This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO4 laser. C...This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO4 laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN's grating period of 28.5 μm and the temperature of 140℃, the maximum idler output power of 155 mW at 3.86 μm has been achieved when the 808 nm pump power is 8.5 W, leading to an optical-to-optical conversion efficiency of 1.82%.展开更多
Optical tweezers have been a valuable research tool since their invention in the 1980s. One of the most important developments in optical tweezers in recent years is the creation of two-dimensional arrays of optical t...Optical tweezers have been a valuable research tool since their invention in the 1980s. One of the most important developments in optical tweezers in recent years is the creation of two-dimensional arrays of optical traps. In this paper, a method based on interference is discussed to form gradient laser fields, which may cause the spatial modulation of particle concentration. The parameters related to the optical tweezers array are discussed in detail and simulated by the Matlab software to show the influence of important parameters on the distribution of particle concentration. The spatial redistribution of particles in a laser interference field can also be predicted according to the theoretical analysis.展开更多
This study aimed to explore the application of surface-enhanced Raman scattering(SERS)in the rapid diagnosis of gastric cancer.The SERS spectra of 68 serum samples from gastric cancer patients and healthy volunteers w...This study aimed to explore the application of surface-enhanced Raman scattering(SERS)in the rapid diagnosis of gastric cancer.The SERS spectra of 68 serum samples from gastric cancer patients and healthy volunteers were acquired.The characteristic ratio method(CRM)and principal component analysis(PCA)were used to differentiate gastric cancer serum from normal serum.Compared with healthy volunteers,the serum SERS intensity of gastric cancer patients was relatively high at 722 cm^(-1),while it was relatively low at 588,644,861,1008,1235,1397,1445 and 1586 cm^(-1).These results indicated that the relative content of nucleic acids in the serum of gastric cancer patients rises while the relative content of amino acids and carbohydrates decreases.In PCA,the sensitivity and specificity of discriminating gastric cancer were 94.1%and 94.1%,respectively,with the accuracy of 94.1%.Based on the intensity ratios of four characteristic peaks at 722,861,1008 and 1397 cm^(-1),CRM presented the diagnostic sensitivity and specificity of 100%and 97.4%,respectively,and the accuracy of 98.5%.Therefore,the three peak intensity ratios of I_(722)/I_(861),I_(722)/I_(1008)and I_(722)/I_(1397)can be considered as biologicalfingerprint information for gastric cancer diagnosis and can rapidly and directly reflect the physiological and pathological changes associated with gastric cancer development.This study provides an important basis and standards for the early diagnosis of gastric cancer.展开更多
We introduce an instrument for single wavelength measurement of phase retardation based on the laser feedback phenomenon.A method of multi-wavelength conversion for this instrument is proposed and the conversion resul...We introduce an instrument for single wavelength measurement of phase retardation based on the laser feedback phenomenon.A method of multi-wavelength conversion for this instrument is proposed and the conversion results are analyzed.System calibration is used to eliminate the conversion error.The experimental results show that the maximum error after conversion is 0.26°.Through the present work,the application of laser feedback instrument for single wavelength measurement of a wave plate is expanded to the multi-wavelength range.This will expand the application area of the instruments.展开更多
We put forward another form of the non-planar ring lasers, in which the corner cube prism is the key element and the Nd:YAG crystal is used as a Porro prism to enclose the ring resonator. The phase shift due to the to...We put forward another form of the non-planar ring lasers, in which the corner cube prism is the key element and the Nd:YAG crystal is used as a Porro prism to enclose the ring resonator. The phase shift due to the total internal reflections of the three differently orientated reflection planes of the corner cube prism, Faraday rotation in the Nd:YAG crystal placed in a magnetic field and the different output coupling in S and P polarization form an optical diode and enforce the single-frequency generating power. A round trip analysis of the polarization properties of the resonator is made by the evaluation of Jones matrix.展开更多
This paper presents the theoretical studies on the propagation of optical pulses in a deviated Gaussian gained Kerr medium.Our numerical results have shown,for the first time,that the compression of optical pulse widt...This paper presents the theoretical studies on the propagation of optical pulses in a deviated Gaussian gained Kerr medium.Our numerical results have shown,for the first time,that the compression of optical pulse widths varies considerably for differently deviated Gaussian gain.展开更多
