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Journal articles on the topic 'Laser excitation'

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Published: 4 June 2021
Last updated: 10 March 2023

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1

Mavroyannis, Constantine. "A laser-excited three-level atom." Canadian Journal of Physics 68, no. 3 (March 1, 1990): 321–33. http://dx.doi.org/10.1139/p90-051.

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We considered the excitation spectra for the excited states of a three-level atom, where the strong and the weak atomic transitions are driven by resonant and nonresonant laser fields, respectively. The spectral functions describing the excitation spectra for the electric dipole allowed excited state and for the metastable state of the atom have been derived when both laser fields are quantized as well as when they are treated as classical entities. In the low-intensity limit of the laser field operating in the strong transition, there are two short-lifetime excitations, the spontaneous one and the induced one, which appear at the same frequency, and a long-lifetime excitation induced by the weak laser field. These excitations compete with each other at resonance as well as at finite detunings of the weak laser field. In the high-intensity limit of the laser field operating in the strong transition, the competition is between the short- and the long-lifetime side bands, which are induced by the strong and the weak laser fields, respectively. The ratio of the maximum intensities of the peaks describing the long- and the short-lifetime excitations exhibits a resonance variation with the detuning of the weak laser field. Comparison between the results obtained when the laser fields are treated as quantized and as classical entities is made.
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2

WANG, Z. P., C. M. GU, and W. Z. SHEN. "PHOTOINDUCED LASER EFFECTS IN INDIUM NITRIDE FILM." Modern Physics Letters B 25, no. 03 (January 30, 2011): 185–92. http://dx.doi.org/10.1142/s021798491102550x.

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The optical nonlinear absorption properties in sputtering Indium nitride ( InN ) film were investigated under the excitations of nanosecond, picosecond and femtosecond pulsed lasers by open-aperture transmission Z-scan technique (TZ-scan). Under the condition of hν > Eg, the saturable absorption (SA) phenomena induced by one-photon transition were observed in both nanosecond and picosencond pulsed TZ-scan measurements. When 2hν > Eg > hν, the film presented SA due to the two-photon transition under the excitation of picosecond laser. However, at femtosecond 800 nm, the film showed the two-photon absorption (TPA) instead of SA, and the TPA coefficient tended to a saturable value as the excitation intensity increased. The results indicate that the InN film is a kind of good saturable absorber.
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3

Peng, Tingting, Rui Pu, Baoju Wang, Zhimin Zhu, Kai Liu, Fan Wang, Wei Wei, Haichun Liu, and Qiuqiang Zhan. "The Spectroscopic Properties and Microscopic Imaging of Thulium-Doped Upconversion Nanoparticles Excited at Different NIR-II Light." Biosensors 11, no. 5 (May 10, 2021): 148. http://dx.doi.org/10.3390/bios11050148.

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Lanthanide-doped upconversion nanoparticles (UCNPs) are promising bioimaging nanoprobes due to their excellent photostability. As one of the most commonly used lanthanide activators, Tm3+ ions have perfect ladder-type electron configuration and can be directly excited by bio-friendly near-infrared-II (NIR-II) wavelengths. Here, the emission characteristics of Tm3+-doped nanoparticles under laser excitations of different near-infrared-II wavelengths were systematically investigated. The 1064 nm, 1150 nm, and 1208 nm lasers are proposed to be three excitation strategies with different response spectra of Tm3+ ions. In particular, we found that 1150 nm laser excitation enables intense three-photon 475 nm emission, which is nearly 100 times stronger than that excited by 1064 nm excitation. We further optimized the luminescence brightness after investigating the luminescence quenching mechanism of bare NaYF4: Tm (1.75%) core. After growing an inert shell, a ten-fold increase of emission intensity was achieved. Combining the advantages of NIR-II wavelength and the higher-order nonlinear excitation, a promising facile excitation strategy was developed for the application of thulium-doped upconversion nanoparticles in nanoparticles imaging and cancer cell microscopic imaging.
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4

Khanum, Rizwana, Ching-Hang Chien, Yia-Chung Chang, and Rakesh S. Moirangthem. "Investigation of size-dependent spontaneous and stimulated visible WGM emissions via both ultraviolet and visible excitations for sensing applications." Journal of Applied Physics 132, no. 23 (December 21, 2022): 235304. http://dx.doi.org/10.1063/5.0123678.

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In this work, we investigated both spontaneous and stimulated whispering gallery mode (WGM) emissions of 2 mol. % Li+-doped ZnO (Li-ZnO) microspheres with different sizes under 325 and 488 nm wavelength laser excitations, respectively. It was found that all the microspheres exhibit stimulated emissions under a visible laser excitation source of 488 nm wavelength after the threshold pumping power. Thereafter, we studied the dependence of threshold pumping power on the size of microresonators to achieve stimulated emissions by individual microspheres. Furthermore, two microspheres (MS2 and MS3) are excited via a 325 nm UV laser, and surprisingly, the WGM peaks of higher intensity are observed in the visible rather than in the UV spectral region. We expected that most of the emissions are achieved via defect states transitions instead of inter-band transitions in the microresonators. It was found that WGMs in each microsphere exhibit a linear spectral shift of 3–5 nm with increasing pumping power of 488 nm excitation laser source. We believe that these proposed microspheres can be utilized effectively as WGM-based visible lasers and sensors.
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5

Dixit, A., J. S. Thakur, V. M. Naik, and R. Naik. "Influence of Excitation Frequency on Raman Modes of Thin Films." Advances in Condensed Matter Physics 2013 (2013): 1–4. http://dx.doi.org/10.1155/2013/191282.

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Low energy optical modes of MBE-grown thin films with different values of are investigated using Raman spectroscopy. We also studied the influence of Raman excitation frequency using red and green lasers on scattering intensity of various Raman modes. For those alloys whose bandgap energy is close to the red laser, a huge enhancement in the intensities of A1(LO) mode and its 2A1(LO) replica is observed when excited with red laser as compared to the green laser excitation. We found that the energies of longitudinal optical modes (A1(LO) and 2A1(LO)) vary nonlinearly unlike the E2mode with increasing Ga atomic fraction. A Raman mode~540 cm−1was observed in all films with low energy red laser excitation but was absent with green laser excitation. We attribute this mode to A1(TO) mode of the underneath GaN buffer layer.
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6

Prasad, Vinod, Rinku Sharma, and Man Mohan. "Laser Assisted Electron - Alkali Atom Collisions." Australian Journal of Physics 49, no. 6 (1996): 1109. http://dx.doi.org/10.1071/ph961109.

