Microstructured silica fibres for surgical applications: A truly flexible laser scalpel.

光纤和激光是互补的技术，在许多情况下，如果没有另一种，其中一种的用途是有限的。光纤的柔韧性和导引特性使激光的独特特性得以保持，同时可以灵活地将其传送到需要的任何地方，无论是用于激光焊接的几米、用于遥感应用的几十米或数百米，还是用于通信的数千公里。在激动人心的新应用需求的推动下，对能够在红外(IR)波长区域(2微米以上)传输激光能量的光纤提出了迫切的技术要求。一种这样的应用是在激光医学中用于外科激光的光纤传输：一种真正灵活的激光手术刀。然而，几乎所有的光纤都是由一种名为二氧化硅的玻璃制成的，虽然二氧化硅对可见光辐射是透明的，但有某些类型的辐射是不会传输的。特别是，二氧化硅不会传输红外波长。然而，在过去的几年里，随着一种完全不同类别的纤维的发明，硅纤维技术取得了戏剧性的进步--光子晶体光纤(PCF)，也被称为微结构或多孔纤维。其中一种光纤具有中空芯(一种中空芯微结构光纤--HCMF)，其中大部分能量在空气中传导。在这些纤维中，只有一小部分光与石英玻璃重叠，因此材料对红外能量的强烈吸收被最小化。最近，我(与合作者一起)在世界上第一次证明了二氧化硅纤维的实际波长范围不需要受到这种固有材料吸收的限制。现在有可能实现一种新颖的全二氧化硅HCMF设计，它可以引导进入红外区域，最终为将石英纤维技术与新兴的红外应用相结合铺平了道路。这项研究计划的目的是探索使用这些新型的HCMF为红外激光器提供光纤的可能性，这些新型的HCMF将由我和我的合作者设计和开发。为了证明这些新型纤维的实用性，我将开展一项将这些纤维应用于激光手术的可行性研究：激光手术：某些红外激光器(例如Er：YAG)特别适合激光手术，因为人体组织中所含的水强烈地吸收红外辐射。通过精确地将激光传输到特定区域，可以将对周围组织的损害降至最低。因此，激光在外科手术中的使用越来越多，越来越多的医疗应用使用了2.94微米的Er：YAG激光。目前，最常见的手术激光输送方法是使用关节臂。这些系统有许多不足之处，因为经常存在不对准问题，手臂不可靠，很难安装，这需要专门的、熟练的技术人员。此外，关节臂虽然对向患者发射激光很有用，但可能不如使用刀片的外科医生友好，而且对行动有很大的限制。因此，使用激光进行手术的好处被关节臂对外科医生技能的限制所抵消。坚固的纤维输送系统将缓解这些问题，并从根本上增加手术激光的实用性。全硅纤维比目前正在研究的其他红外引导光纤具有许多优点，尤其是无毒、生物惰性、机械强度和非常灵活。当然，由于传统的二氧化硅纤维不会引入红外光谱，因此以前并未考虑将其用于这一应用。然而，使用HCMF提供手术激光的激进方法最终为将基于硅纤维的技术引入手术台铺平了道路。

Optical fibres and lasers are complementary technologies and in many instances one is of limited use without the other. The flexibility and guidance properties of the fibre allow the unique properties of the laser light to be maintained whilst it is flexibly delivered to wherever required, whether over a few metres for a laser welding application; a few tens or hundreds of metres for a remote sensing application or thousands of km for communications. There is an urgent technological requirement for optical fibres that can transmit laser energy in the infrared (IR) wavelength region (above 2 microns) driven by demands of exciting new applications. One such application is in laser medicine for the fibre delivery of surgical lasers: a truly flexible laser scalpel. However, nearly all optical fibres are fabricated from a glass known as silica and whilst silica is transparent to visible radiation, there are certain types of radiation that it will not transmit. In particular silica will not transmit IR wavelengths. Dramatic advances in silica fibre technology have been made in the last few years, however, with the invention of a radically different class of fibre - the photonic crystal fibre (PCF) also known as the micro-structured or holey fibre. One such fibre has a hollow core (a hollow core microstructured fibre - HCMF) where the majority of power is guided in air. In these fibres only a small fraction of light overlaps with the silica glass and hence the strong material absorption of IR energy is minimised. Recently, I (together with collaborators) have demonstrated for the first time in the world that the practical wavelength range of silica fibres need not be limited by this intrinsic material absorption. It is now possible to realise a novel all silica HCMF design that can guide into the IR region which finally paves the way to integrate silica fibre technology with emerging IR applications. The aim of this research programme is to explore the possibilities of fibre delivery for IR lasers using these novel HCMFs, which will be designed and developed by myself and my collaborators. To demonstrate the usefulness of these novel fibres I will carry out a feasibility study applying these fibres to laser surgery:Laser surgery: Certain IR lasers (e.g. Er:YAG) are particularly suitable for laser surgery because the water contained in human tissue strongly absorbs IR radiation. By precisely delivering the laser to specific areas damage to surrounding tissue can be minimised. Hence, lasers are being increasingly used in surgical procedures with a growing number of medical applications that utilise the Er:YAG laser, operating at 2.94 microns. Currently the most common method of delivery of surgical lasers is achieved using articulated arms. There are a number of shortfalls with these systems in that there are often misalignment issues, the arms are unreliable and they are difficult to install which requires a dedicated, skilled technician. Additionally, the articulated arm, although useful for delivering laser light to the patient, is perhaps less user friendly than a surgeon using a blade and there is significant restriction to movement. Therefore the benefits of using laser light for surgery are offset by the restriction to the surgeon's skill that the articulated arms can impose. A robust fibre delivery system would alleviate these problems and radically increase the usefulness of surgical lasers.All-silica fibres have many advantages over other IR guiding optical fibres currently being investigated for this purpose in particular they are; non-toxic; bio-inert; mechanically strong and very flexible. Of course, because traditional silica fibres do not guide into the IR they have not been considered previously for this application. However, the radical approach of using an HCMF to deliver a surgical laser finally paves the way to introduce silica fibre based technology to the operating table.