Author Affiliations
Abstract
1 Hubei Key Laboratory of Optical Information and Pattern Recognition, Wuhan Institute of Technology, Wuhan 430205, China
2 Quantum Photonics Laboratory, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
Entangled photon pairs are crucial resources for quantum information processing protocols. Via the process of spontaneous parametric downconversion (SPDC), we can generate these photon pairs using bulk nonlinear crystals. Traditionally, the crystal is designed to satisfy a specific type of phase-matching condition. Here, we report controllable transitions among different types of phase matching in a single periodically poled potassium titanyl phosphate crystal. By carefully selecting pump conditions, we can satisfy different phase-matching conditions. This allows us to observe first-order Type-II, fifth-order Type-I, third-order Type-0, and fifth-order Type-II SPDCs. The temperature-dependent spectra of our source were also analyzed in detail. Finally, we discussed the possibility of observing more than nine SPDCs in this crystal. Our work not only deepens the understanding of the physics behind phase-matching conditions, but also offers the potential for a highly versatile entangled biphoton source for quantum information research.
spontaneous parametric downconversion nonlinear crystals phase-matching condition Chinese Optics Letters
2024, 22(2): 021901
Author Affiliations
Abstract
1 Key Laboratory of Weak-Light Nonlinear Photonics and School of Physics, Nankai University, Tianjin 300071, China
2 Laboratory of Infrared Materials and Devices, Research Institute of Advanced Technologies, Ningbo University, Ningbo 315211, China
3 Laser Physics Center, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601, Australia
4 National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
5 Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
Reliable generation of single photons is of key importance for fundamental physical experiments and quantum protocols. The periodically poled lithium niobate (LN) waveguide has shown promise for an integrated quantum source due to its large spectral tunability and high efficiency, benefiting from the quasi-phase-matching. Here we demonstrate photon-pair sources based on an LN waveguide periodically poled by a tightly focused femtosecond laser beam. The pair coincidence rate reaches ∼8000 counts per second for average pump power of 3.2 mW (peak power is 2.9 kW). Our results prove the possibility of application of the nonlinear photonics structure fabricated by femtosecond laser to the integrated quantum source. This method can be extended to three-dimensional domain structures, which provide a potential platform for steering the spatial degree of freedom of the entangled two-photon states.
photon pair spontaneous parametric downconversion femtosecond laser lithium niobate waveguide quasi-phase matching Chinese Optics Letters
2023, 21(4): 042701
Hua-Ying Liu 1,2,3,*†Minghao Shang 1,2,3Xiaoyi Liu 1,3,4Ying Wei 1,2,3[ ... ]Shining Zhu 1,2,3,5
Author Affiliations
Abstract
1 Nanjing University, National Laboratory of Solid State Microstructures, Nanjing, China
2 Nanjing University, School of Physics, Nanjing, China
3 Nanjing University, Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
4 Nanjing University, School of Electronic Science and Engineering, Nanjing, China
5 Nanjing University, College of Engineering and Applied Sciences, Nanjing, China
The large-photon-number quantum state is a fundamental but nonresolved request for practical quantum information applications. We propose an N-photon state generation scheme that is feasible and scalable, using lithium niobate on insulator circuits. Such a scheme is based on the integration of a common building block called photon-number doubling unit (PDU) for deterministic single-photon parametric downconversion and upconversion. The PDU relies on a 107-optical-quality-factor resonator and mW-level on-chip power, which is within the current fabrication and experimental limits. N-photon state generation schemes, with cluster and Greenberger–Horne–Zeilinger state as examples, are shown for different quantum tasks.
deterministic parametric downconversion multiphoton generation lithium niobate on isolator microring resonator deterministic parametric upconversion Advanced Photonics Nexus
2023, 2(1): 016003
Author Affiliations
Abstract
Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Department of Electronic Materials Engineering (EME), Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
The two-photon state with spatial entanglement is an essential resource for testing fundamental laws of quantum mechanics and various quantum applications. Its creation typically relies on spontaneous parametric downconversion in bulky nonlinear crystals where the tunability of spatial entanglement is limited. Here, we predict that ultrathin nonlinear lithium niobate metasurfaces can generate and diversely tune spatially entangled photon pairs. The spatial properties of photons including the emission pattern, rate, and degree of spatial entanglement are analyzed theoretically with the coupled mode theory and Schmidt decomposition method. We show that by leveraging the strong angular dispersion of the metasurface, the degree of spatial entanglement quantified by the Schmidt number can be decreased or increased by changing the pump laser wavelength and a Gaussian beam size. This flexibility can facilitate diverse quantum applications of entangled photon states generated from nonlinear metasurfaces.
