5 6
Diffraction e ffici ency (%)
Exposure Time (Hr.)
圖 4-11 非破壞性讀取測試。
4.7 雙波長全像記錄最佳化之討論
圖 4-9 中得知，光強度比愈低，最大繞射效率就愈大，這是因為較低的 325-nm 曝 光強度會使得較多的反應物形成相位光柵；而最低要求的 325 nm 光源強度應該是多少 呢？光強度比是否可使最大繞射效率最佳化？
10-3 10-2 10-1 100 0
1 2 3 4 5
I0 = 0.44 W/cm2 I0 = 25.2 W/cm2 I0 = 52 W/cm2
IUV/I0 (n 1) max
x10-4
10-3 10-2 10-1 100 100
101 102 103 104 105
I0 = 0.44 W/cm2 I0 = 25.2 W/cm2 I0 = 52 W/cm2
IUV/I0
Writing time (min.)
(a) (b)
圖 4-12 (a)最大全像振幅與光強度比之關係模擬；(b)到達最大全像振幅所需的時間和光 強度之間的關係。
首先根據模型，這要由單重態 325-nm 泵率 ρUV
q
UV0應該大於 T1的衰變速率(1/
20) 來決定；舉例來說，若 qUV0為 10-22 以及
20為 106秒，則最小 325 nm 強度要大於 6×10-7 W·cm-2，才能夠進行雙波長全像記錄；然而在我們的模型當中，三重態第一能階 T1 的 半衰期無限長，因此並沒有辦法決定最低所需之紫光強度。首先我們模擬並描繪出在最大全像振幅隨著光強度比的變化，如圖 4-12(a)所述，可以發現最大全像振幅與絕對的 光強度無關，只與光強度比有關；這與模型的描述一致，在三重態，紫光與紅光會彼此 競爭，因此漂白態 NB的數量與 N3的數量只與光強度比有關；圖 4-12(a)代表光強度比 可使最大全像振幅最佳化，根據光強度比為 0.3 的最大繞射效率，計算可得最佳化全像 振幅約為 5；當光強度比低於此值時，最大全像振幅反而下降；這是因為單重態的泵 率小於三重態的總泵率，使得在干涉亮區的分子空乏，因此全像分佈偏離諧波分佈，所 以利用(4.22)所得之全像振幅變小所致，根據此分析，若要得到最佳化之最大全像振幅，
則單重態泵率要等於三重態的總泵率，也就是 qUV0
ρ
UV = qUV2ρ
UV + qRρ
R，計算可得
0 2 1
2
0
UV UV
UV red UV
R UV
q q q
q I
I
(4.24) 代入 qUV0=1.68×10-21，qUV2 = 8.44×10-23，qR = 4.19×10-24，可得最佳化光強度比為 0.0052，
與圖 4-12 (a)之 0.0082 0.0001 相當接近，因此(4.24)可做為雙波長全像記錄的參考準則。
另一方面，光強度亦會影響到達最大全像振幅的時間，如圖 4-12 (b)所示，我們模 擬並繪出最大全像振幅的寫入時間與光強度比的關係，說明當強度愈強時，到達最大全 像振幅的時間就愈短。
本章節中，我們根據 α 雙酮的介穩態中間能階機制，提出四能階模型說明雙波長 曝光下，PQ 分子的光躍遷行為；根據曝光模型，由於 UV 光光致產物與紅光光致產物 皆會引起光致折射率變化，而在雙波長全像記錄時，UV 光在空間中為均勻分布，紅光 則為諧波分布，因此 UV 光強度與紅光強度與對應的量子效率就會影響全像記錄的動態 曲線；根據模型的解，對三重態分子的 325nm 光源泵率與 647 nm 光源泵率比，同時也 是 UV 光光致產物與紅光光致產物比，qUV2
ρ
UV/ρRρ
R，會影響全像記錄的動態曲線，因此 量子效率的測量就很重要；透過模擬分析，我們可由雙波長光致吸收測量量子效率；實 驗中透過固定強度的 UV 光與不同強度的紅光照射樣品，可得多組樣品光致吸收度的變化，並針對實驗數據進行曲線擬合，可得量子效率 qUV0、qUV2、qR；全像記錄模擬中，
