光學同調斷層掃描(Optical Coherence Tomography, OCT)為一新穎光學顯微系統，是一種即時且具有非侵入性切片能力及高解析度的掃描技術，此系統光源需要寬頻光源來達到最佳的縱向解析度。本實驗研發製作之摻鉻鎂橄欖石雙纖衣晶體光纖具備寬頻的近紅外線自發輻射頻譜，摻雜Cr3+以及Cr4+離子，其光源頻譜範圍分別為700nm~1100nm以及1050nm~1300nm，此輻射波段對人體組織穿透度深且可以避開水吸收的1400nm波段，非常有潛力成為OCT之替代光源。
本論文利用雷射加熱基座生長法生長出c軸及b軸，直徑為40μm之摻鉻鎂橄欖石晶體光纖為纖核，並使用Aluminosilicate玻璃毛細管與Borosilicate玻璃毛細管包覆成雙纖衣晶體光纖。藉由實驗數據結合理論分析探討摻鉻鎂橄欖石雙纖衣晶體光纖的自發輻射功率與頻寬之各項影響因素，觀察並量測不同晶軸方向之摻鉻鎂橄欖石晶體光纖之各項光學特性，包括：放大自發輻射(Amplified Spontaneous Emission,ASE )功率、殘餘激發光功率、光譜量測、極化程度量測。
在光學量測方面以690nm紅光雷射幫浦晶體光纖，在幫浦功率為820mW下，觀察到c軸晶體光纖的ASE功率目前最大值約為2.11mW，大於相同側鍍厚度之b軸晶體光纖的ASE功率約為1.3mW，而b軸晶體光纖則是具有較大的半高寬約為266nm，在峰值波長部分則是b軸晶體光纖之波長約為1014.5nm大於c軸晶體光纖之波長約為940nm，另外b軸晶體光纖平均之極化程度為約16%小於c軸晶體光纖平均之極化程度為約25%。
另外為提升摻鉻鎂橄欖石晶體光纖ASE功率，我們使用以下方式：(1.)對拉提過後的晶纖進行不同側鍍厚度以增加鉻離子濃度，可以從實驗結果看到，在晶軸方向皆為b軸的晶體光纖，側鍍厚度從105nm上升至170nm，其ASE功率在幫浦光功率820mW幫浦與室溫下，從1.3mW上升至3.29mW。(2.)輸入端製鍍薄膜，針對激發光波長範圍為高穿透，對自發輻射波長範圍為高反射，促使輸入端反射更多ASE光源回到晶體光纖中以增加輸出端之光功率。其結果發現ASE功率從0.95mW上升至2mW。

Optical coherence tomography (OCT) is a novel real-time non-invasive optical scanning technique with ultrahigh resolution. Its axial resolution is inversely proportional to the bandwidth of the light source. Cr:Forsterite double cladding crystal fiber has broadband near-infrared spontaneous emission spectrum, which doped Cr3+ and Cr4+ were 700nm~1100nm and 1050nm~1300nm. This radiation band has deep penetration on the human body tissue and it distributed away from the water absorption wavelength. It has great potential as an alternative light source of OCT.
In this study we used the laser heated pedestal growth (LHPG) method to make Cr: Forsterite crystal fibers of 40μm in diameter with c axial and b axial, respectively. The crystal fibers were then grown into double-cladded fiber (DCF) with two capillary tubes of aluminosilicate and borosilicate. By means of experiments and theoretical analysis, the affecting factors of Cr:Forsterite DCF were studied. The optical characteristics of the Cr:Forsterite fibers were measured including: amplified spontaneous emission power, residual power, spectrum measurement, degree of polarization. We used red light laser with 690nm wavelength to pump crystal fiber to observe optical characteristic. With 820mW incident power, ASE power with c axial of 2.11mW is bigger than b axial of 1.3mW. And b axial has 266nm full width at half maximum (FWHM) of the emission spectrum centered at 1014.5nm wavelength. In addition, degree of polarization of b axial and c axial were 16% and 25%.
