Theoretical proposal of a low-loss wide-bandwidth silicon photonic crystal fiber for supporting 30 orbital angular momentum modes

We propose a novel four-ring hollow-core silicon photonic crystal fiber (PCF), and we systematically and theoretically investigate the properties of their vector modes. Our PCF can stably support 30 OAM states from the wavelength of 1.5 μm to 2.4 μm, with a large effective refractive index separation of above 1×10−4. The confinement loss is less than 1×10−9 dB/m at the wavelength of 1.55 μm, and the average confinement loss is less than 1×10−8 dB/m from the wavelength of 1.2 μm to 2.4 μm. Moreover, the curve of the dispersion tends to flatten as the wavelength increases. In addition, we comparably investigate PCFs with different hole spacing. This kind of fiber structure will be a potential candidate for high-capacity optical fiber communications and OAM sensing applications using fibers.本研究提出一种新型四环空心芯硅基光子晶体光纤（Photonic Crystal Fiber，PCF），并从理论层面系统探究了其矢量模式的特性。该光子晶体光纤可在1.5 μm至2.4 μm的波长范围内稳定支持30个轨道角动量（Orbital Angular Momentum，OAM）态，且有效折射率间隔大于1×10^-4。在1.55 μm波长处，其限制损耗低于1×10^-9 dB/m；在1.2 μm至2.4 μm的波长区间内，平均限制损耗低于1×10^-8 dB/m。此外，其色散曲线随波长升高逐渐趋于平坦。同时，本研究还针对不同孔间距的光子晶体光纤开展了对比研究。该类光纤结构有望成为大容量光纤通信以及基于光纤的轨道角动量传感应用的潜在候选方案。