1,721,345 research outputs found
Dataset for "Holographic free-electron light source"
No full textThis data relates to the paper Li, Guanhai, Clarke, Brendan, So, Jinkyu, MacDonald, Kevin and Zheludev, Nikolai (2016) Holographic free-electron light source. Nature Communications, 1-18</span
Nonlinear optics of light induced structural transitions in confined gallium
No full textAn ultra-high-vacuum system has been constructed to facilitate atomic-beam deposition of gallium on cryogenically cooled substrates, including optical fibre tips. Alongside this, a fibre-optic pump-probe diagnostic system, based on semiconductor lasers, has been developed to perform in-situ measurements of the linear and transient nonlinear optical properties of gallium nanostructures, both during and after deposition. This unique combination of deposition and optical diagnostic techniques has provided a new means of studying the growth and optical characteristics of gallium nanostructures under highly controlled conditions. The linear and nonlinear optical properties of a new material structure, namely gallium/glass interfaces prepared by ultrafast pulsed laser deposition (UPLD), have been studied for the first time. The reflectivity characteristics of these high-quality interfaces were measured under varying conditions of temperature and light intensity at 810 nm: At temperatures several degrees below gallium's melting point T_m, excitation intensities of just a few kW.cm"-"2 were seen to induce reflectivity changes of more than 30%. Experiments performed with a nanosecond optical parametric oscillator have illustrated that UPLD gallium/silica interfaces show a nonlinear response to optical excitation in the 440-680 nm wavelength range: Fluences of less than 10 mJ.cm"-"2 were seen to induce reflectivity changes of up to 35%, even at temperatures 15 deg below T_m. It has been found that low power (17 #mu#W average) laser illumination of cryogenically cooled substrates during atomic-beam deposition of gallium leads to the formation of uniformly sized gallium nanoparticles. This phenomenon is believed to be the result of a non-thermal light-assisted particle self-assembly process. Gallium nanoparticles have been seen to show a strongly temperature-dependent nonlinear response to low intensity, infrared (1550 nm) optical excitation: 1 #mu#s pulses with peak intensities in the kW.cm"-"2 range induced reversible reflectivity changes with a magnitude of as much as several percent (in the vicinity of the phase transition temperatures) and a typical relaxation time of #approx#0.5 #mu#s. These various experiments have illustrated that the modification of gallium's transitional properties, brought about by confinement, facilitates the achievement of a large optical nonlinearity via light-induced structural transformations in the metal. The studies of UPLD interfaces have shown that bulk gallium's nonlinearity is exceptionally broadband, that its response time can be as short as a few picoseconds, and that its relaxation time is typically in the nano- to microsecond range. Furthermore, the data collected have enabled the development and quantitative testing of theories to describe the thermal and non-thermal metallization mechanisms underlying the nonlinearity. The nanoparticles' nonlinear response shares certain characteristics with that of the bulk interfaces but the experimental data suggest that, in contrast to the bulk nonlinearity, it is not derived from a structural transition involving gallium's #alpha# phase. (author)Available from British Library Document Supply Centre- DSC:DXN053876 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo
Phase-change Nanophotonics
No full textPhase-change materials, including metals, semiconductors and liquid crystals, have played a key role in the evolution of active nanophotonic and plasmonic functionalities. They present unique opportunities at the nano- (i.e. subwavelength) scale as a source of optical nonlinearity and a platform for high-contrast, low-energy electro-and all-optical switching / memory devices. I will review Southampton’s work in this field: from the demonstration of exceptionally large (including metamaterial-enhanced) phase-change nonlinearities underpinned by light-induced, surface-mediated structural transitions in confined gallium; through the harnessing of non-volatile optically-induced amorphous/crystalline transitions in chalcogenides (such as Ge:Sb:Te) to realize plasmonic hybrid and all-dielectric switchable and laser re-writable metasurfaces; to the recent revelation that germanium and bismuth-based chalcogenide alloys can themselves present switchable and compositionally-tunable plasmonic properties in the UV-VIS spectral range
The physics and technology of metadevices and metasystems
No full textPhotonic metamaterials research has migrated in recent years from the study of almost exclusively plasmonic metal nanostructures to embrace a variety of advanced material platforms, including dielectrics, semiconductors, superconductors, phase-change media, and topological insulators. Optically- and electronically-actuated reconfigurable photonic metasurfaces based on such materials offer a range of low-loss, nonlinear, tuneable and switchable optical functionalities in ultra-compact form-factor – for example, engaging nano(opto)mechanical or phase-change response mechanisms to serve signal modulation, spectral/polarization selection or dispersion manipulation applications. In this talk I will review recent developments in the field, ranging from the demonstration of compositionally-tuneable plasmonic properties in chalcogenides to the integration of active all-dielectric and plasmonic metamaterials with optical fibre waveguides
Superoscillation and Super-resolution
No full textRapid variations of intensity and phase can take place in complex, structured light fields at (sub)nanometre length scales far smaller than the commonly understood half-wavelength (λ/2) diffraction limit. Such fields, and their interactions with matter also structured at the nanoscale, offer important potential applications in imaging, spectroscopy, metrology, and opto-electronic/mechanical nanodevices, and in fundamental studies of light-matter interaction down to the pico- (i.e. atomic) scale
Realization of a continuous time crystal in a photonic metamaterial
No full textTime crystals are a new state of matter. Conventional crystal properties are periodic in space, while the properties of a time crystal are periodic in time. A continuous quantum time crystal has recently been realized, and now, using optically driven many-body interactions in a nano-mechanical photonic metamaterial, a classical continuous time crystal has been created
Picophotonics
No full textPicophotonics is the emerging science of interactions of picometer-scale objects and events with light.We demonstrate dimensional metrology and detection of change in position over time with resolution on nanometric to picometric scales by analyzing scattering of electrons or topologically structured light from the nanostructures using artificial intelligence. We show how these techniques can be applied to characterization and optimization of nano-opto-mechanical metamaterials and to fundamental studies of the dynamics of thermal motion and the physics of phonons in photonicnanostructures
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