我們用可以精確控制的電極加到雷射加熱基座生長法(LHPG)系統上，建立我們邊長晶邊做極化反轉的系統，氧化鋅(ZnO)和氧化鎂(MgO)摻雜的鈮酸鋰晶體被拉成週期性極化反轉的晶體光纖(Periodically Poled Lithium Niobateÿ Crystal Fiber : PPLNCF)，此長晶系統有快速與簡便的好處，然而在熔區附近的自由電子所造成的屏蔽效應必須消除否則外加電場無法使晶體光纖做極化反轉，經由外加電場產生電力吸引所造成的微擺動是解決屏蔽效應的一個方法，因為此方法可以打亂自由電子分佈進而降低屏蔽效應，但是沒有精確地控制微擺動，晶纖極化反轉週期的均勻性會變差同時轉換效率也無法提升。經過分析量測到的系統電流，我們提出了系統電流的近似模型，同時也證實此系統電流與微擺動大小成正比，因此我們把系統電流當作微擺動的迴授信號，據此我們可以把微擺動之變化範圍從25%大幅降到15%。二氧化碳雷射的功率也是決定週期性極化反轉晶體光纖品質的一個重要因素，二氧化碳雷射的功率變化率則被控制在1%之內。所有繁複的工作與精密的控制則靠我們以LabVIEW這套軟體寫的程式來達成。

　　我們提出一個全新且簡單的方法用串接式(Cascaded)倍頻(SHG)加和頻(SFG)來產生可調變波長的藍綠光源,同時僅使用單一個週期性極化反轉的ZnO:PPLN晶體光纖，此晶體光纖之極化反轉週期為15.45 μm，最佳的轉換效率倍頻(SHG)轉換是-9.2 dB, 而串接式(Cascaded)倍頻(SHG)加和頻(SFG)轉換的藍綠光則是-31.9 dB，此藍綠光的3 dB頻寬是3 nm (475-478 nm).為了拓展頻寬調變範圍，我們設計了一種漸變週期結構的晶體光纖經由模擬其3 dB頻寬在藍綠光範圍可達65 nm，我們為了在C-Band 做波長轉換器也製作了極化反轉週期為18.9 μm的晶纖其長度為1.8 mm其等效非線性係數為18.2 pm/V相當於鈮酸鋰非線性係數理想值(34.4 pm/V)的0.53倍，其在C-Band的波長轉換效率約為-59.3 dB。

　　We integrated the laser-heated pedestal growth (LHPG) system with accurately controlled electrodes to build up our in situ poling system. The ZnO and MgO doped periodically poled lithium niobate crystal fiber were fabricated with the poling system. This poling system has the advantage of convenience and fast growth, but the “screen effect” caused by free charges which exist near the molten zone must be eliminated. The micro swing resulted from the electric force is a feasible solution, because it can disarrange the free charges and reduce the “screen effect”. However, without excellently controlled micro swing, the uniformity of the poled domain pitch will loose and the conversion efficiency can not be improved. After analysis of the measured current data, the approximate system current model was presented and the proportional dependence between system current and micro swing was verified. Thus the system current was applied as the micro swing feedback signal, with that the variation of the micro swing was reduced from 25% to 15%. The stability of CO2 laser power is also a dominant factor to determine the quality of poled crystal fiber. The variation of the CO2 laser power was controlled within 1%. All the complicated works and precise control during the crystal fiber growth were accomplished with the LabVIEW program.
　　A novel and simple self-cascaded SHG + SFG scheme is presented for the generation of tunable blue/green light using ZnO doped periodically poled lithium niobate crystal fiber (PPLNCF) with a single designed pitch. A PPLNCF with a uniform period of 15.45μm, the maximum conversion efficiency for the second harmonic generation and the cascaded SHG + SFG blue light can reach up to -9.2 dB and -31.9 dB, respectively. The 3 dB bandwidth of the tunable blue light is 3 nm (475-478 nm). In order to expand the tuning bandwidth range, a QPM gradient periodical structure was designed and can provide a 3 dB bandwidth of 65 nm for the tunable blue/green light output by simulation. We have successfully grown a crystal fiber with the domain pitch of 18.9 μm for the C-band wavelength converter. The crystal length is 1.8 mm, the effective nonlinear coefficient of the lithium niobate crystal fiber is 18.2 pm/V that equals 0.53×dideal (34.4 pm/V). The conversion efficiency for converting the CW laser in C-band is about -59.3 dB.

