Ultrafast Phase Transition of GaAs Surfaces Irradiated by Picosecond Laser Pulses

1984 ◽  
Vol 35 ◽  
Author(s):  
J.M. Liu ◽  
A.M. Malvezzi ◽  
N. Bloembergen
Keyword(s):  
Phase Transition ◽  
Detailed Analysis ◽  
Structural Transition ◽  
Second Harmonic ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Surface Melting ◽  
Time Resolved ◽  
Preliminary Results ◽  
Harmonic Signals

ABSTRACTDetailed analysis of the second harmonic signals in reflection from crystalline GaAs surfaces reveals that the structural transition associated with surface melting occurs in less than 2 ps. Preliminary results of picosecond time-resolved reflectivity measurements are also presented.

Picosecond Photon-Solid Interaction

1984 ◽  
Vol 35 ◽  
Author(s):  
H. Kurz ◽  
N. Bloembergen
Keyword(s):  
Phase Transition ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Time Resolved ◽  
Electron Hole Plasma ◽  
Optical Heating ◽  
Main Emphasis ◽  
Firm Data ◽  
Heating Model ◽  
Recent Experimental Work

ABSTRACTSome of the fundamental aspects of pulsed laser interactions with semiconductors are reviewed within the frame of recent experimental work with picosecond laser pulses. Main emphasis is placed on data obtained in space-time resolved measurements of transmission and reflectivity of picosecond pulse irradiated silicon at different probing wavelengths. Four distinct interaction regimes can be defined, depending on the fluence of the laser pulse. Special attention is devoted to the phase transition from solid to liquid state at the surface. The optical heating model is found to be valid even on a time scale of picoseconds. Firm data of the electron-hole plasma density and lattice temperature are derived. The thermal nature of the phase transition is confirmed.

Fast phase transition process of Ge2Sb2Te5 film induced by picosecond laser pulses with identical fluences

2009 ◽  
Vol 106 (6) ◽  
pp. 063501 ◽  
Author(s):  
Huan Huang ◽  
Fangyuan Zuo ◽  
Fengxiao Zhai ◽  
Yang Wang ◽  
Tianshu Lai ◽  
...  
Keyword(s):  
Phase Transition ◽  
Picosecond Laser ◽  
Transition Process ◽  
Laser Pulses ◽  
Fast Phase ◽  
Picosecond Laser Pulses ◽  
Phase Transition Process

scholarly journals Kinetics and Mechanism of the Photochromism of N-Phenyl-Rhodaminelactame

1989 ◽  
Vol 10 (2) ◽  
pp. 63-72 ◽  
Author(s):  
H. Willwohl ◽  
J. Wolfrum ◽  
R. Gleiter
Keyword(s):  
Quantum Yield ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Laser Flash ◽  
Time Resolved ◽  
First Order ◽  
First Order Kinetics ◽  
Relative Quantum ◽  
Millisecond Time Scale ◽  
Resolution Single

The photochromism of N-phenyl-rhodaminelactame (3' ,6' -bis-(diethylamino)-2-phenyl-spiro[1H-isoindole-1,9'[9H] Xanthaen]-3-[2H]-one) was investigated in solutions of acetonitrile, dioxane and mixtures of dioxane with H20, methanol and ethanol by laser flash time resolved absorption measurements. The colouring reaction kinetics and the relative quantum yield of the red product were measured using nanosecond excimer laser excitation at 308 nm. In most cases, first order kinetics was.observed. The first order rate constants and the quantum yield were found to be dependent on the solvent and the number of laser pulses that had previously irradiated the solution. The thermal fading reaction occurred on a millisecond timescale and showed large deviations from first order kinetics in all solvents. In addition, picosecond laser pulses at 285 nm were used to measure the fluorescence lifetime of the S1 state of the rhodamine derivative with picosecond resolution. Single exponential decays were observed in all solvents and the lifetime ranged between 3 and 6 nanoseconds. We conclude that the photoreaction does not proceed directly from the S1 state, and propose a mechanism for the photochromic process, in which an intermediate decomposes to rotameric isomers of the coloured product, which are not equilibrated on the millisecond time scale of the reverse reaction.

Optical Limiting With Neutral Nickel Dithiolene Complexes

1999 ◽  
Vol 597 ◽  
Author(s):  
W. L. Tan ◽  
W. Ji ◽  
J. L. Zuo ◽  
J. F. Bai ◽  
X. Z. You ◽  
...  
Keyword(s):  
Benzene Solution ◽  
Excited State Absorption ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Optical Limiting ◽  
Linear Absorption ◽  
Time Resolved ◽  
Pump Probe ◽  
Limiting Behavior ◽  
Picosecond Pulses

AbstractWe report an investigation of optical-limiting behavior in two neutral nickel complexes with multi-sulfur 1,2 dithiolene ligands, [Ni(medt)2] I (medt = 5,6-dihydro-6-methyl-1,4-dithiin-2,3- dithiolate) and [Ni(phdt)2] 2 (phdt = 5,6-dihydro-5-phenyl-l,4-dithiin-2,3-dithiolate) in benzene solution. The fluence-dependent transmission of the complexes was observed with nanosecond and picosecond laser pulses at 532-nm wavelength. The limiting thresholds of the complexes were ˜0.3 J/cm2, when measured with the picosecond pulses. Both picosecond time-resolved pump-probe and Z-scan measurement revealed that the limiting effects should originate from excited-state absorption and refraction. The transparency window (400˜900 nm), observed in the linear absorption spectra of the complexes, indicated that their limiting response should cover a wider range than those of fullerenes and phthalocyanines.

Photoluminescence of Eu3+ in Si/SiO2 Nanostructure Films

2000 ◽  
Vol 609 ◽  
Author(s):  
Huimin Liu ◽  
Aziz Mahfoud ◽  
G. A. Nery ◽  
O. Resto ◽  
Luis F. Fonseca ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Life Time ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Photon Absorption ◽  
Intense Laser ◽  
Time Resolved ◽  
Silicon Matrix ◽  
Sputtering Deposition ◽  
Direct Excitation

ABSTRACTEu3+ -doped Si/SiO2 nanocomposites were successfully prepared by Ar sputtering deposition on quartz substrates. The optical properties were studied using time-resolved photoluminescence spectroscopy. Excited by intense picosecond laser pulses with energy greater than1GW/cm2 and wavelength at 532nm the observed photoluminescence consists of a rapidly decaying component with life time of ∼1 s and a slowly component with life time of ∼ 2 ms. The former was recognized as coming from Si/SiO2 nanostructures matrix while the latter as coming from the impurity Eu3+ ions. Using the intense laser excitation a two-photon absorption by silicon matrix occurred, resulting in photo-induced carriers produced in conduction band. A direct recombination from Si/SiO2 nanostructure host gives a weak but fast emission, and creates a large number of nonequilibrium phonon. For Eu3+ emission a set of 5D0 to 7F multiplet transitions were identified. In addition to the direct excitation by 532nm the excited state 5D0 of Eu3+ ions was also found to be populated due to energy transfer from silicon matrix. The mechanism of phonon-assisted energy transfer is discussed.

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