A generic numerical model of a long-wavelength Avalanche Photodiode （APD） based on narrow bandgap semiconductor InAsSb on InAs substrate is reported for the first time. This model has been applied for theoretical ch...A generic numerical model of a long-wavelength Avalanche Photodiode （APD） based on narrow bandgap semiconductor InAsSb on InAs substrate is reported for the first time. This model has been applied for theoretical characterization of a proposed N^＋ InAS/P-InAsSb avalanche photodiode structure for possible application in 2-5 μm wavelength region. The parameters such as gain, excess noise factor and their trade-off with variation of doping concentration and bias voltage have been estimated for the APD taking into account history-dependent theory of avalanche multiplication process, The LWIR APD is expected to fred application in optical gas sensor and in future generation of optical communication system.展开更多
In low-frequency elastic wave through-the-earth communication system,because of multipath transmission caused by characteristics of the layered earth,the time domain equalizer is different from other wireless communic...In low-frequency elastic wave through-the-earth communication system,because of multipath transmission caused by characteristics of the layered earth,the time domain equalizer is different from other wireless communication systems.A modified LMS algorithm of variable step size is proposed based on improvement of traditional LMS.On the base of principle and simulation analysis,the improved Least Mean Square(LMS)algorithm is analyzed and the performances are compared between the improved LMS algorithm and traditional LMS algorithm.In the improved algorithm,the contradiction between convergence speed and the steady-state error is considered at the same time.Therefore,the improved algorithm has good convergence properties and channel-tracking performance.展开更多
A wavelength splitter with ultra-compact and simple structure is proposed and analyzed by using both plane wave expansion （PWE） method and finite difference time domain （FDTD） method. The device is based on direct...A wavelength splitter with ultra-compact and simple structure is proposed and analyzed by using both plane wave expansion （PWE） method and finite difference time domain （FDTD） method. The device is based on directional coupling between two parallel lithium niobate （LiNbO3, LN） nanowire optical waveguides. The wavelength splitter with a coupling region length of 5 um can separate 1.3 um and 1.55 um wavelengths for corresponding outputs with transmittance higher than 97%.展开更多
Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (J...Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (JSSRE) method was proposed to separate multiple modes in long bones. First, the Gabor time-frequency transform was applied to obtain the spectrogram of multimodal signals. Then, a multi-class image segmentation algorithm was used to find the corresponding region of each mode in the spectrogram, including an improved watershed transform and a region growing procedure. Finally, the ridges were extracted and the time domain signals representing individual modes were reconstructed from these ridges in each region. The validations of this method were discussed by simulated multimodal signals with different signal-to-noise ratios (SNR). The correlation coefficients between the original signals without noise and the reconstructed signals were calculated to analyze the results quantitatively. The results showed that the extracted ridges were in good agreement with generated theoretical dispersion curves, and the reconstructed signals were highly related to the original signals, even under the SNR=3 dB situation.展开更多
In this paper, we present a micro-displacement sensor formed by the fixed and movable photonic crystal slabs. In this sensor, a waveguide was created by changing the radius of holes rather than removing them. At a pro...In this paper, we present a micro-displacement sensor formed by the fixed and movable photonic crystal slabs. In this sensor, a waveguide was created by changing the radius of holes rather than removing them. At a proper operating wavelength, the structure could be used as the micro-displacement sensor. The results revealed that the micro-displacement sensor had a sensitivity of 3.6 gm-1, the Q-factor was nearly 180, and the sensing range was 0.0 ~tm - 0.5 p.m. The properties of the micro-displacement sensor are also analyzed theoretically and verified using the finite-difference time-domain （FDTD） method carried out using the software （Rsoft）.展开更多
In this paper, a model of photonic crystal temperature sensor based on crystal microcavity in a straight photonic crystal waveguide is proposed. The transmission characteristics of light in the sensor under different ...In this paper, a model of photonic crystal temperature sensor based on crystal microcavity in a straight photonic crystal waveguide is proposed. The transmission characteristics of light in the sensor under different temperatures are simulated by using finite-difference time-domain (FDTD) method. The thermal expansion and thermal-optic effects of silicon are taken into account. The results show that the resonant wavelength of microcavity increases linearly as the temperature rising. The wavelength shift along with temperature is 6.6 pm /℃.展开更多
文摘A generic numerical model of a long-wavelength Avalanche Photodiode （APD） based on narrow bandgap semiconductor InAsSb on InAs substrate is reported for the first time. This model has been applied for theoretical characterization of a proposed N^＋ InAS/P-InAsSb avalanche photodiode structure for possible application in 2-5 μm wavelength region. The parameters such as gain, excess noise factor and their trade-off with variation of doping concentration and bias voltage have been estimated for the APD taking into account history-dependent theory of avalanche multiplication process, The LWIR APD is expected to fred application in optical gas sensor and in future generation of optical communication system.
