The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Xiangfei Chen - One of the best experts on this subject based on the ideXlab platform.
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Tilting of Bragg Waveguide Gratings Using Two-Dimensional Sampling Structures
Journal of Lightwave Technology, 2020Co-Authors: Yong Zhao, Rulei Xiao, Tao Fang, Ziyang Hu, Xiangfei ChenAbstract:Tilted Bragg grating (TBG) has been intensively investigated for photonic devices such as fiber sensors and on-chip filters. In this article, we present that TBG can be equivalently realized by designing the tilted sampled Bragg grating (TSBG). As its basic grating is uniform and the Sampling Structure is in the order of micrometer, the fabrication of TSBG can be realized with one step of holographic exposure combined with micro-lithography. As examples, we designed and simulated the equivalent light responses of the TSBGs in the multimode planar waveguide and single-mode fiber respectively. Moreover, the fabrication tolerance of TSBG has also been analyzed. The proposed technique may pave a new way for different 2D gratings with good design flexibility and easy fabrication in various photonic devices.
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High-Power Single-Longitudinal-Mode DFB Semiconductor Laser Based on Sampled Moiré Grating
IEEE Photonics Technology Letters, 2019Co-Authors: Hao Wu, Yong Zhao, Rulei Xiao, Min Chen, Jun Lu, Xiangfei ChenAbstract:In this letter, we experimentally demonstrated a 1550-nm high-power single-longitudinal-mode (SLM) distributed feedback (DFB) semiconductor laser based on sampled moiré grating (SMG). By designing the Sampling Structure with micrometer scale, moiré grating (MG) can be equivalently realized along the laser cavity. Then, we can reduce the coupling coefficient near laser facet so as to increase the output power. The cavity length and ridge width of the fabricated laser are 1.0 mm and 3.0 μm, respectively. The measured threshold current and the slope efficiency are 30.0 mA and 0.36 mW/mA at the heat-sink temperature of 25 °C, respectively. When the injection current is 800.0 mA, the maximum output power is about 183.0 mW. The saturation power is significantly improved compared with conventional DFB laser with uniform sampled grating (USG), which was fabricated on the same wafer. In addition, a four-channel DFB laser array based on SMG was also fabricated on the same wafer, showing good wavelength uniformity.
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Study on a DFB Laser Diode Based on Sampled Grating Technique for Suppression of the Zeroth Order Resonance
IEEE Photonics Journal, 2017Co-Authors: Lianyan Li, Yunshan Zhang, Jianping Shen, Xiangfei ChenAbstract:A distributed feedback (DFB) semiconductor laser based on sampled grating with multiple sections, i.e., a straight, a bent, and a tilted waveguide, is proposed to suppress the 0th-order resonance. A Sampling Structure with nonlinear equivalent chirp pattern is carefully designed to compensate the basic grating chirp introduced by the bent and tilted waveguide. The facet reflection can also be reduced due to the tilted waveguide to avoid the influence of random facet phase. As a result, good single longitudinal mode (SLM) property and high wavelength accuracy in the -1st-order subgrating is achieved, even with a large Sampling period. Because the lasing wavelength can be easily adjusted by a Sampling period and the fabrication accuracy requirement is relaxed, it will benefit the realization of low-cost DFB laser arrays with a good SLM property and accurate lasing wavelength.
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Numerical study of three phase shifts and dual corrugation pitch modulated (CPM) DFB semiconductor lasers based on reconstruction equivalent chirp technology
Chinese Science Bulletin, 2010Co-Authors: Xinghua Tu, Yating Zhou, Simin Li, Xiangfei ChenAbstract:A distributed feedback (DFB) semiconductor laser with three phase shifts based on reconstruction equivalent chirp (REC) technology is proposed and investigated numerically. With the combination of multiple phase shifts and corrugation pitch modulated (CPM) Structure, we also propose a novel and more complex Structure named dual CPM, which has a flatter light power distribution along the laser cavity compared with the true double phase shifts DFB laser diode (LD), while the P-I curves are nearly the same. The proposed dual CPM Structure is also designed and analyzed based on REC technology. The simulation results show that, the DFB semiconductor laser with complex Structure such as phase shifts, or even arbitrary variation of the grating period can be achieved equivalently and easily by changing the Sampling Structure. But its external characteristics are almost the same as those DFB lasers with true phase shifts, or true arbitrary variation of the grating period. The key advantage of the REC technology is that it varies only the Sampling Structure and keeps the seed grating (actual grating in Sampling Structure) period constant. So its fabrication needs only low-cost and standard holographic exposure technology. Therefore we believe this method can achieve the high-end and low-cost DFB LD for mass production.
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Asymmetrical Sampling Structure to improve the single-longitudinal-mode property based on reconstruction-equivalent-chirp technology
Optics Letters, 2010Co-Authors: Yating Zhou, Simin Li, Xiangfei ChenAbstract:We propose a special asymmetric Sampling Structure based on reconstruction-equivalent-chirp technology to effectively suppress the side mode oscillation in the zeroth channel in a sampled Bragg grating semiconductor laser, which improves greatly the single-longitudinal mode (SLM) oscillation capability of the laser. A numerical simulation is performed. The proposed Structure guarantees a normalized threshold gain margin between the main mode and the side mode larger than 0.3. A high side-mode suppression ratio is also observed. The proposed method would be of great importance for the fabrication of high-performance and wideband multiwavelength laser arrays with each laser operating in SLM.