我們藉由使用不同的 UV 光強度改變泵率比，得知泵率比對於全像記錄動態曲線的影 響，而最大繞射效率反比與泵率比；全像記錄實驗亦可得到相同的結果，然而，實驗結 果的敏感度皆小於模擬結果的敏感度，這是因為材料對 UV 光的吸收較大，使得全像在 z 方向的成長並不均勻，可用波恩近似法更進一步的探討繞射效率的動態曲線；實驗結 果亦說明，PQ/PMMA 可用於雙波長全像記錄，並具有選擇性記錄與非破壞性讀取的特 性。
4.8 小結
透過模型與實驗的驗證，在雙波長全像記錄中，三重態分子對於 325 nm 與 647 nm 光源的量子效率非常重要，同時其比值可作為評估全像記錄特性的參數之一；這也暗示 要如何改進 PQ/PMMA 感光高分子樣品在雙波長全像記錄的特性；除了第二章中所提及 改進方式外，我們可以尋找一種染料分子摻雜在 PMMA 中，除了保有摻雜式 PMMA 感 光高分子的特性外，其在單重態對致敏光的量子效率要很高，但是在三重態時對致敏光 源的量子效率為零，但對於長波長光源的量子效率很高，因此所有的染料分子都可用於 全像記錄上而不會因為致敏光的曝照而產生漂白效應，降低材料的繞射效率，並可延伸 材料全像記錄的波段至長波長光源；如丁二酮或樟腦等，其三重態的吸收光譜對於 UV 之致敏光吸收為零，但是對於紅外波段皆有吸收，可作為摻雜 PMMA 感光高分子的染 料分子[103]；也就是說，透過了解 PQ 的光反應動態模型，我們可進一步改進感光高分 子的全像特性。
5 第五章、結論
本研究工作中，我們提出菲醌(PQ)分子摻雜 PMMA 作為體積全像應用的材料；透 過二階段熱聚合方法，可以得到高光學品質、光致收縮係數小於 10-5，並且厚度可達 10 公分的樣品，適用於體積全像應用；透過體積全像實驗測量，2 mm 厚的 PQ/PMMA 的 動態範圍 M/#為 2.86，敏感度為 0.31 cm2/J；雖然動態範圍足以應用於體積全像，但是 敏感度卻低於高分子聚合材料與光鏈結系統材料。
透過了解 PQ/PMMA 的光致折射率變化來自於 PQ 與 MMA 一對一結合之光致化學 產物，我們提出加入具有複數乙烯基的單體，製作共基底感光高分子材料，並提出一改 良式二階段熱聚合製程，成功改進 PQ/PMMA 的體積全像特性，達 2.5 倍；在我們的研 究結果中，PQ/poly-(TMPTA-co-MMA)的特性最佳，2 mm 厚的樣品之動態範圍達 7.01，
敏感度達 0.97 cm2/J；此一改良式製程也可用於其他的改進體積全像特性的方法，如共 摻雜有機金屬和非線性分子催化劑(增加 2.5 倍的效能)系統，更進一步增加儲存容量和 敏感度。
透過了解 α 雙酮衍生物受光躍遷的機制，我們發展四能階理論模型，說明 PQ 受光 躍遷的情形；從模型中，我們可以模擬 PQ/PMMA 的光致吸收變化與全像之繞射效率；
並根據其機制，發展雙波長全像記錄模型；雙波長全像記錄的特點在於選擇性記錄與非 破壞性讀取，並將記錄光源的波長延伸至紅光波段；首先可透過雙波長光致吸收變化，
得知基態 PQ 分子與第一三重態 PQ 分子對於不同波長的光的量子效率，從而得知短波 長泵率與長波長泵率與 PQ 受光躍遷之關係，模擬結果與實驗的相互驗證，其結果說明 在雙波長全像記錄中，短波長光泵率與長波長泵率比值會影響全像的最大繞射效率與敏 感度，當泵率比小於第一三重態分子對於短波長光之量子效率與對長波長光之量子效率 比值的 1/10 時，可得到繞射效率較大的全像。
從雙波長曝光模型的模擬與實驗中，要延伸全像記錄的波長，可置換 PQ 為分子之 三重態對於紅外波段感光的光敏感劑，如丁二醇或樟腦等。
6 參考文獻
1. W. E. Leland, M. S. Taqqu, W. Willinger, and D. V. Wilson, "On the self-similar nature of Ethernet traffic (extended version)," Networking, IEEE/ACM Transactions on 2, 1-15 (1994).
