometric structure, specifically needle diameter and filling fraction, of different ZnO nanoneedle arrays and local fluctuations of the SH intensity.…”

Mesoscopic fluctuations of the local density of states in interacting electron systems

“…Recently, multifractality has become a subject of experimental research. For example, an indication of multifractality has been reported in scanning tunneling spectroscopy data in diluted magnetic semiconductor Ga 1−x Mn x As [9], in experimental studies of ultrasound waves propagating through the system of randomly packed Al beads [10], and in experimental data on spreading of light waves in the dielectric nanoneedle array [11].…”