Investigation of dye-doped LCs lasers with the application for the speckle

• Main Authors: Yi-Han Li, 李亦涵
• Other Authors: 林家弘
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/8kv722

碩士 === 國立臺北科技大學 === 光電工程系研究所 === 105 === The distinguished characteristic of dye doped liquid crystal (DD-LC) laser within different geometric shapes of cells and rubbing polyimide (PI) on ITO glass were investigated in this work. After infilling of LC mixtures into a parallel cell with anti-parallel rubbing PI and a wedge cell with only one side rubbing PI, the Fabry-Perot (FP) laser and the random laser (RL) can be produced, respectively. First of all, the output polarization of DD-LC laser can be controlled by the alignment of lasing dye at the output plate, which was influence by the restricted LCs from rubbing PI on ITO glass. Thus, linear polarized light was generated from LC cell with rubbed PI on ITO glass but un-polarized output emission light was produced from the cell without rubbing PI on glass. Besides, we verified the behavior of RL from DD-LC mixtures into different geometric cell by the alpha -stable distribution after grabbing 1000 spectrum slots from different output plate of sample. It shows the Gaussian distribution with alpha=2 for FP laser and Lévy distribution with alpha =1.77 and alpha =1.11 from rubbing and un-rubbing plane of wedge cell. The obvious difference can be attributed to the light scattering within DD-LC mixture with different transport mean free path about 19.9 um, 9.9 um and 5.45 um that was measured by using the coherent backscattering technique. In addition, the spatial coherence of three DD-LC lasers was determined from Young’s double slit experiment that revealed the lowest spatial coherence from the wedge cell without rubbing PI and showed the lowest contrast monochromatic speckle patterns about 0.039.