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Intensed pulsed laser

Pankaj Kr Mishra, Vincent Bettaque, Oriol Vendrell, Robin Santra, Ralph Welsch
Ultrashort, high-intensity THz pulses, e.g., created at free-electron laser facilities, allow for direct investigation as well as the driving of intermolecular modes in liquids like water and thus will deepen our understanding of the hydrogen bonding network. In this work, the temperature-jump (T-jump) of water induced by THz radiation is simulated for ten different THz frequencies in the range from 3 to 30 THz and five different pulse intensities in the range from 1 × 1011 to 5 × 1012 W/cm2 employing both ab initio molecular dynamics (AIMD) and force field molecular dynamics (FFMD) approaches...
May 18, 2018: Journal of Physical Chemistry. A
Carlos Bonazzola, Alejandro Hnilo, Marcelo Kovalsky, Jorge Tredicce
The passively Q-switched, self-pulsing all-solid-state laser is a device of widespread use in many applications. Depending on the condition of saturation of the absorber, which is easy to adjust, different dynamical regimes are observed: continuous-wave emission, stable oscillations, period doubling bifurcations, chaos, and, within some chaotic regimes, extreme events (EEs) in the form of pulses of extraordinary intensity. These pulses are sometimes called "dissipative optical rogue waves." The mechanism of their formation in this laser is unknown...
March 2018: Physical Review. E
Ido Barth, Nathaniel J Fisch
In its usual implementation, the Raman amplifier features only one pump carrier frequency. However, pulses with well-separated frequencies can also be Raman amplified while compressed in time. Amplification with frequency-separated pumps is shown to hold even in the highly nonlinear, pump-depletion regime, as derived through a fluid model, and demonstrated via particle-in-cell simulations. The resulting efficiency is similar to single-frequency amplifiers, but, due to the beat-wave waveform of both the pump lasers and the amplified seed pulses, these amplifiers feature higher seed intensities with a shorter spike duration...
March 2018: Physical Review. E
Xiaoling Zhang, Xin Ren, Fang Zhang
Black phosphorus quantum dots (BPQDs) with an average diameter of ≈ 6 nm and a height of ≈1.1 nm are successfully synthesized by using a pulsed laser ablation (PLA) method in isopropyl ether (IPE) solvent. PL quantum yield of the as-prepared sample is as high as 20.7% which is 3 times that of the BPQDs prepared by probe ultrasonic exfoliation (approximately 7.2%) for the first time. The stable and blue-violet photoluminescence (PL) emission of the BPQDs is observed, which is elucidated that electrons transit from the LUMO energy level to the HOMO energy level as well as energy levels below the HOMO ( H1 and H2 )...
May 16, 2018: Chemistry, An Asian Journal
Claudia Strefezza, Marcello Magri Amaral, José Quinto, Sheila Cynthia Gouw-Soares, Claudia Bianchi Zamataro, Denise Maria Zezell
OBJECTIVE AND BACKGROUND: The correct selections of the cementing agent, the endodontic post material and placement protocol are critical to provide an increased longevity of the teeth that went through endodontic treatment. The irradiation with diode laser before post cementation, can promote an antimicrobial effect. However, there is a lack of information about the effect of 830 nm diode laser on the post bond strength. This study analyzed the effect of dentin root canal irradiation with high-intensity diode laser, at 830 nm, operating in continuous or pulsed mode, on the retention of metal or fiber posts, cemented with self-etching resinous composite (Panavia F) and zinc phosphate cement (ZnPO4 )...
May 16, 2018: Photomedicine and Laser Surgery
Miguel A Rodríguez, Florian Denis-le Coarer, Ángel Valle
A first analysis of fluctuations of the light intensity of vertical-cavity surface-emitting lasers operating in a bistable regime reveals the presence of 1/f noise. In this regime the intensity fluctuates between two recently characterized states with residence times {τ_{1}} and {τ_{2}}. We identify three distinct processes. One of them presents a coherence enhancement phenomenon, and in the other two the distribution of residence times in one of the states follows either a power law P(τ_{1})∼τ_{1}^{-2} or P(τ_{2})∼τ_{2}^{-2}, and this is the cause of the 1/f shape in the spectral density of the intensity...
April 2018: Physical Review. E
L Ceurvorst, A Savin, N Ratan, M F Kasim, J Sadler, P A Norreys, H Habara, K A Tanaka, S Zhang, M S Wei, S Ivancic, D H Froula, W Theobald
Channeling experiments were performed at the OMEGA EP facility using relativistic intensity (>10^{18}W/cm^{2}) kilojoule laser pulses through large density scale length (∼390-570 μm) laser-produced plasmas, demonstrating the effects of the pulse's focal location and intensity as well as the plasma's temperature on the resulting channel formation. The results show deeper channeling when focused into hot plasmas and at lower densities, as expected. However, contrary to previous large-scale particle-in-cell studies, the results also indicate deeper penetration by short (10 ps), intense pulses compared to their longer-duration equivalents...
