Ferroelektrische Materialien reduzierter Dimensionalität für die Photonik
Experimentelle Physik der kondensierten Materie
Zusammenfassung der Projektergebnisse
The teams of Prof. Dr. Karsten Buse (Freiburg), Prof. Dr. Detlef Kip (Hamburg), and Prof. Dr. Wolfgang Sohler (Paderborn) worked for three years in very close collaboration with Prof. Dr. Volkmar Dierolf (Lehigh University, U.S.A.) on the topic “Novel material platforms with reduced dimensionality for next generation ferroelectric photonics”. As the ferroelectric material we selected lithium niobate. The activities on the German side were funded by the Deutsche Forschungsgemeinschaft, DFG, those of the US part by the National Science Foundation, NSF. In order to get dimensionalities reduced to 1D, the method of ion slicing, waver bonding and subsequent ridge waveguide cutting was employed. We were able to improve the technology such that now LNOI waveguides with cross sections of just 1-5 μm2 and losses of about only 1 dB/cm can be made routinely. We showed that the method works for Erbium-doped crystals as well and that the Erbium shows the expected fluorescence, making integrated waveguide lasers possible. For getting phase matching of secondorder nonlinear interactions, a versatile method to structure the ferroelectric domains is needed. We studied writing of domain structures with the help of focused laser beams and discovered that thermoelectric fields can be employed to switch ferroelectric domains. Finally, as an extreme, we synthesized and studied lithium niobate nanocrystals. It turned out that functional doping is possible, similar to doping of bulk crystals. However, thermal annealing has an impact onto the oxidization/reduction state already at much lower temperatures compared to the situation for bulk crystals. This effect stems from the much larger surface and the short distance between any unit cell of the nanocrystals and the surface. A very promising result is that even very small crystals, roughly of the size of 15 nanometers, still show the full nonlinear-optical coefficients known from bulk crystals. All these results are published ; they form the basis for future work, targeting selected applications like, e.g., ultra-high-frequency electro-optic modulators.
Projektbezogene Publikationen (Auswahl)
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“Direct writing of ferroelectric domains on the x- and y-faces of lithium niobate using a continuous wave ultraviolet laser“, Applied Physics Letters 98, 062902 (2011)
H. Steigerwald, Y. J. Ying, R. W. Eason, K. Buse, S. Mailis, and E. Soergel
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“Intrinsic defects pinned at the domain wall in lithium niobate”, 2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011, Munich, Germany
G. Stone, H. Steigerwald, K. Buse, W. Sohler, V. Gopalan, S. Phillpot, and V. Dierolf
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“Light-induced charge-transport in undoped LiNbO3 crystals“, Applied Physics B 105, 35-50 (2011)
F. Lüdtke, N. Waasem, K. Buse, and B. Sturman
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“Synthesis and characterization of Fe-doped LiNbO3 nanocrystals from a triple-alkoxide method“, Physica Status Solidi A 208, 857-862 (2011)
B. Knabe, D. Schütze, T. Jungk, M. Svete, W. Assenmacher, W. Mader, and K. Buse
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“Lithium niobate on insulator (LNOI) for micro-photonic devices”, Laser and Photonics Reviews 6, 488-503 (2012)
G. Poberaj, Hui Hu, W. Sohler, and P. Günter
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“Lithium niobate-on-insulator (LNOI): Status and perspectives”, Proceedings of SPIE - The International Society for Optical Engineering, Volume 8431, 2012, Article number 84311D, Silicon Photonics and Photonic Integrated Circuits III; Brussels; Belgium
Hui Hu, J. Yang, Li Gui and W. Sohler
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“Spontaneous polarization in ultrasmall lithium niobate nanocrystals revealed by second harmonic generation“, Physical Review B 86, 195428 (2012)
B. Knabe and K. Buse
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“Status and prospects of lithium niobate integrated optics”, 2012 Proceedings of the 16th European Conference on Integrated Optics, ECIO '12 Barcelona; Spain
W. Sohler
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“Wafer-scale lithium niobate on insulator (LNOI): A new platform for integrated optics”, 2012 Proceedings of the 16th European Conference on Integrated Optics, ECIO '12 Barcelona; Spain
Hui Hu, Li Gui, R. Ricken, and W. Sohler
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Fabrication of ultra-low-loss ridge waveguides in lithium niobate by diamond blade dicing and high temperature Ti in-diffusion“, Conference on Lasers and Electro-Optics Europe and International Quantum Electronics Conference, CLEO/Europe-IQEC 2013, Munich, Germany
C. E. Rüter, S. Suntsov, and D. Kip
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“Fluorescence in planar and ridge waveguides fabricated in Erbium-doped lithium-niobate-oninsulator (Er:LNOI)”, Conference on Lasers and Electro-Optics Europe and International Quantum Electronics Conference, CLEO/Europe-IQEC 2013, Munich, Germany
C. E. Rüter, D. Kip, G. Stone, V. Dierolf, H. Hu, and W. Sohler
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“Investigation of Er fluorescence in planar and ridge waveguides fabricated in lithium-niobate-oninsulator (LNOI)“, Conference on Lasers and Electro-Optics, CLEO, 2013, San Jose
C. E. Rüter, D. Kip, G. Stone, V. Dierolf, H. Hu, and W. Sohler
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“Nonlinear-optical response and Raman signals of nanocrystalline lithium niobate“, Conference on Lasers and Electro-Optics and International Quantum Electronics Conference, CLEO/Europe-IQEC 2013, Munich, Germany
B. Knabe, K. Buse, G. Stone, and V. Dierolf
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“Characterization of diced ridge waveguides in pure and Er-doped lithium-niobateon-insulator (LNOI) substrates”, Proceedings of SPIE - The International Society for Optical Engineering, Volume 8982, 2014, Article number 89821G; Optical Components and Materials XI; San Francisco, CA; United States
C. E. Rüter, S. Suntsov, D. Kip, G. Stone, V. Dierolf, H. Hu and W. Sohler
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“Photorefractive damage resistance in Ti:PPLN waveguides with ridge geometry”. Applied Physics B, September 2015, Volume 120, Issue 4, pp 737–749
S. Pal, B. K. Das, and W. Sohler
