和一般傳統雷射相比，隨機雷射不需要固定的反射鏡作為共振腔，其形成機制主要是利用散射介質形成類似共振腔結構的封閉散射迴路，使光在其中產生多重散射而產生雷射光輸出。藉由這種機制產生的雷射光，有多頻與多方向輸出、製程簡單、元件尺寸小等特性，可以運用在照明、雷射成像、積體光路微型光源或醫療上。
　　本論文主要研究染料摻雜液晶添加奈米粒子填入內徑為20μm的空芯光纖所產生之隨機雷射現象，同時藉由改變溫度與電場來調變隨機雷射輸出的特性，而產生之隨機雷射可藉由全反射傳輸出光纖，使得輸出方向固定而減少收光之損耗。我們發現添加奈米粒子可以有效降低染料摻雜液晶之光纖樣品的臨界脈衝能量，其中添加鈦酸鋇奈米粒子後能使臨界脈衝能量減少約2.95μJ/mm2，添加銀奈米粒子後則使臨界脈衝能量大幅減少約12.91μJ/mm2。同時，利用調控外界溫度的方式，可改變隨機雷射的輸出波長與強度。另外，利用外加電場的方式，我們可將輸出隨機雷射切換於共振型與非共振型之間。最後，我們添加不同濃度之奈米粒子至染料摻雜液晶中並觀察其輸出特性來求得最佳的奈米粒子濃度，其中最佳鈦酸鋇奈米粒子濃度為0.3wt%，其臨界脈衝能量約為27.56μJ/mm2，最佳銀奈米粒子濃度則為0.4wt%，其臨界脈衝能量約為16.27μJ/mm2。

Compared with conventional lasers, random lasing can be generated by using an active medium and scattering materials without any requirement of fixed reflection mirrors to form a cavity. The scattering materials can provide multiple light scattering paths to form scattering loop paths for random lasing. Lasing emitted from such mechanism provides some unique characteristics, such as the multi-mode lasing, multi-direction emission, simple manufacturing process, and small device sizes. Therefore, random lasing leads to many potential applications for lighting, spackle-free imaging, miniature light source in integrated photonic circuits or medical arena.
In this thesis, random lasing with resonant feedback can be observed from a 20μm-core hollow optical fiber filled with dye-doped liquid crystals(DDLCs) containing nanoparticles. At the same time, the tunable emission properties of the generated random lasing is realized by changing the operation temperature and the applied electric field. Besides, the generated lasing emission can be confined in the fiber core by the total internal reflection effect with a fixed direction, which can reduce the losses while measuring the emission signals. We found that the threshold pumping energy of the DDLC with nanoparticles in fibers can be effectively reduced. The threshold pumping energy can be reduced about 2.95μJ/mm2 by doping BaTiO3 nanoparticles, and 12.91μJ/mm2 of threshold pumping energy can be reduced by doping Ag nanoparticles. We have also observed that the emission wavelength and intensity can be controlled by the operation temperature. In addition, the emission can be switched between resonant random lasing and non-resonant random lasing by applying the external electric field.
Finally, to obtain the optimum lasing efficiency, we observed DDLCs containing different concentrations of nanoparticles. Optimum lasing efficiency can be obtained by using 0.3wt% BaTiO3 nanoparticles with 27.56μJ/mm2 threshold pumping energy, and by using 0.4wt% Ag nanoparticles with 16.27μJ/mm2 threshold pumping energy.