2. Cisco, "Cisco Visual Networking Index: Global Mobile Data Traffic Forecast Update, 2012–2017," (Cisco system, 2013),
http://www.cisco.com/en/US/solutions/collateral/ns341/ns525/ns537/ns705/ns827/white_pape r_c11-520862.html.
3. R. a. A. Johnson,
(2012),http://www.good.is/posts/the-world-of-data-we-re-creating-on-the-internet.
4. D. Day, M. Gu, and A. Smallridge, "Review of optical data storage," Infrared Holography for Optical Communications, 1-22 (2003).
5. W. M. J. Coene, D. Bruls, A. Immink, A. van der Lee, A. Hekstra, J. Riani, S. Van Beneden, M. Ciacci, J. Bergmans, and M. Furuki, "Two-dimensional optical storage," in
Acoustics, Speech, and Signal Processing, 2005. Proceedings.(ICASSP'05). IEEE International Conference on(IEEE, 2005), pp. v/749-v/752 Vol. 745.
6. D. A. Thompson, and J. S. Best, "The future of magnetic data storage techology," Ibm. J.
Res. Dev. 44, 311-322 (2000).
7. S. S. P. Parkin, M. Hayashi, and L. Thomas, "Magnetic domain-wall racetrack memory,"
Science 320, 190-194 (2008).
8. M. Sugawara, M. Kanazawa, K. Mitani, H. Shimamoto, T. Yamashita, and F. Okano,
"Ultrahigh-definition video system with 4000 scanning lines," SMPTE motion imaging journal 112, 339-346 (2003).
9. C. A. Brackett, "DENSE WAVELENGTH DIVISION MULTIPLEXING NETWORKS - PRINCIPLES AND APPLICATIONS," IEEE J. Sel. Areas Commun. 8, 948-964 (1990).
10. J. M. H. Elmirghani, and H. T. Mouftah, "All-optical wavelength conversion:
technologies and applications in DWDM networks," Communications Magazine, IEEE 38, 86-92 (2000).
11. J. P. Laude, DWDM fundamentals, components, and applications (Artech House, 2002).
12. J. M. Kahn, and K. P. Ho, "Spectral efficiency limits and modulation/detection techniques for DWDM systems," Selected Topics in Quantum Electronics, IEEE Journal of 10, 259-272 (2004).
13. A. Banerjee, Y. Park, F. Clarke, H. Song, S. Yang, G. Kramer, K. Kim, and B. Mukherjee,
"Wavelength-division-multiplexed passive optical network (WDM-PON) technologies for broadband access: a review [Invited]," Journal of optical networking 4, 737-758 (2005).
14. E. L. Wooten, K. M. Kissa, A. Yi-Yan, E. J. Murphy, D. A. Lafaw, P. F. Hallemeier, D.
Maack, D. V. Attanasio, D. J. Fritz, and G. J. McBrien, "A review of lithium niobate modulators for fiber-optic communications systems," Selected Topics in Quantum Electronics, IEEE Journal of 6, 69-82 (2000).
15. J. C. Dainty, "Laser speckle and related phenomena," in Berlin and New York,
Springer-Verlag (Topics in Applied Physics. Volume 9), 1975. 298 p(1975).
16. P. Hariharan, and S. A. Benton, "Optical holography: principles, techniques and applications," Phys Today 40, 127 (1987).
17. G. Meltz, W. Morey, and W. Glenn, "Formation of Bragg gratings in optical fibers by a transverse holographic method," Opt. Lett. 14, 823-825 (1989).
