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研究生(外文):Guo Lun Hong
論文名稱(外文):Random lasing of dye-doped LC in capillary fiber tube
指導教授(外文):Ja-hon Lin
口試委員(外文):Jin-Jei WuYin-Chieh LaiWen-Feng Hsieh
外文關鍵詞:Liquid crystalfiberRandom laser
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Comparing to traditional lasers, the mechanism of random lasers have been extensively studied by many researchers because no traditional cavity mirrors are needed. In general, the distributed dielectric materials are needed in addition to the gain medium. Therefore, the serious light scattering will occur to result in the electric field confinement and makes the gain become greater than losses so that stimulated emission generation eventually. Generally, several emission lines with different central wavelengths can be simultaneously excited in random laser without frequency selection or filtering effect from traditional mirrors. These spectral linewidth will be narrowing with pumping power increasing. In this work, different kinds of nematic liquid crystals were chosen as a scattering medium to mix with the laser dye as the gain medium and then filled it into the hollow fiber tube by capillary effect. In order to generate random lasing in this fiber tube, a frequency doubling Q-switched green laser was used as the excitation source. In our observation, several narrow peaks can be seen through infilling DCM and PM597 doped E7 into hollow core fiber tube. The output slope efficiency increase obviously while the pumping energy was greater than the certain threshold to confirmed the stimulated emission light generation in our dye-doped LC infilling fiber tube (DDLC-IF). Besides, the wavelength of the emission peaks will shift to the shorter wavelength at higher exciting energy. In this work, the other NLC MDA-00-3461 mixed PM597 was infill into capillary fiber tube to produce broaden linewidth than E7 that was consisted of several characteristic frequency, but linewidth will shrink at higher pulse energy to demonstrate the presence of random lasing.

Chinese abstract I
English abstract II
Acknowledgment IV
Content V
List of table VI
List of figures VII
Chapter 1. Introduction 1
1.1 Types of liquid crystals 1
1.2 Liquid crystal laser 5
1.3 Random lasing 8
1.4 Motivation 10
Chapter 2. Theoretical background 11
2.1 Liquid crystal optical 11
2.1.1 Thermal effect on NLC 11
2.2 Random laser 13
2.2.1 Theory of random laser 13
2.2.2 ? factor 14
Chapter 3. Experiment 17
3.1 Sample preparation 17
3.2 Experimental setup 18
3.2.1 Emission spectrum measurement 18
Chapter 4. Results and discussion 19
4.1 Random lasing from PM597 and E7 19
4.1.1 0.5%PM597 doped E7 19
4.1.2 1%PM597 doped E7 24
4.2 Random lasing from DCM and E7 28
4.2.1 0.7%DCM doped E7 28
4.2.2 1%DCM doped E7 32
4.3 Random lasing from PM597 and MDA-00-3461 35
4.3.1 0.5%PM597 doped MDA-00-3461 35
Chapter 5. Conclusions 40
References 41
Appendix 44

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