目錄

致謝……………………………………………………………………………………i
中文摘要…………………………………….……………….……………….…….…ii
ABSTRACT……………………………………………………………………….iii
目錄……………………………………………………………………………….…….v
表目錄………………………………………………………………………….…......vii
圖目錄……………………………………………………………………………..…viii
第一章 簡介…………………………………………………………………………….1
1.1 隨機雷射簡介………………………………….....………………………….….….1
1.1.1 隨機雷射的理論與機制……………………………………...……..………..1
1.1.2 隨機雷射的種類……………………………………………………...………2
1.1.3 液晶隨機雷射………………………………………………………...………3
1.1.4 銀奈米材料隨機雷射……………………………………………...…………7
1.1.5 光纖隨機雷射………………………………………………………...……..10
1.2研究動機……………………………..………………….……………………….…11
第二章 材料特性及樣品製備與量測...........................................................................12
2.1 向列型液晶簡介…………………...…………………………………....……..….12
2.1.1 雙折射性…………………..………………………………...…………..…..13
2.1.2 向列型液晶之秩序參數與溫度效應………………………………….....…15
2.1.3 向列型液晶之外加電場影響…………………………………………...…..17
2.2 材料介紹…………………………………………………..…………….……..….19
2.3 樣品製作………………………………………………………………...……..….22
2.4 實驗光路架設………………………………...…………………….……..……....24
第三章 染料摻雜液晶填入空芯光纖………………………………………………...26
3.1 染料摻雜液晶填入空芯光纖之輸出頻譜量測……………...……………......….26
3.2 外界溫度對染料摻雜液晶光纖樣品之影響……………………...…………...…31
第四章 染料摻雜液晶添加鈦酸鋇奈米粒子填入空芯光纖……………………..….35
4.1 染料摻雜液晶添加鈦酸鋇奈米粒子填入空芯光纖之輸出頻譜量測…………..35
4.2 外界溫度對染料摻雜液晶添加鈦酸鋇奈米粒子之光纖樣品輸出的影響….….38
4.3 外加電場對染料摻雜液晶添加鈦酸鋇奈米粒子之光纖樣品輸出的影響….….44
4.4 染料摻雜液晶添加不同濃度之鈦酸鋇奈米粒子對輸出的影響…………...…...46
第五章 染料摻雜液晶添加銀奈米粒子填入空芯光纖…………………………..….54
5.1 染料摻雜液晶添加銀奈米粒子填入空芯光纖之輸出頻譜量測………………..54
5.2 外界溫度對染料摻雜液晶添加銀奈米粒子之光纖樣品輸出的影響….……….57
5.3 外加電場對染料摻雜液晶添加銀奈米粒子之光纖樣品輸出的影響….……….61
5.4 染料摻雜液晶添加不同濃度之銀奈米粒子對輸出的影響……………..….…...63
第六章 結論與未來展望……………………………………………………………...70
參考文獻…………………………………...………………………………………..…72

[1] R. Quimby, “Photonic and lasers,” Wiley, 2006.
[2] B. Tobias and K. Stefan “Anderson localization and its ramifications: disorder, phase coherent and electron correlation,” Springer, New York, 2003.
[3] B. Redding, M. Choma and H. Cao, “Speckle-free laser imaging using random laser illumination,” Nature photonics, Vol. 6, pp.355–359, 2012.
[4] H. Cao, “Lasing in random media,” Waves random media, Vol. 13, R1–R39, 2003.
[5] R. Polson and Z. V. Vardeny, “Random lasing in human tissues,” Appl. Phys. Lett., Vol. 85, pp.1289-1291, 2004.
[6] D. S. Wiersma, P. Bartolini, A. Lagendijk, and R. Righini, "Localization of light in a disordered medium," Nature, Vol. 390, pp.671-673, 1997.
[7] H. Cao, J. Y. Xu, X. Liu, and P. H. Chang, “Random lasers with coherent feedback,” IEEE J, Vol. 9, pp.111-119, 2003.
[8] S. Mujumdar, “Quantification of lineshape fluctuations in coherent random lasers,” SPIE Newsroom, pp.003258, 2010.
[9] S. M. Morris, A. D. Ford, M. N. Pivnenko, and H. J. Coles, “Electronic control of nonresonant random lasing from a dye-doped smectic A*,” Appl. Phys. Lett., pp. 141103, Vol. 86, 2005
[10] H. Cao, Y. G. Zhao, S. T. Ho, E. E. Seeling, Q. H. Wang, and R. P. H. Chang, “Random laser action in semiconductor powder,” Phys. Rev. Lett., Vol. 82, pp. 2278–2281, 1999.
