Applications of ultra-long Raman lasers in Photonics

拉曼散射是一个基本的过程，当电磁辐射通过物质传输时，它会影响电磁辐射。1928年，C. 1972年，在单模光纤中首次观察到受激拉曼散射。在光学中的受激拉曼散射（SRS）过程中，通过材料介质传输的光子放弃其能量以产生对应于同时行进通过光纤的一些其他辐射的更高波长的新光子，加上以振动状态（声子）的形式被光纤吸收的一些剩余能量。这些振动态的能量取决于材料的性质，因此能量从较低波长转移到较高波长（增益谱）的方式是特定介质的特征。对于石英光纤，当能量从泵浦转移到频率低约13.2 THz的辐射时，实现最大的拉曼转换效率。近年来，光纤中拉曼效应的开发已经打开了光子学中许多重要应用的大门，这些应用对光子学和通信工业产生了直接影响。仅依靠材料的性质将能量从一个频率转移到另一个频率的可能性是非常强大和有吸引力的，例如，在拉曼光纤激光器、分布式放大器和频率转换器的创建中已经转化。在前面提到的应用中，分布式放大可能是未来电信行业短期效果更高的技术，因为它似乎是部署未来大容量光通信链路的关键，这要归功于它能够提高系统性能并扩大工作波长范围。最近，我们已经证明，拉曼效应可用于将长光纤通信链路作为一个整体转换为超长激光器，在此过程中创建了现有的最长腔激光器。当通过这样的超长激光传输信息时，拉曼增益分布接近理想，并且信号在传输过程中不受功率变化的影响，这可以在降低噪声和改善系统性能方面带来重要好处。无损传输一直是光通信的长期梦想目标，它将带来线路中的噪声降低，并为非线性物理和应用数学领域的研究创造了令人兴奋的可能性。但是超长激光器是非常有趣的设备，它不仅可以用作几乎无损的通信信道，还可以用作光源。超长拉曼激光传输跨度代表了一个简单但相当激进的新概念，由于其众多的潜在应用以及与概念本身相关的令人兴奋的基础物理学，近年来引起了人们的极大兴趣。作为这一想法的创始人，主要研究者和阿斯顿大学的光子学研究小组完全适合扩大和推进这项任务。2这项建议的资金将证明是无价的，因为它可以获得将这项原创性研究提升到下一个水平所需的人力和基本设备。

Raman scattering is a fundamental process that affects electromagnetic radiation when this is transmitted through matter. The effect was first reported in 1928 by C. V. Raman, who was awarded the 1930 Nobel Prize for his discovery, and in 1972 stimulated Raman scattering was observed for the first time in single-mode optical fibres. In the process of stimulated Raman scattering (SRS) in optical, a photon that is being transmitted through the material medium gives up its energy to create a new photon at a higher wavelength corresponding to some other radiation simultaneously travelling through the fibre, plus some residual energy which is absorbed by the fibre in the form of vibrational states (phonons). The energy of these vibrational states is dependent on the material properties, so the way the energy is transferred from the lower wavelengths to the higher wavelengths (gain spectrum) is a characteristic of the particular medium. For a silica fibre, the maximum Raman conversion efficiency is achieved when the energy is transferred from the pump to radiation with frequency about 13.2 THz lower.In recent years, the exploitation of the Raman effect in optical fibre has opened the door to many important applications in photonics that have had an immediate impact in the photonics and communications industry. The possibility of shifting energy from one frequency to another by relying solely on the properties of the material is a very powerful and attractive one that has translated, for example, in the creation of Raman fibre lasers, distributed amplifiers and frequency converters. Of the previously mentioned applications, distributed amplification is perhaps the technology with the potential for a higher short-term effect in the future of telecomms industry, as it seems to hold the key for the deployment of future high-capacity optical communication links, thanks to its ability to increase system performance and expand the range of operating wavelengths. Recently, we have demonstrated that the Raman effect can be used to transform long fibre optic communication links as a whole into ultra-long lasers, creating in the process the longest cavity laser in existence. When transmitting information through such an ultra-long laser, Raman gain distribution is close to ideal, and the signal is spared from suffering power variations during transmission, which can bring important benefits in terms of noise reduction and improved system performance.Lossless transmission has been a long-term dream goal of optical communications that would bring with it a reduction of the noise in the line, as well as create exciting possibilities for research in the fields of nonlinear physics and applied mathematics. But ultra-long lasers are very interesting devices that can be used not only as virtually lossless communication channels, but also as light sources.Ultra-long Raman laser transmission spans represent a simple but quite radical new concept that has attracted much interest in recent times, both due to their numerous potential applications and to the exciting underlying physics associated with the concept itself.As originators of the idea, the principal investigator and the Photonics Research Group at Aston University are perfectly suited to the task of expanding and advancing it. The funding of this proposal would prove invaluable for acquiring the manpower and basic equipment required to take this original research to the next level.