发表机构
Istanbul Okan University; Pamukkale University（伊斯坦布尔奥坎大学; 帕穆克卡莱大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究侧耦合光子晶体微腔的品质因子离散调控机制，发现每行因子由倏逝Bloch通道衰减决定，并需有限元胞修正，设计在1550nm灵敏度达634nm/RIU。
AI 中文摘要
通过平面波展开和时域有限差分计算，研究了浸没在水性分析物中的硅柱二维光子晶体中，与W1波导侧耦合的点缺陷微腔。缺陷柱半径的平方变化使得共振频率连续穿越横磁带隙，这与一阶微扰理论对恢复至晶格位点的介电面积的预测一致。品质因子则由腔与波导之间的间隔决定，该间隔以晶格行数计数：在参考缺陷半径下，每增加一行，品质因子乘以7.10，而将缺陷柱移动至多十分之一晶格周期，品质因子变化小于7%。每行因子在两种缺陷半径下，且无需可调参数，遵循晶体在导模波矢处最慢倏逝Bloch通道的衰减规律。在有限元胞中信任这些数值之前，需要进行两项检查：包层厚度的收敛性以及去除波导端面反射。若不进行这些检查，每行因子会偏低，品质因子误差可达两倍。按1550纳米波长缩放，该设计给出每折射率单位634纳米的灵敏度，微扰理论可复现此结果，且对独立归一化透射谱的Fano拟合确认了线宽。该波长下水的吸收使参考几何结构的品质因子降低三分之一，并将其上限限制在约9200，这限制了进一步增加行数的益处。
英文摘要
A point-defect cavity side-coupled to a line-defect waveguide in a two-dimensional photonic crystal of silicon rods in water is studied with plane-wave expansion and finite-difference time-domain computations. The defect-rod radius tunes the resonance continuously within the band gap, as first-order perturbation theory predicts, whereas the quality factor changes in discrete steps set by the number of lattice rows between cavity and guide; displacing the defect rod by up to a tenth of a period changes it by less than 7 percent. Each added row multiplies the quality factor by a factor that follows, without an adjustable parameter, from the decay of the evanescent Bloch channel of the bulk crystal that is phase-matched to the guided mode; the channel at zero wavevector along the guide predicts little more than half that factor. Two biases of a finite computational domain, leakage across the cladding and a standing wave set up by reflections at the ends of the truncated guide, lower the per-row factor and change the quality factor by up to a factor of two if left uncorrected. Scaled to 1550 nm the design gives a sensitivity of 634 nm per refractive index unit, which perturbation theory reproduces, and the linewidth agrees with that of a transmission spectrum normalized to a cavity-free reference. Absorption by water caps the quality factor near 9200 and limits the useful number of barrier rows. The guided mode lies inside the light cone, so a slab of finite height needs a different guide.
Comments26 pages, 7 figures, 5 tables. Data, code and supplementary material: doi:10.5281/zenodo.22912910
