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The anthrax vaccine candidate AV7909 is being developed as a next-generation vaccine for post-exposure prophylaxis (PEP) against inhalational anthrax. In clinical studies, two vaccinations with AV7909 administered either two or four weeks apart induced an enhanced immune response compared to BioThrax® (Anthrax Vaccine Adsorbed) (AVA). Anthrax toxin-neutralizing antibody (TNA) levels on Day 70 following initial vaccination that were associated with protection of animals exposed to inhalational anthrax were previously reported for the 0, 4-week AV7909 vaccination regimen. The current study shows that a 0, 2-week AV7909 vaccination regimen protected guinea pigs (GPs) and nonhuman primates (NHPs) against a lethal inhalational anthrax challenge on Days 28 and 70 after the first immunization. An earlier induction of protective TNA levels using a 0, 2-week AV7909 vaccination regimen may provide benefit over the currently approved AVA PEP 0, 2, and 4-week vaccination regimen.

The anthrax vaccine candidate AV7909 is being developed as a next-generation vaccine for a post-exposure prophylaxis (PEP) indication against anthrax. AV7909 consists of the anthrax vaccine adsorbed (AVA) (Emergent BioSolutions Inc., Lansing, MI) bulk drug substance adjuvanted with the immunostimulatory oligodeoxynucleotide (ODN) compound, CPG 7909. The addition of CPG 7909 to AVA enhances both the magnitude and the kinetics of antibody responses in animals and human subjects, making AV7909 a suitable next-generation vaccine for use in a PEP setting. Emergent has produced a thermostable (lyophilized) formulation of AV7909 vaccine utilizing drying technology. The purpose of the study described here was to assess the immunogenicity and efficacy of the lyophilized formulation of the AV7909 vaccine candidate as compared with the liquid formulation in the guinea pig general-use prophylaxis (GUP) model. The study also provides initial information on the relationship between the immune response induced by the thermostable formulation of the vaccine, as measured by the toxin neutralization assay (TNA), and animal survival following lethal anthrax aerosol challenge. Results demonstrated that there were no significant differences in the immunogenicity or efficacy of lyophilized AV7909 against lethal anthrax spore aerosol challenge in the guinea pig model as compared to liquid AV7909. For both vaccine formulations, logistic regression modeling showed that the probability of survival increased as the pre-challenge antibody levels increased.

Tightly focused, highly spatially multiplexed femtosecond laser pulses, coming at sub-MHz repetition rates, were used to mask-less pattern thin plasmonic films film at ultrafast rates, approaching 25 million of microelements per second. For this purpose, the initial pulses were multiplexed by fused silica diffractive optical elements into linear arrays of 31, 51 and 101 circular light spot and then scanned over the films by a galvanometric scanner through a long-focus objective or high-NA aspherical lens. These optical scheme and 5-μJ pulse energy supported the only 31- and 51-beam micro-patterning, with the corresponding aperture, field-of-view and sub-100 nJ energetic limitations for the laser processing of the film. The resulting large (~105–106 holes per array) arrays of micro-holes of variable diameters and periods in thin films of different thickness and diverse plasmonic materials - Ag, Cu, Al and Au-Pd alloy (80%/20%) - were for the first time systematically characterized in the broad IR-range (1.5–25 μm) in terms of plasmonic effects in extraordinary optical transmission, indicating for the increasing wavenumber a smooth transition from the common Bethe-Bouwkamp transmission to its plasmon-enhanced analogue, ending up with common geometrical (wave-guide-like) transmission. Finally, promising label- and luminescence-free laboratory-scale, robust and high-sensitivity sampling of chemicals and biosamples via plasmonic and chemical contributions, uneven and structurally-sensitive regarding different functional groups of the model analyte molecules and band structure of the plasmonic metal, was demonstrated for the large IR-sensing arrays of micro-holes in plasmonic films, with the obvious perspectives for down-scaling of sensing elements for vis-IR surface-enhanced spectroscopies.