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Lasar assisted inelastic scattering of electrons by alkali atoms is studied theoretically. The non-perturbative quasi-energy method, which is generalised for many atomic states, is used to describe the laser–atom interaction, and the electron–atom interaction is treated within the first Born approximation. We have calculated the total cross section for the excitation of sodium atoms due to simultaneous electron–photon collisions. We show the effect of laser and collision parameters, e.g. laser intensity, polarisation and incident electron energy, on the excitation process.
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7

Litfin, G., G. Heise, and H. Welling. "UV-laser excitation of color center lasers." Optics Communications 59, no. 2 (August 1986): 137–41. http://dx.doi.org/10.1016/0030-4018(86)90465-7.

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8

Stevenson, Christopher L., and Tuan Vo-Dinh. "Laser-Excited Synchronous Luminescence Spectroscopy." Applied Spectroscopy 47, no. 4 (April 1993): 430–35. http://dx.doi.org/10.1366/0003702934334967.

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The use of lasers as excitation sources for molecular luminescence often results in improvements in sensitivity and limits of detection (LODs). Synchronous luminescence (SL) spectroscopy, in which both excitation and emission wavelengths are scanned simultaneously, provides a convenient means to improve selectivity (often dramatically) in the analysis of multicomponent mixtures using room-temperature luminescence. We report here on the first use of a dye laser as an excitation source for SL at room temperature. The performance of the laser synchronous luminescence (LSL) system is described for the analysis of four polyaromatic compounds; for one of these—tetracene—the LOD was 680 zeptomoles (10−21 mol) in the volume probed by the laser. In addition to impressive sensitivity and selectivity, the laser system used is quite small and can be considered as an attractive source for portable SL instruments designed for in-field screening of environmental samples.
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9

Goller, B., and M. Kubbies. "UV lasers for flow cytometric analysis: HeCd versus argon laser excitation." Journal of Histochemistry & Cytochemistry 40, no. 4 (April 1992): 451–56. http://dx.doi.org/10.1177/40.4.1372632.

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Applying flow cytometric single cell analysis, we compared the performance of UV excitation from argon ion and HeCd lasers using various UV-excitable fluorochromes of cell kinetic and cell physiological relevance. The AT-specific DNA fluorochromes DAPI, Hoechst 33258, and Hoechst 33342 showed no significant differences of G1-phase resolution and cell cycle distribution. With the HeCd laser, high-resolution cell kinetic analysis applying the novel BrdU/Hoechst-PI quenching technique showed superior resolution and an almost normalized G2M/G1 channel ratio of the first cell cycle. Indo-1 analysis for detection of intracellular free calcium gave similar results for both excitation sources, although the indo-1 ratio of activated cells was lower for HeCd excitation. Monochlorobimane as an indicator fluorochrome of glutathione content could not be excited sufficiently with the 325-nm line of the HeCd laser and exhibited poor resolution between positive and negative cells. However, the second glutathione-specific fluorochrome o-phtalaldehyde gave even better results with the HeCd laser. Our data indicate that air-cooled HeCd lasers are cheap and reliable UV-excitation sources for most UV-excitable fluorochromes, and might be an alternative to the expensive water-cooled argon and krypton laser.
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10

Masters, AT, RT Sang, WR MacGillivray, and MC Standage. "New Data from Laser Interrogation of Electron-Atom Collisions Experiments." Australian Journal of Physics 49, no. 2 (1996): 499. http://dx.doi.org/10.1071/ph960499.

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Recent data from two methods in which high resolution laser radiation is used to assist in determining electron-atom collision parameters are presented. The electron superelastic method has yielded the first measurement of Stokes parameters for electron de-excitation of the 32D5/2–32P3/2,1/2 transition of atomic Na, the upper level having been optically prepared by resonant, stepwise excitation from the 32S1/2 ground level via the 32P3/2 level using two single mode lasers. As well, we report on the development of a model to determine the optical pumping parameters for superelastic scattering from the 32P3/2 level when it is prepared by two lasers exciting from the F = 1 and F = 2 states respectively of the 32S1/ 2 ground level. Data are also presented for collision parameters for the excitation of the 61So–61 PI transition of the I = 0 isotope of Hg by electrons of 50 eV incident energy. The technique employed for these measurements is the stepwise electron–laser excitation coincidence method, in which the electron excited atom is further excited by resonant laser radiation, and fluorescence photons emitted by relaxation from the laser excited state are detected in coincidence with the scattered electron.
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11

Zon, B. A., and A. S. Kornev. "Laser-induced nuclear excitation." Journal of Experimental and Theoretical Physics 110, no. 5 (May 2010): 731–36. http://dx.doi.org/10.1134/s1063776110050018.

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12

Lam, Kai-Shue. "Coherent laser excitation ofBa137andBa138." Physical Review A 45, no. 5 (March 1, 1992): 3084–92. http://dx.doi.org/10.1103/physreva.45.3084.

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13

Shang, Zhenzhen, Zhi Wang, and Guang Dai. "Stability-Enhanced Emission Based on Biophotonic Crystals in Liquid Crystal Random Lasers." Materials 16, no. 1 (December 26, 2022): 200. http://dx.doi.org/10.3390/ma16010200.

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A new design of a bio-random laser based on a butterfly wing structure and ITO glass is proposed in this article. Firstly, the butterfly wing structure was integrated in a liquid crystal cell made of ITO glass. The integrated liquid crystal cell was injected with liquid crystal and dye to obtain a bio-random laser. A non-biological random laser was obtained with a capillary glass tube, liquid crystal and dye. The excitation spectra and thresholds were recorded to evaluate the performance of the biological and non-biological random lasers. The results show that the excitation performance stability of the bio-random laser is improved and the number of spikes in the spectra is reduced compared with the non-biological random laser. Finally, the equivalent cavity length of the biological and non-biological random lasers was compared and the optical field distribution inside the butterfly wing structure was analyzed. The data show that the improvement of the excitation performance stability of the bio-random laser is related to the localization of the optical field induced by the photonic crystal structure in the butterfly wing.
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14

Sato, Hidetoshi, Satoshi Wada, and Hideo Tashiro. "Fluorescence Backgroundless Ti: Sapphire Laser Using Acousto-Optical Tunable Filter for Raman Spectroscopic Measurements." Applied Spectroscopy 56, no. 10 (October 2002): 1303–7. http://dx.doi.org/10.1366/000370202760355019.