18. H. Lee, X. Gu, and D. Psaltis, "Volume holographic interconnections with maximal capacity and minimal cross talk," J. Appl. Phys. 65, 2191-2194 (1989).
19. G. A. Rakuljic, V. Leyva, and A. Yariv, "Optical data storage by using orthogonal wavelength-multiplexed volume holograms," Opt. Lett. 17, 1471-1473 (1992).
20. G. A. Rakuljic, and V. Leyva, "Volume holographic narrow-band optical filter," Opt. Lett.
18, 459-461 (1993).
21. D. Psaltis, and G. W. Burr, "Holographic data storage," Computer 31, 52-60 (1998).
22. J. Ashley, M. P. Bernal, G. Burr, H. Coufal, H. Guenther, J. Hoffnagle, C. Jefferson, B.
Marcus, R. Macfarlane, and R. Shelby, "Holographic data storage technology," Ibm. J. Res.
Dev. 44, 341-368 (2000).
23. H. J. Coufal, G. T. Sincerbox, and D. Psaltis, Holographic data storage (Springer-Verlag New York, Inc., 2000).
24. L. Eldada, and L. W. Shacklette, "Advances in polymer integrated optics," IEEE J. Sel.
Top. Quantum Electron. 6, 54-68 (2000).
25. D. Gabor, "A new microscopic principle," Nature 161, 777-778 (1948).
26. Y. N. Denisyuk, "On the reflection of optical properties of an object in a wave field of light scattered by it," Doklady Akademii Nauk SSSR 144, 1275 (1962).
27. E. N. Leith, and J. Upatnieks, "Reconstructed wavefronts and communication theory,"
JOSA 52, 1123-1128 (1962).
28. J. W. Goodman, and S. C. Gustafson, "Introduction to Fourier optics," Opt. Eng. 35, 1513-1513 (1996).
29. H. Kogelnik, "Coupled wave theory for thick hologram gratings," Bell Sys. Tech. J. 48, 2909-2947 (1969).
30. S. Yin, H. Zhou, F. Zhao, M. Wen, Z. Yang, J. Zhang, and F. T. S. Yu, "Wavelength multiplexed holographic storage in a sensitive photorefractive crystal using a visible-light tunable diode laser," Opt. Comm. 101, 317-321 (1993).
31. J. W. An, N. Kim, and K. W. Lee, "Volume holographic wavelength demultiplexer based on rotation multiplexing in the 90 geometry," Opt. Comm. 197, 247-254 (2001).
32. J. Hukriede, D. Runde, and D. Kip, "Fabrication and application of holographic Bragg gratings in lithium niobate channel waveguides," J. Phys. D-Appl. Phys. 36, R1-R16 (2003).
33. O. Beyer, I. Nee, F. Havermeyer, and K. Buse, "Holographic recording of Bragg gratings for wavelength division multiplexing in doped and partially polymerized poly(methyl methacrylate)," Appl. Opt. 42, 30-37 (2003).
34. A. Sato, M. Scepanovic, and R. K. Kostuk, "Holographic edge-illuminated polymer Bragg gratings for dense wavelength division optical filters at 1550 nm," Appl. Opt. 42, 778-784 (2003).
35. P. B. D. P. M. C. Ubaldi, "Infrared Holography for Optical Communications."
36. B. Liedberg, C. Nylander, and I. Lundström, "Biosensing with surface plasmon resonance—how it all started," Biosensors and Bioelectronics 10, i-ix (1995).
37. H. Grandin, B. Städler, M. Textor, and J. Vörös, "Waveguide excitation fluorescence microscopy: a new tool for sensing and imaging the biointerface," Biosensors and Bioelectronics 21, 1476-1482 (2006).
38. X. Hoa, A. G. Kirk, and M. Tabrizian, "Towards integrated and sensitive surface plasmon resonance biosensors: a review of recent progress," Biosensors and Bioelectronics 23, 151-160 (2007).
39. R. B. Millington, A. G. Mayes, J. Blyth, and C. R. Lowe, "A hologram biosensor for proteases," Sensors and Actuators B: Chemical 33, 55-59 (1996).