The characteristics and the structure of TeO2 acoustic-optic tunable filter used in communication are discussed briefly based on the acoustic-optic theory and it is shown that a large optical incident angle and a long...The characteristics and the structure of TeO2 acoustic-optic tunable filter used in communication are discussed briefly based on the acoustic-optic theory and it is shown that a large optical incident angle and a long interaction length are suitable for the optical add/drop multiplexer based on the TeO2 acoustic-optic tunable filter. The distribution of acoustic energy flow in the device supports the large optical incident angle. The long interaction length depends on the change of the device structure to some degree. The measured results of the samples show that the diffraction efficiency reaches at 96% in the tuning range larger than lOOnm and the bandwidth is about 2nm. It can be found that there is a good consistency with the basic theoretical mode. The optimized design result shows that the diffraction efficiency can arrive at 100%, and the bandwidth can be less than 0.4nm. Thus, the non-collinear TeO2 acoustic-optic tunable filter can play an important role in the coming general optical network.展开更多
The robustness of the software-synchronized all-optical sampling for optical performance monitoring is estimated for 10-Gb/s fiber communication systems. It reveals that the software-synchronized algorithm is sensitiv...The robustness of the software-synchronized all-optical sampling for optical performance monitoring is estimated for 10-Gb/s fiber communication systems. It reveals that the software-synchronized algorithm is sensitive to the signal degradation caused by chromatic dispersion and nonlinearity in optical fibers. The influence of timing jitter and amplitude fluctuation of the sampling pulses is also investigated. It is found that stringent requirements are imposed on the quality of the sampling pulse and the tolerance of 1-dB Q penalty is measured. Considering the practically available optical sampling pulse sources, the results indicate that the amplitude fluctuation of the sampling pulses has the dominant impacts on the software-synchronized method.展开更多
For the segmentation of X-ray angiograms (XRA), the essential feature and the prior knowledge of angiographic image were analyzed, and a multi-feature based fuzzy recognition (MFFR) algorithm was proposed to infer...For the segmentation of X-ray angiograms (XRA), the essential feature and the prior knowledge of angiographic image were analyzed, and a multi-feature based fuzzy recognition (MFFR) algorithm was proposed to infer the local vessel structure in this paper. Guided by the prior knowledge of artery vessel, a probability tracking operator (PTO) can rapidly track along the artery tree, and walk across the weak region or gaps because of disturbance or preprocessing to angiographic image. Another, the accurate measurement of the vascular axis-lines and diameters can be synchronously implemented in the tracking process. To correctly evaluate the proposed method, a simulated image of CAT and some clinical XRA images were used in the experimentations. The algorithms performed better than the conventional one: given one start-point, on average 92.7% of the visible segments or branches was automatically delineated; the correctness ratio of vessel structure inference reached to 90.0% on the average.展开更多
Conventional semi-active laser guidance takes advantage of the laser designator to illuminate the stable and uniform laser spot on target precisely.The seeker collects the reflected light by a quadrant detector and ou...Conventional semi-active laser guidance takes advantage of the laser designator to illuminate the stable and uniform laser spot on target precisely.The seeker collects the reflected light by a quadrant detector and outputs the relative position information to guide the missile to the illuminating laser spot.However,the designation and guidance accuracy could be jeopardized by the randomly drifting of laser spot caused by the instability of designation platform and air turbulence.In this work,ghost imaging technique is adapted to a quadrant detector semi-active seeker by utilizing structured illumination on the target.With a series of structured illumination masks,the signals from the quadrant detector are multiplexed to perform calculation of the target relative position as well as image reconstruction of the illuminated area simultaneously.Automatic target recognition methods could be further applied to the reconstructed image to calculate the designating error and correct the guidance.The results of simulation and experiment demonstrate that the proposed method could improve the guidance accuracy in many circumstances which would lead to attacking deviation if conventional semi-active laser guidance is used.展开更多