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The background noise inherent to tunable lasers, which emit broad band spontaneous fluorescence from the laser-active medium, is detrimental for sensitive Raman measurement. Using the diffraction effect in an acousto-optic device, we have developed a fluorescence backgroundless Ti: sapphire laser suited for near-infrared Raman spectroscopy. A Raman excitation profile consisting of series of Raman spectra of deoxygenated hemoglobin aqueous solutions was measured by changing excitation wavelengths, revealing the high potential of this laser as a spectroscopic light source.
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15

Bhuyan, C. Abinash, Kishore K. Madapu, and Sandip Dhara. "Excitation-dependent photoluminescence intensity of monolayer MoS2: Role of heat-dissipating area and phonon-assisted exciton scattering." Journal of Applied Physics 132, no. 20 (November 28, 2022): 204303. http://dx.doi.org/10.1063/5.0107470.

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We studied the excitation-dependent photoluminescence (PL) quantum yield (QY) of monolayer MoS2 (1L-MoS2) with various flake areas grown on SiO2/Si substrates. The PL measurements were carried out by 532, 488, and 325 nm excitations which fulfill the conditions of quasi-resonant excitation of A-exciton, above bandgap, and far above the bandgap excitations, respectively. The PL QY was found to be reduced by decreasing the excitation wavelength, and it is attributed to variation in the thermal energy dissipated to the lattice. PL emission from 1L-MoS2 was observed with 325 nm excitation in large-area flakes (≥532 μm2) because of efficient heat dissipation. In the literature, PL emission of 1L-MoS2 is hardly reported with 325 nm laser excitations. Under 325 nm laser irradiation, 50% of excitation energy is converted to heat, which substantially increases the local temperature. From the temperature-dependent Raman analysis, the rise in the local temperature is approximated to be ∼382 K in the case of a small-area flake, whereas such an effect is alleviated in large-area flakes. Moreover, inter-valley exciton scattering dominates as the excitation wavelength decreases because of a substantial rise in the phonon population for small-area flakes. As a consequence of inter-valley exciton scattering, dark excitons (K-Σ) dominate over the bright excitons (K-K) under the 325 nm excitation. Hence, total suppression of PL emission was observed for small-area flakes because of dark exciton recombination. The noticeable PL emission of large-area flakes is attributed to the improved bright exciton recombination.
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16

Fisher, W. G., E. A. Wachter, Michael Armas, and Colin Seaton. "Titanium: Sapphire Laser as an Excitation Source in Two-Photon Spectroscopy." Applied Spectroscopy 51, no. 2 (February 1997): 218–26. http://dx.doi.org/10.1366/0003702971939910.

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The passively mode-locked titanium: sapphire laser provides new opportunities for acquiring two-photon spectral data in the near-infrared, a region not commonly accessible to synchronously pumped dye lasers. This source generates pulses with peak powers near 100 kW at average powers over 1 W and is capable of yielding two-photon signals roughly two orders of magnitude larger than is possible with synchronously pumped dye lasers. However, the multimode output of this laser exhibits significant temporal and spectral pulse profile variations as the laser wavelength is tuned. As a consequence, peak powers of the titanium:sapphire laser can vary independently from average power across the tuning range. This wavelength dependence, coupled with the quadratic dependence of the two-photon signal upon the instantaneous power of the laser, precludes simple average power correction of nonlinear spectral band shapes. Here, we investigate the key properties of the titanium:sapphire laser as an excitation source for two-photon spectroscopy. We also identify a chemical reference suitable for obtaining source-corrected excitation spectra in the near-infrared using a double-beam, ratiometric approach; this is based on a source-in-dependent two-photon excitation spectrum for the laser dye coumarin-480 that has been obtained with a single-frequency titanium:sapphire laser. From these data, correction factors are generated for correction of multimode source data.
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17

SELG, M., M. KINK, R. KINK, J. MAKSIMOV, and I. MARTINSON. "TEMPERATURE DEPENDENCE OF LASER-INDUCED HOT LUMINESCENCE OF SELF-TRAPPED EXCITONS IN SOLID XENON." Surface Review and Letters 09, no. 01 (February 2002): 609–13. http://dx.doi.org/10.1142/s0218625x02002713.

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Hot luminescence of self-trapped excitons in solid xenon has been investigated in a wide temperature range (from LHeT to 100 K), using X-ray and two-photon excimer laser (ArF and KrF) excitation. Hot luminescence of bulk Xe crystals of volume 2 cm 3 appears to be very sensitive to both the temperature and the quality of the samples, while its highest intensity has been registered under KrF laser excitation. The experimental results are in good accordance with a recent nonperturbative quantum relaxation theory of strong local vibrational excitations.
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18

Renner, O., L. Juha, J. Krasa, E. Krousky, M. Pfeifer, A. Velyhan, C. Granja, et al. "Low-energy nuclear transitions in subrelativistic laser-generated plasmas." Laser and Particle Beams 26, no. 2 (June 2008): 249–57. http://dx.doi.org/10.1017/s0263034608000293.

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AbstractThe aim of the reported research is to contribute to investigation of new processes and methods interlinking nuclear and laser-plasma physics. With respect to requirements of nuclear experiments at medium-size high-power lasers, the selection of proper candidates for studying the excitation and decay of low-lying nuclear states is reviewed. An experimental approach to the identification of low-energy nuclear transitions is discussed, simple estimates of the 181Ta excitation yield in the laser-generated plasma provide a theoretical basis for planning future work. First tests and results of the experiments at the laser facility PALS are presented.
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19

Jani, Mahendra G., Roger J. Reeves, Richard C. Powell, Gregory J. Quarles, and Leon Esterowitz. "Alexandrite-laser excitation of a Tm:Ho:Y_3Al_5O_12 laser." Journal of the Optical Society of America B 8, no. 4 (April 1, 1991): 741. http://dx.doi.org/10.1364/josab.8.000741.