spontaneous parametric downconversion metasurface spatial entanglement Chinese Optics Letters
2023, 21(1): 010005
Author Affiliations
Abstract
1 Key Laboratory of Science and Technology on Electronic Information Control, Chengdu 610029, China
2 Center for Information Photonics & Communications, School of Information Science & Technology, Southwest Jiaotong University, Chengdu 610031, China
3 Science and Technology on Communication Security Laboratory, Institute of Southwestern Communication, Chengdu 610041, China
We experimentally demonstrated the use of intelligent impairment equalization (IIE) for microwave downconversion link linearization in noncooperative systems. Such an equalizer is realized based on an artificial neural network (ANN). Once the training process is completed, the inverse link transfer function can be determined. With the inverse transformation for the detected signal after transmission, the third-order intermodulation distortion components are suppressed significantly without requiring any prior information from an input RF signal. Furthermore, fast training speed is achieved, since the configuration of ANN-based equalizer is simple. Experimental results show that the spurious-free dynamic range of the proposed link is improved to 106.5 dB · Hz2/3, which is 11.3 dB higher than that of a link without IIE. Meanwhile, the training epochs reduce to only five, which has the potential to meet the practical engineering requirement.
microwave photonics linearized downconversion link intelligent impairment equalization artificial neural network Chinese Optics Letters
2023, 21(2): 023902
稀土掺杂发光材料一直是科研领域研究的热点, 被广泛应用于白光LED、 温度传感、 显示显像、 新能源和激光等领域。 基质的结构对于稀土离子光致发光特性有非常重要的影响, 在众多发光基质材料中, 硼酸盐具有透光范围宽、 光学损伤阈值高、 较好的热稳定性和化学稳定性等优点。 碱土-稀土金属硼酸盐Sr3Y2(BO3)4具有出色的光学性能, 对其发光性能的研究具有重要意义。 稀土离子Eu3+具4f6电子层, 是一种典型的下转换发光中心离子, 常被选作红色发光材料的激活剂。 Dy3+具4f9电子层, 也是一种典型的下转换发光中心离子, 在紫外光激发下, 在蓝色光区和橙色光区有较强的荧光发射。 采用高温固相法合成了Sr3Y2(BO3)4∶Eu3+/Dy3+荧光粉, 通过XRD和SEM对样品的结构和形貌进行了表征, XRD结果表明, 1 000 ℃烧结5 h, H3BO3过量20%为最佳制备条件, 且少量的Eu3+和Dy3+掺杂并未改变Sr3Y2(BO3)4的晶格结构。 SEM图像表明Sr3Y2(BO3)4基质的平均晶粒尺寸为2~4 μm, 10%Eu3+单掺和5%Eu3+/5%Dy3+双掺样品与基质Sr3Y2(BO3)4的SEM图像相比, 形貌和尺寸并没有发生明显的改变。 Sr3Y2(BO3)4∶Eu3+荧光粉的发光结果表明, 分别在395和466 nm激发下, 浓度为5%, 10%和15%的Eu3+单掺Sr3Y2(BO3)4荧光粉的主要发光位于593和613 nm的红光发射, 峰强度随着Eu3+浓度的增加呈现先增加后降低的变化形式, 掺杂浓度为10%时发光强度最大, 说明存在浓度猝灭现象。 色坐标结果显示, 激发波长由395 nm变化到466 nm, Sr3Y2(BO3)4∶Eu3+荧光粉的发光颜色从橙红色向红色转变。 引入Dy3+后, Sr3Y2(BO3)4∶Eu3+/Dy3+样品的发射光谱出现Dy3+的486 nm的蓝光发射(4F9/2→6H15/2)和576 nm的橙光发射(4F9/2→6H13/2), 并且随着Dy3+浓度的增加, 对Eu3+的5D0→7F1, 2, 3, 4跃迁有抑制作用。 色坐标结果显示通过调整掺杂离子Eu3+和Dy3+的比例可实现Sr3Y2(BO3)4∶Eu3+/Dy3+荧光粉的颜色从红色区域向橙色区域转变, 说明其在显示方面具有良好的应用前景。
颜色可调 下转换发光 Sr3Y2(BO3)4∶Eu3+/Dy3+; Color adjustable Downconversion luminescence Sr3Y2(BO3)4∶Eu3+/Dy3+; 光谱学与光谱分析
2022, 42(7): 2063
