Single-pulse cell stimulation with a near-infrared picosecond laser

2005 ◽  
Vol 87 (24) ◽  
pp. 243901 ◽  
Author(s):  
Shigeki Iwanaga ◽  
Nicholas Smith ◽  
Katsumasa Fujita ◽  
Satoshi Kawata ◽  
Osamu Nakamura
Keyword(s):  
Near Infrared ◽  
Single Pulse ◽  
Picosecond Laser ◽  
Cell Stimulation

Chain-Length-Dependent Termination in Acrylate Radical Polymerization Studied via Pulsed-Laser-Initiated RAFT Polymerization

2007 ◽  
Vol 60 (10) ◽  
pp. 779 ◽  
Author(s):  
Michael Buback ◽  
Pascal Hesse ◽  
Thomas Junkers ◽  
Thomas Theis ◽  
Philipp Vana
Keyword(s):  
Radical Polymerization ◽  
Chain Length ◽  
Near Infrared ◽  
Pulsed Laser ◽  
Monomer Concentration ◽  
Nir Spectroscopy ◽  
Single Pulse ◽  
Rate Coefficients ◽  
Radical Chain ◽  
Chain Flexibility

The chain-length dependence of the termination rate coefficient, kt, in methyl acrylate (MA) and dodecyl acrylate (DA) radical polymerization has been determined via the single pulse pulsed-laser polymerization near-infrared reversible addition–fragmentation chain transfer (SP-PLP-NIR-RAFT) technique. Polymerization is induced by a laser SP and the resulting decay in monomer concentration, cM, is monitored via NIR spectroscopy with a time resolution of microseconds. A RAFT agent ensures the correlation of radical chain length and monomer-to-polymer conversion. The obtained rate coefficients for termination of two radicals of approximately the same chain length, i, are represented by power-law expressions, kt(i,i) ∝ i–α. For both monomers, composite model behaviour of kt(i,i) showing two distinct chain length regimes is observed. The exponent αs referring to short chain lengths is close to unity, whereas the exponent αl, which characterizes the chain-length dependency of large radicals, is slightly above the theoretical value for coiled chain-end radicals. The crossover chain length, ic, which separates the two regions, decreases from MA (ic = 30) to DA (ic = 20). The results for MA and DA are consistent with earlier data reported for butyl acrylate. There appears to be a correlation of αs and ic with chain flexibility.

COMPARATIVE STUDIES ON THE THIRD-ORDER NONLINEAR OPTICAL PROPERTIES OF THREE METAL-ORGANIC COMPOUNDS

2011 ◽  
Vol 20 (02) ◽  
pp. 229-236 ◽  
Author(s):  
PENGFEI ZHANG
Keyword(s):  
Near Infrared ◽  
Heavy Atom ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Optical Limiting ◽  
Infrared Region ◽  
Photon Absorption ◽  
Third Order ◽  
The Third ◽  
Planar Transition

The third-order optical nonlinearities of three planar transition metal ( Ni, Cu and Pd ) compounds with rigid quadridentate Schiff base derived from S-benzyl dithiocarbazate, were investigated systematically by Z-scan technique with picosecond laser pulses at 1064 nm. The three compounds exhibit both strong two-photon absorption and effective self-focusing performance. Due to the heavy atom effect, the second hyperpolarizability of PdZ molecule (〈γ〉 = 1.2 × 10-29 esu) was found to be the highest compared to that of the other two molecules. The optical limiting properties were also measured, and the results suggest that PdZ may be a promising candidate for the application to optical limiting in the near-infrared region.

scholarly journals Resonant dual-pulse laser ignition technique based on oxygen REMPI pre-ionization

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ciprian Dumitrache ◽  
Carter Butte ◽  
Azer Yalin
Keyword(s):  
Near Infrared ◽  
Multiphoton Ionization ◽  
Single Pulse ◽  
Combustion Efficiency ◽  
Laser Ignition ◽  
Plasma Parameters ◽  
Laser Plasmas ◽  
Measurement Results ◽  
Gas Ionization ◽  
Inverse Bremsstrahlung Absorption

AbstractThis contribution investigates a novel laser ignition method based on a dual-pulse resonant pre-ionization scheme. The first laser pulse efficiently creates initial gas ionization (seed electrons) through a 2 + 1 resonantly-enhanced multiphoton ionization (REMPI) scheme targeting molecular oxygen (λ ~ 287.6 nm). This pulse is followed by a second non-resonant near-infrared pulse (λ = 1064 nm) for energy addition into the gas via inverse bremsstrahlung absorption. The sequence of two pulses creates a laser induced plasma that exhibits high peak electron number density and temperature (ne ~ 8 × 1017 cm-3 at t = 100 ns and T ~ 8000 K at t = 10 μs, respectively). These plasma parameters are similar to those attained for typical single-pulse near-infrared laser plasmas but with the advantage of substantially lower pulse energy (by factor of ~ 2.5) in the dual-pulse REMPI case. A combustion study focusing on ignition of propane/air mixtures shows that the dual-pulse REMPI method leads to an extension of the lean flammability limit, and an increase in combustion efficiency near the lean limit, as compared to laser ignition with a single NIR pulse. The measurement results and observed gas dynamics are discussed in the context of their impact on combustion applications.

