- Special Issue
- Lithium Niobate Based Photonic Devices
- 16 Article (s)
High-quality-factor optical microresonators fabricated on lithium niobate thin film with an electro-optical tuning range spanning over one free spectral range [Invited]
Zhe Wang, Chaohua Wu, Zhiwei Fang, Min Wang, Jintian Lin, Rongbo Wu, Jianhao Zhang, Jianping Yu, Miao Wu, Wei Chu, Tao Lu, Gang Chen, and Ya Cheng
We demonstrate high-quality (intrinsic Q factor ∼2.8 × 106) racetrack microresonators fabricated on lithium niobate thin film with a free spectral range (FSR) of ∼86 pm. By integrating microelectrodes alongside the two straight arms of the racetrack resonator, the resonance wavelength around 1550 nm can be red shifted by 92 pm when the electric voltage is raised from -100 V to 100 V. The microresonators with the tuning range spanning over a full FSR are fabricated using photolithography assisted chemo-mechanical etching. We demonstrate high-quality (intrinsic Q factor ∼2.8 × 106) racetrack microresonators fabricated on lithium niobate thin film with a free spectral range (FSR) of ∼86 pm. By integrating microelectrodes alongside the two straight arms of the racetrack resonator, the resonance wavelength around 1550 nm can be red shifted by 92 pm when the electric voltage is raised from -100 V to 100 V. The microresonators with the tuning range spanning over a full FSR are fabricated using photolithography assisted chemo-mechanical etching.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060002 (2021)
Integrated thin film lithium niobate Fabry–Perot modulator [Invited]|Editors' Pick
Mengyue Xu, Mingbo He, Yuntao Zhu, Lin Liu, Lifeng Chen, Siyuan Yu, and Xinlun Cai
Integrated traveling-wave lithium niobate modulators need relatively large device lengths to achieve low drive voltage. To increase modulation efficiency within a compact footprint, we report an integrated Fabry–Perot-type electro-optic thin film lithium niobate on insulator modulator comprising a phase modulation region sandwiched between two distributed Bragg reflectors. The device exhibits low optical loss and a high tuning efficiency of 15.7 pm/V. We also confirm the modulator’s high-speed modulation performance by non-return-to-zero modulation with a data rate up to 56 Gbit/s. Integrated traveling-wave lithium niobate modulators need relatively large device lengths to achieve low drive voltage. To increase modulation efficiency within a compact footprint, we report an integrated Fabry–Perot-type electro-optic thin film lithium niobate on insulator modulator comprising a phase modulation region sandwiched between two distributed Bragg reflectors. The device exhibits low optical loss and a high tuning efficiency of 15.7 pm/V. We also confirm the modulator’s high-speed modulation performance by non-return-to-zero modulation with a data rate up to 56 Gbit/s.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060003 (2021)
Efficient second harmonic generation in silicon covered lithium niobate waveguides
Bin Fang, Shenglun Gao, Zhizhang Wang, Shining Zhu, and Tao Li
We theoretically propose a hybrid lithium niobate (LN) thin-film waveguide that consists of an amorphous silicon stripe and etch-free z-cut LN for highly efficient wavelength conversion, circumventing the challenging etching on LN material. Profiting from the spatial symmetry breaking of the waveguide, the asymmetric hybrid modes can spontaneously achieve phase matching with small modal area and large spatial mode overlap, enabling enhanced second harmonic generation with a normalized conversion efficiency over 3900% W-1·cm-2 (0.5-mm-long propagation distance). The choice of integrating silicon with LN alleviates the fabrication challenge, making the platform potentially compatible with silicon photonics. We theoretically propose a hybrid lithium niobate (LN) thin-film waveguide that consists of an amorphous silicon stripe and etch-free z-cut LN for highly efficient wavelength conversion, circumventing the challenging etching on LN material. Profiting from the spatial symmetry breaking of the waveguide, the asymmetric hybrid modes can spontaneously achieve phase matching with small modal area and large spatial mode overlap, enabling enhanced second harmonic generation with a normalized conversion efficiency over 3900% W-1·cm-2 (0.5-mm-long propagation distance). The choice of integrating silicon with LN alleviates the fabrication challenge, making the platform potentially compatible with silicon photonics.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060004 (2021)
