Au-Hyperdoped Si Nanolayer: Laser Processing Techniques and Corresponding Material Properties.

The absorption of light in the near-infrared region of the electromagnetic spectrum by Au-hyperdoped Si has been observed. While silicon photodetectors in this range are currently being produced, their efficiency is low. Here, using the nanosecond and picosecond laser hyperdoping of thin amorphous Si films, their compositional (energy-dispersion X-ray spectroscopy), chemical (X-ray photoelectron spectroscopy), structural (Raman spectroscopy) and IR spectroscopic characterization, we comparatively demonstrated a few promising regimes of laser-based silicon hyperdoping with gold.

Laser-Induced Transferred Antibacterial Nanoparticles for Mixed-Species Bacteria Biofilm Inactivation.

In the present study, copper and silver nanoparticles with a concentration of 20 µg/cm were synthesized using the method of laser-induced forward transfer (LIFT). The antibacterial activity of the nanoparticles was tested against bacterial biofilms that are common in nature, formed by several types of microorganisms (mixed-species bacteria biofilms): , and The Cu nanoparticles showed complete inhibition of the bacteria biofilms used. In the course of the work, a high level of antibacterial activity was demonstrated by nanoparticles.

FT-IR Analysis of Bacteria Inactivation by Femtosecond IR Laser Radiation.

We report the successful inactivation of strain by femtosecond infrared (IR) laser radiation at the resonant wavelengths of 3.15 μm and 6.04 μm, chosen due to the presence of characteristic molecular vibrations in the main structural elements of the bacterial cells in these spectral ranges: vibrations of amide groups in proteins (1500-1700 cm), and C-H vibrations in membrane proteins and lipids (2800-3000 cm).

Nanoscale Vacancy-Mediated Aggregation, Dissociation, and Splitting of Nitrogen Centers in Natural Diamond Excited by Visible-Range Femtosecond Laser Pulses.

Natural IaA+B diamonds were exposed in their bulk by multiple 0.3 ps, 515 nm laser pulses focused by a 0.25 NA micro-objective, producing in the prefocal region (depth of 20-50 μm) a bulk array of photoluminescent nanostructured microtracks at variable laser exposures and pulse energies.

"Stealth Scripts": Ultrashort Pulse Laser Luminescent Microscale Encoding of Bulk Diamonds via Ultrafast Multi-Scale Atomistic Structural Transformations.

The ultrashort-laser photoexcitation and structural modification of buried atomistic optical impurity centers in crystalline diamonds are the key enabling processes in the fabrication of ultrasensitive robust spectroscopic probes of electrical, magnetic, stress, temperature fields, and single-photon nanophotonic devices, as well as in "stealth" luminescent nano/microscale encoding in natural diamonds for their commercial tracing. Despite recent remarkable advances in ultrashort-laser predetermined generation of primitive optical centers in diamonds even on the single-center level, the underlying multi-scale basic processes, rather similar to other semiconductors and dielectrics, are almost uncovered due to the multitude of the involved multi-scale ultrafast and spatially inhomogeneous optical, electronic, thermal, and structural elementary events. We enlighten non-linear wavelength-, polarization-, intensity-, pulsewidth-, and focusing-dependent photoexcitation and energy deposition mechanisms in diamonds, coupled to the propagation of ultrashort laser pulses and ultrafast off-focus energy transport by electron-hole plasma, transient plasma- and hot-phonon-induced stress generation and the resulting variety of diverse structural atomistic modifications in the diamond lattice.

Up/Down-Scaling Photoluminescent Micromarks Written in Diamond by Ultrashort Laser Pulses: Optical Photoluminescent and Structural Raman Imaging.

Elongated photoluminescent micromarks were inscribed inside a IaAB-type natural diamond in laser filamentation regime by multiple 515 nm, 0.3 ps laser pulses tightly focused by a 0.25 NA micro-objective.

Spectrally-selective mid-IR laser-induced inactivation of pathogenic bacteria.

Micrometer-thick layers of bacteria were prepared on fluorite substrates and scanned by focused mid-IR femtosecond laser radiation that was spectrally tuned to achieve the selective excitation of either the stretching C-H vibrations (3 μm), or stretching C = O, C-N vibrations (6 μm) of the amide groups in the bacteria. The enhanced biocidal efficiency of the latter selective excitation, compared to the more uniform 3-μm laser excitation, was demonstrated by performing viability assays of laser-treated bacterial layers. The bacterial inactivation by the 6-μm ultrashort laser pulses is attributed to dissociative denaturation of lipids and proteins in the cell membranes and intra-cell nucleic acids.