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RSS2014 Vol. 38, No. 4
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2014, 38(4): 435-440.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.001
[Abstract]
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Abstract:
In order to study effect of nanosecond laser processing parameters (such as wavelength, laser fluence, scanning speed) and thickness of the copper layer on the processing quality of laser etching copper clad laminate (including depth and roughness), a 50W 1064nm infrared fiber laser and a 10W 355nm ultraviolet solid-state laser were used for etching the copper clad laminate(CCL) in the comparative experiments. The action mechanisms of infrared laser and ultraviolet laser were analyzed. In the experiments, the 1064nm fiber laser with proper process parameters could etch the copper layer entirely and keep epoxy resin board intact. However, for the 355nm laser, the damage to the organic layer was unavoidable because of the high absorptivity to ultraviolet and photochemical effect. Besides, the infrared fiber laser had a higher processing efficiency. Therefore, with characteristics of high stability and stronger integration, 1064nm infrared fiber laser is more adapt to the large-scale industrial processing of CCL.
In order to study effect of nanosecond laser processing parameters (such as wavelength, laser fluence, scanning speed) and thickness of the copper layer on the processing quality of laser etching copper clad laminate (including depth and roughness), a 50W 1064nm infrared fiber laser and a 10W 355nm ultraviolet solid-state laser were used for etching the copper clad laminate(CCL) in the comparative experiments. The action mechanisms of infrared laser and ultraviolet laser were analyzed. In the experiments, the 1064nm fiber laser with proper process parameters could etch the copper layer entirely and keep epoxy resin board intact. However, for the 355nm laser, the damage to the organic layer was unavoidable because of the high absorptivity to ultraviolet and photochemical effect. Besides, the infrared fiber laser had a higher processing efficiency. Therefore, with characteristics of high stability and stronger integration, 1064nm infrared fiber laser is more adapt to the large-scale industrial processing of CCL.
2014, 38(4): 441-444.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.002
Abstract:
In order to improve the lithotripsy rate and degree and reduce the side effects during the process of lithotripsy, nanosecond holmium laser lithotripsy system with high peak power output was designed on the base of electro-optical Q-switched technology. Theoretical analysis was made from the aspects of cooling temperature, transmittance and cavity length. Under the conditions of cooling temperature 22℃, repetition rate 3Hz and pump energy 200J, experimental verification was made. The maximum single pulse energy of 443mJ and pulse width of 90ns were obtained. The lithotripsy system can supply high peak power output of nanosecond holmium laser and can crush the lithosis of any component within short lithotripsy time at high lithotripsy rate and degree. The results demonstrate that the system has high performance and lays the foundation for the next step of industry.
In order to improve the lithotripsy rate and degree and reduce the side effects during the process of lithotripsy, nanosecond holmium laser lithotripsy system with high peak power output was designed on the base of electro-optical Q-switched technology. Theoretical analysis was made from the aspects of cooling temperature, transmittance and cavity length. Under the conditions of cooling temperature 22℃, repetition rate 3Hz and pump energy 200J, experimental verification was made. The maximum single pulse energy of 443mJ and pulse width of 90ns were obtained. The lithotripsy system can supply high peak power output of nanosecond holmium laser and can crush the lithosis of any component within short lithotripsy time at high lithotripsy rate and degree. The results demonstrate that the system has high performance and lays the foundation for the next step of industry.
2014, 38(4): 445-448.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.003
Abstract:
In order to measure the carrier mobility of weak conductive material accurately, the charge carrier mobility of Alq3 was measured with the method of time of flight (TOF). The experimental conditions of TOF were analyzed theoretically and verified experimentally. The effects of the wavelength of the excitation light source, the single pulse energy and the selection of integration time constant of circuit measurement on the material carrier mobility measurement results were discussed. The results show that TOF is a typical optical measurement method. But it is possible to obtain accurate and reliable test results when measuring the carrier mobility of weak conductive material by means of TOF only if selecting appropriate measurement conditions strictly. This conclusion is helpful for the accurate measurement of carrier mobility of organic electroluminescent device.
In order to measure the carrier mobility of weak conductive material accurately, the charge carrier mobility of Alq3 was measured with the method of time of flight (TOF). The experimental conditions of TOF were analyzed theoretically and verified experimentally. The effects of the wavelength of the excitation light source, the single pulse energy and the selection of integration time constant of circuit measurement on the material carrier mobility measurement results were discussed. The results show that TOF is a typical optical measurement method. But it is possible to obtain accurate and reliable test results when measuring the carrier mobility of weak conductive material by means of TOF only if selecting appropriate measurement conditions strictly. This conclusion is helpful for the accurate measurement of carrier mobility of organic electroluminescent device.
2014, 38(4): 449-454.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.004
Abstract:
In order to realize fast and precise centering with non-diffracting spot as straight-line datum under complex background noise, the fluctuation of phase angle of non-diffraction spot with polar angle under polar coordinates was obtained with the phase scanning method. The deviation was the difference between the phase of non-diffraction spots on the ring direction and the phase of standard sinusoidal stripes. Finally, the centering of the non-diffraction spot can be realized after a number of iterations. Theoretical analysis and experimental verification show the method has the good ability of anti-noise, less time consumption and sub-pixel level accuracy.