Sum-frequency spectrum of non-selective (multi-line) CO laser radiation generated in ZnGeP2 crystal under noncritical spectral phase-matching conditions was experimentally studied with spectral resolution of ∼0.1 cm−1. The number of spectral lines for this spectrum was found to be about an order of magnitude larger than for previously reported one. Its spectral structure looked like a broadband mid-IR comb of multi-line groups having complicated substructure. That is attractive for the atmosphere sounding by both differential absorption technique and absorption line profile spectroscopy. A list of the atmosphere gases and pollutants that could be detected by these procedures was considered. An opportunity of absorption line profile measuring by means of CO laser sum-frequency comb was experimentally demonstrated for CO2 molecules.

Broadband sum frequency conversion of a slab RF discharge Q-switched CO laser system was performed with two BaGa2GeSe6 crystals resulting in its spectrum lying within 1.7–6.0 μm spectral range. The first BaGa2GeSe6 crystal was located in the CO laser cavity and operated as both CO laser sum frequency (second harmonic) generator and laser output coupler. Another BaGa2GeSe6 crystal was applied for external third harmonic generation, i.e. as sum frequency generator for fundamental CO laser radiation and its sum frequencies obtained within the cavity. Peak powers of fundamental CO laser radiation, its second and third harmonics were up to 4.7 kW, 100 W and 0.5 W, respectively.

The experimental study of the single-shot 1030-nm femtosecond laser ablation of bulk silicon and silver in air and liquid media (deionized water, isopropyl alcohol) is reported. The main laser ablation mechanisms were studied via analysis of the resulting microcrater surface morphology and elemental composition in single- and multi-shot (number of pulses N = 10, 100) regimes by scanning electron microscopy with a built-in module for energy-dispersive X-ray spectroscopy. It was concluded, that multi-shot ablation in liquids leads to the lesser extent of the processed surface oxidation, than in dry conditions. The monitoring of the ablative plumes dynamics was implemented with the use of time-resolved emission spectroscopy in the non-filamentation regime, corresponding to the formation of nanoparticles without fragmentation of the ablation products. It was demonstrated, that the lifetime of the plume emission in liquid is significantly shorter, than in air: 5 and 15 ns, correspondingly, for silicon, and 10 and 30 ns for silver.

Metal nanoparticles have attracted much attention due to their unique properties. One of the important aspects is particle size control for the use of their colloids in various applications. Colloidal solutions of silver nanoparticles were generated in water from silver films of variable thickness at different intensities of a nanosecond fiber laser marker (Bulat) on Yb3+ ions and its scanning speeds over the film surfaces in the laser-plasma ablation regime. The obtained colloidal nanoparticles were characterized by scanning electron microscopy, optical transmission spectroscopy, and dynamic light scattering. A monotonic increase in the extinction coefficient and in the size of the colloidal particles was observed as a function of laser intensity and exposure.

The effect of laser pulsewidth, tuned in the range τ = 0.3–10 ps, on infrared (IR) laser ablation (LA) thresholds of bulk gold, silver and silicon in air and in liquid environments (deionized water, isopropyl alcohol (IPA)) was studied in this work. The influence of laser pulsewidth on the morphology and yield of the ejected nanoparticles (NPs), as well as its impact on the efficiency of NP generation, was studied by UV–vis spectral measurement of the extinction coefficient spectra of NP colloids, fabricated by multi-pass ablation of bulk targets in both solvents at different pulse duration values, by analytical disc centrifuge and by high-resolution scanning electron microscopy. The ablation thresholds are raising with the increase of laser pulsewidth, exhibiting sublinear dependences. The extinction coefficient dependence on τ exhibited a non-monotonous character in case of water medium for all materials, and was gradually descending in case of LA in IPA. Additional MD-TTM (molecular dynamics- two-temperature model) modeling was performed for single-shot laser exposition of bulk Au target in air with τ = 0.3 ps and 4 ps, which allowed distinguishing the main mechanisms of the material removal, the formation of NPs, and the observed crater topography. The performed simulations supported the trend on the ablation threshold increase with the increase of laser pulse duration.

Selenium and silicon nanoparticles were obtained by nanosecond laser ablation in distilled water and characterized by scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy. The antibacterial properties of their coatings regarding Gram-positive and Gram-negative bacteria were demonstrated. The presence of singlet oxygen and other reactive oxygen species on the surface of the silicon nanoparticles, leading to oxidative damage to bacterial membranes and further death of the bacteria, was considered a possible mechanism of their antibacterial modality.