[11] R.K. Thareja, A. Mitra, “Random laser action in ZnO,” Appl. Phys. B, Vol. 71, pp.181–184, 2000.
[12] S. F. Yu, C. Yuen, S. P. Lau, W. I. Park, and G. C. Yi, “Random laser action in ZnO nanorod arrays embedded in ZnO epilayers,” Appl. Phys. Lett., Vol. 84, pp.3241-3243, 2004.
[13] H. C. Hsu, C. Y. Wu, and W. F. Hsieh, “Stimulated emission and lasing of random-growth oriented ZnO nanowires,” J. Appl. Phys. Vol. 97, pp.064315-064314, 2005.
[14] G. Strangi, S. Ferjani, V. Barna, A. D. Luca, C. Versace, N. Scaramuzza, and R. Bartolino, “Random lasing and weak localization of light in dye-doped nematic liquid crystals,” Opt. Express, Vol. 14, pp.7737–7744, 2006.
[15] C. R. Lee, S. H. Lin, C. H. Guo, S. H. Chang, T. S. Mo, and S. C. Chu, “All-optically controllable random laser based on a dye-doped polymer-dispersed liquid crystal with nano-sized droplets,” Opt. Express, Vol. 18, pp.2406-2412, 2010.
[16] C. W. Chen, H. C. Jau, C. T. Wang, C. H. Lee, I. C. Khoo, and T. H. Lin “Random lasing in blue phase liquid crystals,” Opt. Express, Vol. 20, pp.23978-23984, 2012.
[17] B. He, Q. Liao, Y. Huang, “Random lasing in a dye doped cholesteric liquid crystal polymer solution,” Opt. Materials, Vol. 31, pp.375–379, 2008.
[18] A. Tulek, Z. V. Vardeny , “Studies of random laser action in π-conjugated polymers,” J. Opt., Vol. 12, pp.024008, 2010.
[19] Z. Hua, H. Zheng, L. Wang, X. Tian, T. Wang, Q. Zhang, G. Zou, Y. Chen, Q. Zhang, “Random fiber laser of POSS solution-filled hollow optical fiber by end pumping,” Opt. Communications, Vol. 285, pp.3967–3970, 2012.
[20] G.D. Dice, S. Mujumdar, A.Y. Elezzabi, “Photoluminescence enhancement in CdS nanoparticles by surface-plasmon resonance,“ Appl. Phys. Lett., Vol. 99, pp. 041906, 2011.
[21] G. D. Dice, A.Y. Elezzabi, “Random lasing from a nanoparticle-based metal–dielectric–dye medium,” Appl. Opt., Vol. 9, pp.186-193, 2007
[22] Y. Sun, Z. Wang, X. Shi, Y. Wang, X. Zhao, S. Chen, J. Shi, J. Zhou, and D. Liu “Coherent plasmonic random laser pumped by nanosecond pulses far from the resonance peak of silver nanowires,” J. Opt. Soc. Am. B, Vol. 30, pp.2523-2528, 2013.
[23] L. W. Li, L. G. Deng, “Random lasers in dye-doped polymer-dispersed liquid crystals containing silver nanoparticles,” Physica B, Vol. 407, pp.4826–4830, 2012.
[24] Q. Qiao, C. X. Shan, J. Zheng, H. Zhu, S. F. Yu, B. H. Li, Y. Jia and D. Z. Shen, “Surface plasmon enhanced electrically pumped random lasers,” Nanoscale, Vol. 5, pp.513-517, 2013.
[25] Q. Song, S. Xiao, Z. Xu, J. Liu, X. Sun, V. Drachev,V. M. Shalaev, O. Akkus, and Y. L. Kim,‘‘Random lasing in bone tissue,’’ Opt. Lett., Vol. 35, pp.1425-1427, 2010.
[26] L. M. Blinov and V, G. Chigrinov, “Electrooptic effects in liquid crystal materisl,” Springer, New York, 1994.
[27] Yariv, A., “Optical Electronics in Modern Communications”, 5th Ed., Oxford University Press, New York, 1997.
