具形狀雙折射微結構之手徵光子晶體的光學特性

Optical Properties of Chiral Photonic Crystals Containing Birefringent Microstructural Forms

本文利用有限元素法分析以高空間頻率光柵作為手徵光子晶體缺陷的光子局域化現象。透過修改光柵參數，如溝槽深度、填充因子和混合材料的折射率，把高空間頻率光柵所產生的形狀雙折射效應引入手徵結構，而這樣的缺陷對於和螺旋結構有相同手性的圓偏振光會產生穿透度上的峰值。由形狀雙折射效應所產生的人造介電材料，在光的限制和操控上會扮演十分重要的角色，會影響缺陷模態的位置，能量穿透度以及相位延遲。而改變與光柵相互搭配的介質，缺陷波長會隨著介質折射率的變化產生線性的改變。這種具有光柵結構的手徵性光子系統能夠提供另一種可能性的方法來建構實際的光子裝置，例如生物/化學感測器或折射率計。 Photonic localization in a chiral photonic structure with defective high-spatial-frequency gratings was investigated by using the finite element method. The form-birefringence effect, caused by grating high-spatial frequency, is introduced into the chiral structure by modifying the grating parameters, such as groove depth, filling factor, and refractive index of the intermixing material. This defect gives rise to a peak in transmission for circularly-polarized light having the same handedness as the helical structure. The artificial dielectrics, caused by the form-birefringence effect, play a fundamental role in restraining and manipulating light to affect the location, power transmittance and phase retardation of the defect mode. By changing the intermixing material of the grating into a different medium, the linearity of the sweep in a defective wavelength depends on the refractive index of the medium. This procedure can be applied to real photonic devices. For example, an optical refractometer or a (bio-)chemical sensor can be designed by replacing the intermixing material by the medium to be measured.