To increase the ASE(amplified spontaneous emission) power of the Cr:Forsterite fibers, two methods were used as follows: (1.)Doing Cr2O3 side deposition on crystal fibers while having smaller core size to reduce the number of times of fiber growth afterwards and thereby increasing the chromium ion concentration.With 820mW incident power and room temperature, crystal fiber with b axial, its ASE power increased from 1.3mW to 3.29mW with deposition thickness is 105nm and 170nm, respectively. (2.) Coating on input facet of DCF which is both anti-reflection (AR) for pump wavelengths and high-reflection (HR) for ASE wavelengths. It helped reflect more ASE light back to the DCF to increase the output power at the output end.We found that ASE power increased from 0.95mW to 2mW

[1] B.R. Wu, C.F. Lin, L.W. Laih, and T.T. Shih,"ExtremelybroadbandInGaAsP/InPsuperluminescent diodes, "Electron. Lett., 36, 2093 (2000).
[2] J. W. Lou, T. J. Xia, O. Boyraz, C. X. Shi, G. A. Nowak, and M.N.Islam, "Broader and flatter suppercontinuum spectra indispersion-tailoredfibers, "Technical Degist, 32 (1997).
[3] Y. Shi and O. Poulsen, " High-power broadband single modePr3+-dopedfibersuperfluorescence light source, " Electron. Lett., 29,1945 (1993).
[4] M. G. Pomper, “Molecular imaging: an overview,” Acad. Radiol.,8,1141 (2001).
[5] K.Takada, I.Yokohama, K. Chida, and J.Noda, " New measurementsystem for fault location in optical waveguide devices based on aninterferometric technique, " Appl. Opt.,26, 1603 (1987).
[6] B. Danielson and C. Whittenberg, " Guided-wave with micrometerresolution, " Appl. Opt.,26,2836 (1987).
[7] D. Engin, " Complex optical low coherence reflectometry withtunable source, " IEEE Photon, Technol.Lett.,16, 1346(2004).
[8] D. Anderson and F. Bell, " Optical time-domain reflectometry, "Tektronix Inc., Wilsonville (1997).
[9] D. Huang, E. Swanson, C. Lin, J. Schuman, W. Stinson, W. Chang,M. Hee, T. Flotte, K. Gregory, C. Puliafito, and J.Fujimoto, " Opticalcoherence tomography, " Science, 254, 1178 (1991).
[10] M. Hee, J. Izatt, E. Swanson, D. Huang, J. Schuman, C. Lin, C.Puliafito, and J.Fujimoto, " Optical Coherence Tomography forOphthalmic Imaging, " IEEE Eng. Med. Biol., 95, 0739-5175(1995).
[11] V.Petricevic, S.K. Gayen, R.R. Alfano, K. Yamagishi, H. AnZai, andY. Yamaguchi, " Laser action in chromium-doped forsterite, "Appl.Phys. Lett., 52, 1040 (1988).
[12] V.Petricevic, S.K. Gayen, and R.R. Alfano, " Laser action inchromium-activated forsterite for near-infrared excitation: Is Cr4+thelasing ion?, " Appl. Phys. Lett., 53, 2590 (1988).
[13] V.Petricevic, S.K. Gayen, and R.R. Alfano, " Continuous-wave laser operation of chromium-doped forsterite, " Received September 21, 1988; accepted March 12, (1989).
[14] A. Sennaroglu, C. Pollock, and H. Nathel, " Generation of TunableFemtosecond Pulses in the 1.21-1.27 pm and 605-635 nm wavelengthregion by using a regeneratively initiated Self-Mode-LockedCr4+:Forsterite Laser, " IEEE J. Quantum Electron., Vol. 30, No.8, August (1994).
[15] A. Sennaroglu, F. Kaertner, and J. Fujimoto, " Low-threshold, roomtemperature femtosecond Cr4+:Forsterite laser, " J. Opt. Soc. Am. Vol. 15, No. 20, October (2007).
[16] A. Sennaroglu, " Analysis and optimization of lifetime thermalloading in continuous-wave Cr4+-doped solid-state laser, " J. Opt.Soc. Am. B, Vol. 18, No.11, November (2001).
[17] Cz. Koepke, K. Wisniewski, and M. Grinberg, "Excited statespectr-oscopy of chromium ions in various valence states inglass," J.Alloys and Compounds, 341, 19 ( 2002).
[18] U. Hommerich, X. Wu, and V. R. Davis, " Demonstrationofroom-temperature laser action at 2.5 μmfromCr2+:Cd0.85Mn0.15Te, "Opt. Lett., 22, 1180 (1997).