[28] W. L. Zhang, N. Cue, K. M. Yoo, “Emission linewidth of laser action in random gain media, Opt. Lett., Vol. 20, pp.961-963, 1995.
[29] D. S. Wiersma and S. Cavalieri, “Light emission: A temperature-tunable random laser,” Nature, Vol. 414, pp.708-709, 2001.
[30] S. Mujumdar, S. Cavalieri, and D. S. Wiersma, "Temperature-tunable random lasing: numerical calculations and experiments," J. Opt. Soc. Am. B Vol. 21, pp.201-207, 2004.
[31] S. Ferjani, V. Barna, A. De Luca, C. Versace, N. Scaramuzza, R. Bartolino and G. Strangi, “Thermal behavior of random lasing in dye doped nematic liquid crystals,” Appl. Phys. Lett., Vol. 89, pp.121109, 2006.
[32] S. Ferjani, A. D. Luca, V. Barna, C. Versace and G. Strangi, “Thermo-recurrent nematic random laser,” Opt. Lett., Vol. 17, pp. 2042-2047, 2009.
[33] C. R. Lee, J. D. Lin, B. Y. Huang, S. H. Lin, T. S. Mo, S. Y. Huang, C. T. Kuo, and H. C. Yeh, “Electrically controllable liquid crystal random lasers below the Fréedericksz transition threshold,” Opt. Express, Vol. 19, pp. 2391-2400, 2011.
[34] S. Morris, D. J. Gardiner, P. J. W. Hands, M. M. Qasim, T. D. Wilkinson, I. H. White, and H. J. Coles, “Electrically switchable random to photonic band-edge laser emission in chiral nematic liquid crystals,” Appl. Phys. Lett., Vol. 100, pp. 071110, 2012.
[35] C. R. Lee, J. D. Lin, B. Y. Huang, T. S. Mo, and S. Y. Huang, “All-optically controllable random laser based on a dye-doped liquid crystal added with a photoisomerizable dye,” Opt. Express, Vol. 18, pp. 25896-25905, 2010.
[36] L. W. Li, L. G. Deng, “Random lasers in dye-doped polymer-dispersed liquid crystals containing silver nanoparticles,” Physica B, Vol. 407, pp.4826–4830, 2012.
[37] Q. Qiao, C. X. Shan, J. Zheng, H. Zhu, S. F. Yu, B. H. Li, Y. Jia and D. Z. Shen, “Surface plasmon enhanced electrically pumped random lasers,” Nanoscale , Vol. 5, pp.513-517, 2013.
[38] J. P. Kottmann, O. J. F. Martin, “Influence of the cross section and the permittivity in the plasmon-resonance spectrum of silver mamowires,” Appl. Phys. B, Vol. 73, pp.299, 2001.
[39] K. L. Kelly , E. Coronado , L. L. Zhao , and G. C. Schatz, “The optical properties of metal nanoparticles:  The influence of size, shape, and dielectric environment,” J. Phys. Chem. B, Vol. 107, pp.668–677, 2003.
[40] C. J. S. Matos, L. S. Menezes, A. M. B. Silva, M. A. M. Gámez, A. S. L. Gomes, and C. B. Araújo, “Random fiber laser,” Phys. Rev. Lett. Vol. 99, pp.153903, 2007.
[41] P. G. Gennes and J. Prost, “The physics of liquid crystals”, 2ed ed., Clarendon Press, Oxford, 1995.
[42] L. M. Blinov and V, G. Chigrinov, “Electrooptic effects in liquid crystal materisl,” Springer, New York, 1994.
[43] B. Bahadur, “Liquid crystals: application and uses,” World Scientific, Singapore, 1990.
[44] P. Yeh, and C. Gu, “Optics of liquid crystal displays,” John Wiley & Sons, New York, 1999.
[45] A. Yariv, “Optical electronics in modern communications”, 5th Ed., Oxford University Press, New York, 1997.
[46] J. Li, S. Wu, S. Brugioni, R. Meticci, S. Faetti, “Infrared refractive indices of liquid crystals,” J. Appl. Phys., Vol. 97, pp.073501, 2005.
