P. A. Danilov

Silicon as a virtual plasmonic material: Acquisition of its transient optical constants and the ultrafast surface plasmon-polariton excitation

Ultrafast intense photoexcitation of a silicon surface is complementarily studied experimentally and theoretically, with its prompt optical dielectric function obtained by means of time-resolved optical reflection microscopy and the underlying electron-hole plasma dynamics modeled numerically, using a quantum kinetic approach. The corresponding transient surface plasmon-polariton (SPP) dispersion curves of the photo-excited material were simulated as a function of the electron-hole plasma density, using the derived optical dielectric function model, and directly mapped at several laser photon energies, measuring spatial periods of the corresponding SPP-mediated surface relief nanogratings. The unusual spectral dynamics of the surface plasmon resonance, initially increasing with the increase in the electron-hole plasma density but damped at high interband absorption losses induced by the high-density electron-hole plasma through instantaneous bandgap renormalization, was envisioned through the multi-color mapping.

Multi-beam pulsed-laser patterning of plasmonic films using broadband diffractive optical elements.

Multi-sector broadband diffractive optical elements (DOEs) were designed and fabricated from fused silica for high-efficiency multiplexing of femtosecond and nanosecond Gaussian laser beams into multiple (up to one 100) optically tunable microbeams with increased high-numerical aperture (NA) focal depths. Various DOE-related issues, such as high-NA laser focusing, laser pulsewidth, and DOE symmetry-dependent heat conduction effects, as well as the corresponding spatial resolution, were discussed in the context of high-throughput laser patterning. The increased focal depths provided by such DOEs, their high multiplexing efficiency and damage threshold, as well as easy-to-implement optical shaping of output microbeams provide advanced opportunities for direct, mask-free, and vacuum-free high-throughput subtractive (ablative) and displacive pulsed-laser patterning of various nanoplasmonic films for surface-enhanced spectroscopy, sensing, and light control.

Laser-Induced Translative Hydrodynamic Mass Snapshots: Noninvasive Characterization and Predictive Modeling via Mapping at Nanoscale

X. W. Wang, A. A. Kuchmizhak, 2, 3, ∗ X. Li, S. Juodkazis, 4 O. B. Vitrik, 3 Yu. N. Kulchin, V. V. Zhakhovsky, 6 P. A. Danilov, 7 A. A. Ionin, S. I. Kudryashov, 7, 8, 9 A. A. Rudenko, and N. A. Inogamov 5 Center for Micro-Photonics, Swinburne University of Technology, John st., Hawthorn 3122, Victoria, Australia School of Natural Sciences, Far Eastern Federal University, Vladivostok, Russia Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Science, Vladivostok 690041, Russia Melbourne Centre for Nanofabrication, ANFF, 151 Wellington Road, Clayton, VIC 3168, Australia Dukhov Research Institute of Automatics, ROSATOM, Moscow 127055, Russia Landau Institute for Theoretical Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia Lebedev Physical Institute, Russian Academy of Sciences, Moscow 119991, Russia ITMO University, St. Peterburg 197101, Russia National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow 115409, Russia (Dated: May 5, 2017)

Femtosecond laser-induced stress-free ultra-densification inside porous glass

Unusually high densification ≤26% was obtained without lateral residual stresses within the laser beam waist inside porous glass during its multi-shot femtosecond laser irradiation, which may induce in the glass the related high refractive index change ~0.1. Corresponding laser irradiation regimes, resulting in such ultra-densification, decompaction and voids inside the glass, were revealed as a function of laser pulse energy and scanning rate, and were discussed in terms of thermal and hydrodynamic processes in the silica network.

Femtosecond laser ablation of single-wall carbon nanotube-based material

Single- and multi-shot femtosecond laser surface ablation of a single-wall carbon nanotube-based substrate at 515- and 1030 nm wavelengths was studied by scanning electron microscopy and micro-Raman spectroscopy. The laser ablation proceeds in two ways: as the low-fluence mesoscopic shallow disintegration of the surface nanotube packing, preserving the individual integrity and the semiconducting character of the nanotubes or as the high-fluence deep material removal apparently triggered by the strong intrinsic or impurity-mediated ablation of the individual carbon nanotubes on the substrate surface.

Diffraction microgratings as a novel optical biosensing platform

Using a micro-hole grating in a supported silver film as a laser-fabricated novel optical platform for surface-enhanced IR absoprtion/reflection spectroscopy, characteristic absorption bands of Staphylococcus aureus, in particular, its buried carotenoid fragments, were detected in FT-IR spectra with 10-fold analytical enhancement, paving the way for the spectral express-identification of pathogenic microorganisms.

