Novel Ferroelectric Photonic Band-Gap Structures: a Feasibility Study

当材料以周期性方式形成图案时，通常通过在微米尺度上的孔的周期性图案中钻孔来产生光子带隙。这种周期性图案化的介质中的光的性质发生了巨大的变化，某些特定波长的相互作用变得非常强烈。这项初步研究的冒险和创新之处在于将光子带隙图案与高度非线性的外延单晶铁电材料以波导形式相结合，从而在横向图案中增加了光的垂直限制。有了这样的组合，我们可以设想在光学设备效率方面取得巨大的进步，这反过来将允许以微型设备格式在光通信中更快地传输和处理数据。在这项可行性研究中要回答的一个关键问题是，是否可以生长出足够高的光学质量和足够低的光学损耗，以证明理论预测的非线性光学效应的增强。考虑到概念的证明，我们选择在众所周知的LiNbate/LiTalate非线性光学系统中演示一些简单的关键器件。我们试图证明，通过液相外延和熔融外延生长高质量薄膜的定制设计和专用外延生长将为后续的光子带隙图案化和新型器件演示提供所需质量的材料。在这项为期一年的研究结束时，这将为一个涉及更广泛的更奇异的材料和更复杂的设备格式的全面计划奠定基础。据我们所知，这是第一次将光子带隙工程中令人振奋的新进展与高度非线性的铁电外延层相结合。我们在实现这一为期一年的课程目标方面处于独特的地位，这是因为华威和布里斯托尔的团队之间的合作，这两个团队结合了他们各自在材料生长和表征以及光学设备设计、制造和测试方面的专业知识。

A photonic band gap is created when a material is patterned in a periodic fashion, typically by drilling in a periodic pattern of holes on a scale of microns. The properties of light in this periodically-patterned medium are vastly changed, with interactions at some specific wavelengths becoming very much stronger. The adventure and innovation in this pilot study is in the combination of photonic band gap patterning with highly nonlinear epitaxial single-crystal ferroelectric materials in a waveguiding format, thus adding vertical confinement of light to the lateral patterning. With such a combination,we can conceive of making massive gains in optical device efficiency which, in turn, will allow faster speeds of data transfer and processing in optical communications in miniaturised device formats. A key question to answer in this feasibility study is whether ferroelectric waveguiding layers can be grown with sufficiently high optical quality and sufficiently low optical loss to demonstrate the enhancements in nonlinear optical effects predicted by theory. With proof of concept in mind, we have chosen to demonstrate a number of simple key devices in the well-known lithium niobate/lithium tantalate nonlinear optical system. We seek to show that custom-designed and dedicated epitaxial growth of high-quality films by both liquid phase epitaxy and epitaxial growth by melting will yield material of the necessary quality for subsequent photonic band-gap patterning and novel device demonstration. This will set the platform for a full programme involving a wider range of more exotic materials and more elaborate device formats at the end of this one-year study. To our knowledge, this is the first time that such a programme to combine the exciting new advances in photonic band-gap engineering with highly nonlinear ferroelectric epitaxial layers has been undertaken. We are uniquely placed to achieve the aims of this one-year programme because of the collaboration between groups at Warwick and Bristol, which combines their respective expertise in materials growth and characterisation and optical device design, fabrication and testing.