中文摘要 i
Abstract ii
Table of Contents iv
List of Tables vi
List of Figures vii
Chapter 1 Introduction 1
Chapter 2 Phase-matching and poling mechanisms 4
2.1 Nonlinear interaction and birefringent phase matching 4
2.2 Theory of quasi-phase matching 11
2.3 LiNbO3 crystal structure and properties 15
2.3.1 Historical review of LiNbO3 15
2.3.2 Properties and crystal structure of LiNbO3 17
2.3.3 Ferro- and para- electric states 18
2.3.4 Compositional dependence 20
2.4 Poling techniques 22
2.4.1 Li+ out-diffusion 22
2.4.2 Ti3+, Mg2+ in-diffusion 22
2.4.3 Electron beam writing 23
2.4.4 Proton exchange 24
2.4.5 External electric field　24
2.4.6 Periodic laminar ferroelectric domains 24
2.4.7 Heat modulation 25
Chapter 3 Fabrication and characterization of PPLN crystal fibers 27
3.1 Growth setup 27
3.1.1 Laser-heated-pedestal growth (LHPG)　27
3.1.2 Electrodes and applied electric field 31
3.2 Micro swing caused by free charges 34
3.2.1 Screen effect caused by free charges 34
3.2.2 Verification of free charges and induced charges 35
3.3 Poled samples analysis 38
3.3.1 Domain inversion caused by micro-swing 38
3.3.2 Micro-swing and applied voltage control 40
3.4 Micro-swing control　41
3.4.1 Growth control system integration　41
3.4.2 Applied electric field with multi-pulses in a square wave 44
3.5 Measured current analysis and application 45
3.5.1 Current waveform dependence on the applied electric field 45
3.5.2 Current model　48
3.5.3 Simulation of the current 49
3.5.4 Advanced micro-swing control by current feedback 53
3.6 Fabrication of the devices for the application experiments 56
Chapter 4 Applications of PPLN fibers 58
4.1 Second harmonic generation 58
4.2 Cascaded SHG + SFG to generate blue/green laser 59
4.2.1 Cascaded SHG + SFG theory 59
4.2.2 Cascaded SHG + SFG simulation　62
4.2.3 Optical measurement 64
4.2.4 Bandwidth broadening by gradient periods 69
4.3 Wavelength conversion by cascaded SHG + DFG　75
4.3.1 Cascaded SHG + DFG theory 75
4.3.2 Measurement and analysis of SHG in Cascaded SHG + DFG 75
4.3.3 Optical measurement and simulation of DFG 83
Chapter 5 Conclusions and future work 89
5.1 Conclusions 89
5.2 Future work 90
References 92
Biography 99
Publication List 100

References

Chapter 1

[1.1] P. A. Franken, A. E. Hill, C. W. Peter, and G. Weinreich, “Generation of optical harmonics,” Phys. Rev. Lett., vol. 7, pp. 118-119, (1961).
[1.2] J. A. Armstrong, N. Bloembergen, J. Ducuing, and P. S. Pershan, “Interactions between light waves in a non-linear dielectric,” Phys. Rev., vol. 127, pp. 1918-1939, (1962).
[1.3] K. Mizuuchi, K. Yamamoto, and T. Taniuchi, “Second harmonic generation of blue light in LiTaO3 waveguide,” Appl. Phys. Lett., vol. 58, pp. 2732-2734, (1991).
[1.4] C. J. Van Der Poel, J. D. Bierlein, J. B. Brown, and S. Colak, “Efficient type I blue second harmonic generation in periodically segmented KTiOPO4 waveguides,” Appl. Phys. Lett., vol. 57, pp. 2074-2076, (1990).
[1.5] L. F. Johnson and A. A. Ballman, “Coherent emission from rare earth ions in electro-optic crystals,” J. Appl. Phys., vol. 40, pp. 297–302, (1969).
[1.6] T. Y. Fan, G. J. Dixon, and R. L. Byer, “Efficient GaAlAs diode-laser-pumped operation of Nd:YLF at 1.047μm with intracavity doubling to 523.6 nm,” Opt. Lett., vol.11, pp. 204–206, (1986).
[1.7] M. M. Fejer, G. A. Magel, D. H. Jundt, and R. L. Byer, “Quasi-phase-matched second harmonic generation: tuning and tolerances,” IEEE J. Quantum Electron., vol. 28, pp. 2631–2654, (1992).