Single-shot selective femtosecond laser ablation of multi-layered Ti/Al and Ni/Ti films: “Cascaded” heat conduction and interfacial thermal effects

Single-shot femtosecond laser ablation of Ti(Al/Ti)5 and (Ni/Ti)5 films on silicon substrates was studied as a function of laser fluence by means of scanning electron microscopy, energy-dispersive x-ray spectroscopy, and optical profilometry. Ablation occurs as gradual threshold-like selective removal of a few top layers at lower fluences and rather continuous removal at higher fluences, exponentially increasing versus ablated depth, with the final complete (through) ablation of the entire films. The observed selective rupture at the different internal interfaces was related to thermomechanically and chemically enhanced (interface-facilitated) explosive boiling, with the corresponding energy deposition provided by “cascaded” heat transfer in the poorly conducting Ti and Ni, and highly conducting Al layers and the interfacial thermal (Kapitza) resistance effect.

Multi-zone single-shot femtosecond laser ablation of silica glass at variable multi-photon ionization paths

Single-shot femtosecond laser ablation of silica glass was studied at moderate peak intensities, providing laser energy deposition in the material via multi-photon absorption prior formation of dense opaque plasma, in order to evaluate the corresponding nonlinear absorption coefficients. For this purpose, tightly focused 515-nm, 220-fs laser pulses produce on a silica glass surface at variable pulse energies single-shot micro-craters, characterized by 3D-scanning confocal laser microscopy. Our analysis of crater diameter dependences on incident laser energy in terms of focusing parameters (Liu analysis) reveals in certain intensity ranges different multi-photon—one-, two-, and four-photon—absorption mechanisms with the increasing integer number of photons. Their depth profiles were considered as sets of distances, representing nonlinear transmission of the incident focused Gaussian beams until the fixed ablation threshold iso-fluence level, and analyzed in terms of the multi-photon absorption mechanisms. These inter-band transitions involve the electronic density-of-states tails in the bandgap (one- and two-photon transitions) and between the main valence and conduction bands (four-photon transitions). In these intensity ranges the depth of the single-shot craters can be fitted, accounting for the derived multi-photon absorption mechanisms, to evaluate the corresponding multi-photon absorption coefficients. The intensity-dependent variation of multi-photon absorption mechanisms provides the three-zone ablation both across the surface and into the bulk of the silica glass.

One – step nanosecond laser microstructuring, sulfur hyperdoping, and annealing of silicon surfaces in liquid carbondisulfide

We perform a single-shot IR nanosecond laser processing of commercial silicon wafers in ambient air and under a 2 mm thick carbon disulfide liquid layer. We characterize the surface spots modified in the liquid ambient and the spots ablated under the same conditions in air in terms of its surface topography, chemical composition, band-structure modification, and crystalline structure by means of SEM and EDX microscopy, as well as of FT-IR and Raman spectroscopy. These studies indicate that single-step microstructuring and deep (up to 2-3% on the surface) hyperdoping of the crystalline silicon in its submicron surface layer, preserving via pulsed laser annealing its crystallinity and providing high (103 - 104 cm−1) spectrally at near- and mid-IR absorption coefficients, can be obtained in this novel approach, which is very promising for thin - film silicon photovoltaic devicesWe perform a single-shot IR nanosecond laser processing of commercial silicon wafers in ambient air and under a 2 mm thick carbon disulfide liquid layer. We characterize the surface spots modified in the liquid ambient and the spots ablated under the same conditions in air in terms of its surface topography, chemical composition, band-structure modification, and crystalline structure by means of SEM and EDX microscopy, as well as of FT-IR and Raman spectroscopy. These studies indicate that single-step microstructuring and deep (up to 2-3% on the surface) hyperdoping of the crystalline silicon in its submicron surface layer, preserving via pulsed laser annealing its crystallinity and providing high (103 - 104 cm−1) spectrally at near- and mid-IR absorption coefficients, can be obtained in this novel approach, which is very promising for thin - film silicon photovoltaic devices

Microstructures as IR-sensors with Staphylococcus aureus bacteria

Using a micro-hole grating in a supported silver film as a laser-fabricated novel optical platform for surface-enhanced IR absoprtion/reflection spectroscopy, characteristic absorption bands of Staphylococcus aureus, especially – its buried carotenoid fragments – were detected in FT-IR spectra with 10-fold analytical enhancement, paving the way to spectral express-identification of the pathogenic microorganisms.