在資訊量爆炸的時代，光通訊已逐漸取代原先的電子訊號傳輸，成為不可或缺的方法，但目前技術尚未發展成熟，任何有關於光傳輸、光訊號調變元件之研究，對於未來之發展將給予莫大的支持及幫助。
其中，定向耦合器除了可以作為開關、頻率及偏振選擇之元件外，也可滿足光波導元件在強度分光上之功能，且如果將其設計製做在電光材料上，又可以透過電壓去調控輸出端之表現，快速且方便。
本研究在鈮酸鋰晶體上，利用模擬退火法設計出非週期性晶疇排列之結構。此結構在定向耦合器之耦合區域中，可藉由施加電壓的不同，改變定向耦合器的輸出表現，且表現有別於以往文獻中週期性交錯電極之定向耦合器。
在設計中，增加了元件之製程容忍度及調制電壓之容忍度，也增加的元件表現的自由度。利用以上的表現組合出電壓斷路器、1×4路由器、光源和邏輯閘(NAND,AND,XOR,XNOR,NOR,OR)，皆是具有實用性之設計，期待在未來可以實作出元件，並不斷地優化設計，讓其成為具有高競爭力之元件。

In the era of information explosion, optical communication is desired to replace electronic transmission because of the increase of the data-carrying capacity nowadays; however, it is not mature enough. And therefore researches, which are related with optical transmission and optical signal modulation devices, such as directional couplers, would give great support in the future.
The function of the optical directional coupler is not only the switch, the selective device of frequency and polarization, but also the amplitude divider. Moreover, the directional coupler, which is based on electro-optic (EO) crystal, can achieve a fast modulator by modulating the applied voltage.
In this study, the electro-optically switched directional couplers in APPLN (aperiodically poled lithium niobate) were designed by the AOS (aperiodic optical superlattice) technique with the aid of the simulated annealing (SA) optimization method. The split ratio based on the design can be manipulated by applying voltage along the crystal z axis and performances, which are compared with the periodical designs in the previous literatures, can be even improved.
The optimized APPLN structures can increase the tolerance for fabrication and working voltage, which allows the possibility of output performances being more flexible. Based on this advantage, we could further apply designs to practical applications, such as voltage circuit breaker, 1 × 4 signal router, integrated light source, and logic gates (NAND, AND, XOR, XNOR, NOR, OR). In the future, we expect to realize the optimized device to be a highly competitive device.

[1] T. H. Maiman, "Stimulated optical radiation in ruby," 1960.
[2] S. E. Miller, "Integrated optics: An introduction," Bell System Technical Journal, vol. 48, pp. 2059-2069, 1969.
[3] W. Zachariasen, "Skr," Norske Vid-Ada., Oslo, Mat. Naturv, 1928.
[4] A. Srivastava, Y. Sun, J. Sulhoff, C. Wolf, M. Zirngibl, R. Monnard, et al., "1Tb/s Transmission of 100 WDM 10 Gb/s Channels Over 400 km of True WaveTMFiber," in Optical Fiber Communication Conference, 1998.
[5] E. A. Marcatili, "Dielectric rectangular waveguide and directional coupler for integrated optics," Bell System Technical Journal, vol. 48, pp. 2071-2102, 1969.
[6] M. Papuchon, Y. Combemale, X. Mathieu, D. Ostrowsky, L. Reiber, A. Roy, et al., "Electrically switched optical directional coupler: Cobra," Applied Physics Letters, vol. 27, pp. 289-291, 1975.
[7] H. Kogelnik and R. V. Schmidt, "Switched directional couplers with alternating Δβ," Quantum Electronics, IEEE Journal of, vol. 12, pp. 396-401, 1976.
[8] R. Schmidt and P. Cross, "Efficient optical waveguide switch/amplitude modulator," Optics letters, vol. 2, pp. 45-47, 1978.
[9] S. A. Samson, R. F. Tavlykaev, and R. V. Ramaswamy, "Two-section reversed/spl Delta//spl beta/switch with uniform electrodes and domain reversal," Photonics Technology Letters, IEEE, vol. 9, pp. 197-199, 1997.
[10] 楊松霖, "以週期性晶疇極化反轉鈦擴散鈮酸鋰波導晶片作為偏振可調定向耦合器之研究," 國立中央大學, vol. 光電科學研究所碩士論文, 2013.
[11] Y. Lee, F. Fan, Y. C. Huang, B. Gu, B. Dong, and M. Chou, "Nonlinear multiwavelength conversion based on an aperiodic optical superlattice in lithium niobate," Optics letters, vol. 27, pp. 2191-2193, 2002.
[12] P. Y. Amnon Yariv, "Optical waves in crystals," chap.11, p. 407, 2003.
[13] G. Edwards and M. Lawrence, "A temperature-dependent dispersion equation for congruently grown lithium niobate," Optical and Quantum Electronics, vol. 16, pp. 373-375, 1984.
[14] D. H. Jundt, "Temperature-dependent Sellmeier equation for the index of refraction,ne, in congruent lithium niobate," Optics Letters, vol. 22, pp. 1553-1555, 1997.
[15] P. Y. Amnon Yariv, "Optical waves in crystals," chap.7, p. 232, 2003.
[16] R. V. Schmidt and R. C. Alferness, "Directional coupler switches, modulators, and filters using alternating Δβ techniques," Circuits and Systems, IEEE Transactions on, vol. 26, pp. 1099-1108, 1979.
[17] 呂學璁, "以非週期性晶疇極化反轉鈮酸鋰晶體作為電光波長調變光參量產生器," 國立中央大學, vol. 光電科學研究所碩士論文, 2010.