40. L. Hesselink, S. S. Orlov, and M. C. Bashaw, "Holographic data storage systems," Proc.
IEEE 92, 1231-1280 (2004).
41. V. Marinova, R. C. Liu, S. H. Lin, M.-S. Chen, Y. H. Lin, and K. Y. Hsu, "Near-infrared properties of Rh-doped Bi< sub> 12</sub> TiO< sub> 20</sub> crystals for photonic applications," Opt. Lett. 38, 495-497 (2013).
42. K. Buse, A. Adibi, and D. Psaltis, "Non-volatile holographic storage in doubly doped lithium niobate crystals," Nature 393, 665-668 (1998).
43. A. Adibi, K. Buse, and D. Psaltis, "Two-center holographic recording," J. Opt. Soc. Am.
B 18, 584-601 (2001).
44. R. A. Lessard, and G. Manivannan, "Holographic Recording Materials - an Overview,"
Holographic Materials 2405, 2-23 (1995).
45. D. Close, A. Jacobson, J. Margerum, R. Brault, and F. McClung, "Hologram recording on photopolymer materials," Appl. Phys. Lett. 14, 159 (1969).
46. F. K. Bruder, R. Hagen, T. Rölle, M. S. Weiser, and T. Fäcke, "From the Surface to Volume: Concepts for the Next Generation of Optical–Holographic Data‐Storage Materials,"
Angewandte Chemie International Edition 50, 4552-4573 (2011).
47. C. H. Zhao, J. Liu, Z. H. Fu, and R. T. Chen, "Shrinkage-corrected volume holograms based on photopolymeric phase media for surface-normal optical interconnects," Appl. Phys.
Lett. 71, 1464-1466 (1997).
48. S. S. Orlov, and L. Hesselink, "Holographic shift multiplexing in thin volumetric media,"
JOSA B 20, 1912-1921 (2003).
49. L. Shou-Jun, L. Guo-Dong, H. Qing-Sheng, W. Min-Xian, J. Guo-Fan, S. Meng-Quan, W.
Tao, and W. Fei-Peng, "Holographic grating formation in dry photopolymer film with shrinkage," Chinese Phys 13, 1428 (2004).
50. A. Hoskins, A. Hill, B. Sissom, C. Stanhope, and K. Curtis, "Temperature compensation strategy for holographic storage," in Optical Data Storage Topical Meeting, 2006(IEEE, 2006), pp. 218-220.
51. A. Hoskins, B. Sissom, and K. Curtis, "Tolerances of a page-based holographic data storage system," in Optical Data Storage(Optical Society of America, 2007).
52. D. A. Waldman, C. J. Butler, and D. H. Raguin, "CROP holographic storage media for optical data storage greater than 100 bits/μm2," in Optical Science and Technology, SPIE's
48th Annual Meeting(International Society for Optics and Photonics, 2003), pp. 10-25.
53. W. L. Wilson, K. R. Curtis, K. E. Anderson, M. C. Tackitt, A. J. Hill, M. Pane, C.
Stanhope, T. Earhart, W. Loechel, and C. Bergman, "Realization of high-performance holographic data storage: the InPhase Technologies demonstration platform," in Optical
Science and Technology, SPIE's 48th Annual Meeting(International Society for Optics and
Photonics, 2003), pp. 178-191.54. X. Tan, H. Horimai, T. Shimura, S. Ichimura, R. Fujimura, and K. Kuroda, "Collinear technology for holographic versatile disc (HVD) system," in Proceedings of SPIE(2006), p.
63432W.
55. A. Bloom, R. Bartolini, and P. Hung, "The effect of polymer host on volume phase holographic recording properties," Polymer Engineering & Science 17, 356-358 (1977).
56. G. J. Steckman, I. Solomatine, G. Zhou, and D. Psaltis, "Holographic data storage in phenanthrenequinone doped PMMA," Organic Photonic Materials and Devices 3623,
56. G. J. Steckman, I. Solomatine, G. Zhou, and D. Psaltis, "Holographic data storage in phenanthrenequinone doped PMMA," Organic Photonic Materials and Devices 3623,