In order to realize fast and precise centering with non-diffracting spot as straight-line datum under complex background noise, the fluctuation of phase angle of non-diffraction spot with polar angle under polar coordinates was obtained with the phase scanning method. The deviation was the difference between the phase of non-diffraction spots on the ring direction and the phase of standard sinusoidal stripes. Finally, the centering of the non-diffraction spot can be realized after a number of iterations. Theoretical analysis and experimental verification show the method has the good ability of anti-noise, less time consumption and sub-pixel level accuracy.
2014, 38(4): 455-458.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.005
Abstract:
To study the influence of the structure parameters of a square five-core photonic crystal fiber (PCF) on coupling characteristics, according to the characteristics of its five super-modes, a method to calculate the coupling length of the PCF was given. The effect of the wavelength and the structure parameters on the coupling characteristics of the PCF was numerically studied in detail with the finite element method. The results show that the coupling length increases with the increase of the core-to-core distance, air-filling ratio, core refractive index and core diameter. However, the coupling length decreases with the increase of the wavelength. The results will provide the theoretical foundations for the design of directional couplers based on five-core PCFs.
To study the influence of the structure parameters of a square five-core photonic crystal fiber (PCF) on coupling characteristics, according to the characteristics of its five super-modes, a method to calculate the coupling length of the PCF was given. The effect of the wavelength and the structure parameters on the coupling characteristics of the PCF was numerically studied in detail with the finite element method. The results show that the coupling length increases with the increase of the core-to-core distance, air-filling ratio, core refractive index and core diameter. However, the coupling length decreases with the increase of the wavelength. The results will provide the theoretical foundations for the design of directional couplers based on five-core PCFs.
2014, 38(4): 459-462.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.006
Abstract:
To solve the measurement of ignition point, the key parameter of ignition-proof magnesium alloy, the colorimetric temperature measurement method was used for the theoretical analysis and experimental verification. A colorimetric temperature measurement device with new structure was designed. The time of the ignition of magnesium alloy was determined from the mutation point of optical radiant energy received by the temperature measurement device and then the ignition temperature was obtained. The static calibration coefficients were gotten from the static calibration of the moderate temperature blackbody furnace. Moderate temperature blackbody furnace was utilized to calibrate statically to obtain static calibration coefficient. Magnesium alloy was ignited with an electrical heating slice resistance with the advantages of simple operation, saving time and test materials. The results of the ignition test of AZ80 with Nd (mass fraction of 0.0075) by colorimetric temperature measurement device and infrared thermometer were 1164.7K and 1148.2K, respectively, whose relative error was 1.4%. The results show that this method solves the difficulty of testing the ignition point of magnesium alloy successfully and has very important reference value for the related research of flame retardant magnesium and on-line monitoring of magnesium alloy smelting.
To solve the measurement of ignition point, the key parameter of ignition-proof magnesium alloy, the colorimetric temperature measurement method was used for the theoretical analysis and experimental verification. A colorimetric temperature measurement device with new structure was designed. The time of the ignition of magnesium alloy was determined from the mutation point of optical radiant energy received by the temperature measurement device and then the ignition temperature was obtained. The static calibration coefficients were gotten from the static calibration of the moderate temperature blackbody furnace. Moderate temperature blackbody furnace was utilized to calibrate statically to obtain static calibration coefficient. Magnesium alloy was ignited with an electrical heating slice resistance with the advantages of simple operation, saving time and test materials. The results of the ignition test of AZ80 with Nd (mass fraction of 0.0075) by colorimetric temperature measurement device and infrared thermometer were 1164.7K and 1148.2K, respectively, whose relative error was 1.4%. The results show that this method solves the difficulty of testing the ignition point of magnesium alloy successfully and has very important reference value for the related research of flame retardant magnesium and on-line monitoring of magnesium alloy smelting.
2014, 38(4): 463-468.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.007
Abstract:
In order to improve the quality of medical fusion images, a novel medical image fusion algorithm based on bidimensional empirical mode decomposition (BEMD) feature classification and multi-pulse coupled neural network was proposed. Firstly, the multimodal medical images were decomposed into two-dimensional intrinsic mode functions (BIMF) and the residuals by means of BEMD, and then the BIMF layer and the residuals coefficients were put into pulse coupled neural network (PCNN) to get their firing maps. The pixels with the same firing times were extracted and classified. The pixels with larger firing times were classified as texture and the rest were classified as the background. The extreme values of the texture collection were counted to determine the grayscale pixel distribution. Finally the pixels representing the texture were input into the PCNN and the other pixels were put into the dual-channel PCNN to get fusion coefficients. The experimental results show that the proposed algorithm has solved the problem of PCNN with superior performance comparing to the traditional fusion algorithms, which can improve the quality of the fused image.