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20

Chen, Defu, Ying Wang, Buhong Li, Huiyun Lin, Xuechun Lin, and Ying Gu. "Effects of pulse width and repetition rate of pulsed laser on kinetics and production of singlet oxygen luminescence." Journal of Innovative Optical Health Sciences 09, no. 06 (August 2016): 1650019. http://dx.doi.org/10.1142/s179354581650019x.

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Pulsed and continuous-wave (CW) lasers have been widely used as the light sources for photodynamic therapy (PDT) treatment. Singlet oxygen (1O2) is known to be a major cytotoxic agent in type-II PDT and can be directly detected by its near-infrared luminescence at 1270[Formula: see text]nm. As compared to CW laser excitation, the effects of pulse width and repetition rate of pulsed laser on the kinetics and production of 1O2 luminescence were quantitatively studied during photosensitization of Rose Bengal. Significant difference in kinetics of 1O2 luminescence was found under the excitation with various pulse widths of nanosecond, microsecond and CW irradiation with power of 20[Formula: see text]mW. The peak intensity and duration of 1O2 production varied with the pulse widths for pulsed laser excitation, while the 1O2 was generated continuously and its production reached a steady state with CW excitation. However, no significant difference ([Formula: see text]) in integral 1O2 production was observed. The results suggest that the PDT efficacy using pulsed laser may be identical to the CW laser with the same wavelength and the same average fluence rate below a threshold in solution.
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21

Mavroyannis, Constantine. "A laser-excited three-level atom. II numerical results." Canadian Journal of Physics 68, no. 4-5 (April 1, 1990): 411–21. http://dx.doi.org/10.1139/p90-065.

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Numerical calculations are presented for the interference spectra of a laser-excited three-level atom, where the strong and the weak atomic transitions are driven by resonant and nonresonant laser fields, respectively. The spectral functions describing the interference spectra for the electric dipole allowed excited state have been considered in the low- and high-intensity limit of the laser field operating in the strong transition. The interference spectra arise from the competition between short-lifetime spontaneous processes and short- and long-lifetime excitations induced by the strong and the weak laser fields, respectively. Both laser fields have been treated as quantized and as classical entities. The computed spectra have been presented graphically for different values of the Rabi frequencies and detunings of the weak laser field. It is shown that the decrease in the intensity of the short-lifetime excitation may provide a measure of the spectral width of the long-lifetime excitation.
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22

Gvishi, R., G. S. He, P. N. Prasad, U. Narang, M. Li, F. V. Bright, B. A. Reinhardt, J. C. Bhatt, and A. G. Dillard. "Spectroscopic Studies of New Blue Laser Dyes in Tetrahydrofuran Solution and in Composite Glass." Applied Spectroscopy 49, no. 6 (June 1995): 834–39. http://dx.doi.org/10.1366/0003702953964552.

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We have investigated the linear absorption, emission wavelength-dependent excitation, fluorescence polarization excitation, and lasing properties of new UV-blue dyes. The dyes are didecyl para-polyphenyl heptamer (DDPPH), didecyloxy para-polyphenyl heptamer (DDOPPH), and bisbenzothiazole 3,4- didecyloxy thiophene (BBTDOT). We studied the effect of dye concentration on absorption and emission and the origin of the peaks in tetrahydrofuran solution and in a composite glass. We show that, in a composite glass, it is possible to impregnate the dye with density of several orders without aggregation effects. The two heptamer dyes were found to be very photostable. All three dyes are promising candidates as laser dyes in the UV. Under excitation with a frequency-doubled dye laser (300 nm), the DDPPH lased at 377 nm. The DDOPPH lased at 425 nm and the BBTDOT lased at ∼450 nm when excited by the third harmonic of a Nd:YAG laser (355 nm). The output from the second heptamer in tetrahydrofuran was photostable (less than 10% decrease) for more than 900,000 pulses and with a slope efficiency of approximately 20%.
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23

Belov, M. L., Yu V. Fedotov, D. A. Kravtsov, and V. A. Gorodnichev. "Eye-Safe Wavelength Laser Fluorimeter for Noncontact Monitoring the Ecological Condition of Objects in Natural Environment." Mechanical Engineering and Computer Science, no. 5 (June 21, 2018): 30–42. http://dx.doi.org/10.24108/0518.0001398.

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Presently, a problem of ecological monitoring of natural environment is critical.Laser methods are the most powerful to provide noncontact and remote ecological monitoring of natural environment. Among laser monitoring methods, laser fluorescent ones are of strong interest.Today, there are laser fluorescent devices designed to monitor ecological condition of various objects in natural environment. To produce laser-induced fluorescence excitation, laser fluorescent devices use a variety of radiation sources in the spectral band from 226 to 635 nm.However, to have an advanced laser fluorescent device for noncontact ecological monitoring of natural environment, devices to be created should be multifunctional and use an eye-safe wavelength for fluorescence excitation.A fluorescence excitation wavelength of 355 nm (the third harmonic of a YAG: Nd laser) appears to be promising. This wavelength is eye-safe and can be used to monitor ecological condition of a large number of nature-made objects.The paper conducts a capability analysis of noncontact laser fluorescent monitoring of ecological condition of natural environment using the eye-safe fluorescence excitation wavelength of 355 nm. Describes a laser fluorimeter mock-up and presents experimental results of laser-induced fluorescence spectra of nature-made objects.The experimental studies have shown that the noncontact laser fluorimeter using the eye-safe fluorescence excitation wavelength of 355nm potentially allows us to control the ecological condition of a large number of nature-made objects.The fluorescence intensities in the certain spectral ranges (for example, within the spectral range of ~ 425 – 450 nm) and a spectrum profile of plant fluorescence (in the spectral range of 670 - 750 nm) can be used as the controlled variables.
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24

Kopyshinsky, A. V. "Laser-induced incandescence of silicon surface under 1064-nm excitation." Semiconductor Physics Quantum Electronics and Optoelectronics 15, no. 4 (December 12, 2012): 376–81. http://dx.doi.org/10.15407/spqeo15.04.376.

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25

Anderson, April, Quentin Low, Bradley Bone, Wenjun Zhou, Bradley Dubbels, Jolene Bradford, and Kyle Gee. "New fluorophore for multiplexing with violet laser excitation (P3289)." Journal of Immunology 190, no. 1_Supplement (May 1, 2013): 211.2. http://dx.doi.org/10.4049/jimmunol.190.supp.211.2.