Chenglong Feng - One of the best experts on this subject based on the ideXlab platform.
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STAP for Airborne Radar based on Dual-Frequency Space-Time Coprime Sampling Structure
IEEE Access, 1Co-Authors: Bin Tang, Xiaoxia Zheng, Qiang Wang, Siyuan Wang, Xu Wang, Mengxun Fang, Chenglong FengAbstract:To overcome the space-time adaptive processing (STAP) performance loss caused by discarding the non-uniform parts of difference coarray and copulse for coprime Sampling Structure under the condition of single-frequency operation, this paper proposes a new STAP algorithm to improve the precision of filter weight vector estimation by the dual-frequency operation. By selecting a single proper additional operation frequency, we can obtain the different coarray and copulse, thus fill two missed virtual sensors and pulses of the difference Structures in the single-frequency operation simultaneously. Compared with the single-frequency operation, the dual-frequency operation method can acquire the bigger uniform linear array (ULA) and coherent processing interval (CPI) pulse train to improve the system degrees of freedom (DOF), and result in higher angle-Doppler resolution. In addition, the coprime array has the little mutual coupling effect because of the larger inter-sensors spacing. Therefore, the resulting method can alleviate mutual coupling and enhance the system DOF.
Mei Jiang - One of the best experts on this subject based on the ideXlab platform.
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Space-Time Adaptive Processing for Airborne Radars With Space-Time Coprime Sampling Structure
IEEE Access, 2018Co-Authors: Xiaoye Wang, Zhaocheng Yang, Huiping Huang, Jianjun Huang, Mei JiangAbstract:Coprime arrays and coprime time samplers have been receiving attractive attention recently due to their advantages of large apertures and achievable degrees of freedom with low cost. In this paper, different from traditional airborne radar with uniform transmitting pulses, the considered radar is configured with a coprime array in receiver and transmits the pulses with coprime repetition intervals. Because this Sampling Structure violates the conditions of the conventional clutter rank estimation rules, we first propose a novel method to estimate the clutter rank based on effective aperture-bandwidth product. Then, two space-time adaptive processing (STAP) algorithms, namely, the sample matrix inverseand principal components-STAP, are proposed by using the reconstructed virtual space-time snapshots. Additionally, a thoroughly theoretical convergence analysis of the proposed algorithms is conducted. Exclusive simulation results are provided to demonstrate the effectiveness of the proposed STAP algorithms.
Bin Tang - One of the best experts on this subject based on the ideXlab platform.
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STAP for Airborne Radar based on Dual-Frequency Space-Time Coprime Sampling Structure
IEEE Access, 1Co-Authors: Bin Tang, Xiaoxia Zheng, Qiang Wang, Siyuan Wang, Xu Wang, Mengxun Fang, Chenglong FengAbstract:To overcome the space-time adaptive processing (STAP) performance loss caused by discarding the non-uniform parts of difference coarray and copulse for coprime Sampling Structure under the condition of single-frequency operation, this paper proposes a new STAP algorithm to improve the precision of filter weight vector estimation by the dual-frequency operation. By selecting a single proper additional operation frequency, we can obtain the different coarray and copulse, thus fill two missed virtual sensors and pulses of the difference Structures in the single-frequency operation simultaneously. Compared with the single-frequency operation, the dual-frequency operation method can acquire the bigger uniform linear array (ULA) and coherent processing interval (CPI) pulse train to improve the system degrees of freedom (DOF), and result in higher angle-Doppler resolution. In addition, the coprime array has the little mutual coupling effect because of the larger inter-sensors spacing. Therefore, the resulting method can alleviate mutual coupling and enhance the system DOF.
Xiaoye Wang - One of the best experts on this subject based on the ideXlab platform.
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Space-Time Adaptive Processing for Airborne Radars With Space-Time Coprime Sampling Structure
IEEE Access, 2018Co-Authors: Xiaoye Wang, Zhaocheng Yang, Huiping Huang, Jianjun Huang, Mei JiangAbstract:Coprime arrays and coprime time samplers have been receiving attractive attention recently due to their advantages of large apertures and achievable degrees of freedom with low cost. In this paper, different from traditional airborne radar with uniform transmitting pulses, the considered radar is configured with a coprime array in receiver and transmits the pulses with coprime repetition intervals. Because this Sampling Structure violates the conditions of the conventional clutter rank estimation rules, we first propose a novel method to estimate the clutter rank based on effective aperture-bandwidth product. Then, two space-time adaptive processing (STAP) algorithms, namely, the sample matrix inverseand principal components-STAP, are proposed by using the reconstructed virtual space-time snapshots. Additionally, a thoroughly theoretical convergence analysis of the proposed algorithms is conducted. Exclusive simulation results are provided to demonstrate the effectiveness of the proposed STAP algorithms.
