Optical spin or circular polarization provides a new degree of freedom to control light–matter interaction in the fundamentals and applications of light. To broaden the bandwidth of chiral (spin-controlled) coupling in photonic integrated circuits, we propose fork-type inversely tapered nanowire waveguides to compensate for the out-of-step phase evolution of adiabatic coupling between ${{\rm TE}_0}$ and ${{\rm TM}_0}$ (${{\rm TE}_1}$) modes excited from the $x$- and $y$-polarization components of spin polarized light in free space, respectively. We design and simulate two kinds of devices based on air and ${{\rm Si}_3}{{\rm N}_4}$ up-claddings to show the feasibility of broadening the bandwidth of chiral silicon photonic circuits by using fork-type inverse tapers. Numerical results show that the bandwidth can approach 70 nm under high directionality of above 0.90. This broadband chiral coupling via the new phase synchronizing technique with fork-type inverse tapers may pave the way to develop on-chip spin photonics or polarization-based photonic integrated devices.

中文翻译：

---

基于叉型反锥形纳米线波导的宽带手性硅光子电路

光学自旋或圆偏振提供了一种新的自由度，可以控制光的基本原理和应用中的光-物质相互作用。为了拓宽光子集成电路中手性（自旋控制）耦合的带宽，我们提出了叉型反锥形纳米线波导，以补偿$ {{\ rm TE} _0}之间绝热耦合的失步相位演化。$和$ {{\ rm TM} _0} $（$ {{\ rm TE} _1} $）模式分别受自由空间中自旋偏振光的$ x $和$ y $偏振分量激发。我们基于空气和$ {{\ rm Si} _3} {{\ rm N} _4} $设计和模拟两种设备上覆层，以显示通过使用叉型反锥度来扩大手性硅光子电路带宽的可行性。数值结果表明，在高于0.90的高方向性下，带宽可以接近70 nm。通过新型相位同步技术与叉型反锥度的宽带手性耦合，可以为开发片上自旋光子或基于偏振的光子集成器件铺平道路。