[1.8] J. Zimmermann, J. Struckmeier, M. R. Hofmann, and J. P. Meyn, “Tunable blue laser based on intracavity frequency doubling with a fan-structured periodically poled LiTaO3 crystal,” Opt. Lett., vol. 27, 604–606, (2002).
[1.9] S. E. Harris, “Tunable optical parametric oscillators,” Proc. IEEE, vol. 58, pp. 2096–2113, (1969).
[1.10] R. A. Baumgartner and R. L. Byer, “Optical parametric amplification,” IEEE J. Quantum Electron., QE-15, pp. 432–444, (1979).
[1.11] L. Myers, R. Eckardt, M. M. Fejer, R. Byer, W. Bosenberg, and J. Pierce, “Quasi-phase-matched optical parametric oscillators in bulk periodically poled LiNbO3,” J. Opt. Soc. Am. B, vol. 12, pp. 2102–2116, (2002).
[1.12] K. Kato, “Second-harmonic and sum-frequency generation to 4950 and 4589 Å in KTP,” IEEE J. Quantum Electron., QE-24, pp. 3–4, (1988).
[1.13] P. Xu, K. Li, G. Zhao, S. N. Zhu, Y. Du, S. H. Ji, Y. Y. Zhu, N. B. Ming, L. Luo, K. F. Li, and K. W. Cheah, “Quasi phase-matched generation of tunable blue light in a quasi periodic structure,” Opt. Lett., vol. 29, pp. 95–97, (2004).
[1.14] J. A. Armstrong, N. Bloembergen, J. Ducuing, and P. S. Pershan, “Interactions between light waves in a nonlinear dielectric,” Phys. Rev., vol. 127, pp. 1918–1939, (1962).
[1.15] L. E. Myers, G. D. Miller, R. C. Eckardt, M. M. Fejer, and R. L. Byer, “Quasi-phase-matched 1.064-μm-pumped optical parametric oscillator in bulk periodically poled LiNbO3,” Opt. Lett., vol. 20, pp. 52–54, (1995).
[1.16] E. J. Lim, M. M. Fejer, R. L. Byer, and W. J. Kozlowsky, “Blue light generation by frequency doubling in periodically poled lithium niobate channel waveguide,” Elecrron. Lett., vol. 25, pp. 731-732, (1989).
[1.17] E. J. Lim, M. M. Fejer, and R. L. Byer, “Second-harmonic generation of green light in periodically poled planar lithium niobate waveguide,” Electron. Lett., vol. 25, pp. 174-175, (1989).
[1.18] X.-M. Liu, H.-Y. Zhang, Y.-L. Guo, and Y.-H. Li, “Optimal design and applications for quasi-phase-matching three wave mixing,” IEEE J. Quantum Electron., vol. 38, pp. 1225–1233, (2002).
[1.19] M. Taya, M. C. Bashaw, and M. M. Fejer, “Photorefractive effects in periodically poled ferroelectrics,” Opt. Lett., vol. 21, pp. 857–859, (1996).
[1.20] D. H. Jundt, “Lithium niobate single crystal fiber growth and quasi-phase matching,” Ph.D. dissertation Stanford University, (1991).
[1.21] L. M. Lee, C. C. Kuo, J. C. Chen, T. S. Chou, Y. C. Cho, S. L. Huang, and H. W. Lee, “Periodical poling of MgO doped lithium niobate crystal fiber by modulated pyroelectric field,” Opt. Commun., vol. 253, pp. 375–381, (2005).
[1.22] L. Becouarn, E. Lallier, M. Brevignon, and J. Lehoux,“Cascaded second-harmonic and sum-frequency generation of a CO2 laser by use of a single quasi-phase-matched GaAs crystal,” Opt. Lett., vol. 23, pp. 1508–1510, (1998).
[1.23] M. H. Chou, I. Brener, M. M. Fejer, E. E. Chaban, and S. B. Christman, “1.5 μm-band wavelength conversion based on cascaded second-order nonlinearity in LiNbO3 waveguides,” IEEE Photonics Technol. Lett., vol. 11, pp. 653-655, (1999).
Chapter 2

[2.1] J. A. Armstrong, N. Blombergen, J. Ducuing, and P. S. Pershan, “Interaction between light waves in a nonlinear dielectric,” Phys. Rev., vol. 127, pp. 1918-1939, (1962).
[2.2] A. Yariv, “Optical electrionics in modern communications,” Oxford, 5th edition, (1997).
