Laser-driven formation of a high-pressure phase in amorphous silica.
Because of its simple composition, vast availability in pure form and ease of processing, vitreous silica is often used as a model to study the physics of amorphous solids. Research in amorphous silica is also motivated by its ubiquity in modern technology, a prominent example being as bulk material in transmissive and diffractive optics for high-power laser applications such as inertial confinement fusion (ICF). In these applications, stability under high-fluence laser irradiation is a key requirement, with optical breakdown occurring when the fluence of the beam is higher than the laser-induced damage threshold (LIDT) of the material. The optical strength of polished fused silica transmissive optics is limited by their surface LIDT. Surface optical breakdown is accompanied by densification, formation of point defects, cratering, material ejection, melting and cracking. Through a combination of electron diffraction and infrared reflectance measurements we show here that synthetic vitreous silica transforms partially into a defective form of the high-pressure stishovite phase under high-intensity (GW cm(-2)) laser irradiation. This phase transformation offers one suitable mechanism by which laser-induced damage grows catastrophically once initiated, thereby dramatically shortening the service lifetime of optics used for high-power photonics.
Department of Materials Science and Engineering, University of California Berkeley, Berkeley, California 94720, USA. asalleo@parc.com
Alberto
A
Salleo
Seth T
ST
Taylor
Michael C
MC
Martin
Wendy R
WR
Panero
Raymond
R
Jeanloz
Timothy
T
Sands
François Y
FY
Génin
D004307:Dose-Response Relationship, Radiation; D006358:Hot Temperature; D007834:Lasers; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008968:Molecular Conformation; D044367:Phase Transition / Q000528:radiation effects*; D011312:Pressure; D012822:Silicon Dioxide / Q000737:chemistry* / Q000528:radiation effects*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
D012822:Silicon Dioxide