本文旨在研究產生量子壓縮光源，並致力於將光路積體化，不僅提供光路更高的擴展性在操作上也更加穩定。透過單通光參量放大器產生非古典光源-壓縮態，依照海森堡的不確定性原理，知道光學中最小擾動極限，透過壓縮光的正交項能夠達到比標準量子極限更小的擾動；而相對的其另一個正交項會大於標準量子極限，能夠在量子感測領域中提供更高的精準度。此外，為了要實現大型量子光路，使用絕熱耦合器做為分光器，能提供製程高容忍度和高工作寬頻的特性。
本研究藉由鈮酸鋰基板成功的將壓縮光源和波長分光器整合在同一晶片上，從受激拉曼絕熱過程的理論出發，設計絕熱耦合器，並使用光束傳播法模擬波導耦合條件，到一系列的製程過程，經由半導體製程技術使晶片具有準相位匹配的週期性晶疇反轉結構及鈦擴散式波導，其中包括黃光微影、薄膜、擴散、研磨拋光、蝕刻，最後量測晶片特性(1)絕熱耦合器的消光比，在波長 1550nm 有高達 23.4dB，消光比大於 20dB 和大於10dB 分別有 18、68nm 頻寬，(2)非線性光學-倍頻現象，歸一化轉換效率有 15.8%/W/cm2
，(3)透過平衡零差檢測方法量測壓縮光，我們預計此晶片可以產生壓縮光和反壓縮光分別為-0.67dB、0.72dB。
未來可以設計不同耦合器，或是採用其他波導種類，甚至可以更換基板材料，使得晶片非線性轉換效率更高、能承受更高泵浦光能量、傳播損耗更低，製備出品質更好的晶片式壓縮光源，量子光源是量子光路系統中的首要條件，藉由此研究可以將量子光源在晶片上產生，作為光量子發展的一部份，提供穩定壓縮光源的價值，有文獻做了定向耦合器當作 50:50 分光鏡[1]，不只能增加兩道光的模態疊合程度，也能進一步將光路積體化，完成整個量子積體光路系統。

This research is aimed to produce squeezed vacuum state in single-pass optical parametric amplifier (OPA) in nonlinear optics. The process based on a single-spatial-mode periodically poled lithium niobate (PPLN) waveguide, also called on-chip squeezer. In this work, we provide more compact, robustness and scalability via integrated photonic circuits rather than conventional optical measurement scheme. According to Heisenberg 's uncertainty principle,
there is minimum fluctuation in optical field, that is standard quantum limit (SQL). By utilizing squeezing light, we can obtain noise level below SQL in one quadrature (may in amplitude or phase), and another quadrature will be amplified higher than SQL. This characteristic can apply
in quantum sensing area providing extra precise metrology. Additionally, in order to realize large photonic quantum circuits (PQCs), we designed adiabatic coupler (AC) which has fabrication tolerant and broadband operation properties as a beam splitter to separate pump and signal wavelength.
We had developed squeezing light source and beam splitter integrated on Ti-diffused periodically poled lithium niobate (PPLN) waveguides. From stimulated Raman adiabatic passage (STIRAP) theory, we built up adiabatic coupler geometric structure and simulation through beam propagation method (BPM), to fabrication process flow with lithography, thin
film, diffusion, chemical-mechanical polishing, etch. Finally, measuring the chip characteristic (1)Extinction ratio of adiabatic coupler achieve up to 23.4dB at 1550nm. In addition, extinction ratio more than 20dB and 10dB has 18nm、68nmrespectively. (2)Nonlinear optics process second harmonic generation (SHG), the chip demonstrates normalize SHG conversion efficiency 15.8%/W/cm2. with 15mm quasi phase matching (QPM) length. (3)By balance homodyne detection (BHD) method to measure squeezing level, we estimated the squeezing and antisqueezing levels can be -0.67dB and 0.72dB, respectively.
