Freeform Silica Fibre Optics via Ultrafast Laser Manufacturing

微结构光纤正在改变从电信到医疗保健领域的科学技术。其独特的引导特性继续推动现有光子学的极限，并推动新的创新和科学发现。然而，这种潜力的极限正在逼近，因为许多理论上的变革性纤维由于制造挑战而无法在实践中实现。有了这个奖学金，我的目标是通过开发一种不受传统制造限制的自由光纤制造工艺来释放这种未被满足的潜力。绝大多数光纤是为电信部门生产的，以满足呈指数级增长的数据容量需求。电信中使用的光纤类型通常是传统的阶跃折射率光纤，由低折射率掺杂二氧化硅包层包围的二氧化硅玻璃芯组成。固体光纤价格低廉，并且具有相当低的损耗，但其性能受到材料吸收、散射和高色散等因素的限制。在过去的几十年中，出现了另一种类型的光纤-微结构光纤（MOF）。MOF利用结构材料芯包层，其中光通过复杂的波导机制被引导。根据类型的不同，MOF可以提供优于传统光纤的几个优点，包括宽光谱传输，低弯曲损耗，低延迟和高功率传输。值得注意的是，某些MOF在光纤的中空区域内引导光。这些所谓的空芯光纤克服了实芯光纤面临的问题，如材料吸收、色散、光学损伤和延迟，并实现了充气传感器和光源的创新丰富领域。MOF通过称为堆叠和绘制的方法制造。堆叠和拉伸是一个两步过程：首先，圆形玻璃毛细管，棒和管横向堆叠，通常添加间隔物，以形成被称为预制件的纤维的放大近似。其次，通过高温炉将预制件拉成纤维。到目前为止开发的MOF的设计在很大程度上受到限制性堆叠过程的引导，例如，六边形填充Kagomé纤维和圆管反谐振纤维。不幸的是，理论上已经显示出巨大潜力的几种类型的MOF不能合理地叠加，因此MOF的广泛适用性开始趋于稳定。为了释放这种潜力，我们将开发一种能够生产自由形态纤维的新的预制件制造工艺，即，纤维具有任意结构的横截面，而不影响纤维质量。在所提出的方法中，预制件的短段使用定制的激光制造方法进行精确和任意的加工。然后将这些片段轴向结合以形成预成型件，该预成型件使用传统方法拉伸成纤维。在最近的早期可行性论证的基础上，该研究金将促进对基于激光的预制件制造方法的全面改革，并研究最佳的玻璃粘合技术。在众多的好处中，自由形态光纤将带来大幅降低的损耗、增加的稳定性、更快的数据传输速度和新颖的光谱引导。研究金的后期阶段将专注于开发具有前所未有的引导性能的光纤，并探索具有新颖几何形状的光纤的应用。我们的目标是开发一种工业上可用的自由形态石英光纤制造方法，并进一步提高高分辨率玻璃宏观制造和先进的键合和组装能力。这项工作有望开辟光纤研究的新领域，并培养一支敬业的研究团队。

At a glance: Microstructured optical fibres are transforming science and technology in fields spanning telecommunications through to healthcare. Their unique offering of guiding properties continues to push the limits of established photonics and drive novel innovation and scientific discovery. However, a limit to this potential is approaching because many theoretically transformative fibres cannot be realised in practice due to manufacturing challenges. With this fellowship, I aim to unlock this unmet potential by developing a freeform optical fibre manufacturing process, which is unbound from conventional manufacturing constraints. The vast majority of optical fibre is produced for the telecommunications sector to satisfy exponentially rising data capacity needs. The type of fibre used in telecoms is typically conventional step-index fibre, comprised of a silica glass core surrounded by a lower-index doped-silica cladding. Solid fibre is inexpensive and guides with reasonably low-loss, but is fundamentally limited in performance by material absorption, scattering and high-dispersion amongst other factors.Over the past few decades, another type of optical fibre has emerged - microstructured optical fibre (MOF). MOF utilises a structured-material core-cladding in which light is guided through complex waveguiding mechanisms. Depending on the type, MOF can offer several advantages over conventional fibre including broad spectral transmission, low bend-loss, low latency and high-power delivery. Remarkably, certain MOFs guide light within a hollow region of the fibre. These so-called hollow-core fibres overcome problems faced by solid-core fibres such as material absorption, dispersion, optical damage and latency, as well as enabling an innovation-rich field of gas-filled sensors and light sources.MOF is manufactured by an approach known as stack-and-draw. Stack-and-draw is a two-step process: firstly, circular glass capillaries, rods and tubes are stacked laterally, often with added spacers, to form a scaled-up approximation of the fibre known as a preform. Secondly, the preform is drawn to fibre through a high-temperature furnace. The design of MOF developed so far has been heavily steered by the restrictive stacking process, e.g., hexagonally-packed Kagomé fibre and circle-tubular antiresonant fibre. Unfortunately, several types of MOF that have shown huge potential theoretically cannot be reasonably stacked, and so the vast applicability of MOF is beginning to plateau.To unlock this potential, we will develop a new preform manufacturing process capable of producing freeform fibre, i.e., fibre with arbitrarily structured cross-section, without compromising on fibre quality. In the proposed approach, short segments of the preform are precisely and arbitrarily machined using tailored laser-manufacturing methods. These segments are then bonded axially to form the preform which is drawn to fibre using traditional methods. Building upon a recent early feasibility demonstration, the fellowship will facilitate an overhaul of the laser-based approach to fabricating preforms and investigation of optimal glass bonding techniques. Amongst a trove of benefits, freeform fibre will bring drastically lower loss, increased stability, faster data transfer speeds and novel spectral guidance.The later stages of the fellowship will focus on developing fibre with unprecedented guiding performance and exploring applications of fibre with novel geometry. We aim to develop an industry-ready manufacturing method for freeform silica optical fibre, and further improve high-resolution glass macro-fabrication and advanced bonding and assembly capabilities. This work is expected to open up a new field of fibre optics research and nurture a team of dedicated researchers.