Development of a Near-Market-Ready Miniature Raman Probe

拉曼探针是光纤耦合设备，其使用光纤将激发激光传输到样品，捕获所得的拉曼信号，并将该信号传输回光谱仪进行分析。因此，它们在相对于拉曼光谱仪的样品定位方面提供了多功能性。传统的拉曼探针具有以cm测量的尺寸，但是在诸如医疗保健、制造和计量等领域中存在需要毫米级甚至亚毫米拉曼探针的应用。微型光纤耦合拉曼探针的制造并不简单，因为它们通常由用于对泵浦和拉曼信号进行聚焦、准直和滤波的多个微光学部件组成，并且尽管已经展示了毫米级探针，但是已经证明它们对于广泛的商业应用来说过于昂贵。最近，我们展示了如何使用称为超快激光辅助蚀刻（ULAE）的新兴制造技术来制造微型拉曼探针，该技术依赖于超短激光脉冲的非线性吸收，以直接在电介质材料（如熔融石英玻璃）内写入结构修改。如果控制得当，激光改性材料的KOH化学蚀刻速率与原始材料相比可以提高约1000倍，从而能够制造具有微米级精度的精密毫米级熔融石英微光学元件。除了促进用常规方法难以实现的自由形式微光学器件的制造之外，ULAE的关键优点是微光学器件可以与用于光纤和其他部件的无源对准结构单片集成。这方面可能是特别有利的批量制造，以规避时间和成本所涉及的主动alignment.We最近已经证明了使用ULAE制造一个原型的亚毫米光纤耦合拉曼探针，表现出许多性能方面所需的商业产品。然而，仍有几个技术准备水平（TRL）和市场准备水平（MRL）方面需要开发，以使当前的拉曼探针接近市场准备状态。该项目将通过以下方式解决这些问题：（i）演示空间选择性多层涂层集成到拉曼探针上，（ii）演示拉曼探针光学表面的CO2激光抛光，（iii）演示拉曼探针可以大规模制造，以及（iv）与我们的项目合作伙伴合作量化拉曼探针技术的性能。我们的目标是，拉曼探针将是“产品之一”的公司，我们将分拆出赫瑞瓦特大学（HWU）后不久，该项目的结束。

Raman probes are fibre-coupled devices that use fibre optics to transmit excitation laser light to a sample, capture the resulting Raman signal, and transmit that signal back to a spectrometer for analysis. As such, they provide versatility in terms of sample positioning relative to a Raman spectrometer. Conventional Raman probes have dimensions measured in cm's, but there are applications in areas such as healthcare, manufacturing, and metrology, that require mm-scale and even sub-mm Raman probes. The manufacture of miniature fibre-coupled Raman probes is not trivial, as they usually consist of multiple micro-optic components for focusing, collimating, and filtering the pump and Raman signals, and although mm-scale probes have been demonstrated, they have proven to be too expensive for widespread commercial applications. Recently, we demonstrated how miniature Raman probes can be manufactured using an emerging manufacturing technique known as Ultrafast-Laser-Assisted Etching (ULAE), which relies on the nonlinear absorption of ultrashort laser pulses to directly write structural modifications inside a dielectric material such as fused silica glass. If correctly controlled, the laser-modified material can exhibit a ~1000-fold increase in KOH chemical etch rate compared to the pristine material, enabling fabrication of exquisite mm-scale fused silica micro-optic components with micron-scale precision. In addition to facilitating the manufacture of freeform micro-optics that would be difficult to realise with conventional approaches, a key advantage of ULAE is that the micro-optics can be monolithically integrated with passive alignment structures for fibres and other parts. This aspect could be particularly advantageous for volume manufacturing, to circumvent the time and cost involved in active alignment.We have recently demonstrated the use of ULAE to manufacture a prototype sub-mm fibre-coupled Raman probe that exhibits many performance aspects required for a commercial offering. There remains, however, several Technology Readiness Level (TRL) and Market Readiness Level (MRL) aspects that require development to take the current Raman probe to a near-market-ready state. This project will address these aspects by (i) demonstrating the integration of spatially selective multi-layer coatings onto the Raman probe, (ii) demonstrating the CO2 laser polishing of the Raman probe's optical surfaces, (iii) demonstrating that Raman probes can be manufactured at scale, and (iv) quantifying the performance of the Raman probe technology in collaboration with our project partners. Our aim is that the Raman probe will be "product one" for a company that we will spin-out from Heriot-Watt University (HWU) shortly after the end of the project.