Directly generating vortex beams in the second harmonic by a spirally structured fundamental wave
Jun Li, Haigang Liu, Yan Li, Xianping Wang, Minghuang Sang, and Xianfeng Chen
Based on nonlinear wave mixing, we experimentally propose a scheme for directly generating optical orbital angular momentum (OAM) by a spirally structured fundamental wave interacting with a nonlinear medium, in which the nonlinear susceptibilities are homogenous. In the experiment, the second-harmonic generation of a fundamental wave carrying positive (negative) integers and fractional OAM states was investigated. This study presents a convenient approach for dynamic control of OAM of vortex beams, which may feature their applications in optical manipulation and optical communication. Based on nonlinear wave mixing, we experimentally propose a scheme for directly generating optical orbital angular momentum (OAM) by a spirally structured fundamental wave interacting with a nonlinear medium, in which the nonlinear susceptibilities are homogenous. In the experiment, the second-harmonic generation of a fundamental wave carrying positive (negative) integers and fractional OAM states was investigated. This study presents a convenient approach for dynamic control of OAM of vortex beams, which may feature their applications in optical manipulation and optical communication.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060005 (2021)
Polarization diversity two-dimensional grating coupler on x-cut lithium niobate on insulator
Renyou Ge, Hao Li, Ya Han, Lifeng Chen, Jian Xu, Meiyan Wu, Yongqing Li, Yannong Luo, and Xinlun Cai
We propose and demonstrate a polarization diversity two-dimensional grating coupler based on the lithium niobate on insulator platform, for the first time, to the best of our knowledge. The optimization design, performance characteristics, and fabrication tolerance of the two-dimensional grating coupler are thoroughly analyzed utilizing the three-dimensional finite-difference time-domain method. Experimentally, -7.2 dB of coupling efficiency is achieved with 1 dB bandwidth of 64 nm. The polarization-dependent loss is about 0.4 dB around 1550 nm. Our work provides new polarization multiplexing approaches for the lithium niobate on insulator platform, paving the way for critical applications such as high-speed polarization multiplexed electro-optical modulators. We propose and demonstrate a polarization diversity two-dimensional grating coupler based on the lithium niobate on insulator platform, for the first time, to the best of our knowledge. The optimization design, performance characteristics, and fabrication tolerance of the two-dimensional grating coupler are thoroughly analyzed utilizing the three-dimensional finite-difference time-domain method. Experimentally, -7.2 dB of coupling efficiency is achieved with 1 dB bandwidth of 64 nm. The polarization-dependent loss is about 0.4 dB around 1550 nm. Our work provides new polarization multiplexing approaches for the lithium niobate on insulator platform, paving the way for critical applications such as high-speed polarization multiplexed electro-optical modulators.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060006 (2021)
Locally periodically poled LNOI ridge waveguide for second harmonic generation [Invited]
Biao Mu, Xianfang Wu, Yunfei Niu, Yan Chen, Xinlun Cai, Yanxiao Gong, Zhenda Xie, Xiaopeng Hu, and Shining Zhu
Periodically poled lithium niobate on insulator (LNOI) ridge waveguides are desirable for high-efficiency nonlinear frequency conversions, and the fabrication process of such waveguides is crucial for device performance. In this work, we report fabrication and characterization of locally periodically poled ridge waveguides. Ridge waveguides were fabricated by dry etching, and then the high-voltage pulses were applied to locally poled ridge waveguides. Second harmonic generation with normalized conversion efficiency of 435.5% W-1·cm-2 was obtained in the periodically poled LNOI ridge waveguide, which was consistent with the triangular domain structure revealed by confocal microscopy. Periodically poled lithium niobate on insulator (LNOI) ridge waveguides are desirable for high-efficiency nonlinear frequency conversions, and the fabrication process of such waveguides is crucial for device performance. In this work, we report fabrication and characterization of locally periodically poled ridge waveguides. Ridge waveguides were fabricated by dry etching, and then the high-voltage pulses were applied to locally poled ridge waveguides. Second harmonic generation with normalized conversion efficiency of 435.5% W-1·cm-2 was obtained in the periodically poled LNOI ridge waveguide, which was consistent with the triangular domain structure revealed by confocal microscopy.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060007 (2021)
