基于定向耦合效应设计可以任意弯曲的二维光子晶体分束器

Arbitrarily Bent Beam Splitter Using Photonic Crystal Co-directional Coupling Mechanism

利用二维光子晶体的自准直和定向耦合效应设计了一种由一个自准直区域、耦合区和两个周期性介质波导组成分束器,利用平面波展开法从理论上研究了耦合区的色散关系,计算得到了耦合长度,同时使用时域有限差分方法模拟了电磁波在其中的传输特性,得到了稳态的电场分布,讨论了光波从自准直区域到光子晶体波导高效耦合的技术。结果表明:在相位匹配条件下,从自准直区域传播到耦合区域的的电磁波可以有效的分束到两个周期性介质波导中,同时能够弯曲任意角度,而且透射率保持在90%以上。最后,在设计的分束器基础上提出了一种增大点源和像点之间距离的方法。

By utilizing the self-collimation and co-directional coupling mechanism, an arbitrarily bent beam splitter is designed and analyzed theoretically, which is composed of a self-collimation zone, a coupled zone and two periodic dielectric waveguides. Dispersion relation in the coupled zone is analyzed theoretically using plane-wave expansion method, and the coupled length is calculated. The transmission character of electromagnetic wave in splitter is simulated by finite-difference time-domain simulations, and the steady electric field distribution is obtained. Effective coupling technique of coupling lightwave from self-collimation zone to coupled zone is discussed. The result shows that if the phase matching conditions are satisfied the light can be injected into the coupling section and transferred into the two output branches efficiently, the angle can be bent to arbitrary value, and the transmittance is above 90%. A new method which enlarges the distance of point source and image point based on the designed splitter is proposed.