In future work, we can design different coupler and even can change the waveguide type which enhance the nonlinear conversion efficiency, durability for high-power pump and low propagation loss. Due to above mentioned optimizations, we can fabricate more quality on-chip squeezer. The quantum light source is preliminary condition in quantum network system. By means of the thesis contribution, we can offer a stable nonclassical light which is squeezing light. In other group, they integrated directional coupler (DC) as 50:50 beam splitter (BS) on chip cascade OPA process [1]. Not only did it improve the spatial mode matching, but it minimizes optical setup. We believe that our work combine the DC can toward integrated quantum system further.

[1] F. Mondain et al., "Chip-based squeezing at a telecom wavelength," Photonics
Research, vol. 7, no. 7, 2019.
[2] G. Moody, L. Chang, T. J. Steiner, and J. E. Bowers, "Chip-scale nonlinear photonics
for quantum light generation," AVS Quantum Science, vol. 2, no. 4, 2020.
[3] D. F. Walls, "Squeezed states of light," Nature, vol. 306, no. 5939, pp. 141-146, 1983.
[4] F. Lenzini et al., "Integrated photonic platform for quantum information with
continuous variables," Science Advances, vol. 4, no. 12, pp. 1-8, 2018.
[5] J. L. O'Brien, A. Furusawa, and J. Vučković, "Photonic quantum technologies," Nature
Photonics, vol. 3, no. 12, pp. 687-695, 2009.
[6] R. Schnabel, N. Mavalvala, D. E. McClelland, and P. K. Lam, "Quantum metrology for
gravitational wave astronomy," Nat Commun, vol. 1, p. 121, Nov 16 2010.
[7] K. Takase et al., "Generation of Schrödinger cat states with Wigner negativity using a
continuous-wave low-loss waveguide optical parametric amplifier," Optics Express,
vol. 30, no. 9, 2022.
[8] R. E. Slusher, L. W. Hollberg, B. Yurke, J. C. Mertz, and J. F. Valley, "Observation of
squeezed states generated by four-wave mixing in an optical cavity," Phys Rev Lett, vol.
55, no. 22, pp. 2409-2412, Nov 25 1985.
[9] D. K. Serkland, M. M. Fejer, R. L. Byer, and Y. Yamamoto, "Squeezing in a quasi-phasematched LiNbO_3 waveguide," Optics Letters, vol. 20, no. 15, pp. 1649-1649, 1995.
[10] G. Kanter, P. Kumar, R. Roussev, J. Kurz, K. Parameswaran, and M. Fejer, "Squeezing
in a LiNbO3 integrated optical waveguide circuit," Optics Express, vol. 10, no. 3, p.
177, 2002.
[11] M. Stefszky, R. Ricken, C. Eigner, V. Quiring, H. Herrmann, and C. Silberhorn,
"Waveguide Cavity Resonator as a Source of Optical Squeezing," Physical Review
Applied, vol. 7, no. 4, 2017.
[12] T. Kashiwazaki et al., "Continuous-wave 6-dB-squeezed light with 2.5-THz-bandwidth
from single-mode PPLN waveguide," APL Photonics, vol. 5, no. 3, 2020.
[13] F. Kaiser, B. Fedrici, A. Zavatta, V. D’Auria, and S. Tanzilli, "A fully guided-wave
squeezing experiment for fiber quantum networks," Optica, vol. 3, no. 4, 2016.
[14] X.-M. Jin, M. S. Kim, and B. J. Smith, "Quantum photonics: feature introduction,"
Photonics Research, vol. 7, no. 12, 2019.
[15] E. Miller, "THE BELL TECHNICAL SYSTEM Integrated Optics : An Introduction,"
THE BELL SYSTEM technical journal, vol. 48, no. 7, pp. 2059-2069, 1969.
[16] S. Bogdanov, M. Y. Shalaginov, A. Boltasseva, and V. M. Shalaev, "Material platformsfor integrated quantum photonics," Optical Materials Express, vol. 7, no. 1, 2016.
[17] O. Alibart et al., "Quantum photonics at telecom wavelengths based on lithium niobate
waveguides," Journal of Optics (United Kingdom), vol. 18, no. 10, 2016.
[18] Y. Zhao, Y. Okawachi, J. K. Jang, X. Ji, M. Lipson, and A. L. Gaeta, "Near-Degenerate
Quadrature-Squeezed Vacuum Generation on a Silicon-Nitride Chip," Phys Rev Lett,
vol. 124, no. 19, p. 193601, May 15 2020.
