[en] Trigonal fluoride LaF₃, widely known as a host crystal for Ln³⁺-lasants, was found to be an attractive many-phonon Raman material and a subject for the investigation of different χ⁽³⁾-nonlinear optical effects. We present the manifestation of photon-phonon interactions related to stimulated Raman scattering (SRS) and Raman-induced four-wave mixing (RFWM) processes, initiated by picosecond excitation at room temperature. Sesqui-octave-spanning Stokes and anti-Stokes frequency comb generation as well as many-step cascaded and cross-cascaded up-conversion χ⁽³⁾-nonlinear processes have been observed. The recorded spectral lines originated by SRS and RFWM are identified and attributed to the three observed SRS-promoting phonon modes. The lower limit of the steady-state Raman gain coefficient for near-IR first Stokes generation was estimated. Moreover, a brief review of known Ln³⁺ : LaF₃ laser crystals and SRS-active fluorides is given. (paper)

[en] Crystal growth, spectroscopic investigations and laser characterization of Er³⁺, Yb³⁺, and Ce³⁺ co-doped Ca₂Al₂SiO₇ (CAS) crystal were realized. The Er³⁺–Yb³⁺ energy transfer efficiency in CAS crystal was found to be around 75–78%. 275 mW of CW power at 1555 nm was demonstrated for the first time with a single crystal under diode pumping. The achieved differential slope efficiency was closed to 10%. Er³⁺, Yb³⁺, Ce³⁺: CAS appears as one of the most promising crystalline hosts for 1.5 µm laser emission, when compared to other crystals of the literature. (paper)

[en] The effects of CW laser radiation with a wavelength of λ = 532 nm on ethyl methacrylate copolymer films doped with the Ag(hfac)COD silver precursor were studied. Laser heating of the polymer composite (up to 150–170 °C), induced by the formation of highly absorbing silver nanoparticles (NPs), brings about an accelerated photo-thermochemical decomposition of the precursor, plastification of the polymer, local transition of the composite matrix to a colloidal state and intense thermocapillary convection in the dynamic active colloid formed. As a result, a directed transport of silver NPs from the center of the laser beam to its periphery takes place, leading to the formation of a ring structure with a very high concentration of silver NPs. (paper)

[en] A stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) laser with high signal-to-noise ratio (SNR) based on a compounded nonlinear polarization rotation effect (CNPRE) is proposed and demonstrated. In order to effectively reduce homogeneous broadening of EDF and then to the alleviate mode competition, two sandwich configurations formed by a polarization dependent isolator (PDI) or a segment of single-mode fiber sandwiched between two polarization controllers (PC), are introduced into the ring cavity to generate the CNPRE. A home-made asymmetry twin-core fiber (ATCF) is also incorporated in the ring cavity as a comb filter. With only 150 mW pump power, there are up to 45-wavelengths lasing with the approximate amplitude in a 3 dB bandwidth generated at room temperature. The wavelength spacing between the adjacent peaks is 0.29 nm and the highest SNRs reach 41.5 dB by optimizing the state of polarization of PCs. The power fluctuation and wavelength shift for each lasing wavelength are less than 0.05 dB and 0.02 nm, respectively. This indicates that the proposed multi-wavelength fiber laser can be stably operated at room temperature. (paper)

[en] Time-bin entangled single-photons are highly demanded for long distance quantum communication. We propose a heralded source of tunable narrowband single photons entangled in well-separated multiple temporal modes (time bins) with controllable amplitudes. The detection of a single Stokes photon generated in a cold atomic ensemble via Raman scattering of a weak write pulse heralds the preparation of one spin excitation stored within the atomic medium. A train of read laser pulses deterministically converts the atomic excitation into a single anti-Stokes photon delocalized in multi-time-bins. The waveforms of bins are well-controlled by the read pulse parameters. A scheme to measure the phase coherence across all time bins is suggested. (paper)

[en] We study quantum coherence of strongly interacting cold bosons in a double-well potential driven by a laser field. The system is initially in a Fock state and, either with or without a static tilting field, evolves into coherent states. The coherence is resonantly enhanced by photon-assisted tunneling. For the tilted wells, it reveals a two-branch pattern that corresponds to multiple photon absorption or emission. (paper)

