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Lithium niobate on insulator (LNOI) waveguides, as an emerging technology, have proven to offer a promising platform for integrated optics, due to their strong optical confinement comparable to silicon on insulator (SOI) waveguides, while possessing the versatile properties of lithium niobate, such as high electro-optic coefficients. In this paper, we show that mode hybridization, a phenomenon widely found in vertically asymmetric waveguides, can be efficiently modulated in an LNOI ridge waveguide by electro-optic effect, leading to a polarization mode converter with 97% efficiency. Moreover, the proposed device does not require tapering or periodic poling, thereby greatly simplifying the fabrication process. It can also be actively switched by external fields. Such a platform facilitates technological progress of photonics circuits and sensors.
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Design of an X-cut thin-film lithium niobate waveguide as a passive polarization rotator
The transverse-electric and transverse-magnetic modes of an X-cut thin-film lithium niobate waveguide vary in effective indices and exchange power when the waveguide makes an oblique angle with its crystallographic Z-axis, i.e. its optics axis. We leverage this phenomenon to design a passive fundamental-mode polarization rotator. In our design, the lithium niobate waveguide is tilted at an optimum angle with respect to its Z-axis, such that material anisotropy induces phase-matched polarization conversion. We discuss the rotator’s ideal-device length, crosstalk, and bandwidth. The proposed design yields compact (shorter than 1 mm), low-loss, passive polarization rotators for telecom wavelengths.
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- Award ID(s):
- 1807735
- PAR ID:
- 10531322
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 29
- Issue:
- 26
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 44174
- Size(s):
- Article No. 44174
- Sponsoring Org:
- National Science Foundation
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