Contrary to expectations, a measurement of the random walk in the ring laser gyro (RLG) as a function of laser power P shows that it is not consistent with the Psub〉1/2 rule. In the experiment, the random walk and ...Contrary to expectations, a measurement of the random walk in the ring laser gyro (RLG) as a function of laser power P shows that it is not consistent with the Psub〉1/2 rule. In the experiment, the random walk and laser power are tested and recorded at different discharge currents. The random walk decreases with increasing power, but with a rate much less than the theoretical value according to current literature. In order to solve the inconsistency above, we derive the expression for the random walk in RLGs based on laser theory. Theoretical analysis shows that, accumulating effects of lower energy level due to its limited lifetime lead to additional quantum noise from spontaneous emission. Results show that the random walk in the RLGs consists of two components. The former decreases with increasing power according to the P-1/2 rule, whereas the other is power-independent. Thus far, the power-independent quantum limit has not appeared in the literature; therefore, the expressions for RLGs should be modified to describe the lowloss RLGs exactly, where the power-independent term takes a relatively larger proportion. The findings are significant to the further reduction of quantum limit in low-loss RLGs.展开更多
Ghost imaging and diffraction, inspired by the Hanbury Brown and Twiss effect, have potential in both classical and quantum optics regimes on account of their nonlocal characteristics and subwavelength resolution capa...Ghost imaging and diffraction, inspired by the Hanbury Brown and Twiss effect, have potential in both classical and quantum optics regimes on account of their nonlocal characteristics and subwavelength resolution capabil- ity, and therefore have aroused particular interest. By extending the correspondence imaging scheme, we utilize the positive and negative intensity correlations in diffraction and perform subwavelength diffraction with pseudo-thermal light. In the experiment, a subwavelength (λ/2) resolution and a better signal-to-noise ratio (10.3% improvement) are simultaneously achieved. The scheme can be utilized as a complement to the existing ghost imaging scheme to improve image quality.展开更多
The polarization state is modulated by tilting birefringence component placed in the feedback external cavity.The variation of the polarization state in one period of modulation is found to be similar to sine wave.The...The polarization state is modulated by tilting birefringence component placed in the feedback external cavity.The variation of the polarization state in one period of modulation is found to be similar to sine wave.The periods become increasingly smaller.The maximum of variation in one period decreases against the rotated angle.The experimental phenomenon is subjected to the change of optical path and secondary reflection.The phenomenon is analyzed theoretically based on geometrical optics and crystal optics.High-accuracy measurements of absolute and relative angles can be realized based on the experimental phenomenon.The angle resolution is 0.1 arcsec in theory.展开更多
In this letter, a modified grouped bit-flipping decoding algorithm for low-density parity-check (LDPC) coded pulse position modulation (PPM) signals is proposed. The improvement in performance is observed by Monte...In this letter, a modified grouped bit-flipping decoding algorithm for low-density parity-check (LDPC) coded pulse position modulation (PPM) signals is proposed. The improvement in performance is observed by Monte Carlo simulations. The coding gain is more than 1 and 2 dB for the order numbers of PPM of 4 and 16 respectively.展开更多
基金Project supported in part by the National Natural Science Foundation of China (Grant Nos 10474071, 60637010, 60671036 and60278001)Tianjin Applied Fundamental Research Project, China (07JCZDJC05900)
文摘This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO4 laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN's grating period of 28.5 μm and the temperature of 140℃, the maximum idler output power of 155 mW at 3.86 μm has been achieved when the 808 nm pump power is 8.5 W, leading to an optical-to-optical conversion efficiency of 1.82%.
基金Project supported by the National Natural Science Foundation of China (Grant No 20505002)the Excellent Young Scholars Research Fund of Beijing Institute of Technology (Grant No 000Y06-23)the Excellent Scholars Research Fund of Beijing(Grant No 20071D1600300394)
文摘Optical tweezers have been a valuable research tool since their invention in the 1980s. One of the most important developments in optical tweezers in recent years is the creation of two-dimensional arrays of optical traps. In this paper, a method based on interference is discussed to form gradient laser fields, which may cause the spatial modulation of particle concentration. The parameters related to the optical tweezers array are discussed in detail and simulated by the Matlab software to show the influence of important parameters on the distribution of particle concentration. The spatial redistribution of particles in a laser interference field can also be predicted according to the theoretical analysis.
基金This work was supported by the Natural Science Foundation of Guangdong Province,China(2018 A0303131000)the project of Academician workstation of Guangdong Province,China(2014B090905001)the Fundamental Research Funds for the Central Universities,China(21617406)and the key project of Scientific and Technological projects of Guang Zhou,China(201604040007,201604020168).