[19] S. B. Mirov, V. V. Fedorov, K. Graham, and I. S. Moskalev "CW and pulsed Cr2+:ZnS and ZnSe microchip lasers, "Technical Digest,Conference on Lasers and Electro-Optics,120 (2002).
[20] J. McKay, K. L. Schepler and G. C. Catella, "Efficientgrating-tunedmid-infrared Cr2+:CdSe laser," Optics Letters,24, 1575 (1999).
[21] S. Kuck, K. Petermann, and G. Huber, "Spectroscopicinvestigationof the Cr4+-center in YAG, " OSA Proceedings onAdvancedSolid-State Lasers, 10, 92 (1991).
[22] Al. A. Kaminskii, " Laser crystal,"1st ed, Springer-VerlagBerlinHeidelberg New York, pp. 241, 381, 382 (1981).
[23] S. Aoshima, H. Itoh, K. Kuroyanagi, Y. Takiguchi, Y.Ohbayashi, I.Hirano, and Y. Tsuchiya, " Tunablepicosecondall solid-state Cr:LiSAF laser, " IEEE, IMTC’94, 937 (1994).
[24] Yen-KuangKuo, Man-Fang Huang, and Milton Bimbaum, "TunableCr4+:YSO Q-switched Cr:LiCAF laser," J. of QuantumElectron., 31, 657 (1995).
[25] T. Fujii, M. Nagano, and K. Nemoto, "Spectroscope and laseroscillation characteristics of high Cr4+-doped forsterite, " J. of QuantumElectron., 32, 1497 (1996).
[26] S. Kuck, J. Koetke, K. Petermann, U. Pohlmann, and G.Huber,"Spectroscopic and laser studies of Cr4+:YAG andCr4+:Y2SiO5, " OSAProceedings on Advanced Solid-StateLasers, 15, 334 (1993).
[27] Deer WA, Howie RA, Zussman J (1982) Rock Forming Minerals 2nded, vol 1 A, p 5, Longman, London
[28] WeiyiJia,HuiminLiu,S.Jaffe,andW.M.Yen, "Spectroscope of Cr3+and Cr4+ ions in forsterite, " Physical Review B volume 43, Number 7 (1991)
[29] 許峻揚,"高效率及低閥值摻鈦藍寶石晶體光纖雷射,"國立台灣大學電機資訊學院光電工程學研究所(2015)
[30] N. V. Kuleshov, V. G. Shcherbitsky, V. P. Mikhailov, S. Hartung,T. Danger, S. Kück, K. Petermann, and G. Huber, " Excited-stateabsorption and stimulated emission measurements in Cr4+:forsterite, " J. of Lumin. 75, 319 (1997)
[31] N. V. Kuleshov, A. V. Podlipensky, V. G. Shcherbitsky, A. A.Lagatsky, and V. P. Mikhailov,’’ Excited-state absorption in the range of pumping and laser efficiency of Cr4+:forsterite,’’ OPTICS LETTERS / Vol. 23, No. 13 / July 1(1998).
[32] Jennifer L. Mass, James M. Burlitch,David E. Budil, Jack H. Freed,Duane B. Barber, Clifford R. Pollock, Mikio Hischi, and Rudiger Dieckmann , " Quenching of the Fluorescence from Chromium(III) Ions in Chromium-Doped Forsterite by an Aluminum Codopant "Chem. Mater1996, 7. 1008,1014 (1995)
[33] G. Keiser, "Optical Fiber communications, 3rd ed, " McGraw-Hill,Ch. 2, Ch. 3 (2000).
[34] BahaaE. A. Saleh,Malvin Carl Teich,” Fundamentals ofPhotonics,”ch3(1991)
[35] https://en.wikipedia.org/wiki/Czochralski_process#cite_note-1
[36] http://cnfolio.com/ELMnotes15
[37] 李正中, "薄膜光學與鍍膜技術",第七版,藝軒出版社,2012
[38] 林晏聖, "以側鍍方法提升四價摻鉻晶體光纖螢光強度之研究, "國立中山大學光電工程研究所碩士論文(2004).
[39] Y. S. Lin, "Ce3+- Doped YAG Functional Crystal Fibers ," Doctoral Dissertation, National Taiwan University (2011).