This paper′s aim is to study the numerical method of Fourier eigen transform. The characteristics of eigen bases, the Hermite function are analyzed. And a valuable result of eigen coefficients a n by mean...This paper′s aim is to study the numerical method of Fourier eigen transform. The characteristics of eigen bases, the Hermite function are analyzed. And a valuable result of eigen coefficients a n by means of Gauss Hermite integral is gotten. Through talking about amplitude frequency peculiarities of basic signals, we prove that the method applied in this paper possesses higher precision and smaller computation quantity. Finally, we conducted quasi real time FET analysis in seismicity, tentatively probed into the feasibility of FET in seismic prediction, obtained something of practical value.展开更多
The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental result...The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental results show that the gratings can reflect and focus the incident light on the absorber of the photodiode, and thus can simultaneously achieve high speed and high efficiency. For the gratings’ integrated photodiodes, the responsivity is improved over a wide spectral range, and when the absorber was 600 nm and the mesa diameter was40 μm, a responsivity of 0.46 A/W at a wavelength of 1.55 μm and a 3 dB bandwidth of 21.6 GHz under a reverse bias of 3 V were simultaneously obtained.展开更多
An in-line fiber Fabry-Perot interferometer （FPI） based on the hollow-core photonic crystal fiber （HCPCF） for refractive index （RI） measurement is proposed in this paper. The FPI is formed by splicing both ends ...An in-line fiber Fabry-Perot interferometer （FPI） based on the hollow-core photonic crystal fiber （HCPCF） for refractive index （RI） measurement is proposed in this paper. The FPI is formed by splicing both ends of a short section of the HCPCF to single mode fibers （SMFs） and cleaving the SMF pigtail to a proper length. The RI response of the sensor is analyzed theoretically and demonstrated experimentally. The results show that the FPI sensor has linear response to external RI and good repeatability. The sensitivity calculated from the maximum fringe contrast is -136 dB/RIU. A new spectrum differential integration （SDI） method for signal processing is also presented in this study. In this method, the RI is obtained from the integrated intensity of the absolute difference between the interference spectrum and its smoothed spectrum. The results show that the sensitivity obtained from the integrated intensity is about -1.34× 10^5 dB/RIU. Compared with the maximum fringe contrast method, the new SDI method can provide the higher sensitivity, better linearity, improved reliability, and accuracy, and it＇s also convenient for automatic and fast signal processing in real-time monitoring of RI.展开更多
文摘This paper′s aim is to study the numerical method of Fourier eigen transform. The characteristics of eigen bases, the Hermite function are analyzed. And a valuable result of eigen coefficients a n by means of Gauss Hermite integral is gotten. Through talking about amplitude frequency peculiarities of basic signals, we prove that the method applied in this paper possesses higher precision and smaller computation quantity. Finally, we conducted quasi real time FET analysis in seismicity, tentatively probed into the feasibility of FET in seismic prediction, obtained something of practical value.
基金funded by the National Natural Science Foundation of China(NSFC)(Nos.61574019,61674020,and 61274044)the 111 Project(No.B07005)+2 种基金the Beijing Municipality Natural Science Foundation(No.4132069)the Program for Changjiang ScholarsInnovative Research Team in University through the Ministry of Education of China(No.IRT0609)
文摘The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental results show that the gratings can reflect and focus the incident light on the absorber of the photodiode, and thus can simultaneously achieve high speed and high efficiency. For the gratings’ integrated photodiodes, the responsivity is improved over a wide spectral range, and when the absorber was 600 nm and the mesa diameter was40 μm, a responsivity of 0.46 A/W at a wavelength of 1.55 μm and a 3 dB bandwidth of 21.6 GHz under a reverse bias of 3 V were simultaneously obtained.
基金This research is supported by the National Natural Science Foundations of China （Grant Nos. 61174018 and 61505097） and Fundamental research funds of Shandong University, China （Grant No.2014YQ009）.
文摘An in-line fiber Fabry-Perot interferometer （FPI） based on the hollow-core photonic crystal fiber （HCPCF） for refractive index （RI） measurement is proposed in this paper. The FPI is formed by splicing both ends of a short section of the HCPCF to single mode fibers （SMFs） and cleaving the SMF pigtail to a proper length. The RI response of the sensor is analyzed theoretically and demonstrated experimentally. The results show that the FPI sensor has linear response to external RI and good repeatability. The sensitivity calculated from the maximum fringe contrast is -136 dB/RIU. A new spectrum differential integration （SDI） method for signal processing is also presented in this study. In this method, the RI is obtained from the integrated intensity of the absolute difference between the interference spectrum and its smoothed spectrum. The results show that the sensitivity obtained from the integrated intensity is about -1.34× 10^5 dB/RIU. Compared with the maximum fringe contrast method, the new SDI method can provide the higher sensitivity, better linearity, improved reliability, and accuracy, and it＇s also convenient for automatic and fast signal processing in real-time monitoring of RI.
