Finite Difference Time Domain Modeling of Lasing Actions in Cholesteric Liquid Crystals

• Main Authors: Zai-FongPeng, 彭載峰
• Other Authors: Shih-Hui Chang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/41844883304024792258

碩士 === 國立成功大學 === 光電科學與工程學系 === 100 === Tunable properties of Cholesteric liquid crystals (CLC), such as changing its periodic pitch distance and refractive index through applied electric field, temperature and pressures, make CLC a potential candidate for tunable laser cavity. In this thesis, we use finite-difference time- domain (FDTD) method, including split field transformation for periodic boundary condition, perfect matching layer (PML) for absorbing boundary condition, and four level laser model for dye gain medium doped in CLC, to analyze lasing actions in CLC. We use FDTD code developed in this thesis work to simulate one dimensional CLC laser. We observed lasing actions through band edge modes in cholesteric liquid crystals and analyzed its lasing threshold. By using simple laser cavity model, we estimated the gain coefficient from the pumping rate and the loss coefficient from the transmission spectrum of the passive CLC cavity. By varying the pitch distance, refractive index and incident angle, we achieved in controlling the lasing wavelength and lowering the pumping threshold.