[18] S. Miyazawa, "Ferroelectric domain inversion in Ti‐diffused LiNbO3 optical waveguide," Journal of Applied Physics, vol. 50, pp. 4599-4603, 1979.
[19] J. Webjorn, F. Laurell, and G. Arvidsson, "Blue light generated by frequency doubling of laser diode light in a lithium niobate channel waveguide," Photonics Technology Letters, IEEE, vol. 1, pp. 316-318, 1989.
[20] A. C. Nutt, V. Gopalan, and M. C. Gupta, "Domain inversion in LiNbO3 using direct electron‐beam writing," Applied physics letters, vol. 60, pp. 2828-2830, 1992.
[21] A. Agronin, Y. Rosenwaks, and G. Rosenman, "Ferroelectric domain reversal in LiNbO3 crystals using high-voltage atomic force microscopy," Applied Physics Letters, vol. 85, pp. 452-454, 2004.
[22] D. Feng, N. B. Ming, J. F. Hong, Y. S. Yang, J. S. Zhu, Z. Yang, et al., "Enhancement of second‐harmonic generation in LiNbO3 crystals with periodic laminar ferroelectric domains," Applied Physics Letters, vol. 37, pp. 607-609, 1980.
[23] L. E. Myers, R. Eckardt, M. Fejer, R. Byer, W. Bosenberg, and J. Pierce, "Quasi-phase-matched optical parametric oscillators in bulk periodically poled LiNbO3," JOSA B, vol. 12, pp. 2102-2116, 1995.
[24] Y.-y. Zhu and N.-b. Ming, "Second-harmonic generation in a Fibonacci optical superlattice and the dispersive effect of the refractive index," Physical Review B, vol. 42, p. 3676, 1990.
[25] N. Metropolis, A. W. Rosenbluth, M. N. Rosenbluth, A. H. Teller, and E. Teller, "Equation of state calculations by fast computing machines," The journal of chemical physics, vol. 21, pp. 1087-1092, 1953.
[26] B. J. T. M. S. P. Brooks, "The Statistician," pp. 241-257, 1995.
[27] J.-Y. Lai, Y.-J. Liu, H.-Y. Wu, Y.-H. Chen, and S.-D. Yang, "Engineered multiwavelength conversion using nonperiodic optical superlattice optimized by genetic algorithm," Optics express, vol. 18, pp. 5328-5337, 2010.
[28] E. L. Wooten, K. M. Kissa, A. Yi-Yan, E. J. Murphy, D. A. Lafaw, P. F. Hallemeier, et al., "A review of lithium niobate modulators for fiber-optic communications systems," Selected Topics in Quantum Electronics, IEEE Journal of, vol. 6, pp. 69-82, 2000.
[29] S. K. Raghuwanshi, A. Kumar, and S. Kumar, "1× 4 signal router using three Mach-Zehnder interferometers," Optical Engineering, vol. 52, pp. 035002-035002, 2013.
[30] T. Fan, A. Cordova-Plaza, M. J. Digonnet, R. Byer, and H. J. Shaw, "Nd: MgO: LiNbO3 spectroscopy and laser devices," JOSA B, vol. 3, pp. 140-148, 1986.
[31] C. P. Hussell and R. V. Ramaswamy, "High-index overlay for high reflectance DBR gratings in LiNbO3 channel waveguides," Photonics Technology Letters, IEEE, vol. 9, pp. 636-638, 1997.
[32] J. Sochtig, R. Gross, I. Baumann, W. Sohler, H. Schutz, and R. Widmer, "DBR waveguide laser in erbium-diffusion-doped LiNbO 3," Electronics Letters, vol. 31, pp. 551-552, 1995.
[33] E. Lim, M. Fejer, and R. Byer, "Second-harmonic generation of green light in periodically poled planar lithium niobate waveguide," Electronics Letters, vol. 25, pp. 174-175, 1989.
[34] W. Bomberger, T. Findakly, and B. Chen, "Integrated optical logic devices," in Integrated optics and millimeter and microwave integrated circuits, 1982, pp. 23-31.
[35] A. Lattes, H. Haus, F. Leonberger, and E. Ippen, "An ultrafast all-optical gate," Quantum Electronics, IEEE Journal of, vol. 19, pp. 1718-1723, 1983.
[36] H. D. Law, "Integrated Optoelectronic Logic," in 1984 Los Angeles Techincal Symposium, 1984, pp. 69-75.
[37] J. H. Kim, Y. M. Jhon, Y. T. Byun, S. Lee, D. H. Woo, and S. H. Kim, "All-optical XOR gate using semiconductor optical amplifiers without additional input beam," Photonics Technology Letters, IEEE, vol. 14, pp. 1436-1438, 2002.
[38] Y. L. Lee, B.-A. Yu, T. J. Eom, W. Shin, C. Jung, Y.-C. Noh, et al., "All-optical AND and NAND gates based on cascaded second-order nonlinear processes in a Ti-diffused periodically poled LiNbO3 waveguide," Optics express, vol. 14, pp. 2776-2782, 2006.
[39] Z. Li and G. Li, "Ultrahigh-speed reconfigurable logic gates based on four-wave mixing in a semiconductor optical amplifier," IEEE Photonics Technology Letters, vol. 18, p. 1341, 2006.
[40] Y. Ding, L. Liu, C. Peucheret, and H. Ou, "Fabrication tolerant polarization splitter and rotator based on a tapered directional coupler," Optics express, vol. 20, pp. 20021-20027, 2012.