[19] C. C. Kores, C. Canalias, and F. Laurell, "Quasi-phase matching waveguides on lithium
niobate and KTP for nonlinear frequency conversion: A comparison," APL Photonics,
vol. 6, no. 9, 2021.
[20] S. Saravi, T. Pertsch, and F. Setzpfandt, "Lithium Niobate on Insulator: An Emerging
Platform for Integrated Quantum Photonics," Advanced Optical Materials, vol. 9, no.
22, 2021.
[21] P. K. Chen, I. Briggs, S. Hou, and L. Fan, "Ultra-broadband quadrature squeezing with
thin-film lithium niobate nanophotonics," Opt Lett, vol. 47, no. 6, pp. 1506-1509, Mar
15 2022.
[22] A. Yariv and P. Yeh, Optical waves in crystals. New York: Wiley, 1984.
[23] A. A. Ballman, "Growth of Piezoelectric and Ferroelectric Materials by the CzochraIski
Technique," Journal of the American Ceramic Society, vol. 48, no. 2, pp. 112-113, 1965.
[24] 孔勇發, 許京軍, 張光寅, 劉思敏, and 陸猗, 多功能光電材料 – 鈮酸鋰晶體.
科學出版社, 2005.
[25] H. P.Chung et al., "Adiabatic light transfer in titanium diffused lithium niobate
waveguides," Optics Express, vol. 23, no. 24, p. 30641, 2015.
[26] Q.-H. Tseng, A. Niko, T.-D. Pham, H.-P. Chung, L.-M. Deng, and Y.-H. Chen,
"Broadband tunable electro-optic switch/power divider as potential building blocks in
integrated lithium niobate photonics," Optics Express, vol. 30, no. 11, 2022.
[27] D. J. Griffiths and D. F. Schroeter, Introduction to Quantum Mechanics, Third edition
ed. Cambridge University Press, 2018.
[28] D. McMahon, Quantum mechanics demystified, 2nd Edition ed. McGraw-Hill
Education, 2013, p. 528.
[29] D. F. Walls and G. J. Milburn, Quantum Optics, 2nd Edition ed. Springer, 2008, p. 437.
[30] L. S. Braunstein and P. Van Loock, "Quantum information with continuous variables,"
Reviews of Modern Physics, vol. 77, no. 2, pp. 513-577, 2005.
[31] L. A. Wu, H. J. Kimble, J. L. Hall, and H. Wu, "Generation of squeezed states by
parametric down conversion," Phys Rev Lett, vol. 57, no. 20, pp. 2520-2523, Nov 17
1986.
[32] G. L. Mansell,"Squeezed light sources for current and future interferometric
gravitational-wave detectors",PhD thesis,Australian National University,2018。
[33] M. Fox, Quantum Optics: An Introduction. Oxford University Press, 2006, p. 400
[34] A. Sch¨onbeck,"Compact squeezed-light source at 1550 nm",PhD thesis,University of
Hamburg,2018。
[35] C. Gerry and P. Knight, Introductory Quantum Optics. Cambridge University Press,
2004, p. 317.
[36] M. S. Stefszky,"Generation and Detection of Low-Frequency Squeezing for
Gravitational-Wave Detection",PhD thesis,Australian National University,2012。
[37] R. W. Boyd, Nonlinear Optics, 4th Edition ed. Academic Press, 2020, p. 634.
[38] L. E. Myers et al., "Quasi-Phasematched Optical Parametric Oscillators in Periodically
Poled LiNbO_3," Optics and Photonics News, vol. 6, no. 12, pp. 30-30, 1995.
[39] U. L. Andersen, T. Gehring, C. Marquardt, and G. Leuchs, "30 Years of Squeezed Light
Generation," Physica Scripta, vol. 91, no. 5, 2016.
[40] J. J. Sakurai, S. F. Tuan, Ed. Modern Quantum Mechanics, Revised Edition ed. AddisonWesley, 1993.