On-chip erbium-doped lithium niobate waveguide amplifiers [Invited]
Qiang Luo, Chen Yang, Zhenzhong Hao, Ru Zhang, Dahuai Zheng, Fang Bo, Yongfa Kong, Guoquan Zhang, and Jingjun Xu
Lithium niobate on insulator (LNOI), as an emerging and promising optical integration platform, faces shortages of on-chip active devices including lasers and amplifiers. Here, we report the fabrication of on-chip erbium-doped LNOI waveguide amplifiers based on electron beam lithography and inductively coupled plasma reactive ion etching. A net internal gain of ～30 dB/cm in the communication band was achieved in the fabricated waveguide amplifiers under the pump of a 974 nm continuous laser. This work develops new active devices on LNOI and may promote the development of LNOI integrated photonics. Lithium niobate on insulator (LNOI), as an emerging and promising optical integration platform, faces shortages of on-chip active devices including lasers and amplifiers. Here, we report the fabrication of on-chip erbium-doped LNOI waveguide amplifiers based on electron beam lithography and inductively coupled plasma reactive ion etching. A net internal gain of ～30 dB/cm in the communication band was achieved in the fabricated waveguide amplifiers under the pump of a 974 nm continuous laser. This work develops new active devices on LNOI and may promote the development of LNOI integrated photonics.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060008 (2021)
Lithium niobate planar and ridge waveguides fabricated by 3 MeV oxygen ion implantation and precise diamond dicing
Jinhua Zhao, Xueshuai Jiao, Yingying Ren, Jinjun Gu, Sumei Wang, Mingyang Bu, and Lei Wang
We report on the fabrication and optimization of lithium niobate planar and ridge waveguides at the wavelength of 633 nm. To obtain a planar waveguide, oxygen ions with an energy of 3.0 MeV and a fluence of 1.5×1015 ions/cm2 are implanted in the polished face of LiNbO3 crystals. For planar waveguides, a loss of 0.5 dB/cm is obtained after annealing at 300°C for 30 min. The ridge waveguide is fabricated by the diamond blade dicing method on optimized planar waveguides. The guiding properties are investigated by prism coupling and end-face coupling methods. We report on the fabrication and optimization of lithium niobate planar and ridge waveguides at the wavelength of 633 nm. To obtain a planar waveguide, oxygen ions with an energy of 3.0 MeV and a fluence of 1.5×1015 ions/cm2 are implanted in the polished face of LiNbO3 crystals. For planar waveguides, a loss of 0.5 dB/cm is obtained after annealing at 300°C for 30 min. The ridge waveguide is fabricated by the diamond blade dicing method on optimized planar waveguides. The guiding properties are investigated by prism coupling and end-face coupling methods.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060009 (2021)
High-Q lithium niobate microring resonators using lift-off metallic masks [Invited]
Ke Zhang, Zhaoxi Chen, Hanke Feng, Wing-Han Wong, Edwin Yue-Bun Pun, and Cheng Wang
High-Q lithium niobate (LN) optical micro-resonators are an excellent platform for future applications in optical communications, nonlinear optics, and quantum optics. To date, high-Q factors are typically achieved in LN using either dielectric masks or femtosecond laser ablation, while the more standard and commonly available lift-off metallic masks are often believed to lead to rough sidewalls and lowered Q factors. Here, we show that LN microring resonators with strong light confinement and intrinsic Q factors over 1 million can be fabricated using optimized lift-off metallic masks and dry etching processes, corresponding to a waveguide propagation loss of ～0.3 dB/cm. The entire process is fully compatible with wafer-scale production and could be transferred to other photonic materials. High-Q lithium niobate (LN) optical micro-resonators