April 2018: Physical Review. E
Esben F Thomas, Anders A Søndergaard, Benjamin Shepperson, Niels E Henriksen, Henrik Stapelfeldt
A moderately intense 450 fs laser pulse is used to create rotational wave packets in gas phase I_{2} molecules. The ensuing time-dependent alignment, measured by Coulomb explosion imaging with a delayed probe pulse, exhibits the characteristic revival structures expected for rotational wave packets but also a complex nonperiodic substructure and decreasing mean alignment not observed before. A quantum mechanical model attributes the phenomena to coupling between the rotational angular momenta and the nuclear spins through the electric quadrupole interaction...
April 20, 2018: Physical Review Letters
Kyle Seyler, Ding Zhong, Bevin Huang, Xiayu Linpeng, Nathan P Wilson, Takashi Taniguchi, Kenji Watanabe, Wang Yao, Di Xiao, Michael A McGuire, Kai-Mei Fu, Xiaodong Xu
Monolayer valley semiconductors, such as tungsten diselenide (WSe2 ), possess valley pseudospin degrees of freedom that are optically addressable but degenerate in energy. Lifting the energy degeneracy by breaking time-reversal symmetry is vital for valley manipulation. This has been realized by directly applying magnetic fields or via pseudo-magnetic fields generated by intense circularly polarized optical pulses. However, sweeping large magnetic fields is impractical for devices, and the pseudo-magnetic fields are only effective in the presence of ultrafast laser pulses...
May 14, 2018: Nano Letters
Allan S Johnson, Dane R Austin, David A Wood, Christian Brahms, Andrew Gregory, Konstantin B Holzner, Sebastian Jarosch, Esben W Larsen, Susan Parker, Christian S Strüber, Peng Ye, John W G Tisch, Jon P Marangos
Laser-driven high-harmonic generation provides the only demonstrated route to generating stable, tabletop attosecond x-ray pulses but has low flux compared to other x-ray technologies. We show that high-harmonic generation can produce higher photon energies and flux by using higher laser intensities than are typical, strongly ionizing the medium and creating plasma that reshapes the driving laser field. We obtain high harmonics capable of supporting attosecond pulses up to photon energies of 600 eV and a photon flux inside the water window (284 to 540 eV) 10 times higher than previous attosecond sources...
May 2018: Science Advances
Yong He, Xiaodan Liu, Yangyang Lv, Fei Liu, Jiyu Peng, Tingting Shen, Yun Zhao, Yu Tang, Shaoming Luo
Rapid detection of soil nutrient elements is beneficial to the evaluation of crop yield, and it's of great significance in agricultural production. The aim of this work was to compare the detection ability of single-pulse (SP) and collinear double-pulse (DP) laser-induced breakdown spectroscopy (LIBS) for soil nutrient elements and obtain an accurate and reliable method for rapid detection of soil nutrient elements. 63 soil samples were collected for SP and collinear DP signal acquisition, respectively. Macro-nutrients (K, Ca, Mg) and micro-nutrients (Fe, Mn, Na) were analyzed...
May 11, 2018: Sensors
Maria Chernysheva, Mohammed Al Araimi, Graham A Rance, Nicola J Weston, Baogui Shi, Sayah Saied, John L Sullivan, Nicholas Marsh, Aleksey Rozhin
Composites of single-walled carbon nanotubes (SWNTs) and water-soluble polymers (WSP) are the focus of significant worldwide research due to a number of applications in biotechnology and photonics, particularly for ultrashort pulse generation. Despite the unique possibility of constructing non-linear optical SWNT-WSP composites with controlled optical properties, their thermal degradation threshold and limit of operational power remain unexplored. In this study, we discover the nature of the SWNT-polyvinyl alcohol (PVA) film thermal degradation and evaluate the modification of the composite properties under continuous high-power ultrashort pulse laser operation...
May 10, 2018: Scientific Reports
Li-Xiang Hu, Tong-Pu Yu, Zheng-Ming Sheng, Jorge Vieira, De-Bin Zou, Yan Yin, Paul McKenna, Fu-Qiu Shao
Generation of attosecond bunches of energetic electrons offers significant potential from ultrafast physics to novel radiation sources. However, it is still a great challenge to stably produce such electron beams with lasers, since the typical subfemtosecond electron bunches from laser-plasma interactions either carry low beam charge, or propagate for only several tens of femtoseconds. Here we propose an all-optical scheme for generating dense attosecond electron bunches via the interaction of an intense Laguerre-Gaussian (LG) laser pulse with a nanofiber...
