Ceramics production: COld-cOntainer processing for Long-wavelength mid-infrared fibreoptics. (COOL)

我们正在制造新型光纤，这种光纤可以传输并能够发射长波长的中红外光。为什么？中红外光波的振荡频率范围与分子键的特征振动频率范围相匹配。在(共振)吸收相同频率的中红外光时，分子键振动的幅度增加。第一次，我们制作了一种记录光纤，在激光泵浦下，它发射出创纪录的中红外光的广泛频率：被称为中红外超连续谱(SC)的中红外彩虹[1]。将这种宽广的中红外光照射到分子样品上，并在其与样品相互作用后再次收集光，发现一些中红外频率的亮度减弱，不再刺激样品中特定的分子振动。这被称为中红外光谱学，它允许我们感知和成像分子样本的分子组成，包括各种分子气体、液体和固体：温室气体、炸药、食品和生物组织。到目前为止，由于中红外光源一直很弱，所以光源/样品/探测器都必须非常接近。新的明亮[1，2]中红外光纤SC源是一项颠覆性技术，将有助于建立便携式实时中红外分子传感和成像的新范例，为更广泛的应用打开中红外光谱区域。我们正在通过集中开发基于中红外光纤的坚固、功能设计、安全、紧凑和具有成本效益的便携式光纤设备和系统来开发这一新范式。为了提高SC光源的效率，实现长波长中红外光纤激光器，以及将中红外光被动路由到需要的地方，需要使用超纯光纤。目前，长波长中红外光纤的制造和提纯相当复杂，需要大约8个工周。通过应用本项目将开发的创新加工方法，这一漫长的加工过程可以被大幅削减，并提高超纯度。目前，玻璃熔化和净化采用的是电阻加热，但生产时间过长。我们首次证明了微波辅助加热可以实现玻璃的高速熔化。在这个项目中，我们将开发微波方法，优化微波腔，通过微波加热进行快速玻璃熔化和后续的快速玻璃超净化。为什么微波加热这么快？-因为微波直接耦合到中红外玻璃熔体，而不是耦合到容器，容器保持寒冷和不受影响。玻璃熔化温度可以达到比正常高得多的温度：(I)提供更快的熔体均化(0.5h而不是36h)和(Ii)促进高蒸气压力，以快速进行玻璃熔体的多蒸馏。该项目旨在实现新的冷容器处理，以实现前所未有的快速制造长波长中红外硫化物玻璃，其高纯度水平需要制造新的长波长中红外玻璃光纤设备，用于破坏性的便携式实时分子传感和成像。在这个项目中，我们将通过新的快速加工方法展示：一、用于传输长波长中红外光的新型超纯纤维；二、用于高效便携式分子传感的新型超纯长波长中红外SC光纤光源等。首次研制了用于泵浦光纤的长波长中红外光纤激光器。Petersen，Tang，Benson，Seddon et al，Nat.光子。8830(2014)2.Yu等人，Opt.，40(6)1081(2015).首页--期刊主要分类--期刊细介绍--期刊题录与文摘--文摘内容《固体》，356(41-42)2134(2010)。

We are making new types of optical fibre that transmit, and can emit, long-wavelength mid-infrared light. Why? Mid-infrared light-waves oscillate at frequencies within a range that matches the frequency-range of characteristic vibrations of molecular bonds. The molecular bond vibration increases in amplitude on (resonantly) absorbing mid-infrared light of the same frequency. For the first time, we made a record optical fibre that, on being laser pumped, emitted a record broad range of frequencies of mid-infrared light: 'a mid-infrared rainbow' called a mid-infrared supercontinuum (SC) of light [1]. Shining this broad SC of mid-infrared light onto a molecular sample, and collecting the light again after its interaction with the sample, reveals some mid-infrared frequencies are diminished in brightness, gone to stimulate particular molecular vibrations in the sample. This is called mid-infrared spectroscopy and it allows us to sense and image the molecular makeup of a molecular sample, including numerous molecular gases, liquids and solids as diverse as: greenhouse-gases, explosives, food and biological tissue. To date, because mid-infrared light sources have been characteristically weak the source/sample/ detector have all had to be in close proximity. The new bright [1,2] mid-infrared fibre SC sources are a disruptive technology which will help establish a new paradigm in PORTABLE, REAL-TIME mid-infrared molecular sensing and imaging, opening up the mid-infrared spectral region for more general use. We are developing this new paradigm through focused development of portable fibre devices and systems which are robust, functionally designed, safe, compact and cost effective, and which are based on mid-infrared optical fibers. Hyper-pure optical fibres are required to increase the efficiency of the SC sources and to realise long-wavelength mid-infrared fibre lasers, and also for passive routeing of mid-infrared light to where it is needed. Currently, making and purifying the long-wavelength mid-infrared optical fibres is rather intricate and takes about 8 man-weeks. This long-winded processing could be hugely cut, and hyper-purity improved, by applying the innovative processing methods to be developed in this Project. Currently, resistive heating is used for glass-melting and purification but production times are exceedingly long. We demonstrated for the first time [3] that microwave-assisted heating can achieve high-speed glass-melting. In this Project, we will develop the microwave approach, optimise microwave-cavities and carry out rapid glass melting and follow-on rapid glass hyper-purification via microwave-heating.Why is the microwave heating so fast? -because the microwaves directly couple to the mid-infrared glass melt and not to the container, which remains cold and uncompromised. Far higher glass-melting temperatures can be attained than normal which: (i) gives faster melt-homogenisation (0.5 h instead of 36 h) and (ii) facilitates high vapour pressures for fast multi-distillations of the glass-melt.This Project aims to achieve novel cold-container processing to enable the unprecedented rapid manufacture of long-wavelength mid-infrared selenide and telluride chalcogenide glasses of new levels of hyper-purity needed to make new long-wavelength mid-infrared glass fibre-optic devices for disruptive portable, real-time molecular sensing and imaging. In this Project we will demonstrate, by means of new rapid processing:i. new hyper-pure fibres for conduiting long-wavelength mid-infrared light;ii. new hyper-pure long-wavelength mid-infrared SC fibre sources for efficient portable molecular sensing andiii. first time long-wavelength mid-infrared fibre lasers for pumping the fibre SC.REFERENCES1. Petersen, Tang, Benson, Seddon et al., NAT. PHOTON. 8 830(2014).2. Yu et al., Opt. Lett., 40(6)1081(2015).3. Prasad, Seddon et al., J. Non-Cryst. Solids, 356(41-42) 2134(2010).