Fiber Optics for Fundamental Science and Applications

光纤是现代互联网的支柱，它跨越的科学领域要比唯一的电信领域大得多。增加光纤的输入光功率通常会增加信号的传输距离，但功率增加太大会引起非线性效应，这在电信中是避免的，因为它会导致信号失真。克尔效应是一种非线性效应，描述了光传播时有效折射率的功率依赖性。非线性折射率可以通过自相位调制和交叉相位调制等技术来控制时空变化。布里渊散射是另一种非线性效应，其中光纤波导的声学模式通过电伸缩与光耦合。这项发现计划的总体愿景是研究光纤中的非线性光-物质相互作用，以推进基础科学和实际应用。目的1是研究与爱因斯坦广义相对论（GR）一致的偏振相关光在非线性光纤中的传播运动学。这种联系可以从以下事实看出：根据GR，光沿着零等的测地线运动。这可以得到光在各向同性折射率为n的介质中的两个一阶运动方程：dl/dt=±c/n。对于非线性折射率和偏振依赖，必须使用涵盖黎曼几何的芬斯勒几何。注意GR的基础是黎曼几何。利用更一般的芬斯勒几何对偏振依赖的非线性光运动学的基本理解，可以为理解我们的宇宙产生新的想法，比如暗能量问题，因为芬斯勒几何嵌入了时空扭转和时空曲率等特征。GR中的时空曲率已经给我们提供了类似黑洞的概念，这是最近用视界望远镜看到的。目的2建立基于前向和后向布里渊散射的光纤传感分布式多参数（温度、应变和声阻抗）模型。声波模式通过布里渊散射与光的耦合使得光纤本身充当传感介质成为可能。目的三是发展用于产生分数轨道角动量纠缠光子对的金属楔形硫族化物薄光纤。薄金属楔使分数轨道角动量模式和硫族核心处的局部尖锐金属曲率降低了非线性阈值光功率。这将提供一种光纤兼容的量子纠缠光子对源，有可能加速量子加密通信的应用。该研究项目将理论与应用相结合，为加拿大科技行业和学术界培养一批高技能的研究生和本科生。

Optical fibers, the backbone of the modern internet, span a much larger area of scientific fields than the sole telecomm domain. Increasing the input light power in fibers normally increases the signal transmission distance, however, too large of a power increase will induce nonlinear effects, which are avoided in the telecomm since they lead to signal distortion. The Kerr effect is a nonlinear effect that describes the power dependence of the effective refractive index for light propagation. The nonlinear refractive index can be controlled both spatially and time varying, by techniques such as self-phase and cross-phase modulations. Brillouin scattering is another nonlinear effect, where acoustic modes of the fiber waveguide are coupled to the light via electrostrictions. The overarching vision of this discovery program is to study the nonlinear light-matter interactions in fibers for the purpose of advancing fundamental science and practical applications. Objective 1 is to study the Kinematics of polarization dependent light propagation in nonlinear fibers consistent with the Einstein's General Relativity (GR). This link is seen from the fact that according to GR, the light follows the geodesic of null magnitude. This can give rise to two first-order equations of motion for light in a medium with the case of isotropic refractive index n: dl/dt=±c/n. For the nonlinear refractive index and the polarization dependence one must use Finsler geometry that covers Riemannian geometry. Note that GR has its base in Riemannian geometry. The fundamental understanding of polarization dependent nonlinear light kinematics using more general Finsler geometry can generate new ideas in understanding of our universe such as issues of dark energy, because Finsler geometry embeds features like space-time torsion as well as space-time curvature. Space-time curvature in GR already gives us ideas like black-hole that is shown recently with Event Horizon Telescope. Objective 2 is to develop distributed multi-parameter (temperature, strain and acoustic impedance) model for fiber sensing based on the combined forward and backward Brillouin scatterings. Coupling of the acoustic modes with the light via Brillouin scattering enables the possibility of fiber itself acting as a sensing medium. Objective 3 is to develop thin metallic wedged chalcogenide fibers for the purpose of fractional orbital angular momentum entangled photon pair generation. The thin metallic wedge enables the fractional orbital angular momentum mode and local sharp metallic curvature at the chalcogenide core reduces the nonlinear threshold light power. This will supply a fiber-compatible quantum entangled photon pair source that has the potential to speed up the application of quantum encryption communication. Combining theory and application, this research program will train a cohort of highly-skilled graduate and undergraduate students for Canadian technological industries and academia.