由於光通訊的快速成長與需求，傳輸資訊量每年皆以倍數成長，加上消除OH－離子光纖的技術突破，使得低損耗波段可傳輸的波長擴展為1300nm~1600nm。伴隨著光纖通訊的需求急速增加，亦發展出分波多工技術，但仍要有光放大器加以搭配，才能充分發揮這項新技術。Cr4+:YAG晶體，其自發輻射光譜涵蓋了1300nm ~1600 nm的範圍，且其吸收頻譜在900nm~1200nm波長範圍內，與目前摻鉺光纖放大器980nm激發光源相容，故非常適合於晶體光纖放大器之應用。

本論文將雷射加熱基座生長法製備的雙纖衣Cr4+:YAG晶體光纖以端面對接耦合方式與通訊用之單模矽光纖對接，並量測其增益效果。目前，訊號光(1400nm)在SMF-CDF-SMF架構，系統插入損耗已降至4.2 dB，雙向各輸入1 W激發光功率時，可產生增益2.4 dB，系統增益已達-1.8 dB。此外，本論文亦對雙纖衣Cr4+:YAG晶體光纖做完整的數值模擬分析，並與實驗結果比對，進而找出實驗上的改善方向。藉數值模擬分析可知訊號光束與激發光束在晶體光纖纖心傳播時，兩光束模態間之疊合效率決定性地影響了訊號光增益大小，模擬當雙纖衣Cr4+:YAG晶體光纖長度16 公分、纖心直徑10 微米時，雙向各輸入1 W激發光功率，可產生10 dB增益，而目前所生長之雙纖衣Cr4+:YAG晶體光纖其疊合效率約在25%~30%之間。

未來我們將試著側鍍高折射率材料的方法降低雙纖衣Cr4+:YAG晶體光纖其纖心與纖衣的折射率差，進而降低模態數目，可望讓訊號光束與激發光束在纖心傳播時有更高的疊合效率，並生長纖心直徑更小的晶體光纖以產生更高的增益。

The maximum capacity of an optical fiber transmission system more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1300nm to 1600nm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, which results in the need for ultra-wideband optical amplifier. Cr4+:YAG has a strong spontaneous emission that covers 1300nm to 1600nm. Besides, its absorption spectrum is between 900nm to 1200nm, which matches with the pumping source in current erbium doped optical amplifier. Such a fiber is, therefore, eminently suitable for optical amplifier applications.

In this article, we will introduce the development of ultra-wideband optical amplifier using the double-clad Cr4+:YAG crystal fiber, which is grown by laser heated pedestal growth(LHPG) technique. Its material properties as well as optical gain will be characterized. By butt-coupling method, a low insertion loss of 4.2 dB was achieved in a SMF-CDF-SMF configuration, and it was measured to demonstrate a gross gain of 2.4 dB at 1 W bi-directional pump power. Moreover, theoretical models and numerical simulations have been developed to predict the experimental results. Numerical simulation indicates that the efficiency of mode overlapping between signal and pump is crucial to gain performance. The mode overlapping efficiency is about 25%~30% for our crystal fiber under current circumstances.

In the future, we will make an attempt to reduce the index contrast between core and cladding for better mode overlapping efficiency. At the same time, we also try to grow crystal fiber of smaller core diameter to improve gain performance.

目錄

中文摘要 i
英文摘要 ii
致謝 iii
目錄 iv
圖目錄 vi
表目錄 ix
第一章 緒論 1
第二章 雙纖衣Cr4+:YAG晶體光纖之特性 8
2.1 YAG晶體之結構與特性8
2.2 Cr4+:YAG之能階模型與吸收及放射頻譜13
2.3雙纖衣Cr4+:YAG晶體光纖之生長方法15
2.4雙纖衣Cr4+:YAG晶體光纖之晶體分析22
2.5雙纖衣Cr4+:YAG晶體光纖中之傳輸26
第三章 理論分析與數值模擬37
3.1 理論模型37
3.1.1速率方程式37
3.1.2激發光源、訊號光源與ASE之光強度變化40
3.1.3 ASE功率與訊號光增益之計算41
3.2 數值模擬分析42
第四章 雙纖衣Cr4+:YAG晶體光纖放大器樣品製備48
4.1 雙纖衣Cr4+:YAG晶體光纖樣品端面研磨拋光48
4.2 雙纖衣Cr4+:YAG晶體光纖之架設53
第五章 雙纖衣Cr4+:YAG晶體光纖放大器之特性量測55
5.1 耦合光源進入雙纖衣Cr4+:YAG晶體光纖55
5.2 插入損耗量測61
5.2.1單邊插入損耗量測61
5.2.2雙邊插入損耗量測63
5.3 增益實驗量測架構與結果 65
5.3.1 單向激發雙纖衣Cr4+:YAG晶體光纖 65
5.3.2 雙向激發雙纖衣Cr4+:YAG晶體光纖 70
第六章 結論 72
參考文獻75
中英文對照表79
附錄82