School of Information Science & Technology, Center for Information Photonics & Communications, Southwest Jiaotong University, Chengdu 610031, Sichuan , China
Exploiting microwave photonic (MWP) techniques to generate and distribute high-frequency millimeter-wave (mm-wave) signals, termed mm-wave radio over fiber (m-RoF) signals, holds considerable potential for achieving high-density and high-capacity fifth-generation and beyond networks. Herein, we experimentally validate a broadband m-RoF uplink fronthaul transmission system using the MWP downconversion concept, which comprises receiving and processing radio-frequency (RF) signals in the unlicensed V-band at around 60 GHz. The proposed system harnesses the simple cascaded modulator topology, in which an ultrawideband off-the-shelf Mach–Zehnder modulator (MZM) renders a simple-structured remote radio head by directly encoding the broadband 60 GHz uplink RF signal into the optical carrier. The nonlinear transfer function of another MZM at the center unit is explored to achieve subharmonic downconversion using cost-effective low-frequency local oscillator signals. Based on proof-of-concept experiments, mm-wave four quadrature amplitude modulation orthogonal frequency-division multiplexing signals centered at frequencies ranging from 51 GHz to 70 GHz are successfully downconverted into signals at the intermediate frequency (IF) of 1.4 GHz. In the case of 1.2 m mm-wave, free-space, and 5 km m-RoF transmissions, the obtained IF signals with a total bandwidth of 2.4 GHz achieve a bit-to-error ratio performance lower than the 7% hard-decision forward error correction limit of 3.8 × 10-3. A gross bit rate of 10 Gbit/s can be achieved over a total spectrum of up to 10 GHz, which fully covers the globally unlicensed V-band of 57-66 GHz.
激光与光电子学进展
2022, 59(13): 1336002
1 上海市现代光学系统重点实验室教育部光学仪器与系统工程中心, 上海 200093
2 上海理工大学光电信息与计算机工程学院, 上海200093
紫外下转换发光薄膜在很多光电器件中有重要应用，由于转换效率可以准确地表征发光薄膜的性能，所以研究发光薄膜在紫外激励下的转换效率十分关键。利用积分球收集激发和发射光子，结合发射光谱的光子能量分布，建立了转换效率的计算方法，克服了发光薄膜的各向异性以及波导效应干扰。基于该测试方法搭建的测试系统实现了对220~400 nm 紫外光激励下Lumogen 薄膜和Coronene 薄膜的转换效率测试。测试实验验证了该系统的可行性和可靠性，在研究紫外激励下发光薄膜发光效率上具有较大的应用价值。
薄膜 发光薄膜 积分球 转换效率 紫外下转换 光学学报
2015, 35(10): 1031001
哈尔滨工业大学深圳研究生院， 广东 深圳 518055
三次谐波产生（THG）与三光子参量下转换(TPDC)由于频率跨度大，相位匹配条件很难实现。波导模式色散是有效补偿材料色散的工具。但是THG或TPDC的非线性极化强度为奇函数，如果模场分布存在正负分布，则奇函数几乎为0。提出非对称等离子体沟道波导设计，沟道中引入高阶非线性有机材料(DDMEBT)。晶体硅(Si)在沟道底部以破坏波导的对称性。金属包层采用损耗较小的银(Ag)。通过设计波导几何参数，在基频（FF）零阶模式和第三次诣波（TH）一阶模式间获得了有效的相位匹配条件（PMC），相应THG或TPPC的重叠积分远高于对称波导情况。
非线性光学 参量下转换 等离子体沟道波导 相位匹配 模式色散 光学学报
2015, 35(s1): s119002
江西理工大学 冶金与化学工程学院, 江西 赣州341000
采用射频磁控溅射法制备了CaWO4∶Yb3+薄膜并考察了沉积气压和时间对其结构、形貌和发光性能的影响。在不同的气压下, 薄膜的XRD结果与四方相白钨矿结构相吻合, 并且沿(004)方向择优生长。SEM图像显示, 薄膜表面由椭圆形颗粒和孔洞组成。在260 nm激发下, Yb3+在994 nm处发出强近红外光, 并且其强度随着溅射气压的升高总体是不规律的, 而随着溅射时间的增加先增强后减弱。由于优良的发光性能, CaWO4∶Yb3+薄膜可作为潜在增强硅太阳能电池性能的发光转化膜。
薄膜 磁控溅射 下转换 CaWO4 CaWO4 thin film magnetron sputtering downconversion