[47] D. K. Yang, and S. T. Wu, “Fundamentals of liquid crystal devices,” Wiley, New York, 2006.
[48] W. P. Partridge, N. M. Laurendeau, C. C. Johnson, and R. N. Steppel, ” Performance of pyrromethene 580 and 597 in a commercial Nd:YAG-pumped dye-laser system,” Appl. Opt., pp.1630, 1994.
[49] J. R. Heath, “Nanoscale materials,” Acc. Chem. Res., Vol. 32, pp.388–388, 1999.
[50] K. A. Willets and R. P. V. Duyne, “Localized surface plasmon resonance spectroscopy and sensing,” A. R. Phys. Chem., Vol. 58, pp.267-297, 2007.
[51] L. M. Blinov and V. G. Chigrinov, “Electroopic effect in liquid crystal material”, Springer, New York, 1994.
[52] K. Totsuka, M. A. I. Talukder, M. Matsumoto, and M. Tomita, “Excitation power dependent spectral shift in photoluminescence in dye molecules in strongly scattering optical media,” Phys. Rev. B, Vol. 59, pp.50-53, 1999.
[53] R. V. Ambartsumyan, N. G. basov, P. G. kryukov, and V. S. letokhov, “A laser with nonresonant feedback,” Soviet Phys. Jetp., Vol. 24, pp.481-485, 1967.
[54] O. V. Yaroshchuk, L. O. Dolgov, “Electro-optics and structure of polymer dispersed liquid crystals doped with nanoparticles of inorganic materials,” Opt. Materials, Vol. 29, pp.1097-1102, 2007.
[55] S. Takei, K. Mochiduki, N. Kubo and Y. Yokoyama, “Nanoparticle free polymer blends for light scattering films in liquid crystal displays,” Appl. Phys. Lett. Vol. 100, pp.263108, 2012.
[56] A. E. Vasdekis, G. E. Town, G. A. Turnbull, I. D. W. Samuel, “Fluidic fibre dye lasers,” Opt. Express, Vol. 15, pp.3962-3967, 2007.
[57] F. J. Duarte and L. W. Hillman, “Dye Laser Principles” Academic, New York, 1990.
[58] T. W. Hänsch, “Repetitively Pulsed Tunable Dye Laser for High Resolution Spectroscopy,” Appl. Opt. Vol. 11, pp.895-898, 1972.
[59] S. Kundu, M. Akimoto, I. Hirayama, M. Inoue, S. Kobayashi, and K. Takatoh, “Enhancement of contrast ratio by using ferroelectric nanoparticles in the alignment layer of liquid crystal display,” Jpn. J. Appl. Phys., Vol. 47, pp.4751-4754, 2008.
[60] M. Kaczmarek, O. Buchnev, and I. Nandhakumar, “Ferroelectric nanoparticles in low refractive index liquid crystals for strong electro-optic response,” Appl. Phys. Lett., Vol. 92, pp.103307, 2008.
[61] Y. Jeong, B. Yang, B. Lee, H. S. Seo, S. Choi, and K. Oh,“Electrically controllable long-period liquid crystal fiber gratings,” IEEE Photonics Technol. Lett., Vol. 12, pp.519–521, 2000.
[62] M. Green and S. J. Madden, “Low loss nematic liquid crystal cored fiber waveguides,” Appl. Opt., Vol. 28, pp.5202-5203, 1989.
[63] I. C. Khoo, “Liquid Crystals,” Wiley, New York, 1994.
[64] C. F. Bohren, D. R. Huffman, “Absorption and scattering of light by small particles,” John Wiley & Sons, pp.234-288, 1998.
[65] H. C. V. Hulst, “Light scattering by small particles,” Wiley, New York, 1957.
[66] J. Thisayukta, H. Shiraki, Y. Sakai, T. Masumi, S. Kundu, Y. Shiraishi, N. Toshima and S. Kobayashi, “Dielectric properties of frequency modulation twisted nematic LCDs doped with silver nanoparticles,” Jpn. J. Appl. Phys., Vol. 43, pp.5430, 2004.