[1] 山下真司，“圖解光纖通信原理與散新應用技術”，建興文化，2003年。
[2] D. W. Hewak, “Progress towards a 1300 nm fiber amplifier,” IEE Colloquium, vol. 26, pp. 12/1-12/5, 1998.
[3] S. Q. Man, H. W. Liu, Y. H. Wong, E. Y. B. Pun, and P. S. Chung, “Tellurite glasses for 1.3 μm optical amplifiers,” Lasers and Electro-Optics Society (LEOS) Annual Meeting, vol. 1, pp. 196-197, 1998.
[4] S. Aozasa, H. Masuda, H. Ono, T. Sakamoto, T. Kanamori, Y. Ohishi, and M. Shimizu, “1480-1510 nm-band Tm doped fiber amplifier (TDFA) with a high power conversion efficiency of 42%,” Optical Fiber Communication (OFC)Conference, vol. 4, pp. PD1, 2001.
[5] Y. Miyajima, T. Kamukai, and T. Sugawa, “1.31-1.36 μm optical amplification in Nd3+-doped fluorozirconate fiber,” Electron. Lett., vol. 26, pp. 194-195, 1990.
[6] G. P. Agrawal and N. K. Dutta, “Long-wavelength semiconductor lasers,” New York: Van Nostrand Reinhold, 1986, Ch. 3.
[7] A. Mecozzi and J. M. Wiesenfeld, “The roles of semiconductor optical networks,” Optics & Photonics News, pp. 37-42, March 2001.
[8] E. Desurvire, “Erbium-Doped Fiber Amplifiers: Principles and Applications,” New York: Wiley, 1994, Ch. 4.
[9] S. Shimada and H. Ishio, “Optical Amplifiers and their Applications,” New York: Wiley, 1994, Ch. 2.
[10] Y. Shi and O. Poulsen, “High-power broadband single mode Pr3+-doped fiber superfluorescence light source,” Electron. Lett., vol. 29, no. 22, pp. 1945-1946, 1993.
[11] N. Islam, “Raman amplifiers for telecommunications,” IEEE J. Quant. Electron., vol. 8, no. 3, pp. 548-559, May/June 2002.
[12] R. S. Feigelson, W. L. Kway, and R. K. Route, “Single crystal fibers by the laser-heated pedestal growth method,” Opt. Eng., vol. 24, pp. 1102-1107, 1985.
[13] J. S. Haggerty, “Production of fibers by a floating zone fiber drawing technique,” Final Report NASA-CR-120948, May 1972.
[14] C. A. Burrus and J. Stone, “Single-crystal fiber optical devices: A Nd:YAG fiber laser,” Appl. Phys. Lett., vol. 26, pp. 318-320, 1975.
[15] M. M. Fejer, G. A. Magel, and R. L. Byer, “High-speed high-resolution fiber diameter variation measurement system,” Appl. Opt., vol. 24, pp. 2362-2368, 1985.
[16] S. Sudo, A. Cordova-Plaza, R. L. Byer, and H. J. Shaw, “MgO:LiNbO3 single-crystal fiber with magnesium-ion in-diffused cladding,” Opt. Lett., vol. 12, pp. 938-940, 1987.
[17] S. Ishibashi, K. Naganuma, and I. Yokohama, “Cr,Ca:Y3Al5O12 laser crystal grown by the laser-heated pedestal growth method,” J. Crys. Growth, vol. 183, pp. 614-621, 1998.
[18] S. Ishibashi and K. Naganuma, “Diode-pumped Cr4+:YAG single-crystal fiber laser,” OSA Trends in Optics and Photonics, 34, Advanced Solid-State Lasers, H. Injeyan, U. Keller, and C. Marshall, eds. (Optical Society of America, Washington, DC), pp. 426-430, 2000.
[19] M. A. Gulgun, W. Y. Ching, Y. N. Xu, and M. Ruhle, “Electron states of YAG probed by energy-loss near-edge spectrometry and ab initio calculations,” Phil. Mag. B, vol. 79, p. 921, 1999.
[20] A. Sennaroglu, “Analysis and optimization of lifetime thermal loading in continuous-wave Cr4+-doped solid-state lasers,” J. Opt. Soc. Am., vol. 18, no. 11, pp. 1578-1586, 2001.
[21] H. Eilers, W. M. Dennis, W. M. Yen, S. Kuck, K. Peterman, G. Huber, and W. Jia, “Performance of a Cr:YAG laser,” IEEE J. Quant. Electron., vol. 29, p.2508, 1993.
[22] S. Kuck, K. Petermann, and G. Huber, “Spectroscopic investigation of the Cr4+-center in YAG,” OSA Proceedings on Advanced Solid-State Lasers, vol.10, pp. 92-94, 1991.
[23] B. M. Tissue, W. Jia, L. Lu, and W. M. Yen, “Coloration of Chromium-doped Yttrium Aluminum Garnet Single-crystal Fibers Using a Divalent Codopant,” J. Appl. Phys., vol. 70, p.3775(1991)