文摘This study aimed to explore the application of surface-enhanced Raman scattering(SERS)in the rapid diagnosis of gastric cancer.The SERS spectra of 68 serum samples from gastric cancer patients and healthy volunteers were acquired.The characteristic ratio method(CRM)and principal component analysis(PCA)were used to differentiate gastric cancer serum from normal serum.Compared with healthy volunteers,the serum SERS intensity of gastric cancer patients was relatively high at 722 cm^(-1),while it was relatively low at 588,644,861,1008,1235,1397,1445 and 1586 cm^(-1).These results indicated that the relative content of nucleic acids in the serum of gastric cancer patients rises while the relative content of amino acids and carbohydrates decreases.In PCA,the sensitivity and specificity of discriminating gastric cancer were 94.1%and 94.1%,respectively,with the accuracy of 94.1%.Based on the intensity ratios of four characteristic peaks at 722,861,1008 and 1397 cm^(-1),CRM presented the diagnostic sensitivity and specificity of 100%and 97.4%,respectively,and the accuracy of 98.5%.Therefore,the three peak intensity ratios of I_(722)/I_(861),I_(722)/I_(1008)and I_(722)/I_(1397)can be considered as biologicalfingerprint information for gastric cancer diagnosis and can rapidly and directly reflect the physiological and pathological changes associated with gastric cancer development.This study provides an important basis and standards for the early diagnosis of gastric cancer.
基金Supported by the National Natural Science Foundation of China under Grant No 61036016Scientific and Technological Achievements Transformation and Industrialization Project by the Beijing Municipal Education Commission。
文摘We introduce an instrument for single wavelength measurement of phase retardation based on the laser feedback phenomenon.A method of multi-wavelength conversion for this instrument is proposed and the conversion results are analyzed.System calibration is used to eliminate the conversion error.The experimental results show that the maximum error after conversion is 0.26°.Through the present work,the application of laser feedback instrument for single wavelength measurement of a wave plate is expanded to the multi-wavelength range.This will expand the application area of the instruments.
文摘We put forward another form of the non-planar ring lasers, in which the corner cube prism is the key element and the Nd:YAG crystal is used as a Porro prism to enclose the ring resonator. The phase shift due to the total internal reflections of the three differently orientated reflection planes of the corner cube prism, Faraday rotation in the Nd:YAG crystal placed in a magnetic field and the different output coupling in S and P polarization form an optical diode and enforce the single-frequency generating power. A round trip analysis of the polarization properties of the resonator is made by the evaluation of Jones matrix.
文摘This paper presents the theoretical studies on the propagation of optical pulses in a deviated Gaussian gained Kerr medium.Our numerical results have shown,for the first time,that the compression of optical pulse widths varies considerably for differently deviated Gaussian gain.
文摘The characteristics and the structure of TeO2 acoustic-optic tunable filter used in communication are discussed briefly based on the acoustic-optic theory and it is shown that a large optical incident angle and a long interaction length are suitable for the optical add/drop multiplexer based on the TeO2 acoustic-optic tunable filter. The distribution of acoustic energy flow in the device supports the large optical incident angle. The long interaction length depends on the change of the device structure to some degree. The measured results of the samples show that the diffraction efficiency reaches at 96% in the tuning range larger than lOOnm and the bandwidth is about 2nm. It can be found that there is a good consistency with the basic theoretical mode. The optimized design result shows that the diffraction efficiency can arrive at 100%, and the bandwidth can be less than 0.4nm. Thus, the non-collinear TeO2 acoustic-optic tunable filter can play an important role in the coming general optical network.
基金supported by the National Natural Sci-ence Foundation of China (No. 60777024)the Open Fund of Key Laboratory of Optical Communication and Lightwave Technologies,Beijing University of Posts and Telecommunications, Ministry of Education, China
文摘The robustness of the software-synchronized all-optical sampling for optical performance monitoring is estimated for 10-Gb/s fiber communication systems. It reveals that the software-synchronized algorithm is sensitive to the signal degradation caused by chromatic dispersion and nonlinearity in optical fibers. The influence of timing jitter and amplitude fluctuation of the sampling pulses is also investigated. It is found that stringent requirements are imposed on the quality of the sampling pulse and the tolerance of 1-dB Q penalty is measured. Considering the practically available optical sampling pulse sources, the results indicate that the amplitude fluctuation of the sampling pulses has the dominant impacts on the software-synchronized method.