基金supported by the National Natural Science Foundation of China(No.61071016)
文摘In low-frequency elastic wave through-the-earth communication system,because of multipath transmission caused by characteristics of the layered earth,the time domain equalizer is different from other wireless communication systems.A modified LMS algorithm of variable step size is proposed based on improvement of traditional LMS.On the base of principle and simulation analysis,the improved Least Mean Square(LMS)algorithm is analyzed and the performances are compared between the improved LMS algorithm and traditional LMS algorithm.In the improved algorithm,the contradiction between convergence speed and the steady-state error is considered at the same time.Therefore,the improved algorithm has good convergence properties and channel-tracking performance.
基金supported by the National Natural Science Foundation of China(No.61040064)
文摘A wavelength splitter with ultra-compact and simple structure is proposed and analyzed by using both plane wave expansion （PWE） method and finite difference time domain （FDTD） method. The device is based on directional coupling between two parallel lithium niobate （LiNbO3, LN） nanowire optical waveguides. The wavelength splitter with a coupling region length of 5 um can separate 1.3 um and 1.55 um wavelengths for corresponding outputs with transmittance higher than 97%.
基金supported by the National Natural Science Foundation of China(Grant No. 11174060)the PhD Programs Foundation of the Ministry of Education of China(Grant Nos. 20090071110066 and 20110071130004)the New Century Excellent Talents of the Ministry of Education of China(Grant No. NCET-10-0349)
文摘Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (JSSRE) method was proposed to separate multiple modes in long bones. First, the Gabor time-frequency transform was applied to obtain the spectrogram of multimodal signals. Then, a multi-class image segmentation algorithm was used to find the corresponding region of each mode in the spectrogram, including an improved watershed transform and a region growing procedure. Finally, the ridges were extracted and the time domain signals representing individual modes were reconstructed from these ridges in each region. The validations of this method were discussed by simulated multimodal signals with different signal-to-noise ratios (SNR). The correlation coefficients between the original signals without noise and the reconstructed signals were calculated to analyze the results quantitatively. The results showed that the extracted ridges were in good agreement with generated theoretical dispersion curves, and the reconstructed signals were highly related to the original signals, even under the SNR=3 dB situation.
文摘In this paper, we present a micro-displacement sensor formed by the fixed and movable photonic crystal slabs. In this sensor, a waveguide was created by changing the radius of holes rather than removing them. At a proper operating wavelength, the structure could be used as the micro-displacement sensor. The results revealed that the micro-displacement sensor had a sensitivity of 3.6 gm-1, the Q-factor was nearly 180, and the sensing range was 0.0 ~tm - 0.5 p.m. The properties of the micro-displacement sensor are also analyzed theoretically and verified using the finite-difference time-domain （FDTD） method carried out using the software （Rsoft）.
基金surpported by the National 863 Project of China (No.2007AA03Z413)the National Nature Science Foundation of China (No.60727004)the Project of Education Office of Shanxi Province of China (No.09JS041)
文摘In this paper, a model of photonic crystal temperature sensor based on crystal microcavity in a straight photonic crystal waveguide is proposed. The transmission characteristics of light in the sensor under different temperatures are simulated by using finite-difference time-domain (FDTD) method. The thermal expansion and thermal-optic effects of silicon are taken into account. The results show that the resonant wavelength of microcavity increases linearly as the temperature rising. The wavelength shift along with temperature is 6.6 pm /℃.
