Study of second harmonic generation in poled and un-poled silica multilayer structures

Silica is the ideal material for a wide range of optical applications on account of its many desirable linear properties. For many important non-linear optical applications, such as second harmonic generation (SHG), silica cannot be used as it doesn't possess an even ordered optical non-linearity. For some time now thermal poling has been used to create an artificial second order non-linearity in silica. While early results suggested that the resulting non-linearity was not large (less than 1 pm/V) or extensive enough (only 5 microns penetration into the substrate) to be practical, there has been a concerted effort to find new ways to improve upon and harness this 'rtificial' non-linearity. In this presentation, we will show our recent results in SHG in both poled and unpoled multi-layer silica structures. We believe that these structures, of alternating doped and undoped silica, can be used to increase the size of the non-linear region in glass and improve the efficiency of poled devices. The second harmonic generated in our samples is compared to that produced in both a silica substrate and quartz. We show that a non-zero second order non-linearity is intrinsic to multi-layer structures and study the impact of varying the number of layers and doped/un-doped duty cycle. We then investigate impact of poling on the SHG in these samples. For un-poled samples we study the effect of using different dopants or varying the concentration. We conclude by discussing applications of these structures