[24] G. A. Magel, M. M. Fejer, and R. L. Byer, “Quasi-phase-matched second harmonic generation of blue light in periodically poled LiNbO3,” Appl. Phys. Lett., vol. 56, pp. 108-110, 1990.
[25] L. Hesseling and S. Redfield, “Photorefractive holographic recording in strontium barium niobate fiber,” Opt. Lett., vol. 13, pp. 877-879, 1988.
[26] R. S. Feigelson, D. Gazit, and D. K. Fork, “Superconducting Bi-Ca-Sr-Cu-O fibers grown by the laser-heated pedestal growth method,” Science, vol. 240, pp. 1642-1645, 1988.
[27] 張金倉，霍玉晶，何豫生，“激光加熱浮區生長強織構高溫超導晶纖的研究”，中國激光，第20 卷，第8 期，1993 年。
[28] G. Keiser, “Optical Fiber communications,” 3rd ed, McGraw-Hill, 2000, Ch. 2, Ch. 3.
[29] J. D. Love, W. M. Henry, W. J. Stewart, R. J. Black, S. Lacroix, and F. Gonthier, “Tapered single-mode fibers and devices Part1: Adiabaticity criteria, ” IEE Proc., vol. 138, pp. 343-354, 1991.
[30] B. E. A. Saleh and M.C. Teich, “Fundamentals of Photonics,” 1st ed, John Wiley & Sons 1991, Ch.6, Ch.7.
[31] P. C. Becker, N. A. Olsson, and J. R. Simpson, “Erbium-Doped Fiber Amplifiers: Fundamentals and Technology,” 1st ed, Academic Press, pp. 147-148, 1999.
[32] N. I. Borodin, V. A. Zhitnyuk, A. G. Okhrimchuk, and A. V. Shestakov, “Oscillation of a Y3Al5O12 : Cr4+ laser in wavelength region of 1.34-1.6 μm, ” Bull. Acad. Sci. USSR, Phys. Ser., vol. 54, pp. 54-60, 1990.
[33] I. J. Miller, A. J. Alcock, and J. E. Bernard, “Experimental Investigation of Cr4+ in YAG as a passive Q-switch,” in OSA Proceedings on Advanced Solid-state Lasers, vol. 13, pp. 322-325, 1992.
[34] H. Eilers, K. R. Hoffman, W. M. Dennis, S. M. Jacobsen, and W. M. Yen, “Saturation of 1.064μm absorption in Cr,Ca:Y3Al5O12 crystals,” Appl. Phys. Lett., vol. 61, pp. 2958-2960, 1992.
[35] K. Spariosu, W. Chen, R. Stultz, M. Birnbaum, and A. V. Shestakov “Dual Q switching and laser action at 1.06 and 1.44 μm in a Nd3+:YAG-Cr4+:YAG oscillator at 300 K,” Opt. Lett. vol. 18, pp. 814-816, 1993.
[36] E. Eilers, U. Hommerich, S. M. Jacobsen, and W. M. Yen, “Spectroscopy and dynamics of Cr4+:Y3Al5O12,” Phys. Rev. B, vol. 49, no. 22, pp. 15505-15513, 1994.
[37] Y. Shimony, Z. Burshtein, and Y. Kalisky, “Cr4+:YAG as passive Q-switch and Brewster plate in a pulsed Nd:YAG laser,” IEEE J. Quant. Electron., vol.31, no. 10, pp. 1738-1741, 1995.
[38] S. Kuck, K. Petermann, U. Pholmann, and G. Huber, “Near-infrared emission of Cr4+-doped garnets: Lifetimes, quantum efficiencies, and emission cross sections,” Phys. Rev. B, vol. 51, no. 24, pp. 17323-17331, 1995.
[39] S. C. Lopez, R. P. M. Green, G. J. Crofts, and M. J. Damzen, “Intensity-induced birefringence in Cr4+:YAG,” J. Mod. Opt., vol. 44, pp.209-219, 1997.
[40] A. Suda, A. Kadoi, K. Nagasaka, H. Tashiro, and K. Midorikawa,“Absorption and oscillation characteristics of a pulsed Cr4+:YAG laser investigated by a doubled-pulse pumping technique,” IEEE. J. Quant. Electron., vol. 35, no. 10, pp. 1548-1553, 1999.
[41] J. C. Diettrich, I. T. McKinnie, and D. M. Warringtion, “The influence of active ion concentration and crystal parameters on pulsed Cr:YAG laser performance,” Opt. Commun. vol. 167, pp. 133-140, 1999.
[42] R. Feldman, Y. Shimony, and Z. Burshtein, “Dynamics of chromium ion valence transformations in Cr,Ca:YAG crystals used as laser gain and passive Q-switching media,” Opt. Mater., vol. 24, pp. 333-344, 2003.
[43] P. C. Becker, N. A. Olsson, and J. R. Simpson, “Erbium-Doped Fiber Amplifiers: Fundamentals and Technology,” 1st ed, Academic Press, pp. 180-185, 1999.