Using aluminum as an example, ultrafast sub-ablative broad-range (EUV-IR) spectral tuning of surface plasmon resonance in metals by IR femtosecond laser pulses was demonstrated by theoretical modeling of prompt surface optics for strongly photoexcited materials and of their surface plasmon-polariton (SPP) dispersion curves, as well as by experimental multi-shot laser imprinting of surface plasmon-polaritons as large-scale regular surface ripples with minimal sub-diffraction periods down to 200 nm. According to laser-pump self-reflection and charge emission experiments, the key issue in the prompt optical tuning (spectral red-shifting) of EUV surface plasmon resonance in aluminum by the IR laser pulses is related to ultrafast surface charging of its surface via intense electron emission during the laser pump pulse, depleting its surface electron density and simultaneously decreasing its surface/bulk plasma frequencies, at the corresponding negligible surface ablative etching.

Paper presents the study of Ge2Sb2Te5 (GST) thin films phase transitions’ dynamics determined by the rate of their optical coefficients change. The phase transitions were initialized by laser pulses with 15 ns duration at a wavelength of 532 nm and confirmed by X-ray diffraction analysis. Energy fluence was 22 mJ/cm2 for film crystallization and 54 mJ/cm2 for reamorphization. The time for a complete change of GST film reflectivity associated with the crystallization process was 23 ns, while the time for a transmissivity change was 32 ns. Taking into account that the reflection is determined to a greater extent by the surface, and the transmission is exclusively by the film thickness, the estimated crystallization rate was ∼3.125 m/s. The time for a complete change in the reflectivity during the film reamorphization 62 ns, and the transmissivity changed in 65 ns. The estimated reamorphization rate was ∼1.538 m/s.

We report the facile synthesis of colloidal Si@Au and Si@Ag nanoparticles (NPs) through nanosecond IR laser plasma-mediated reduction of 0.03 mM aqueous solutions of chloroauric acid (HAuCl4) and silver nitrate (AgNO3) at different laser intensities on the surface of Si NPs during the ablation of the silicon wafer. The resulting hybrid colloidal NPs were analysed by UV–vis transmission spectroscopy, dynamic light scattering, scanning electron microscopy, energy-dispersive x-ray and x-ray photoelectron spectroscopy.

Milligram-per-second production of selenium nanoparticles in water sols was realized through 7-W, 2 MHz-rate femtosecond laser ablation of a crystalline trigonal selenium pellet. High-yield particle formation mechanism and ultimate mass-removal yield were elucidated by optical profilometry and scanning electron microscopy characterization of the corresponding crater depths and topographies. Deposited selenium particles were inspected by scanning and transmission electron microscopy, while their hydrosols (nanoinks) were characterized by optical transmission, Raman and dynamic light scattering spectroscopy. 2D patterns and coatings were ink-jet printed on thin supported silver films and their bare silica glass substrates, as well as on IR-transparent CaF2 substrates, and characterized by electron microscopy, energy-dispersive x-ray spectroscopy, and broadband (vis-mid IR) transmission spectroscopy, exhibiting crystalline selenium nanoparticles with high refractive index as promising all-dielectric sensing building nanoblocks in nanophotonics.

Ultrafast plasmonics of novel materials has emerged as a promising field of nanophotonics bringing new concepts for advanced optical applications. Ultrafast electronic photoexcitation of a diamond surface and subsequent surface plasmon-polaritons (SPPs) excitation are studied both theoretically and experimentally - for the first time. After photoexcitation on the rising edge of the pulse, transient surface metallization was found to occur for laser intensity near 18 TW/cm$^2$ due to enhancement of the impact ionization rate; in this regime, the dielectric constant of the photoexcited diamond becomes negative in the trailing edge of the pulse thereby increasing the efficacy with which surface roughness leads to inhomogeneous energy absorption at the SPP wave-vector. These transient SPP waves imprint permanent fine and coarse surface ripples oriented perpendicularly to the laser polarization. The theoretical modeling is supported by the experiments on the generation of laser-induced periodic surface structure on diamond surface with normally incident 515-nm, 200-fs laser pulses. Sub-wavelength ($\Lambda \approx 100$ nm) and near wavelength ($\Lambda \approx 450$ nm) surface ripples oriented perpendicularly to the laser polarization emerged within the ablative craters with the increased number of laser shots; the spatial periods of the surface ripples decrease with the increasing exposure following known cumulative trends. The comparison between experimental data and theoretical predictions makes evident the role of transient changes of the dielectric permittivity of diamond during the initial stage of periodic surface ripple formation upon irradiation with ultrashort laser pulses., Comment: 11 pages, 14 figures, has been resubmitted to PRB

