Manipulation of random laser from dye-doped twisted nematic liquid crystal within wedge cell

• Main Authors: LIN SHENG HUNG, 林聲宏
• Other Authors: LIN JＡ HON
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/ws2r2d

碩士 === 國立臺北科技大學 === 光電工程系研究所 === 104 === In this work, the orthogonal linear polarized random lasing beams was determined by the local director of LCs at two output plates from dye-doped twisted nematic liquid crystals (DD-TNLC) within the wedge cell. In addition, we also indicated that the resonant property of random laser can be successfully manipulated by means of a number of parameters, such as temperature, pump polarization and focused pump position. Through the thermal control, the lasing threshold of DD-TNLC laser decreased and slope efficiency increased with temperature while the operation temperature was below 25oC. At even higher temperature, the slope efficiency of random laser is declined because of thermal frustration. Besides, we controlled the output intensity of random laser through the orientation of the pump polarization relative to the rubbing direction at the incident plate. After spatially shift of the cell to vary the location of focused pump beam onto the cell with different thickness, we could also change the emission wavelength of DD-TNLC laser. In comparison with the FP laser, we demonstrated that the random laser reveal the lower speckle noise and higher discrimination after illuminating the Air Force test chart. All the measured results demonstrated that the controllable characteristics of DD-TNLC that will be practical used to the sensor, speckle noise suppression in some optical systems.