AI 中文总结
该研究通过理论和实验证明，光子分子（多耦合纤芯波导）利用非线性轨迹对初始条件的极端敏感性，能在相同输入功率下产生比单芯光纤更宽的超连续谱，为非线性光纤设计提供了简单改进方案。
AI 中文摘要
在高非线性光纤中产生宽光谱光，在光谱学、显微镜和医学成像中具有广泛应用。为产生这种“超连续谱”，将超短光脉冲注入高非线性光纤，随后在称为自相位调制的过程中，光纤的非线性效应使脉冲在传输过程中产生啁啾，进而使光谱开始展宽，触发进一步的级联非线性过程。超连续谱产生相关的动力学在数学上被描述为脉冲轮廓随时间演化且占据单一空间模式。本文从理论和实验上证明，由多个耦合纤芯构成的波导——即“光子分子”——相比单一纤芯，在相同输入功率下能产生更强的自相位调制。这看似违背直觉，因为人们通常认为将所有光功率集中在单个波导中可获得最强的非线性效应。这种增强的展宽源于非线性动力学分岔点附近轨迹的极端敏感性，该敏感性会导致脉冲时间形状发生畸变，进而产生更宽的光谱。该效应与耦合谐振器系统中奇异点相关的敏感性类似，但不会遭受噪声的寄生影响。这表明，通过引入多个纤芯这一常规非线性光纤设计的简单改进，由自相位调制注入的超连续谱光源可产生显著更宽的光谱。更广泛地说，这证明非线性动力学相关的初始条件敏感性可用于在光学中产生更强的非线性效应。
英文摘要
The generation of a wide spectrum of light in highly nonlinear optical fibers has broad application in spectroscopy, microscopy and medical imaging. To generate such a 'supercontinuum', an ultrashort pulse of light is injected into a highly nonlinear fiber. Then, in a process called self-phase modulation, the nonlinearity of the fiber causes the spectrum to start broadening as the pulse becomes chirped during propagation, seeding further cascaded nonlinear processes. The dynamics associated with supercontinuum generation are captured mathematically as a pulse profile evolving in time and occupying a single spatial mode. Here, we theoretically and experimentally demonstrate that a waveguide composed of multiple coupled cores - a photonic molecule' - rather than just a single core, gives rise to greater self-phase modulation for a given input power. This is perhaps counterintuitive because it may be naively expected that the strongest nonlinear effects would be achieved by concentrating all optical power in one waveguide. The increased broadening arises due to the extreme sensitivity of trajectories near a separatrix of the nonlinear dynamics. This sensitivity leads to a distortion of the temporal shape of the pulse, resulting in a broader spectrum. The effect is reminiscent of the sensitivity associated with exceptional points in coupled-resonator systems, but does not suffer in the same way from the parasitic effects of noise. This suggests that by including multiple cores, a straightforward modification of conventional nonlinear fiber design, supercontinuum sources seeded by self-phase modulation can generate a significantly wider spectrum. More broadly, this demonstrates that the sensitivity to initial conditions associated with nonlinear dynamics may be utilized to generate stronger nonlinear effects in optics.
