基于波导间能量耦合效应的光子晶体频段选择与能量分束器

基于波导间能量耦合效应的光子晶体功率分束器具有结构紧凑、带宽较宽、弯曲损耗低、分光角度大和不受外界电磁场干扰等优点.本文利用时域有限差分方法,理论研究了二维三角晶格光子晶体耦合波导的功率分束特性,设计得出了一种能够在宽频谱范围内针对不同频率区间实现不同分光比的功能器件.在此基础上通过改变耦合区介质柱形状以及输出分支波导与能量耦合波导的连接位置,最终针对三个相邻频率范围内的入射光信号,较好地实现了三均分、二均分、单一输出通道这3种能量分配输出模式.该功能器件具有透过率对比度高、结构紧凑等特性,对于发展全光功能器件在大规模全光复杂集成领域内的实际应用具有一定的促进作用.

Photonic crystal frequency band selecting and power splitting devices based on the energy coupling effect between waveguides

The photonic crystal power splitter based on the energy coupling effect between waveguides has the advantages of compact structure, wide bandwidth, low bending loss, large angle of separation, and no external electromagnetic interference. In this paper, the power splitting characteristics of two-dimensional triangular-lattice photonic crystal coupled waveguide are theoretically studied by using the finite-difference time-domain method, and a functional device is designed in order to achieve different output power ratios within different frequency ranges.
In the two-dimensional photonic crystal structure with triangular lattice, we set two adjacent straight waveguides and the light beam is introduced from one of them. Because of the energy coupling effect between the two line defects, the light energy propagates alternately in them. Based on this principle, structures of different coupling lengths are simulated and the interference effect of each surface is considered. The device with the best coupling length is achieved for three different output energy propagating characteristics at different frequencies, which include three-division, two-division and single output cases. That is to say, the incident light beam within a frequency band travels through a particular waveguide; light in another frequency band only flows through the other two output waveguides; light in the third frequency band is assigned to all the three output waveguides equally. However, the frequency band width for the high-quality light beam splitting area as well as the transmittance contrast of the other two functional band areas are not very ideal.
Based on the above numerical results, two transmission modes in the coupling waveguides are achieved by changing the cross section shape of the dielectric column in the coupling region and also by changing the connecting position between the output branch waveguide and the energy-coupling waveguide. Through the above change, the splitting performance is further optimized.
By detecting and analyzing the relative intensity of the three output waveguides, we can determine the range of the incident light beam. Furthermore, the frequency ranges of the three different light output characteristics can be adjusted flexibly by changing the cross section shape of the dielectric column in the coupling region or by changing the connecting position of output waveguides. The functional device proposed in this paper has a high transmittance contrast ratio and a compact structure, which will promote the practical application of the all-optical functional devices in the fields of large-scale all-optical complex integration.