光子晶體為近年來被發現的新領域，且開始投入大量的研究，光子晶體是一種人造的周期性結構。此一人造結構就如同自然界物質的原子晶格排列，只不過原子的排列周期以埃(1埃=10-10公尺)，而光子晶體周期則習慣以光的波長為使用單位。由於光波與電子的機率波都是波函數，因此我們可以知道，光在光子晶體中的波形，應該類似於電子在物質內分布模式。
　　利用膽固醇液晶具有之螺旋結構，引致空間折射率周期變化，且其具有極大的雙折射性，我們將之視為”一維的光子晶體”。在膽固醇液晶添加雷射染料後，由於其具有光子晶體能隙特性，其結構即如同共振腔，所以在適當激發下，可做成一個不用外加共振腔的雷射元件。
　　另外，本論文除了探討此新型雷射元件之特性外，也針對此元件的應用做一些研究，如開關方法,頻率調整…等。

This letter addresses a dye-doped planar cholesteric cell as a one-dimensional photonic crystal, which can be lased at the band edges of the photonic band gap. The effect of the composition of the material and the thickness of a cholesteric cell (CLC) on the lasing action, and the photo-control of the lasing frequency, are experimentally investigated. Adding a tunable chiral monomer (TCM) allows the CLC’s reflection band to be tuned by varying the intensity and/or exposure time of the UV curing light, enabling the lasing frequency of the CLC sample to be tuned.

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