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Abstract Flow cytometry instruments with solid state violet laser diodes are becoming more common due to their small size, low power requirements, cost, and reliability. The use of violet-excited fluorochromes in multiparametric flow cytometry has been essential in the expansion of multicolor flow cytometry, enabling greater numbers of markers to be detected in one sample. We have developed a novel violet-excited dye, Pacific Green™ dye, which has an excitation/emission maximum of 411 and 500 nm, respectively. This development addresses the need to transfer well-resolved markers off the Blue 488 nm and Red 635 nm excitation lines and onto the Violet 405 nm excitation line, thus enabling the detection of other markers with the 488 nm and 635 nm lasers. Pacific Green™ dye can be used for three color immunophenotyping using violet laser excitation with Pacific Blue™ and Pacific Orange ™ dyes with minimal compensation without 488 nm excitation. Data is shown for human lymphocytes and mouse splenocytes stained with Pacific Green™ direct conjugates. Six color immunophenotyping data is shown using direct conjugates of Pacific Green™, Alexa Fluor® 488, phycoerythrin, PE-Cy®7, Pacific Blue™ and Pacific Orange™ conjugates. Pacific Green™ dye can be used with the far red emitting QDot®605, 655, and 705 conjugates for higher multiplexing with violet laser excitation. Pacific Green™ dye can be paired with fixable blue or yellow-emitting viability stain with violet excitation to exclude dead cells.
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26

Fedorov, Anatolii. "Lasers developed in the Institute of Atmospheric Optics of the SB RAS (a review)." ADVANCES IN APPLIED PHYSICS 9, no. 5 (November 20, 2021): 417–29. http://dx.doi.org/10.51368/2307-4469-2021-9-5-417-429.

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The results of research on the development of the first electric discharge lasers on active media N2, CO2, Cu, CuBr and excimer molecules at the Institute of Atmospheric Optics named after V. E. Zueva SB RAS are given. It created one of the world's first Cu-lasers with a pulse production of copper vapors due to the explosion of conductors and a transverse excitation discharge. For a copper laser, record specific generation parameters were obtained almost equal to the limit: radiation energy 2.4 J/l, peak power 120 MW/l with an efficiency of 0.16 %. For the CuBr laser operating in frequency mode, for the first time, an average radiation power of more than 100 W was obtained. In the dual pulse excitation mode, conditions were found that limit the growth of the efficiency of the CuBr laser. For him, a record efficiency of 2.7 % was obtained. For the first time, a nitrogen laser was developed with a maximum efficiency of 0.27 % with an energy of 0.8 mJ, a peak power of 160 kW. For the first time, a miniature XeCl laser with a longitudinal excitation discharge was developed, which worked both with and without buffer gases He, Ne and Ar.
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27

PANCHENKO, A. N., V. M. ORLOVSKII, and V. F. TARASENKO. "Efficient e-beam and discharge initiated nonchain HF(DF) lasers." Laser and Particle Beams 21, no. 2 (April 2003): 223–32. http://dx.doi.org/10.1017/s0263034603212106.

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The spectral and amplitude-temporal parameters of HF (DF) lasers pumped by nonchain chemical reactions initiated by radially convergent or planar e-beams and self-sustained discharge were studied. Intrinsic efficiency of the HF lasers up to ∼10% was obtained for both excitation methods. It was shown that the high efficiency of an e-beam-initiated HF laser may be attained as a result of the simultaneous formation of atomic and molecular fluorine and of the participation of F2 in population inversion. A laser pulse has a complex profile caused by the successive generation of P-lines and the overlap during the radiation pulse of both the rotational lines of the same vibration band and of individual vibration bands. Experimental conditions providing high intrinsic efficiency of a discharge nonchain HF (DF) laser are determined. Intrinsic efficiency of HF and DF lasers up to ηin ∼ 10% and 7%, respectively, is obtained using excitation by inductive and LC generators in the SF6-H2 (D2) mixtures. High discharge uniformity obtained with the use of special shaped electrodes along with uniform UV preionization is a key parameter for improving the intrinsic efficiency of discharge HF (DF) lasers. It was found that in this excitation condition, output spectra of the HF laser significantly widen and cascade laser action on some rotational lines of the vibrational transitions of HF molecules ν(3–2) → ν(2–1) → ν(1–0) is observed. This can explain the high intrinsic efficiency obtained. Specific output of the discharge HF laser over 8 J/L (140 J/L×atm) and total laser efficiency ηt ∼ 4.5% were achieved. For the discharge DF laser, specific output and total efficiency were as high as 6.5 J/L and 3.2%, respectively.
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28

Itoh, Noriaki, Chihiro Itoh, and Jun'ichi Kanasaki. "Comparison of Electronic-Excitation-Induced Structural Modification of Carbon-Based Nanomaterials with that of Semiconductor Surfaces." Nano 11, no. 06 (June 2016): 1630001. http://dx.doi.org/10.1142/s1793292016300012.

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Modification by electronic excitation of semiconductor surfaces and carbon-related quasi-two-dimensional (2D) nanostructured materials, namely graphene, carbon nanotubes is reviewed. Defect creation in these materials takes place not by low-intensity photoirradiation, but by laser or electron irradiation. The defect creation processes are different from ordinary photochemical processes in molecules or in some solids like alkali halides, which can be modified by a localized exciton. It is pointed out that there are common features in defect creation by electronic excitation in semiconductor surfaces and carbon-related quasi-2D nanomaterials: the yield-intensity relation shows strong superlinearity for laser irradiation near the bandgap energies and linearity or weak superlinearity for higher energy electron or photon irradiation. These results are explained in terms of multi-hole localization, in which bonds are weakened more strongly and more energy is available upon recombination with trapped electrons in comparison with excitons. The multi-hole localized state is considered to be realized by the creation of dense excitons or by cascade excitation for laser irradiation and by multiple excitations or multiple exciton generation by single impacts for electron irradiation. The review includes also polymerization of C[Formula: see text] films by electronic excitation, which is induced by low-intensity photoirradiation as well as by laser or electron irradiation. The experimental observation that laser or electron irradiation polymerize C[Formula: see text] films differently from low-intensity photoirradiation is explained in terms of multi-hole localization similar to the defect formation mechanism. Although fragmentation of C[Formula: see text] is due to electronic excitation of the molecule, it is included in the review because its yield is strongly superlinear for laser irradiation near bandgap energies and weakly superlinear for high-energy electron or photon irradiation as for other cases.
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Архипов, Р. М., М. В. Архипов, В. С. Егоров, И. А. Чехонин, М. А. Чехонин, and С. Н. Багаев. "Излучение резонансной среды, возбуждаемое лазерным излучением с периодической фазовой модуляцией в режиме сильной связи поля и вещества." Журнал технической физики 127, no. 12 (2019): 967. http://dx.doi.org/10.21883/os.2019.12.48694.180-19.