[41] T. Hirano, K. Kotani, T. Ishibashi, S. Okude, and T. Kuwamoto, "3 dB squeezing by
single-pass parametric amplification in a periodically poled KTiOPO4 crystal," Optics
Letters, vol. 30, no. 13, 2005.
[42] T. H. Nikolay V Vitanov, Bruce W Shore, and Klaas Bergmann, "Laser-induced
population transfer by adiabatic passage techniques," Annual Review of Physical
Chemistry, vol. 52, no. 1, pp. 763-809, 2001.
[43] B. W. Shore, "Picturing stimulated Raman adiabatic passage: a STIRAP tutorial,"
Advances in Optics and Photonics, vol. 9, no. 3, 2017.
[44] K. Bergmann, H. Theuer, and B. W. Shore, "Coherent population transfer among
quantum states of atoms and molecules," Reviews of Modern Physics, vol. 70, no. 3, pp.
1003-1025, 1998.
[45] T. A. Laine and S. Stenholm, "Adiabatic processes in three-level systems," Physical
Review A, vol. 53, no. 4, pp. 2501-2512, 1996.
[46] Y. Lahini, F. Pozzi, M. Sorel, R. Morandotti, D. N. Christodoulides, and Y. Silberberg,
"Effect of nonlinearity on adiabatic evolution of light," Phys Rev Lett, vol. 101, no. 19,
p. 193901, Nov 7 2008.
[47] R. C. Alferness, R. V. Schmidt, and E. H. Turner, "Characteristics of Ti-diffused lithium
niobate optical directional couplers," Applied Optics, vol. 18, no. 23, pp. 4012–4016,
1979.
[48] E. Paspalakis, "Adiabatic three-waveguide directional coupler," Optics
Communications, vol. 258, no. 1, pp. 30-34, 2006.
[49] B. U. Chen and A. C. Pastor, "Elimination of Li2O out‐diffusion waveguide in
LiNbO3and LiTaO3," Appl. Phys. Lett., vol. 30, no. 11, pp. 570-571, 1977.
[50] K. Nakamura, H. Ando, and H. Shimizu, "Ferroelectric domain inversion caused in LiNbO3plates by heat treatment," Appl. Phys. Lett., vol. 50, no. 20, pp. 1413-1414,
1987.
[51] G. D. Miller,"Periodically poled lithium niobate: modeling, fabrication, and
nonlinear-optical performance",PhD thesis,Stanford university,1998。
[52] R. R. a. W. Sohler, "Loss in low-finesse Ti:LiNbO3 optical waveguide resonators,"
Applied Physics B Photophysics and Laser Chemistry, vol. 36, no. 3, pp. 143-147, 1985.
[53] M. S. Stefszky,"Generation and Detection of Low-Frequency Squeezing for
Gravitational-Wave Detection",Ph.D. Dissertation,Australian National University,April
2012。
[54] N. Takanashi et al., "4-dB Quadrature Squeezing with Fiber-coupled PPLN Ridge
Waveguide Module," IEEE Journal of Quantum Electronics, vol. 56, no. 3, pp. 1-5,
2020.
[55] M. Bazzan and C. Sada, "Optical waveguides in lithium niobate: Recent developments
and applications," Applied Physics Reviews, vol. 2, no. 4, 2015.
[56] C. Wang et al., "Ultrahigh-efficiency wavelength conversion in nanophotonic
periodically poled lithium niobate waveguides," Optica, vol. 5, no. 11, 2018.
[57] A. S. Solntsev et al., "Towards on-chip photon-pair bell tests: Spatial pump filtering in
a LiNbO3 adiabatic coupler," (in English), Appl. Phys. Lett., Article vol. 111, no. 26, p.
4, Dec 2017, Art no. 261108.
[58] T. Umeki, O. Tadanaga, and M. Asobe, "Highly Efficient Wavelength Converter Using
Direct-Bonded PPZnLN Ridge Waveguide," IEEE Journal of Quantum Electronics, vol.
46, no. 8, pp. 1206-1213, 2010.
[59] G. Masada, K. Miyata, A. Politi, T. Hashimoto, J. L. O'Brien, and A. Furusawa,
"Continuous-variable entanglement on a chip," Nature Photonics, vol. 9, no. 5, pp. 316-
319, 2015