[2.3] K. Mizuuchi, K. Yamamoto, M. Kato, and H. Sato, “Broadening of the phase-matching bandwidth in quasi-phase-matched second-harmonic generation,” IEEE J. of Quantum Electron., vol. 30, pp. 1596-1604, (1994).
[2.4] D. H. Jundt, “Temperature-dependent Sellmeier equation for the index of refraction, ne, in congruent lithium niobate,” Opt. Lett., vol. 22, pp. 1553-1555, (1997).
[2.5] L. Lee, Y. Cho, C. Lin, C. Lo and S. Huang, “The study and fabrication of periodically-poled lithium niobate crystal fiber,” Optics and photonics Taiwan II, pp. 108-110, (2002).
[2.6] Yi-Ching Lin, “Study of hi-field periodic poling & kinetics of domain inversion in lithium niobate,” Thesis for Master Degree, Graduate Institute of Electro-Optical Engineering National Taiwan University, (1999).
[2.7] V. Gopalan, T. Mitchell, Y. Furukawa, and K. Kitamura, “The role of nonstoichiometry in 180o domain switching of Li,” Appl. Phys. Lett., vol. 72, pp. 1981-1983, (1998).
[2.8] K. Kitamura, Y. Furukawa, Y. Ji, M. Zgonik, C. Medrano, G. Montemezzani, and P. Günter, “Photorefractive effect in LiNbO3 crystals enhanced by stoichiometry control,” J. Appl. Phys., vol. 82, pp. 1006-1009, (1997).
[2.9] K. Niwa, Y. Furukawa, S. Takekawa and K Kitamura, “Growth and characterization of MgO doped near stoichiometric LiNbO3 crystals as a new nonlinear optical material,” J. Crystal Growth, vol. 208, pp. 493-500, (2000).
[2.10] L. H. Peng, Y. C. Zhang, and Y. C. Lin, “Zinc oxide doping effects in polarization switching of lithium niobate,” Appl. Phys. Lett., vol. 78, pp. 1-3, (2001).
[2.11] T. Volk, M. Wohlecke, N. Rubinina, N. V. Razumovski, F. Jermann, C. fischer, and R. Bower, “LiNbO3 with the damage-resistant impurity indium,” Appl. Phy., vol. 60, pp. 217-225, (1995).
[2.12] D. A. Bryan, R. Gerson, and H. E. Tomaschke, “Increased optical damage resistance in lithium niobate,” Appl. Phys. Lett., vol. 44, pp. 847-849, (1984).
[2.13] L. Arizmendi, “Photonic applications of lithium niobate crystals,” Phys. Stat. Sol. (a) vol. 201, pp. 253-283, (2004).
[2.14] H. D. Megaw, “A note on the structure of lithium niobate,” Acta. Cryst. A24, pp. 583, (1968).
[2.15] A. Prokhorov and Y. Kuz’minov, “Physics and chemistry of crystalline lithium niobate,” The Adam Hilger, (1990).
[2.16] V. Gopalan, T. Mitchell, Y. Furukawa and K. Kitamura, “The role of nonstoichiometry in 180o domain switching of Li,” Appl. Phys. Lett., vol. 72, pp. 1981-1983, (1998).
[2.17] N. Iyi, Y. Yajima and K. Kitamura, “Defect structure model of MgO-doped LiNbO3,” J. Solid State Chem., vol. 148, pp. 118, (1995).
[2.18] Y. Furukawa, K. Kitamura, S. Takekawa, K. Niwa, Y. Yajima, N. Iyi, I. Mnushkina, P. Guggenheim, and J. Martin, “The correlation of MgO-doped near-stoichiometric LiNbO3 composition to the defect structure,” J. Crys. Growth, vol. 211, pp. 230-236, (2000).
[2.19] L. Peng, Y. Zhang, and Y. Lin, “Zinc oxide doping effects in polarization switching of lithium niobate,” Appl. Phys. Lett., vol. 78, pp. 4-6, (2001).
[2.20] J. R. Carruthers, G. E. Peteson, and M. Grasso, “Nonstoichiometry and crystal growth of lithium niobate,” J. Appl. Phys., vol. 42, pp. 1846-1851, (1971).
[2.21] C. Lau, P. Wei, C. Su, and W. Wong, “Fabrication of magnesium-oxide-induced lithium out-diffusion waveguides,” IEEE Photon. Technol. Lett., vol. 4, pp. 872-875, (1992).
