Characterization of ultra-violet-induced changes in planar waveguides

• A simple, low-cost spectrophotometer system operating in reflection absorption mode is used to characterize changes in refractive index and thickness of thin films under 193 nm irradiation. The results indicate overall dilation of the glass and are confirmed by additional surface topographic measurements. We also show that in addition to the net relaxation from laser annealing of the interface, in germanosilicate samples local compaction takes place. Since the net relaxation is triggered by remote interactions, it is not spatially confined to the laser-irradiated area. However, a local positive index change is observed. These results are in agreement with previous hypotheses put forward to explain planar waveguide negative index changes. They also bring to attention the great care necessary in both conducting and interpreting measurements that do not take into account spatial variations arising from the combination of remote and local triggers of both index and thickness changes.

Nyckelord

interfacial relaxation

negative refractive index

material dilation

type IIa gratings

optical fibers

index changes

ultraviolet-irradiation

induced densification

ge-sio2 preforms

bragg gratings

photosensitivity

glass

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)