Three-segment microtracks were for the first time inscribed in bulk fluorite in the scanning mode via multishot exposure by tightly-focused 515-nm ultrashort laser pulses of variable pulse energy and pulsewidth (0.3–3.8 ps). The local micro/nanoscale material modification and related refractive-index changes within the microstructures, envisioned by optical and cross-sectional electron microscopy, result in their form birefringence acquired by polarimetric microscopy. Retardance and thickness of the microstructures were measured by optical polarimetry and confocal scanning Raman/photoluminescence microscopy, respectively, exhibiting the intensity- and pulsewidth-dependent trends, with the maximal effect for ≈1-ps laser pulses. These and complementary optical self-reflectance studies enabled for the first time to consider ultrafine, pulsewidth-dependent interferential longitudinal sub-structure of the birefringent microtracks. Such regular longitudinal sub-structure was proposed to emerge via back-reflection and interference of laser radiation prior near-critical laser-generated plasma in the focus, and the following transverse plasmon propagation in each nanosheet of ionized fluorite in the resulting sub-wavelength interference pattern. Our findings open the way for ultrashort-pulse laser inscription of embedded optical microstructures in non-oxygen fluoride materials and shed light onto the underlying laser-dielectric interactions.

Single-shot ablation of amorphous silicon films of 50-, 100- and 150-nm thickness by laser pulses of variable (0.2–6 ps) widths demonstrates non-monotonous variation of ablation thresholds and characteristic ablation 1/e-radii with their minima at the 0.6-ps pulse-width and the following increase. For the shorter laser pulses the increased thresholds and enhanced transport can be related to fast ambipolar electron-hole plasma diffusion and other electronic energy losses in dense transient plasma prior its energy transfer to the ionic subsystem (electron-ion thermalization) at 0.6 ps, while for the longer laser pulses slower ambipolar diffusion in moderate-density electron-hole plasma, ionic heat conduction and other thermal losses may predominate.

The article presents the results of an in-situ pump–probe study of the change’s kinetics in the optical properties of GeTe thin films associated with reversible phase transitions initiated by nanosecond laser pulses. It was shown that the change of the transmissivity and reflectivity of GeTe films in case of direct phase transition from the amorphous state to the crystalline starts at the same time, while the reverse transition is observed delay change of the transmissivity relative to the reflectivity. The value of this delay for the 100 nm GeTe thin film was estimated at t100 = 24 ns, and for the 50 nm sample – t50 = 13 ns. This time lag in changes of the transmissivity from the reflectivity in case of reamorphization films depending on sample thickness, can be explained by the high contrast of the concentration of free electrons between amorphous and crystalline states, which determine the reflectivity of the surface layer of the sample, while the transmissivity is determined by the total thickness. The experimental dependences of the kinetics of changes in the optical properties of GeTe samples under laser-induced phase transitions are in good consistent with the numerical simulation data of the Stefan problem.

Food pathogens (Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas aeruginosa) in planktonic form were subjected to bactericidal treatment by colloidal nanoparticles. NiOx colloidal nanoparticles, as anti-biotic nanomaterial, were produced by laser ablation in deionized water and air, and comprehensively characterized by x-ray diffraction, scanning electron microscopy, energy dispersive X-ray, Raman, Fourier transformed infrared (FT-IR) spectroscopy, dynamic light scattering size and zeta-potential measurements. Normalized Fourier transformed infrared (FT-IR) spectra of the nanoparticle-inactivated bacteria deposits exhibit for the larger, positively charged water-borne nanoparticles pronounced enhancement of IR-absorption in molecular fragments, comprising the bacterial membrane, which appears to be unfavorable for the inactivation of the food bacteria strains. In contrast, smaller and less charged air-borne nanoparticles exhibit less influence in IR-absorption, but pronounced TEM-envisioned penetration inside these pathogenic bacteria, resulting, according to the complementary microbiological tests, in their efficient inactivation. The study will help to understand the possible mechanisms responsible for the death of bacteria at their interacting with antibacterial nanoparticles.