Ultraviolet-induced densification in fused silica

Ultraviolet-induced densification in fused silica is investigated using birefringence measurements to detect compaction-induced strain. This technique is capable of measuring compaction in the 10 parts per billion range in cm-sized specimens. A universal relation describing ultraviolet-induced compaction is discovered in which, using the total energy absorbed from two-photon absorption as the dose parameter, density changes equal a material dependent constant times the dose parameter to a power of about 0.65. This dose dependence is consistent with past compaction studies using electron beam and gamma radiation. Moreover, the density change per ionization ''event'' is found to be consistent for all radiation types. By comparing density measurements to refractive index change measurements found with interferometry, polarizability changes from ultraviolet-induced densification are extracted and compared with previous results using other radiation sources and melastic densification methods. (C) 1997 American Institute of Physics.