Epitaxial ZnO/LiNbO3/ZnO stacked layer waveguide for application to thin-film Pockels sensors
We produced slab waveguides consisting of a LiNbO3 (LN) core layer that was sandwiched with Al-doped ZnO cladding layers. The ZnO/LN/ZnO stacked layers were grown on sapphire C-planes by electron cyclotron resonance (ECR) plasma sputtering and were subjected to structural, electrical, and optical ch...
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| Format: | Article |
| Language: | English |
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AIP Publishing LLC
2015-05-01
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| Series: | AIP Advances |
| Online Access: | http://dx.doi.org/10.1063/1.4921981 |
| _version_ | 1818343797384282112 |
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| author | Housei Akazawa Hiroshi Fukuda |
| author_facet | Housei Akazawa Hiroshi Fukuda |
| author_sort | Housei Akazawa |
| collection | DOAJ |
| description | We produced slab waveguides consisting of a LiNbO3 (LN) core layer that was sandwiched with Al-doped ZnO cladding layers. The ZnO/LN/ZnO stacked layers were grown on sapphire C-planes by electron cyclotron resonance (ECR) plasma sputtering and were subjected to structural, electrical, and optical characterizations. X-ray diffraction confirmed that the ZnO and LN layers were epitaxial without containing misoriented crystallites. The presence of 60°-rotational variants of ZnO and LN crystalline domains were identified from X-ray pole figures. Cross-sectional transmission electron microscopy images revealed a c-axis orientated columnar texture for LN crystals, which ensured operation as electro-optic sensors based on optical anisotropy along longitudinal and transversal directions. The interfacial roughness between the LN core and ZnO bottom layers as well as that between the ZnO top and the LN core layers was less than 20 nm, which agreed with surface images observed with atomic force microscopy. Outgrowth of triangular LN crystalline domains produced large roughness at the LN film surface. The RMS roughness of the LN film surface was twice that of the same structure grown on sapphire A-planes. Vertical optical transmittance of the stacked films was higher than 85% within the visible and infrared wavelength range. Following the approach adopted by Teng and Man [Appl. Phys. Lett. 56, 1734 (1990)], ac Pockels coefficients of r33 = 24-28 pm/V were derived for c-axis oriented LN films grown on low-resistive Si substrates. Light propagation within a ZnO/LN/ZnO slab waveguide as well as within a ZnO single layer waveguide was confirmed. The birefringence of these waveguides was 0.11 for the former and 0.05 for the latter. |
| first_indexed | 2024-12-13T16:36:17Z |
| format | Article |
| id | doaj.art-cb711c461dad4fcc96a00a701a1f9e71 |
| institution | Directory Open Access Journal |
| issn | 2158-3226 |
| language | English |
| last_indexed | 2024-12-13T16:36:17Z |
| publishDate | 2015-05-01 |
| publisher | AIP Publishing LLC |
| record_format | Article |
| series | AIP Advances |
| spelling | doaj.art-cb711c461dad4fcc96a00a701a1f9e712022-12-21T23:38:23ZengAIP Publishing LLCAIP Advances2158-32262015-05-0155057163057163-1310.1063/1.4921981063505ADVEpitaxial ZnO/LiNbO3/ZnO stacked layer waveguide for application to thin-film Pockels sensorsHousei Akazawa0Hiroshi Fukuda1 NTT Device Innovation Center, NTT Corporation 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan NTT Device Innovation Center, NTT Corporation 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, JapanWe produced slab waveguides consisting of a LiNbO3 (LN) core layer that was sandwiched with Al-doped ZnO cladding layers. The ZnO/LN/ZnO stacked layers were grown on sapphire C-planes by electron cyclotron resonance (ECR) plasma sputtering and were subjected to structural, electrical, and optical characterizations. X-ray diffraction confirmed that the ZnO and LN layers were epitaxial without containing misoriented crystallites. The presence of 60°-rotational variants of ZnO and LN crystalline domains were identified from X-ray pole figures. Cross-sectional transmission electron microscopy images revealed a c-axis orientated columnar texture for LN crystals, which ensured operation as electro-optic sensors based on optical anisotropy along longitudinal and transversal directions. The interfacial roughness between the LN core and ZnO bottom layers as well as that between the ZnO top and the LN core layers was less than 20 nm, which agreed with surface images observed with atomic force microscopy. Outgrowth of triangular LN crystalline domains produced large roughness at the LN film surface. The RMS roughness of the LN film surface was twice that of the same structure grown on sapphire A-planes. Vertical optical transmittance of the stacked films was higher than 85% within the visible and infrared wavelength range. Following the approach adopted by Teng and Man [Appl. Phys. Lett. 56, 1734 (1990)], ac Pockels coefficients of r33 = 24-28 pm/V were derived for c-axis oriented LN films grown on low-resistive Si substrates. Light propagation within a ZnO/LN/ZnO slab waveguide as well as within a ZnO single layer waveguide was confirmed. The birefringence of these waveguides was 0.11 for the former and 0.05 for the latter.http://dx.doi.org/10.1063/1.4921981 |
| spellingShingle | Housei Akazawa Hiroshi Fukuda Epitaxial ZnO/LiNbO3/ZnO stacked layer waveguide for application to thin-film Pockels sensors AIP Advances |
| title | Epitaxial ZnO/LiNbO3/ZnO stacked layer waveguide for application to thin-film Pockels sensors |
| title_full | Epitaxial ZnO/LiNbO3/ZnO stacked layer waveguide for application to thin-film Pockels sensors |
| title_fullStr | Epitaxial ZnO/LiNbO3/ZnO stacked layer waveguide for application to thin-film Pockels sensors |
| title_full_unstemmed | Epitaxial ZnO/LiNbO3/ZnO stacked layer waveguide for application to thin-film Pockels sensors |
| title_short | Epitaxial ZnO/LiNbO3/ZnO stacked layer waveguide for application to thin-film Pockels sensors |
| title_sort | epitaxial zno linbo3 zno stacked layer waveguide for application to thin film pockels sensors |
| url | http://dx.doi.org/10.1063/1.4921981 |
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