近20年來，親手性超穎材料(Chiral metamaterials)的圓二色性已經被大量研究。圓二色性(Circular dichroism, CD)量測在生物分子的鑑別上一直扮演著重要角色，而親手性結構在對於分辨左右旋光差異的CD效應上有著優異的光學活性和負折射率。當電磁波通過手性結構表面時，陣列手性結構可以更有效地改變穿透率來提高光學活性。因此，通過適當的結構設計，可以看到強烈的光學活性現象和增強CD訊號，例如雙層共軛卍字型結構。
我們將金屬的雙層共軛卍字型結構放在矽光波導尾端出光面上形成親手性超表面並觀察圓二色性現象。激發波源將不使用傳統的入射光直接激發結構的方式，而改用可包含低至高階不同模態的光波導波源。模擬上使用有限時域差分法(Finite- difference Time-domain method, FDTD method)做為數值模擬工具。實驗設計主要分為四部份探討1.結構大小效應2.層與層之間的距離效應3.旋轉結構效應4.光波導波源效應。以光波導一階模態作為激發源時，在結構大小改變上共振波長將隨著結構增大而紅移，層與層之間的距離增大時共振波長將藍移。而不同階數的光波導模態對應於不同旋轉角度的結構時顯示出特別的CD結果。一階模態激發時，即使結構旋轉不同角度也可得到相同的CD結果，意即CD值大小不受旋轉角度影響;二階模態激發時，由於模態本身具有對稱性的緣故整體能量會互相抵消，因此我們無法使用這種模態作為激發波源; 三階模態激發時，結構旋轉的角度在不同波長下顯示出了不同大小的CD值，更特別的是在長波長之下還會產生CD值反轉的現象。
因此，我們藉由探討光波導波源跟親手性結構之間的交互作用給出了一種新的測量觀點，使用光波導管不僅在測量上較便利，還可以直接透過調整不同模態來改變輸出CD結果，更可以藉此達到製作多個含有不同結構的波導元件來達到集成的效果。

In the past 20 years, the circular dichroism of chiral metamaterials has been extensively studied. The circular dichroism (CD) measurement has always played an important role in the identification of biomolecules. For a well-designed chiral metamaterial structure, it has excellent optical activity and a negative refractive index that can be distinguished the CD difference when it excited by the left-hand or right-hand circular polarized light. When electromagnetic waves pass through the surface of the chiral structure, the transmittance can be changed by the chiral structure array then the optical activity is improved. Therefore, through proper structural design, we can respect more strongly optical activity and CD signal enhancement, for example, double-layer conjugated gammadion structure is a good candidate could be considered.
In our research, we chose the conjugated gammadion structure that has been widely discussed. The gold double-layer conjugated gammadion structure is placed on the end surface of a silicon optical waveguide to observe the CD signal. The optical waveguide source that contains first, second, and third order waveguide modes instead of the traditional optical source. For the numerical simulation, the Finite-difference Time-domain (FDTD) method is used for all calculations and simulations. For the experimental design could be divided into four parts in discussion: 1. Size effect 2. Layer-to-layer gap effect 3. Structure rotating effect 4. Optical waveguide source effect. When the gammadion structure is excited by first order waveguide mode, the resonance peak red-shifted with the structure size increased. Also, the resonance wavelength is blue-shifted if the gap between the layer-to-layer is increased. To change the rotation angles also revealing totally different CD results. For using the first order waveguide mode, the same CD result can be obtained even if the structure is rotated at different angles, which means that the CD value is not affected by the rotation angle excited by first order waveguide mode; For using the second order waveguide mode, the overall energy will interact with each other due to the symmetric property, so we are not considered to use it to be an excitation source; For using the 3rd order waveguide mode, rotating the structure is affects the CD results strongly. It shows different values correspond to the wavelengths, the CD values even reversed between the shorter and longer wavelength.
In this research, we provide a new concept for experiment design and CD measurement. An optical waveguide with the end face chiral structure is not only convenient in measurement but also has an ability to change the output CD results by adjusting different waveguide modes. Furthermore, each waveguide device can be collected to achieve integrated measurement.

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