基金Supported by the National Basic Research Program of China (Grant No. 2003CB716101)the National Natural Science Foundation of China (Grant No. 60772120)the Key National Science Foundation of China (Grant No. 30730026)
文摘For the segmentation of X-ray angiograms (XRA), the essential feature and the prior knowledge of angiographic image were analyzed, and a multi-feature based fuzzy recognition (MFFR) algorithm was proposed to infer the local vessel structure in this paper. Guided by the prior knowledge of artery vessel, a probability tracking operator (PTO) can rapidly track along the artery tree, and walk across the weak region or gaps because of disturbance or preprocessing to angiographic image. Another, the accurate measurement of the vascular axis-lines and diameters can be synchronously implemented in the tracking process. To correctly evaluate the proposed method, a simulated image of CAT and some clinical XRA images were used in the experimentations. The algorithms performed better than the conventional one: given one start-point, on average 92.7% of the visible segments or branches was automatically delineated; the correctness ratio of vessel structure inference reached to 90.0% on the average.
基金co-supported by National Natural Science Foundation of China(Nos.61922011 and 61675016)the Fundamental Research Funds for the Central Universities。
文摘Conventional semi-active laser guidance takes advantage of the laser designator to illuminate the stable and uniform laser spot on target precisely.The seeker collects the reflected light by a quadrant detector and outputs the relative position information to guide the missile to the illuminating laser spot.However,the designation and guidance accuracy could be jeopardized by the randomly drifting of laser spot caused by the instability of designation platform and air turbulence.In this work,ghost imaging technique is adapted to a quadrant detector semi-active seeker by utilizing structured illumination on the target.With a series of structured illumination masks,the signals from the quadrant detector are multiplexed to perform calculation of the target relative position as well as image reconstruction of the illuminated area simultaneously.Automatic target recognition methods could be further applied to the reconstructed image to calculate the designating error and correct the guidance.The results of simulation and experiment demonstrate that the proposed method could improve the guidance accuracy in many circumstances which would lead to attacking deviation if conventional semi-active laser guidance is used.
文摘Contrary to expectations, a measurement of the random walk in the ring laser gyro (RLG) as a function of laser power P shows that it is not consistent with the Psub〉1/2 rule. In the experiment, the random walk and laser power are tested and recorded at different discharge currents. The random walk decreases with increasing power, but with a rate much less than the theoretical value according to current literature. In order to solve the inconsistency above, we derive the expression for the random walk in RLGs based on laser theory. Theoretical analysis shows that, accumulating effects of lower energy level due to its limited lifetime lead to additional quantum noise from spontaneous emission. Results show that the random walk in the RLGs consists of two components. The former decreases with increasing power according to the P-1/2 rule, whereas the other is power-independent. Thus far, the power-independent quantum limit has not appeared in the literature; therefore, the expressions for RLGs should be modified to describe the lowloss RLGs exactly, where the power-independent term takes a relatively larger proportion. The findings are significant to the further reduction of quantum limit in low-loss RLGs.
基金supported by the National Basic Research Program of China(No.2010CB922904)the National Natural Science Foundation of China (No.61307021)the China Scholarship Council (No.201306025016)
文摘Ghost imaging and diffraction, inspired by the Hanbury Brown and Twiss effect, have potential in both classical and quantum optics regimes on account of their nonlocal characteristics and subwavelength resolution capabil- ity, and therefore have aroused particular interest. By extending the correspondence imaging scheme, we utilize the positive and negative intensity correlations in diffraction and perform subwavelength diffraction with pseudo-thermal light. In the experiment, a subwavelength (λ/2) resolution and a better signal-to-noise ratio (10.3% improvement) are simultaneously achieved. The scheme can be utilized as a complement to the existing ghost imaging scheme to improve image quality.
基金supported by the National Natural Science Foundation of China (No. 61036016)the Scientific and Technological Achievements Transformation and Industrialization Project by the Beijing Municipal Education Commission
文摘The polarization state is modulated by tilting birefringence component placed in the feedback external cavity.The variation of the polarization state in one period of modulation is found to be similar to sine wave.The periods become increasingly smaller.The maximum of variation in one period decreases against the rotated angle.The experimental phenomenon is subjected to the change of optical path and secondary reflection.The phenomenon is analyzed theoretically based on geometrical optics and crystal optics.High-accuracy measurements of absolute and relative angles can be realized based on the experimental phenomenon.The angle resolution is 0.1 arcsec in theory.
文摘In this letter, a modified grouped bit-flipping decoding algorithm for low-density parity-check (LDPC) coded pulse position modulation (PPM) signals is proposed. The improvement in performance is observed by Monte Carlo simulations. The coding gain is more than 1 and 2 dB for the order numbers of PPM of 4 and 16 respectively.