Single-pulse drilling study on Au, Al and Ti alloy by using a picosecond laser

2008 ◽  
Vol 95 (3) ◽  
pp. 739-746 ◽  
Author(s):  
J. Cheng ◽  
W. Perrie ◽  
M. Sharp ◽  
S. P. Edwardson ◽  
N. G. Semaltianos ◽  
...  
Keyword(s):  
Single Pulse ◽  
Picosecond Laser ◽  
Ti Alloy

scholarly journals Passively Q-Switched Yb:CALGO Laser Based on Mo:BiVO4 Absorber

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2364
Author(s):  
Lina Zhao ◽  
Ye Yuan ◽  
Luyang Tong ◽  
Wenyu Zhang ◽  
Zhongshuai Zhang ◽  
...  
Keyword(s):  
Repetition Rate ◽  
Peak Power ◽  
Near Infrared ◽  
Maximum Output Power ◽  
Single Pulse ◽  
Infrared Region ◽  
Maximum Output ◽  
Linear Absorption ◽  
Central Wavelength ◽  
Transmission Electron

A stable, passively Q-switched Yb:CaGdAlO4 laser based on Mo:BiVO4 saturable absorber was demonstrated. Close observations of the structure and morphology of the nanoparticles by using transmission electron microscope, Raman spectrum and linear absorption were measured. The nonlinear transmission of Mo:BiVO4 was characterized by a 30 ps laser with a central wavelength of 1064 nm and a repetition rate of 10 Hz. The experimental maximum output power of the pulsed laser was 510 mW with a repetition rate of 87 kHz and pulse width of 3.18 μs, corresponding to a peak power of 1.84 W and a single pulse energy of 5.8 μJ. The experimental results indicate that Mo:BiVO4-SA is a great candidate for passively Q-switched lasers in the near infrared region.

Single pulse femtosecond laser ablation of silicon – a comparison between experimental and simulated two-dimensional ablation profiles

2018 ◽  
Vol 7 (4) ◽  
pp. 255-264 ◽  
Author(s):  
Regina Moser ◽  
Matthias Domke ◽  
Jan Winter ◽  
Heinz P. Huber ◽  
Gerd Marowsky
Keyword(s):  
Laser Ablation ◽  
Near Infrared ◽  
Femtosecond Laser Ablation ◽  
Single Pulse ◽  
Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
Two Dimensional ◽  
Material Transport ◽  
Hydrodynamic Motion ◽  
Diode Pumped

Abstract Ultrashort laser pulses are widely used for the precise structuring of semiconductors like silicon (Si). We present here, for the first time, a comparative study of experimentally obtained and numerically simulated two-dimensional ablation profiles based on parameters of commercially relevant and widely used near-infrared and diode pumped femtosecond lasers. Single pulse laser ablation was studied at a center wavelength of 1040 nm and pulse duration of 380 fs (FWHM) in an irradiating fluence regime from 1 J/cm2 to 10 J/cm2. Process thresholds for material transport and removal were determined. Three regimes, scaling with the fluence, could be identified: low and middle fluence regimes and a hydrodynamic motion regime. By comparing the simulated and experimental ablation profiles, two conclusions can be drawn: At 2 J/cm2, the isothermal profile of 3800 K is in excellent agreement with the observed two-dimensional ablation. Thus exceeding a temperature of 3800 K can be accepted as a simplified ablation condition at that fluence. Furthermore, we observed a distinct deviation of the experimental from the simulated ablation profiles for irradiated fluences above 4 J/cm2. This points to hydrodynamic motion as an important contributing mechanism for laser ablation at higher fluences.

Three-Photon Induced Optical Limiting of a Novel Multibranched Nonlinear Chromophore Containing Carbazole Moiety

2012 ◽  
Vol 170-173 ◽  
pp. 2851-2854 ◽  
Author(s):  
Zhi Yuan Hu ◽  
Fu Quan Guo ◽  
Bin Guo ◽  
Hao Liang
Keyword(s):  
Cross Section ◽  
Near Infrared ◽  
Optical Power ◽  
Picosecond Laser ◽  
Infrared Region ◽  
Photon Absorption ◽  
Picosecond Laser Pulse ◽  
Transmission Measurements ◽  
Near Infrared Region ◽  
Optical Power Limiting

A novel multibranched nonlinear chromophore containing carbazole moiety，4, 4´, 4´´-tris(9-(3,6-tert-butyl)carbazyl-trans-styryl) -1, 3, 5-triphenylbenzene (TCSTPB)，was synthesized and characterized by 1HNMR and elemental analysis. One-photon absorption in chloroform shows the optical transparent property of the chromophore in the near infrared region. The properties of optical power limiting induced by three-photon absorption (3PA) are demonstrated. Large 3PA coefficients and the corresponding 3PA molecular cross section as high as 10-74 cm6 s2 was obtained pumped by picosecond laser pulse at 1.06 μm from nonlinear transmission measurements.

Sign in / Sign up

Export Citation Format

Share Document