[2.22] S. Sudo, A. Cordova-Plaza, R. Byer and H. Shaw, “MgO: LiNbO3 single-crystal fiber with magnesium-ion in-diffused cladding,” Optics Lett., vol. 12, pp. 938-940, (1987).
[2.23] Y. Zhi, S. Zhu, and J. Hong, “Domain inversion in LiNbO3 by proton exchange and quick heat treatment,” Appl. Phys. Lett., vol. 65, pp. 558-560, (1994).
[2.24] H. Ito, C. Takyu and H. Inaba, “Fabrication of periodic domain grating in LiNbO3 by electron beam writing for application of nonlinear optical processes,” Electron. Lett., vol. 27, pp. 1221-1222, (1991).
[2.25] I. Camlibel, “Spontaneous polarization measurements in several ferroelectric oxides using pulsed-field method,” J. Appl. Phys., vol. 40, pp. 1690-1693, (1969).
[2.26] M. Yamada, N. Nada, M. Saitoh, and K. Watanabe, “First-order quasi-phase matched LiNbO3 waveguide periodical poled by applying an external field for efficient blue second harmonic generation,” Appl. Phys. Lett., vol. 62, pp. 435-436, (1993).
[2.27] L. Myers, R. Eckardt, M. Fejer, R. Byer, W. Bosenbeg, and J. Pierce, “Quasi-phase matched optical parametric oscillators in bulk periodically poled LiNbO3 ,” J. Opt. Soc. Am. B., vol. 12, pp. 2102-2116, (1995).
[2.28] G. Miller, “Periodically poled Lithium Niobate: Modeling, Fabrication, and Nonlinear-optical performance”, Ph. D. dissertation, Stanford university, (1998).
[2.29] D. Feng, N. Ming, J. Hong, Y. Zhu, and Y. Wang, “Enhancement of second-harmonic generation in LiNbO3 crystal with periodic laminar ferroelectric domains,” Appl. Phys. Lett., vol. 37, pp. 607-609, (1980).
[2.30] J. Chen, Q. Zhou, J. Hong, W. Wang, N. Ming and C. Fang, “Influence of growth striations on para-ferroelectric phase transitions: Mechanism of the formation of periodic laminar domains in LiNbO3 and LiTaO3,” J. Appl. Phys., vol. 66, pp. 336-341, (1989).
[2.31] D. H. Jundt, “Lithium niobate: single crystal fiber growth and quasi-phase-matching,” Ph.D. dissertation, Stanford University, (1991).
[2.32] G. Magel, M. Fejer, and R. Byer, “Quasi-phase matched second-harmonic generation of blue light in periodically poled LiNbO3,” Appl. Phys. Lett., vol. 56, pp. 108-110, (1990).
Chapter 3
[3.1] S. Uda and W. A. Tiller, “The influence of an interface electric field on the distribution coefficient of chromium in LiNbO3,” J. Cryst. Growth, vol. 121, pp. 93-110, (1992).
[3.2] Chia-Yao Lo, “Growth, Characterization, and Application of Doped-YAG Single -crystal Fibers,” Ph. D. Dissertation, Institute of Electro-Optical Engineering, National Sun Yat-Sen University, (2004).
[3.3] A. A. Ballman and H. Brown, “Ferroelectric domain reversal in lithium metatantalate,” Ferroelectrics, vol. 4, pp. 189, (1972).
[3.4] Y.S. Luh, R.S. Feigelson, M.M. Fejer, and R. Byer, “Ferroelectric domain structures in LiNbO3 single crystal fiber,” J. Cryst. Growth, vol. 78, pp. 135-143, (1986).
[3.5] L. Huang, N.A.F. Jeager, “Discussion of domain inversion in LiNbO3,” Appl. Phys. Lett. vol. 65, pp. 1763- 1765, (1994).
[3.6] K. Niwa, Y. Furukava, S. Takekawa, K. Kitamura, “Growth and characterization of MgO doped near stoichiometric LiNbO3 crystals as a new nonlinear optical material,” J. Cryst. Growth, vol. 208, pp. 493-500, (2000).
[3.7] A. Brenier, G. Foulon, M. Ferriol, G. Boulon, “The laser heated-pedestal growth of LiNbO3:MgO crystal fiber with ferroelectric domain inversion by in situ electric field poling,” J. Phys. D: Appl. Phys., vol. 30, pp. L37-L39, (1997).


