Whispering-gallery-mode(WGM)microresonators can greatly enhance light-matter interaction,making them indispensable units for frequency conversion in nonlinear optics.Efficient nonlinear wave mixing in microresonators ...Whispering-gallery-mode(WGM)microresonators can greatly enhance light-matter interaction,making them indispensable units for frequency conversion in nonlinear optics.Efficient nonlinear wave mixing in microresonators requires stringent simultaneous optical resonance and phase-matching conditions.Thus,it is challenging to achieve efficient frequency conversion over a broad bandwidth.Here,we demonstrate broadband second-harmonic generation(SHG)in the x-cut thinfilm lithium niobate(TFLN)microdisk with a quality factor above 107by applying the cyclic quasi-phase-matching(CQPM)mechanism,which is intrinsically applicable for broadband operation.Broadband SHG of continuous-wave laser with a maximum normalized conversion efficiency of~15%/m W is achieved with a bandwidth spanning over 100 nm in the telecommunication band.Furthermore,broadband SHG of femtosecond lasers,supercontinuum lasers,and amplified spontaneous emission in the telecommunication band is also experimentally observed.The work is beneficial for integrated nonlinear photonics devices like frequency converters and optical frequency comb generator based on second-order nonlinearity on the TFLN platform.展开更多
针对传统的相关算法在循环前缀(Cyclic prefix)长度较短时识别率较低的缺点,研究了一种基于匹配滤波的正交频分复用(Orthogonal frequency division multiplexing,OFDM)信号盲识别方法。该方法利用不同标准中OFDM信号子载波间隔不同的特...针对传统的相关算法在循环前缀(Cyclic prefix)长度较短时识别率较低的缺点,研究了一种基于匹配滤波的正交频分复用(Orthogonal frequency division multiplexing,OFDM)信号盲识别方法。该方法利用不同标准中OFDM信号子载波间隔不同的特点,通过对子载波间隔的估计来实现对信号的识别分类。在建立信号模型的基础上,对提出的算法进行了详细的描述,分析了频率和时间偏移对算法的影响。针对参数搜索过程的高复杂度问题,采用了粒子群优化算法优良的迭代寻优能力来优化参数搜索过程。仿真结果表明:匹配滤波算法克服了传统方法的不足,具有更高的信号识别率和更好的抗多径信道能力。展开更多
基金supported by the National Natural Science Foundation of China(Nos.12074252,12192252,and 62022058)the National Key Research and Development Program of China(No.2022YFA1205101)+1 种基金the Shanghai Municipal Science and Technology Major Project(No.2019SHZDZX01-ZX06)and the Yangyang Development Fund。
文摘Whispering-gallery-mode(WGM)microresonators can greatly enhance light-matter interaction,making them indispensable units for frequency conversion in nonlinear optics.Efficient nonlinear wave mixing in microresonators requires stringent simultaneous optical resonance and phase-matching conditions.Thus,it is challenging to achieve efficient frequency conversion over a broad bandwidth.Here,we demonstrate broadband second-harmonic generation(SHG)in the x-cut thinfilm lithium niobate(TFLN)microdisk with a quality factor above 107by applying the cyclic quasi-phase-matching(CQPM)mechanism,which is intrinsically applicable for broadband operation.Broadband SHG of continuous-wave laser with a maximum normalized conversion efficiency of~15%/m W is achieved with a bandwidth spanning over 100 nm in the telecommunication band.Furthermore,broadband SHG of femtosecond lasers,supercontinuum lasers,and amplified spontaneous emission in the telecommunication band is also experimentally observed.The work is beneficial for integrated nonlinear photonics devices like frequency converters and optical frequency comb generator based on second-order nonlinearity on the TFLN platform.
文摘针对传统的相关算法在循环前缀(Cyclic prefix)长度较短时识别率较低的缺点,研究了一种基于匹配滤波的正交频分复用(Orthogonal frequency division multiplexing,OFDM)信号盲识别方法。该方法利用不同标准中OFDM信号子载波间隔不同的特点,通过对子载波间隔的估计来实现对信号的识别分类。在建立信号模型的基础上,对提出的算法进行了详细的描述,分析了频率和时间偏移对算法的影响。针对参数搜索过程的高复杂度问题,采用了粒子群优化算法优良的迭代寻优能力来优化参数搜索过程。仿真结果表明:匹配滤波算法克服了传统方法的不足,具有更高的信号识别率和更好的抗多径信道能力。
