Silica Based Non-linear Optical Devices

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Silica glass has long been the preferred material for waveguides in optical telecommunications networks and sensor applications. Currently, most of the existing telecommunications network is composed of silica fiber or waveguides. As a result of the wide deployment of silica based infrastructure, silica components can be made relatively inexpensively. While silica has many desirable properties it has one significant drawback in that it is an amorphous material that does not possess a second order optical non-linearity (SON). The SON is important as this property can be exploited to produce devices like optical modulators or frequency converters. Optical modulators are a major component in current telecommunications networks and wavelength converters have the potential to significantly impact future networks, fiber lasers, and cryptography. Currently, the crystal lithium niobate is used for these types of applications because it is not amorphous and possesses a large SON. Lithium niobate would be a perfectly acceptable solution if it were not for the fact that its index of refraction and thermal expansion are not compatible with the existing silica based infrastructure. In addition to the incompatibility issues, lithium niobate is more expensive and is not as easily formed into the variety of components necessary for many applications. In a perfect world, we would be able to use a silica based device that has a large SON instead of lithium niobate. Two decades ago researchers did actually discover a method, called thermal poling, to create a SON in silica (of about 1 pm/V) but have been unable to increase it to the same level as lithium niobate (about 80 pm/V). Recently we were conduction thermal poling experiments on micro and nano-layered structures in silica and made a startling discovery. Our measurements suggested that the SON in our samples could be as much as 14x higher than previously achievable. Such an increase would result in a SON that is much closer to that of lithium niobate. It is the goal of this research proposal to capitalize on this potential breakthrough and continue to study these structures to see whether we can eventually produce devices capable of competing with lithium niobate. The program will begin with a closer look at the structures themselves to see whether they can be optimized to produce even larger non-linearities. This could involve altering the composition of the glass or changing the spacing/thickness of the layers. We will also produce simulations that we hope will explain the reason for the observed increase in SON. After a considerable amount of work has gone into perfecting the layer structures we hope to move on to producing waveguides that incorporate micro and nano-layers. My students will begin by designing the basic structures using modeling software and then will attempt to develop them in our fabrication facility. We will also be seeking industry partners to develop low loss waveguide structures that incorporate micro and nano-layers. If we are successful in developing micro and nano-layer waveguides we intend to test them as modulators and wavelength converters to determine if there is a significant improvement over pre-existing silica glass based devices. Successfully producing silica based devices with large SON's would represent a major breakthrough and would impact virtually all aspects of the Canadian Photonics industry. We believe that our studies indicate that such a breakthrough could be on the horizon.