Chapter 4

[4.1] G. D. Miller, R. G. Batchko, W. M. Tulloch, D. R. Weise, M. M. Fejer, and R. L. Byer, “42%-efficient single-pass cw second-harmonic generation in periodically poled lithium niobate,” Opt. Lett., vol. 22, pp. 1834-1836, (1997).
[4.2] V. Pruneri, J. Webjörn, P. St. J. Russell, J. R. M. Barr1 and D. C. Hanna, “Intracavity second harmonic generation of 0.532 μm in bulk periodically poled lithium niobate,” Opt. Commun. vol. 116, pp. 159-162, (1995).
[4.3] Graeme W. Ross, Markus Pollnau, Peter G. R. Smith, W. Andrew Clarkson, Paul E. Britton, and David C. Hanna, “Generation of high-power blue light in periodically poled LiNbO3,” Opt. Lett., vol. 23, pp. 171-173, (1998).
[4.4] Y. L. Lu, L. Mao, and N. Ming, “Blue light generation by frequency doubling of an 810 nm cw GaAlAs diode laser in a quasi-phase-matched LiNbO3 crystal,” Opt. Lett., vol. 14, pp. 1037-1039, (1994).
[4.5] Y. K. Su, S. J. Chang, L. W. Ji, C. S, Chang, L. W. Wu, W. C. Lai, T. H. Fang and K. T. Lam, “InGaN/GaN blue light-emitting diodes with self-assembled quantum dots,” Semicond. Sci. Technol., vol. 19, no. 3, pp. 389-392, (2004).
[4.6] W. J. Kozlovsky, W. Lenth, E. E. Latta, A. Moser, and G. L. Bona, “Generation of 41 mW of blue radiation by frequency doubling of a GaAlAs diode laser,” Appl. Phys. Lett., vol. 56, pp. 2291-2292, (1990).
[4.7] Z. Ye, Q. Lou, J. Dong, Y. Weim, and L. Lin, “Compact continuous-wave blue lasers by direct frequency doubling of laser diodes with periodically poled lithium niobate waveguide crystals,” Opt. Lett., vol. 30, no. 1, pp. 73-74,( 2005).
[4.8] P. Xu, K. Li, G. Zhao, S. N. Zhu, Y. Du, S. H. Ji, Y. Y. Zhu, N. B. Ming, L. Luo, K. F. Li, and K. W. Cheah, “Quasi-phase-matched generation of tunable blue light in a quasi-periodic structure,” Opt. Lett., vol. 29, pp. 95-97, (2004).
[4.9] Paul S. Banks, Michael D. Feit, and Michael D. Perry, “High-intensity third-harmonic generation,” J. Opt. Soc. Am. B, vol. 19, no.1, pp. 104, (2002).
[4.10] A. Yariv, “Optical Electronics in Modern Communications,” New York, Oxford, pp. 285-293, (1997).
[4.11] Po-Chun Chiu, “Fabrication of lithium niobate crystal fiber for wavelength conversion,” Thesis for Master Degree, Institute of Electro-Optical Engineering, National Sun Yat-Sen University, (2004).
[4.12] X. Liu, H. Zhang, Y. Guo, and Y. Li, “Optimal design and applications for quasi-phase-matching three-wave mixing,” IEEE J. Quantum Electronics., vol. 38, no. 9, pp. 1225-1233, (2002).
[4.13] Z. Xianglong, C. Xianfeng, W. Fei, C. Yuping, X. Yuxing, C. Yingli, “Second-harmonic generation with broadened flattop bandwidth in aperiodic domain-inverted grating,” Opt. Comm., vol. 204, pp. 407-411,(2002).
[4.14] S. Gao, C. Yang, X. Xiao, and G. Jin, “Broadband and multiple-channel visible laser generation by use of segmented quasi-phase-matching gratings,” Opt. Comm., vol. 233, pp. 205-209, (2004).
[4.15] M. C. Cardakli, A. B. Sahin, O. H. Adamczyk, A. E. Willner, K. R. Parameswaran, and M. M. Fejer, “Wavelength conversion of subcarrier channels using difference frequency generation in a PPLN waveguide,” IEEE Photonics Technology Letters, vol. 14, no. 9, pp. 1328, (2002).
[4.16] S. M. Saltiel, A. A. Sukhorukov, and Y. S. Kivshar, “Multistep Parametric processes in nonlinear optics,” Prog. Opt. vol. 44, pp. 14, (2004).