Guided-wave frequency doubling in surface periodically poled lithium niobate: competing effects
Salvatore Stivala, Alessia Pasquazi, Lorenzo Colace, Gaetano Assanto, Alessandro C. Busacca, Matteo Cherchi, Stefano Riva-Sanseverino, Alfonso C. Cino, Antonino Parisi
We carried out second-harmonic generation in quasi-phase-matched α-phase lithium niobate channel waveguides realized by proton exchange and surface periodic poling. Owing to a limited ferroelectric domain depth, we could observe the interplay between second-harmonic generation and self-phase modulation due to cascading and cubic effects, resulting in a nonlinear resonance shift. Data reduction allowed us to evaluate both the quadratic nonlinearity in the near infrared as well as the depth of the uninverted domains.
Temporal cloaks have inspired the innovation of research on security and efficiency of quantum and fiber communications for concealing temporal events. The existing temporal cloaking approaches possessing ps ~ns cloaking windows employed the third-order nonlinearity mostly. Here we explore a temporal cloak for perpetually concealing pulse events using high efficiency second-order nonlinearity. A temporal pulse event was cloaked as a continuous wave with constant intensity and restored by polarization dependent sum frequency generation processes between the continuous wave and probe. The variet…
Systematic Analysis of Ferroelectric Domain Dynamics in Periodically Poled Lithium Niobate Waveguides Using Two-Photon Microscopy and Digital Imaging Processing
Phase Sensitive Innovations Inc（Phase Sensitive Innovations 公司）；University of Delaware（特拉华大学）
Thin-film lithium niobate on insulator (LNOI) has emerged as a superior integrated-photonics platform for linear, nonlinear, and electro-optics. Here we combine quasi-phase-matching, dispersion engineering, and tight mode confinement to realize nonlinear parametric processes with both high efficiency and wide wavelength tunability. On a millimeter-long, Z-cut LNOI waveguide, we demonstrate ultra-efficient ($1900\pm500 \% $W$^{-1}$cm$^{-2}$) and highly tunable (-1.71 nm/K) second-harmonic generation from 1530 to 1583 nm by type-0 quasi-phase-matching. Our technique is applicable to optical harm…
18-dB on-chip vacuum squeezing in an adaptively poled lithium niobate waveguide
University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California（南加州大学明希电气与计算机工程系）；Research Laboratory of Electronics, MIT（麻省理工学院电子研究实验室）；Department of Electrical and Computer Engineering, University of Hawaii at Mānoa（夏威夷大学马诺阿分校电气与计算机工程系）
In this contribution we investigate the impact of lateral leakage for linear and nonlinear optical waveguides in lithium niobate on insulator (LNOI). Silicon nitride (SiN) loaded and direct patterned lithium niobate cross-sections are investigated. We show that lateral leakage can take place for the TE mode in LNOI ridge waveguides (X-cut lithium niobate), due to the birefringence of the material. This work gives guidelines for designing waveguides in LNOI that do not suffer from the lateral leakage effect. By applying these design considerations, we avoided the lateral leakage effect at the s…
Segment-chirped periodically poled lithium niobate waveguides for broadband supercontinuum generation
National University of Singapore（新加坡国立大学）；Sichuan University（四川大学）；A ∗ STAR Quantum Innovation Centre (Q.InC), Agency for Science, Technology and Research (A ∗ STAR)（A*STAR量子创新中心（Q.InC），科学技术研究局（A*STAR））；Nanyang Technological University（南洋理工大学）
Prospective integrated quantum optical technologies will combine nonlinear optics and components requiring cryogenic operating temperatures. Despite the prevalence of integrated platforms exploiting $χ^{(2)}$-nonlinearities for quantum optics, for example used for quantum state generation and frequency conversion, their material properties at low temperatures are largely unstudied. Here, we demonstrate the first second harmonic generation in a fiber-coupled lithium niobate waveguide at temperatures down to 4.4K. We observe a reproducible shift in the phase-matched pump wavelength within the te…
The absence of the single-photon nonlinearity has been a major roadblock in developing quantum photonic circuits at optical frequencies. In this paper, we demonstrate a periodically-poled thin film lithium niobate microring resonator (PPLNMR) that reaches 5,000,000%/W second harmonic conversion efficiency---almost 20-fold enhancement over the state-of-the-art---by accessing its largest $χ^{(2)}$ tensor component $d_{33}$ via quasi-phase matching. The corresponding single photon coupling rate $g/2π$ is estimated to be 1.2 MHz, which is an important milestone as it approaches the dissipation rat…
Quasi-phasematched interactions in waveguides with quadratic nonlinearities enable highly efficient nonlinear frequency conversion. In this article, we demonstrate the first generation of devices that combine the dispersion-engineering available in nanophotonic waveguides with quasi-phasematched nonlinear interactions available in periodically poled lithium niobate (PPLN). This combination enables quasi-static interactions of femtosecond pulses, reducing the pulse energy requirements by several orders of magnitude, from picojoules to femtojoules. We experimentally demonstrate two effects assoc…