are an excellent platform for future applications in optical communications, nonlinear optics, and quantum optics. To date, high-Q factors are typically achieved in LN using either dielectric masks or femtosecond laser ablation, while the more standard and commonly available lift-off metallic masks are often believed to lead to rough sidewalls and lowered Q factors. Here, we show that LN microring resonators with strong light confinement and intrinsic Q factors over 1 million can be fabricated using optimized lift-off metallic masks and dry etching processes, corresponding to a waveguide propagation loss of ～0.3 dB/cm. The entire process is fully compatible with wafer-scale production and could be transferred to other photonic materials.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060010 (2021)
Nonlinear Talbot self-healing in periodically poled LiNbO3 crystal [Invited]|On the Cover
Bingxia Wang, Shan Liu, Tianxiang Xu, Ruwei Zhao, Peixiang Lu, Wieslaw Krolikowski, and Yan Sheng
The nonlinear Talbot effect is a near-field nonlinear diffraction phenomenon in which the self-imaging of periodic objects is formed by the second harmonics of the incident laser beam. We demonstrate the first, to the best of our knowledge, example of nonlinear Talbot self-healing, i.e., the capability of creating defect-free images from faulty nonlinear optical structures. In particular, we employ the tightly focused femtosecond infrared optical pulses to fabricate LiNbO3 nonlinear photonic crystals and show that the defects in the form of the missing points of two-dimensional square and hexagonal periodic structures are restored in the second harmonic images at the first nonlinear Talbot plane. The observed nonlinear Talbot self-healing opens up new possibilities for defect-tolerant optical lithography and printing. The nonlinear Talbot effect is a near-field nonlinear diffraction phenomenon in which the self-imaging of periodic objects is formed by the second harmonics of the incident laser beam. We demonstrate the first, to the best of our knowledge, example of nonlinear Talbot self-healing, i.e., the capability of creating defect-free images from faulty nonlinear optical structures. In particular, we employ the tightly focused femtosecond infrared optical pulses to fabricate LiNbO3 nonlinear photonic crystals and show that the defects in the form of the missing points of two-dimensional square and hexagonal periodic structures are restored in the second harmonic images at the first nonlinear Talbot plane. The observed nonlinear Talbot self-healing opens up new possibilities for defect-tolerant optical lithography and printing.
Chinese Optics Letters
- Publication Date: Jun. 10, 2021
- Vol. 19, Issue 6, 060011 (2021)
Chinese Optics Letters (COL) invites original articles for a Special Issue on Lithium Niobate Based Photonic Devices to be published in June 25 2021. Lithium niobate (LiNbO3) is a multifunctional crystal with combination of a number of excellent properties, such as electrooptical, acousto-optic, nonlinear optical, piezoelectric, and pyroelectric features. In optics and photonics, the LiNbO3-based devices have been widely applied in various aspects. Typical applications include acoustic- and electro-optic modulators, nonlinear wavelength converters, waveguide amplifiers, and quantum memories. The traditional LiNbO3 based photonic devices are constructed on micro-photonic structures, e.g., optical waveguides. A number of techniques have been utilized to produce low-loss LiNbO3 waveguides towards diverse applications. Recently, thin-film devices based on LiNbO3-On-Insulators (LNOI) technology have emerged as promising candidates due to the on-chip integration and strong confinement of light fields. Exciting LNOI-based devices, such as high speed modulators, highly efficient nonlinear optical elements, or hybrid quantum chips, have been developed through advanced techniques, showing distinguished performance for practical applications. There are continuous interests amid researchers on LiNbO3-based photonic devices and related applications, and a number of research groups are devoted to these interesting works. Regarding to these efforts and achievements, the scope of this special focus, covers all aspects of recent theoretical and experimental research related to LiNbO3–based photonic structures and devices.
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