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In this paper, the radiation of a two-level resonant medium placed in a cavity and excited by a laser pulse with periodic phase modulation is studied theoretically. The analysis is carried out on the basis of an analytical and numerical solution of the system of Maxwell-Bloch equations under conditions when the regime of strong coupling of the field and matter is realized. Under these conditions, this system is similar to a polariton laser. A high excitation efficiency of a polariton laser by a phase-modulated radiation pulse compared with a pulse without phase modulation of the carrier frequency is shown. It is shown that the main reason for the effective excitation of polariton modes of the medium is the occurrence of a difference combination parametric resonance. The results obtained open up new possibilities in the excitation of radiation from polariton lasers by low-power pumping laser radiation with frequency modulation.
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30

TADA, TAKUJI, TSUYOSHI ASAHI, MASAAKI TSUCHIMORI, OSAMU WATANABE, and HIROSHI MASUHARA. "EXCITATION WAVELENGTH DEPENDENCE OF LASER ABLATION MECHANISM OF URETHANE–UREA COPOLYMER FILM STUDIED BY NANOSECOND TIME-RESOLVED INTERFEROMETRY." Journal of Nonlinear Optical Physics & Materials 13, no. 03n04 (December 2004): 373–81. http://dx.doi.org/10.1142/s0218863504002316.

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Etching dynamics of urethane–urea copolymer film was investigated by utilizing nanosecond time-resolved interferometry and tuning excitation wavelength. From the behavior of fringe pattern deformation at the irradiated areas, it is considered that irradiated polymer film was decomposed more effectively with decrease in excitation wavelength. Excitation wavelength dependence of etching dynamics of urethane–urea copolymer film was not well interpreted in terms of total energy density which was stored within the polymer film due to laser irradiation, while photochemical and photothermal processes can explain mostly the results of shorter wavelength (≤ 475 nm) and longer wavelength (≥ 530 nm) excitations, respectively.
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31

Fedenev, A. V., and V. F. Tarasenko. "Simulation of NPL in experiments with e-beam pumping." Laser and Particle Beams 16, no. 2 (June 1998): 327–80. http://dx.doi.org/10.1017/s0263034600011642.

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The main goals of this review article are to show, on the basis of the results accumulated in this field, achievements in simulating the processes in nuclear pumped laser (NPL) active media by experiments on e-beam pumping, and to give a number of characteristic experimental examples, when this simulation has improved understanding of the inversion population processes in NPL active media (Cd+, Xe-lasers) or generated interest in experiments with fission fragments excitation (Ne-laser). In the case of the population of laser operation levels in non-equilibrium recombinating plasma, one can say with sufficient accuracy that the inversion population mechanism is identical for both excitation types.
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32

CHAUHAN, P. K., S. T. MAHMOUD, R. P. SHARMA, and H. D. PANDEY. "Effect of laser ripple on the beat wave excitation and particle acceleration." Journal of Plasma Physics 73, no. 1 (February 2007): 117–30. http://dx.doi.org/10.1017/s002237780600465x.

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Abstract.This paper presents the effect of ripple on the plasma wave excitation process and acceleration of electrons in a laser produced plasma. The plasma wave is generated by the beating of two coaxial lasers of frequencies ω1 and ω2, such that ω1-ω2≅ωp. One of the main laser beams also has intensity spikes. The nonlinearity due to the relativistic mass variation depends not only on the intensity of one laser beam but also on the second laser beam. Therefore the behavior of the first laser beam affects the second laser beam, hence cross-focusing takes place. Owing to the interaction of ripple and the main laser beams, the ripple grows inside the plasma. The behavior of the ripple in the plasma affects the excitation of the electron plasma wave as well as the electron acceleration. The amplitude of the electron plasma wave and the electron energy are calculated, in the presence of ripple.
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33

Bentsman, J., and H. Hvostov. "Vibrational Control of a Laser Illuminated Thermochemical System." Journal of Dynamic Systems, Measurement, and Control 110, no. 2 (June 1, 1988): 109–13. http://dx.doi.org/10.1115/1.3152659.

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Vibrational control is a nonclassical open-loop control principle which proposes a utilization of zero mean parametric excitation of a dynamical system for achieving control objectives. In the present paper, excitations introduced into the incident power of a laser beam in a laser illuminated thermochemical reaction are shown to be capable of inducing asymptotically stable operating regimes with averages located at initially unstable steady states. This opens a possibility of alleviating measurement and actuator related difficulties associated with conventional methods in a stabilization of laser-driven systems.
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34

Georges, Joseph. "Continuous-Wave-Laser versus Pulsed-Laser Excitation for Crossed-Beam Photothermal Detection in Small Volume Applications: Comparative Features." Applied Spectroscopy 59, no. 9 (September 2005): 1103–8. http://dx.doi.org/10.1366/0003702055012645.

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Crossed-beam thermal lens spectrometry can be implemented using continuous-wave- (cw) laser or pulsed-laser excitation. In both cases, the signal depends on the position of the sample with respect to the probe beam waist, the size of the excitation beam, the beam-size ratio into the sample, and the power or energy of the excitation beam. However, due to differences in the rate of formation and relaxation of the thermal lens, both methods exhibit distinct key features. Optimization of the experimental setup and understanding the thermal lens signal are more complicated under cw-laser excitation than with pulsed-laser excitation. Unlike that observed under pulsed excitation, the effect of the excitation beam waist, of the sample size, and of the flow rate are closely related to the effective size of the thermal element and depend on the chopping frequency. Although the intrinsic sensitivities are almost the same, the performance can significantly differ depending on the chopping frequency or pulse repetition rate, which should be high enough to allow fast data collection and efficient signal averaging.
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35

NAKAMURA, Osamu. "Multiphoton-Excitation Scanning Laser Microscopy." Review of Laser Engineering 27, no. 12 (1999): 812–16. http://dx.doi.org/10.2184/lsj.27.812.