May 8, 2018: Scientific Reports
A Kortyna, D M B Lesko, D J Nesbitt
The combination of a pulsed supersonic slit-discharge source and single-mode difference frequency direct absorption infrared spectroscopy permit first high resolution infrared study of the iodomethyl (CH2 I) radical, with the CH2 I radical species generated in a slit jet Ne/He discharge and cooled to 16 K in the supersonic expansion. Dual laser beam detection and collisional collimation in the slit expansion yield sub-Doppler linewidths (60 MHz), an absolute frequency calibration of 13 MHz, and absorbance sensitivities within a factor of two of the shot-noise limit...
May 7, 2018: Journal of Chemical Physics
Pramod Sharma, Soumitra Das, Rajesh K Vatsa
RATIONALE: Multiply charged tin ions ([Sn]8+ to [Sn]13+ ) are considered as ideal-emitters at extreme ultraviolet (EUV) wavelength ~ 13.5 nm, pertinent to advanced micro-electronic device fabrication. Solid tin targets have been widely explored for the generation of these ions, but debris generation has restricted their utilization. Tin-containing molecular clusters have, however, the potential to act as dilute and debris-free sources for the generation of tin ions, as investigated in the present study...
May 7, 2018: Rapid Communications in Mass Spectrometry: RCM
Tamás Szidarovszky, Gabor J Halasz, Attila G Császár, Lorenz S Cederbaum, Agnes Vibok
Rovibronic spectra of the field-dressed homonuclear diatomic Na2 molecule is in- vestigated to identify direct signatures of the light-induced conical intersection (LICI) on the spectrum. The theoretical framework formulated allows the computation of the (1) field-dressed rovibronic states induced by a medium intensity continuous-wave laser light and the (2) transition amplitudes between these field-dressed states with respect to an additional weak probe pulse. The field-dressed spectrum features ab- sorption peaks resembling the field-free spectrum as well as stimulated emission peaks corresponding to transitions not visible in the field-free case...
May 7, 2018: Journal of Physical Chemistry Letters
Hiroyuki Katsuki, Nobuyuki Takei, Christian Sommer, Kenji Ohmori
Coherent control is a technique to manipulate wave functions of matter with light. Coherent control of isolated atoms and molecules in the gas phase is well-understood and developed since the 1990s, whereas its application to condensed matter is more difficult because its coherence lifetime is shorter. We have recently applied this technique to condensed matter samples, one of which is solid para-hydrogen ( p-H2 ). Intramolecular vibrational excitation of solid p-H2 gives an excited vibrational wave function called a "vibron", which is delocalized over many hydrogen molecules in a manner similar to a Frenkel exciton...
May 7, 2018: Accounts of Chemical Research
Cid A F de Paula Gomes, Ernesto C P Leal-Junior, Almir V Dibai-Filho, Adriano R de Oliveira, André S Bley, Daniela A Biasotto-Gonzalez, Paulo de Tarso Camillo de Carvalho
OBJECTIVE: To investigate the clinical effects of incorporation of phototherapy in a therapeutic exercise program for individuals with knee osteoarthritis (OA) when compared to a group that received exercise alone and to a group that received exercise + placebo phototherapy. MATERIALS AND METHODS: This is a randomized, blinded and placebo-controlled trial. Thus, sixty male and female individuals aged 40-80 years with knee pain in the previous 6 months participated of the study, with diagnosis of unilateral knee OA based on the criteria established by the American College of Rheumatology and radiographic confirmation and Grades 2 or 3 of the Kellgren-Lawrence Classification...
May 7, 2018: Lasers in Surgery and Medicine
Jianwei Yu, Xiaoping Ouyang, Li Zhou, Youen Jiang, Baoqiang Zhu, Jianqiang Zhu
We study the feasibility of measuring pulse duration in the far field in high-energy petawatt lasers using single-shot autocorrelation. This single-shot autocorrelation technique makes use of parametric upconversion in media with randomly oriented ferroelectric domains, which supports transverse second-harmonic generation with two counter-propagating fundamental beams. We show that this technique possesses a large time window, capable of measuring pulses with temporal duration ranging from a sub-picosecond to tens of picoseconds...
May 1, 2018: Applied Optics
Daniel J Heath, Taimoor H Rana, Rupert A Bapty, James A Grant-Jacob, Yunhui Xie, Robert W Eason, Ben Mills
Subtractive femtosecond laser machining using multiple pulses with different spatial intensity profiles centred on the same position on a sample has been used to fabricate surface relief structuring. A digital micromirror device was used as an intensity spatial light modulator, with a fixed position relative to the sample, to ensure optimal alignment between successive masks. Up to 50 distinct layers, 335 nm lateral spatial resolution and 2.6 µm maximum depth structures were produced. The lateral dimensions of the structures are approximately 40 µm...
April 30, 2018: Optics Express
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