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研究生:洪國倫
研究生(外文):Guo Lun Hong
論文名稱:染料參雜液晶光纖產生隨機雷射
論文名稱(外文):Random lasing of dye-doped LC in capillary fiber tube
指導教授:林家弘林家弘引用關係
指導教授(外文):Ja-hon Lin
口試委員:吳俊傑賴暎杰謝文峰
口試委員(外文):Jin-Jei WuYin-Chieh LaiWen-Feng Hsieh
口試日期:2012-07-26
學位類別:碩士
校院名稱:國立臺北科技大學
系所名稱:光電工程系研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2012
畢業學年度:100
語文別:英文
論文頁數:44
中文關鍵詞:液晶光纖隨機雷射
外文關鍵詞:Liquid crystalfiberRandom laser
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相對於傳統的雷射,隨機雷射因為不需要傳統的共振腔,因此它的產生機制引起了許多研究者廣泛的研究。一般來說,隨機雷射中除了增益介質還加入散射性的介質,藉由光的嚴重散射達到光場侷限的效果,並使得增益大於損耗進而產生雷射光輸出。由於少了實際共振腔的選頻效果,隨機雷射的出射光中有數個不同中心波長的譜線同時被激發,且這些光譜的線寬會隨著泵激功率的增加而變窄。在本篇論文中,我使用向列型液晶當作散射介質並摻入染料作為增益介質,經毛細現象填入空心光纖的毛線管,再使用Q開關綠光雷射作為激發光源,激發此光纖元件來產生隨機雷射。由實驗我證實利用E7參雜染料DCM和PM597的光纖,所產生的出射光譜有數根相當窄線寬的受激輻射譜線被激發,而且到當泵激能量超過適當的閥值,輸出的斜效率會明顯的上升,證實所產生的出射光為受激輻射光,此外所產生譜線的波長會隨著泵激功率的增加往短波長飄移,推論是由於液晶熱效應所造成。當散射的液晶改成MDA-00-3461參雜PM597的光纖時,所產生的出射譜線較使用E7寬,可以看出有數個特徵頻率組合而成,由輸出強度與泵激功率的關係得到,當泵激功率增加的時候,發現有第二斜效率與臨界值產生。

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.

Outline
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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