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36

Yokoyama, K., P. Murahari, P. Heathcote, L. Nuccio, J. S. Lord, N. A. Morley, and A. J. Drew. "Future directions ofμSR—laser excitation." Physica Scripta 88, no. 6 (December 1, 2013): 068511. http://dx.doi.org/10.1088/0031-8949/88/06/068511.

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37

Taylor, R. S., and K. E. Leopold. "Magnetically induced pulser laser excitation." Applied Physics Letters 46, no. 4 (February 15, 1985): 335–37. http://dx.doi.org/10.1063/1.95623.

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38

Vander Wal, Randall L., and Kirk A. Jensen. "Laser-induced incandescence: excitation intensity." Applied Optics 37, no. 9 (March 20, 1998): 1607. http://dx.doi.org/10.1364/ao.37.001607.

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39

Hallin, Reinhold, Arne Arnesen, Carl Nordling, Olle Vogel, and Anders Wännström. "Laser excitation of ion beams." Vacuum 36, no. 11-12 (November 1986): 939–44. http://dx.doi.org/10.1016/0042-207x(86)90145-4.

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40

Huang, Shihua, Wenlian Li, and Xi Luo. "Laser selective excitation of CaS:Pr." Journal of Luminescence 40-41 (February 1988): 383–84. http://dx.doi.org/10.1016/0022-2313(88)90244-x.

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41

Minamikawa, Takeo, Yoshinori Murakami, Naokazu Matsumura, Hirohiko Niioka, Shuichiro Fukushima, Tsutomu Araki, and Mamoru Hashimoto. "Photo-Induced Cell Damage Analysis for Single- and Multifocus Coherent Anti-Stokes Raman Scattering Microscopy." Journal of Spectroscopy 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/5725340.

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In this study, we investigated photo-induced damage to living cells during single- and multifocus excitations for coherent anti-Stokes Raman scattering (CARS) imaging. A near-infrared pulsed laser (709 nm) was used to induce cell damage. We compared the photo-induced cell damage in the single- and the multifocus excitation schemes with the condition to obtain the same CARS signal in the same frame rate. For the evaluation of cell viability, we employed 4′,6-diamidino-2-phenylindole (DAPI) fluorophores that predominantly stained the damaged cells. One- and two-photon fluorescence of DAPI fluorophores were, respectively, excited by an ultraviolet light source and the same near-infrared light source and were monitored to evaluate the cell viability during near-infrared pulsed laser irradiation. We found lower uptake of DAPI fluorophores into HeLa cells during the multifocus excitation compared with the single-focus excitation scheme in both the one- and the two-photon fluorescence examinations. This indicates a reduction of photo-induced cell damage in the multifocus excitation. Our findings suggested that the multifocus excitation scheme is expected to be suitable for CARS microscopy in terms of minimal invasiveness.
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42

Varshnety, Prateek, Vivek Sajal, Prashant Chauhan, Ravindra Kumar, and Navneet K. Sharma. "Effects of transverse static electric field on terahertz radiation generation by beating of two transversely modulated Gaussian laser beams in a plasma." Laser and Particle Beams 32, no. 3 (June 10, 2014): 375–81. http://dx.doi.org/10.1017/s026303461400024x.

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AbstractResonant excitation of terahertz (THz) radiation by nonlinear coupling of two filamented spatial-Gaussian laser beams of different frequencies and wave numbers is studied in plasma having transverse static electric field. The static ponderomotive force due to filamented lasers is balanced by the pressure gradient force which gives rise to transverse density ripple, while, the nonlinear ponderomotive force at frequency difference of beating lasers couples with density ripple giving rise to stronger transverse nonlinear current which results into the excitation of THz radiation at resonance. The coupling is further enhanced by the presence of static electric field and spatial-Gaussian nature of laser beams. An increase of six-fold in the normalized amplitude of THz is observed by applying a direct current field of about 50 KV. Effects of frequency, laser beam width, and periodicity factor of modulated laser amplitude are studied for the efficient THz radiation generation. These results can be utilized for generating controlled tunable THz sources for medical applications using low filament intensities (~ 1014 W/cm2) of beating lasers.
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43

Wokosin, D., V. F. Centonze, and J. G. White. "UV-excited fluorophore images obtained with IR excitation." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 906–7. http://dx.doi.org/10.1017/s0424820100166993.

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The widespread use of two-photon excitation fluorescence imaging has been somewhat inhibited by the necessity to use large, expensive, high-power, short-pulse lasers. These ultra-short pulse lasers are used as an excitation source in a raster scanning configuration to provide sufficient peak power density in a lens focal volume to generate detectable two-photon absorption events for rapid imaging. Biological studies often benefit from multiple fluorescent labels and multi-labelled samples often require different excitation wavelengths for adequate excitation of the various colored fluorophores. This is achieved inexpensively with the three Krypton Argon laser lines in standard confocal imaging systems, but multiple two-photon excitation lasers--if available-- would be a very expensive system. The lasers commonly used for two-photon imaging are tuneable, but this is not a non-trivial and time consuming process. The tuning range on these lasers allows good access to the blue-emitting and green-emitting fluorophores via two-photon excitation; however, we have found that a fixed-wavelength, compact,
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44

Khwairakpam, Omorjit Singh, Emilio Mariotti, Daniele Scarpa, Piergiorgio Nicolosi, Alen Khanbekyan, Salvatore Ferracane, Alberto Arzenton, and Alberto Andrighetto. "Resonant Laser Ionization and Fine-Structure Study of Silver in an Ablation Plume." Applied Sciences 13, no. 1 (December 27, 2022): 309. http://dx.doi.org/10.3390/app13010309.