Lithium niobate (LN), dubbed by many as the silicon of photonics, has recently risen to the forefront of chip-scale nonlinear optics research since its demonstration as an ultralow-loss integrated photonics platform. Due to its significant quadratic nonlinearity ($χ^{(2)}$), LN inspires many important applications such as second-harmonic generation (SHG), spontaneous parametric down-conversion, and optical parametric oscillation. Here, we demonstrate high-efficiency SHG in dual-resonant, periodically poled z-cut LN microrings, where quasi-phase matching is realized by field-assisted domain eng…
Isotropic fabrication of centimeter-scale, low propagation-loss periodically poled lithium niobate nanophotonic waveguides for efficient second harmonic generation
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences（中国科学院上海光学精密机械研究所）；East China Normal University（华东师范大学）；ShanghaiTech University（上海科技大学）；University of Chinese Academy of Sciences（中国科学院大学）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）；Hefei National Laboratory（合肥国家实验室）；Shanxi University（山西大学）；Shandong Normal University（山东师范大学）
Lithium niobate on insulator (LNOI) is extensively researched for potential applications in telecommunication, sensing and quantum technology. Low-loss waveguides in LNOI have been demonstrated in recent years, with further works investigating their nonlinear optical properties via electric field poling. The fabrication imperfections and minimum feature size of inverted ferroelectric domains currently limit the efficiency and application of nonlinear processes in LNOI. This work looks into focused ion beam poling and demonstrates its potential to overcome the limitations of electric field poli…
We introduce a general technique to generate compressed broadband terahertz pulses based on difference frequency generation of optical pump radiation using aperiodically poled structures. The pump pulse format and poling of the crystals conceived are such that the emergent terahertz pulse is compressed. The approach circumvents pump pulse distortions that result from non-collinear approaches and the need for external compression. It is particularly efficient for the generation of pulses of intermediate durations of few to tens of cycles. For instance, conversion efficiencies in the few percent…
Thin-film lithium niobate (TFLN) is an emerging platform for compact, low-power nonlinear-optical devices, and has been used extensively for near-infrared frequency conversion. Recent work has extended these devices to mid-infrared wavelengths, where broadly tunable sources may be used for chemical sensing. To this end, we demonstrate efficient and broadband difference frequency generation between a fixed 1-micron pump and a tunable telecom source in uniformly-poled TFLN-on-sapphire by harnessing the dispersion-engineering available in tightly-confining waveguides. We show a simultaneous 1-2 o…
Periodically poled thin-film lithium niobate (TFLN) waveguides have emerged as a leading platform for highly efficient frequency conversion in the near-infrared. However, the commonly used silica bottom-cladding results in high absorption loss at wavelengths beyond 2.5 $μ$m. In this work, we demonstrate efficient frequency conversion in a TFLN-on-sapphire platform, which features high transparency up to 4.5 $μ$m. In particular, we report generating mid-infrared light up to 3.66 $μ$m via difference-frequency generation of a fixed 1-$μ$m source and a tunable telecom source, with normalized effic…
Enhancing broadband second harmonic generation in a thin film lithium niobate racetrack resonator with tunable-coupling
Centre suisse d’électronique et de microtechnique (CSEM)（瑞士电子和微技术中心）；Photonic Systems Laboratory, École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院光子系统实验室）
Quantum squeezing in an all-resonant periodically poled lithium niobate microresonator
University of California, Berkeley（加州大学伯克利分校）；Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California（南加州大学明海电气与计算机工程学院）；Materials Sciences Division, Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室材料科学部）
High-power multicycle THz radiation is highly sought after with applications in medicine, imaging, spectroscopy, characterization and manipulation of condensed matter, and could support the development of next-generation compact laser-based accelerators with applications in electron microscopy, ultrafast X-ray sources and sub-femtosecond longitudinal diagnostics. Multicycle THz-radiation can be generated by shooting an appropriate laser through a periodically poled nonlinear crystal, e.g. lithium niobate (PPLN). Unfortunately, the manufacturing processes of PPLNs require substantially strong e…
Integrated optics provides a platform for the experimental implementation of highly complex and compact circuits for practical applications as well as for advances in the fundamental science of quantum optics. The lithium niobate (LN) waveguide is an important candidate for the construction of integrated optical circuits. Based on the bound state in the continuum (BIC) in a LN waveguide, we propose an efficient way to produce polarization-entangled photon pairs. The implementation of this method is simple and does not require the polarization process needed for periodically poled LN. The gener…