[en] New experimental data on the secondary electron yield from a thin layer of ⁵⁷Fe irradiated by emission of the hot dense plasma source created by femtosecond laser pulses with intensity of 10¹⁷ W cm⁻² is presented. Plasma source hard x-ray and electron fluxes are measured for the source characterization. Thorough statistical analysis of the delayed secondary electron spectrum from the ⁵⁷Fe layer in the 20–100 ns temporal window allows exclusion of the ‘null’ hypothesis of the random character of the differences of this spectrum with that obtained using a ⁵⁶Fe target. Thus, statistically valid maxima at ∼5.8 and 7.4 keV can be attributed to the decay of the isomeric nuclear state of ⁵⁷Fe (3/2⁻, 14.41 keV, 98 ns) by the internal conversion process through the atomic K-shell (maximum at 7.4 keV), followed by the Auger process (maximum at 5.8 keV). (paper)

[en] Practical properties and physical characteristics of low intensity lasers have made possible their application to treat soft tissue diseases. Excitation of intracellular chromophores by red and infrared radiation at low energy fluences with increase of mitochondrial metabolism is the basis of the biostimulation effect but free radicals can be produced. DNA lesions induced by free radicals are repaired by the base excision repair pathway. In this work, we evaluate the expression of POLγ and APEX2 genes related to repair of mitochondrial and nuclear DNA, respectively. Skin and muscle tissue of Wistar rats were exposed to low intensity infrared laser at different fluences. One hour and 24 hours after laser exposure, tissue samples were withdrawn for total RNA extraction, cDNA synthesis, and evaluation of POLγ and APEX2 mRNA expression by real time quantitative polymerase chain reaction. Skin and muscle tissue of Wistar rats exposed to laser radiation show different expression of POLγ and APEX2 mRNA depending of the fluence and time after exposure. Our study suggests that a low intensity infrared laser affects expression of genes involved in repair of oxidative lesions in mitochondrial and nuclear DNA. (paper)

[en] With the assistance of weak or strong polarization-dependent loss (PDL) in the cavity, nonlinear polarization rotation mode-locking (NPRML) of an erbium-doped fiber laser (EDFL) is demonstrated to show transformation on the soliton from a single to multiple bunched state with nearly one order of magnitude variation on pulsewidth. With the bent intracavity fiber providing the weak PDL, the NPRML shortens the pulsewidth from only 5.3 ps to 4.9 ps and correspondingly broadens the spectral linewidth from 0.43 nm to 0.56 nm when enlarging the pump power from 100 mW to 325 mW. With the use of an inserted polarizer providing strong PDL in an EDFL, the fundamental soliton pulsewidth is significantly compressed to 390 fs, with the spectral linewidth as wide as 7.14 nm. In particular, the parameters of the soliton pulses are nearly unchanged at different pump powers; however, the soliton pulses split to form tightly bunched pulses circulating in the EDFL cavity. There are as many as 18 solitons tightly bunched together at the maximum pump power of up to 325 mW. Such a tightly bunched package can be elucidated by soliton energy quantization and long-range soliton interaction according to the perturbation theory in a passively mode-locked EDFL. (paper)

[en] The level of ultraviolet-B (UV-B) radiation on the Earth’s surface has increased due to depletion of the ozone layer. Here, we explored the effects of continuous wave He-Ne laser irradiation (632 nm, 5 mW mm^–2, 2 min d^–1) on the physiological indexes of wheat seedlings exposed to enhanced UV-B radiation (10 KJ m^–2 d^–1) at the early growth stages. Wheat seedlings were irradiated with enhanced UV-B, He-Ne laser treatment or a combination of the two. Enhanced UV-B radiation had deleterious effects on wheat photosynthesis parameters including photosystem II (chlorophyll content, Hill reaction, chlorophyll fluorescence parameters, electron transport rate (ETR), and yield), the thylakoid (optical absorption ability, cyclic photophosphorylation, Mg²⁺-ATPase, and Ca²⁺-ATPase) and some enzymes in the dark reaction (phosphoenolpyruvate carboxylase (PEPC), carbonic anhydrase (CA), malic dehydrogenase (MDH), and chlorophyllase). These parameters were improved in UV-B-exposed wheat treated with He-Ne laser irradiation; the parameters were near control levels and the enzyme activities increased, suggesting that He-Ne laser treatment partially alleviates the injury caused by enhanced UV-B irradiation. Furthermore, the use of He-Ne laser alone had a favourable effect on seedling photosynthesis compared with the control. Therefore, He-Ne laser irradiation can enhance the adaptation capacity of crops. (paper)