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We report on a laser photo-ionization study of silver in relation to the Selective Production of Exotic Species (SPES) project at INFN-LNL in the off-line laser laboratory. In this study, two dye lasers and an ablation laser operating at 10 Hz are used alongside a time-of-flight mass spectrometer (TOF-MS). Isotopic separation of the natural, stable isotopes 107Ag and 109Ag was clearly observed in the TOF signal. Resonant photo-ionization of silver was achieved with the use of the scheme 4d105s 2S1/2→ 4d105p 2P3/2o→ 4d106d 2D3/2 with transition wavelengths of 328.163 nm and 421.402 nm, respectively. Doppler-suppressed spectroscopy of these transition lines was performed in an ablation plume. Doppler broadening with collinear injection of excitation lasers and the effect of the linewidths of the excitation lasers were investigated. The fine-structure splitting of the level 4d106d 2D (J = 5/2 and J = 3/2) was confirmed to be 186 ± 2 pm, corresponding to 314 ± 3 GHz.
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45

Vovdenko, S., I. Dmitruk, N. Berezovska, S. Kutovyi, A. Kalyuzhnyy, N. Zubrilin, and O. Dombrovsky. "Laser-Induced Quasiperiodic Metal Structures for Efficient Excitation of Surface Plasmons." Ukrainian Journal of Physics 61, no. 9 (September 2016): 780–83. http://dx.doi.org/10.15407/ujpe61.09.0780.

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46

Yang, Hongbo, Chengxu Tu, Zhouxia Jia, Qingfu Meng, Jinghao Zhang, Jiaxiang Wang, Yalei Zhao, Chenbin Zhu, and Fubing Bao. "Dynamic Characterization of Thermocouples under Double-Pulse Laser-Induced Thermal Excitation." Sensors 23, no. 5 (February 21, 2023): 2367. http://dx.doi.org/10.3390/s23052367.

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This study investigated the dynamic characteristics of thermocouples by using double-pulse laser excitation for dynamic temperature calibration under extreme conditions. An experimental device was constructed for double-pulse laser calibration; the device uses a digital pulse delay trigger to precisely control the double-pulse laser to achieve sub-microsecond dual temperature excitation with adjustable time intervals. The time constants of thermocouples under single-pulse laser excitation and double-pulse laser excitation were evaluated. In addition, the variation trends of thermocouple time constants under different double-pulse laser time intervals were analyzed. The experimental results indicated that the time constant increases and then decreases with the decrease in the time interval of the double-pulse laser. A method for dynamic temperature calibration was established for the evaluation of the dynamic characteristics of temperature sensors.
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47

Eland, Kristine L., Dimitra N. Stratis, Tianshu Lai, Mark A. Berg, Scott R. Goode, and S. Michael Angel. "Some Comparisons of LIBS Measurements Using Nanosecond and Picosecond Laser Pulses." Applied Spectroscopy 55, no. 3 (March 2001): 279–85. http://dx.doi.org/10.1366/0003702011951894.

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Laser-induced breakdown spectra were measured by using a 1.3 ps laser pulse on glass, steel, and copper. Material ablation with the use of picosecond excitation is very precise with well-formed sharp-edged craters. The spectra obtained with 570 nm, 1.3 ps excitation decay more quickly and show significantly lower background emission than those that use 1064 nm, ∼ 7 ns excitation. The background was low enough that excellent laser-induced spectroscopy (LIBS) spectra were obtained on the three samples by using a single 1.3 ps laser pulse and a nongated detector. Similar results were obtained by using nanosecond excitation but with higher relative background signals. The radiance was similar with the use of pico- or nanosecond excitation; however, the radiant intensity was larger with nanosecond excitation because of the larger plasma.
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48

Kaselouris, E., I. K. Nikolos, Y. Orphanos, E. Bakarezos, N. A. Papadogiannis, M. Tatarakis, and V. Dimitriou. "A Review of Simulation Methods of Laser Matter Interactions Focused on Nanosecond Laser Pulsed Systems." Journal of Multiscale Modelling 05, no. 04 (December 2013): 1330001. http://dx.doi.org/10.1142/s1756973713300013.

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A review study of the developments in the field of pulsed laser-solid interaction simulation methods, for moderate laser energies, is presented. The paper is focused on the methods that numerically simulate the interactions of pulsed ns-laser with solid metal targets. Three main regimes for pulsed laser excitation, are well established, namely, the thermoelastic, melting and plasma regimes. The modelling and simulation techniques that may numerically describe these three regimes and the occurring dynamic matter responses are reviewed. Modelling efforts concerning various fields of applications of lasers are briefly discussed.
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49

Fisher, Wait G., and Eric A. Wachter. "Improved Signal Processing in Multi-Photon Imaging." Microscopy and Microanalysis 6, S2 (August 2000): 800–801. http://dx.doi.org/10.1017/s1431927600036497.

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Multi-photon excitation has been used in microscopy for nearly a decade, providing a number of demonstrated advantages over other methods for fluorescence imaging. Because excitation is achieved using longer, less energetic light, photodamage and photobleaching of the sample are reduced. Furthermore, since excitation occurs only at the focal point, this approach allows the practical collection of three-dimensionally resolved fluorescence images of live cells. However, due to the small two-photon cross-section of most fluorophores, pulsed lasers are required to generate detectable signal levels. This is due to the quadratic dependence of twophoton absorption on the instantaneous power of the laser. Typically, these lasers are pulsed at very high repetition frequencies, on the order of 106 pulses per second with pulse durations of a few hundreds of femtoseconds. For example, a titanium:sapphire (Ti:S) laser mode-locked at 76 Mhz can provide up to 100,000 watts of instantaneous power and is ideal for exciting two-photon events.
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50

Salmanov V. M., Guseinov A. G., Jafarov M. A., Mamedov R. M., and Mamedova T. A. "Features of photoconductivity and luminescence of CdS thin films and Cd-=SUB=-1-x-=/SUB=-Zn-=SUB=-x-=/SUB=-S solid solutions under laser excitation." Optics and Spectroscopy 130, no. 10 (2022): 1308. http://dx.doi.org/10.21883/eos.2022.10.54868.2983-22.

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The features of photoconductivity and luminescence of CdS thin films and Cd1-xZnxS solid solutions obtained by chemical pulverization with subsequent pyrolysis under laser excitation have been studied experimentally. Pulsed liquid (473-547 nm) and nitrogen (337 nm) lasers were used as a radiation source. An experimental study was made of the photoconductivity and photoluminescence spectra of Cd1-xZnxS thin films depending on the composition x at different excitation intensities and the relaxation curves of nonequilibrium photoconductivity. It is shown that the observed features in the photoconductivity and photoluminescence spectra of Cd1-xZnxS thin films are due to direct band-to-band transitions. Amplification of light is observed at high intensities of optical excitation in thin CdS films. Keywords: Thin films CdS, Cd1-xZnxS, laser, photoconductivity spectra, photoluminescence
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