Silica Based Non-linear Optical Devices

长期以来，二氧化硅玻璃一直是光通信网络和传感器应用中光波导的首选材料。目前，现有的电信网络大多由石英光纤或光波导组成。由于二氧化硅基础设施的广泛部署，二氧化硅组件的制造成本相对较低。虽然二氧化硅具有许多理想的性质，但它有一个明显的缺点，那就是它是一种不具有二阶光学非线性(SON)的非晶态材料。SON很重要，因为可以利用这一特性来生产光学调制器或变频器等设备。光调制器是当前电信网络中的主要组件，而波长转换器有可能对未来的网络、光纤激光器和密码学产生重大影响。目前，晶体铌酸锂被用于这些类型的应用，因为它不是非晶态的，并且具有大的儿子。如果不是因为铌酸锂的折射率和热膨胀与现有的二氧化硅基础设施不兼容，它将是一个完全可以接受的解决方案。除了不相容的问题外，铌酸锂的价格更高，而且不容易形成许多应用所需的各种组件。在一个完美的世界里，我们可以使用硅基设备，它有一个大的儿子，而不是铌酸锂。二十年前，研究人员确实发现了一种名为热极化的方法，可以在二氧化硅中产生SON(约1 pm/V)，但一直无法将其提高到与铌酸锂相同的水平(约80 pm/V)。最近，我们对二氧化硅中的微纳米层状结构进行了热极化实验，并有了一个惊人的发现。我们的测量表明，我们样本中的儿子可能比以前可以达到的高出14倍。这样的增加将导致SON更接近于铌酸锂的SON。这项研究提案的目标是利用这一潜在的突破，并继续研究这些结构，看看我们最终是否能够生产出能够与铌酸锂竞争的设备。该程序将从仔细观察结构本身开始，看看是否可以对它们进行优化，以产生更大的非线性。这可能涉及改变玻璃的成分或改变层的间距/厚度。我们还将进行模拟，希望能够解释观察到的SON增加的原因。在对层结构进行了大量的完善工作之后，我们希望能够继续生产包含微米和纳米层的光波导。我的学生将从使用建模软件设计基本结构开始，然后尝试在我们的制造设施中开发它们。我们还将寻求行业合作伙伴，开发包含微米和纳米层的低损耗波导结构。如果我们成功地开发了微纳米层波导，我们打算将它们作为调制器和波长转换器进行测试，以确定是否比现有的基于石英玻璃的设备有显着改进。成功地生产具有大SON的硅基设备将是一项重大突破，几乎将影响加拿大光子业的方方面面。我们认为，我们的研究表明，这样的突破可能即将出现。

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.