Laser-induced hydrogen plasma in the density and temperature range of $(0.1–5)\times {10}^{23}{\mathrm{m}}^{-3}$ and $(6000–20000)\mathrm{K}$, respectively, was precisely diagnosed using two-color Thomson scattering technique, inferring the electron number density, electron temperature as well as ion temperature. Simultaneously, spectra of the Balmer series of spectral lines from H-$\beta$ to H-$\zeta$ were measured and plasma emission coefficient calculated within the quasicontiguous frequency-fluctuation model. The theoretical spectra are found to be in good agreement with experimental ones, including higher-density data where discrete lines were observed to merge forming a continuum.

There is a significant disagreement between the experimental and theoretical plasma Stark shift of the hydrogenlike helium Paschen-$\alpha$ line ($\lambda =468.568\mathrm{nm}$). Here, it is demonstrated that the controversy can be resolved by accounting for the plasma polarization shift and other related effects arising from the charged plasma particles penetrating the wave-function extent of the bound electron. For experimental verification, a laser-induced helium plasma with $n_e=1.50\times {10}^{24}{\mathrm{m}}^{-3}$ and $T_e=68200\mathrm{K}$, as independently determined by using the Thomson scattering method, was studied. Excellent agreement is observed between the theoretical and experimental line width and line shift, and more generally, for the entire line shape.

This study explores nonlinear optical effects in diamond crystals doped with nitrogen-vacancy (NV) centers, focusing on the optical Kerr effect in the infrared spectral region. By employing the Z-scan technique with 230 fs laser pulses at a wavelength of 1032 nm, we investigate the nonlinear refractive index of high-purity and NV-containing diamond crystals at NV concentrations of 0.3 ppm and 4.5 ppm. The results demonstrate a pronounced anisotropy in the nonlinear refractive index, which exhibits a four-fold rotational symmetry, with its amplitude reduced by the NV concentration. The reduction in non-linear susceptibility is linked to the negative contribution of NV centers, modeled as two-level systems upon a strong, laser field, red-detuned relative to their resonance frequency. We believe these findings provide new insights into the interplay between NV centers and the nonlinear optical properties of diamond, offering potential pathways for tunable nonlinear optics applications.

Preparation of highly active core–shell/hybrid materials based on up-converting particles combined with semiconductors for photocatalytic application usually requires sophisticated and multi-step synthesis procedures. We propose a new design of a highly efficient NIR-driven photocatalytic system composed of spatially separated thin films of upconverting NaYF₄:Yb,Tm particles (UCPs), and TiO₂. Several samples of UCPs were prepared in the form of thin films and suspensions, directly coated with a titania layer or mixed with P25. Photocatalytic and photoelectrochemical studies have shown that thin film samples achieved significantly higher photocatalytic activity than their suspended counterparts. Moreover, the sample consisting of spatially separated layers of UCPs and P25 presented a significant photocatalytic activity and generated the highest photocurrent intensity. Separating the photocatalyst and upconverter layers allows for an interchangeable photocatalytic system active in a wide range of light.

We present results of experimental and theoretical studies of the Stark broadening of the Li i 460 nm spectral line with forbidden components and of the isolated 497 nm line. Plasma was induced by Nd:YAG laser radiation at 1064 nm with pulse duration ∼4.5 ns. Laser-induced plasma was generated in front of the alumina pellet, with some content of Li ₂ CO ₃ , placed in a vacuum chamber filled with argon under reduced pressure. Plasma diagnostics was performed using the laser Thomson scattering technique, free from assumptions about the plasma equilibrium state and its composition and so independently of plasma emission spectra. Spatially resolved spectra with Li lines were obtained from the measured, laterally integrated ones applying the inverse Abel transform. The Stark profiles were calculated by computer simulation method assuming a plasma in the local thermodynamic equilibrium. Calculations were performed for experimentally-inferred electron densities and temperatures, from 1.422 × 10 ²³ to 3.55 × 10 ²² m ⁻³ and from 1.96 eV to 1.04 eV, respectively. Our studies show very good agreement between experimental Stark profiles and those computer simulated.

We report on experimental and theoretical studies on the Stark profile of the He ii Paschen-$\alpha$ line over a wide range of plasma parameters. This line was emitted from a laser-induced plasma with electron densities in the range of $8.1\times {10}^{22}$–$4.46\times {10}^{24}{\mathrm{m}}^{-3}$ and electron temperatures of $1.2$–$7.6\mathrm{eV}$ as independently measured using the two-color Thomson scattering method. The line shapes were calculated using a computer simulation method, treating the ions and electrons on an equal footing and taking into account the full Coulomb interaction between the hydrogenlike atomic radiator and plasma perturbers penetrating the wave-function extent of the bound electron. We found a very good agreement between the experimental and theoretical Stark widths and shifts, which on average agree within $5\%$. In addition, practical analytical approximations for the linewidth and line shift are provided, validated against extensive calculations in the density and temperature ranges of ${10}^{23}$–${10}^{25}{\mathrm{m}}^{-3}$ and 1–$16\mathrm{eV}$, respectively.