Zeitaufgelöste Analyse der Wechselwirkung von ultrakurz gepulster Laserstrahlung mit Dielektrika

The interaction of pulsed laser radiation (tp = 80 fs) with dielectrics induces free electrons and holes. The dynamics of the electrons is monitored by transient absorption spectroscopy. The recombination time of the electrons is about 200 fs for fused silica and is one order smaller than for BK7 glass. The free electrons relax radiatively by emission of optical radiation or non-radiatively by heating and formation of defects, which causes the modification of the glass by refractive index change or cracking. By speckle photography of irradiated BK7 glass by pulsed laser radiation (tp = 40 ps) the increase of the refractive index by the Kerr effect and the decrease of the refractive index by the formation of free electrons is observed. The relaxation of the defects by energy-transfer processes has durations of some nanoseconds. The spatial distribution of the optical emission of excited sapphire and BK7 glass by pulsed laser radiation (l = 1064 nm, tp = 40 ps) is measured by streak photography. The position of the emission changes with pulse intensity and is caused by self-focusing. Sapphire absorbs the radiation by a 6-photon process and BK7 glass by a 4-photon process. By streak photography of BK7 glass and sapphire the relaxation channels of decaying electrons-hole pairs are detected. Two channels are observed: the decay of electron-holes (decay time t1 <= 200 ps) and the decay of defects, like color centers (decay times 200 ps<= t2<=1 ns und 1 ns <=t_3 <= 10ns). The small decay times can be explained by thermal quenched defect states. Defects decay for temperatures lower than the quenching temperature with decay times of milliseconds. Because the observed decays are measured above the quenching temperature, the defects relax mainly non-radiatively. By time resolved nomarski photography the refractive index changes and the filamentation in quartz, fused silica and BK7 glass is observed after interaction with pulsed laser radiation (l = 810 nm, tp = 80 fs and 3 ps). The dynamics if absorption, modification and cracking are visualized by movies. Sound-waves induced by laser radiation expand with velocities of about 5 km/s. By a delay line the modifications are observed up to 66 ns after excitation.

Grantor dc:publisher

Shaker

Year dc:date

2003

Author dc:creator

• Horn, Alexander

Contributors dc:contributor

• Poprawe, Reinhart

• info:eu-repo/classification/ddc/530
• Dielektrikum
• Laserimpuls
• Femtosekundenbereich
• Strahlenschaden
• Absorptionsspektroskopie
• Pump-Probe-Technik
• Emissionsspektroskopie
• Speckle-Interferometrie
• Physik
• Lasermaterialbearbeitung
• ultrakurpuls
• Brechungsindexänderung
• femtosekunden

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-120990%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59180