In order to improve the quality of medical fusion images, a novel medical image fusion algorithm based on bidimensional empirical mode decomposition (BEMD) feature classification and multi-pulse coupled neural network was proposed. Firstly, the multimodal medical images were decomposed into two-dimensional intrinsic mode functions (BIMF) and the residuals by means of BEMD, and then the BIMF layer and the residuals coefficients were put into pulse coupled neural network (PCNN) to get their firing maps. The pixels with the same firing times were extracted and classified. The pixels with larger firing times were classified as texture and the rest were classified as the background. The extreme values of the texture collection were counted to determine the grayscale pixel distribution. Finally the pixels representing the texture were input into the PCNN and the other pixels were put into the dual-channel PCNN to get fusion coefficients. The experimental results show that the proposed algorithm has solved the problem of PCNN with superior performance comparing to the traditional fusion algorithms, which can improve the quality of the fused image.
2014, 38(4): 469-474.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.008
Abstract:
In order to study three-dimensional photo-generated carrier density and temperature field distribution in semiconductor materials excited by the rectangular laser pulse, the analytical expressions of the temporal and space distributions of plasma wave and thermal wave were obtained by using the eigen function method. The time evolutions of the plasma and thermal wave for different characterized parameters of semiconductor samples and the radial diffusion characterizations of thermal wave in semiconductors were numerically simulated. The simulation results show that the characterized parameters of semiconductor samples such as surface recombination rates, lifetimes and diffusivity have important influences on temporal characteristics of plasma wave and thermal wave, especially at the stage of step changes. In addition, the sensitivity and correlation analysis of multi-parameters estimation shows that the characterization of single or two semiconductor parameters can be realized by fitting step response curve. The theoretical study provides the guidance for parameters measurement of semiconductor materials by the pulsed photothermal techniques using step optical excitation.
In order to study three-dimensional photo-generated carrier density and temperature field distribution in semiconductor materials excited by the rectangular laser pulse, the analytical expressions of the temporal and space distributions of plasma wave and thermal wave were obtained by using the eigen function method. The time evolutions of the plasma and thermal wave for different characterized parameters of semiconductor samples and the radial diffusion characterizations of thermal wave in semiconductors were numerically simulated. The simulation results show that the characterized parameters of semiconductor samples such as surface recombination rates, lifetimes and diffusivity have important influences on temporal characteristics of plasma wave and thermal wave, especially at the stage of step changes. In addition, the sensitivity and correlation analysis of multi-parameters estimation shows that the characterization of single or two semiconductor parameters can be realized by fitting step response curve. The theoretical study provides the guidance for parameters measurement of semiconductor materials by the pulsed photothermal techniques using step optical excitation.
2014, 38(4): 475-479.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.009
Abstract:
In order to study the influence of the structural parameters on the defect modes of 1-D photonic crystal containing positive index materials and negative index materials, the transmission spectrum of the 1-D photonic crystal containing positive index materials and negative index materials B(AB)m(ACB)n(AB)mB was calculated by using the optical transmission matrix. The effect of structural parameters on defect modes of 1-D photonic crystals was analyzed. Then, the mechanism of multi-channel filters was analyzed based on the wave optics. The results show that there are n defect modes that have the ultra-narrow multi-channel filtering properties when the optical thickness of each layer medium equals to 0/4. When n=1 and the optical thickness of C layer medium equals to k(0/4), there are k defect modes that have the ultra-narrow multi-channel filtering properties. When n2 and the optical thickness of C layer medium equals to k(0/4), there are nk defect modes that have the ultra-narrow multi-channel filtering properties. The results have certain reference value to the design and research of photonic crystal.
In order to study the influence of the structural parameters on the defect modes of 1-D photonic crystal containing positive index materials and negative index materials, the transmission spectrum of the 1-D photonic crystal containing positive index materials and negative index materials B(AB)m(ACB)n(AB)mB was calculated by using the optical transmission matrix. The effect of structural parameters on defect modes of 1-D photonic crystals was analyzed. Then, the mechanism of multi-channel filters was analyzed based on the wave optics. The results show that there are n defect modes that have the ultra-narrow multi-channel filtering properties when the optical thickness of each layer medium equals to 0/4. When n=1 and the optical thickness of C layer medium equals to k(0/4), there are k defect modes that have the ultra-narrow multi-channel filtering properties. When n2 and the optical thickness of C layer medium equals to k(0/4), there are nk defect modes that have the ultra-narrow multi-channel filtering properties. The results have certain reference value to the design and research of photonic crystal.
2014, 38(4): 480-483.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.010
Abstract:
In order to locate the long distance perimeter intrusion, an optical fiber intrusion detection system was promoted based on Fox-Smith interferometer with 33 coupler as the main component. Theoretical analysis and experimental verification were carried out on the system and its location method. When the impact force acts on the sensor fiber, the optical wave is modulated by the phase. There is phase difference because of the modulation time difference between both the beams. A series of trap points are gained after the fast Fourier transform of the demodulated phase signal. The results showed the average location error was 83m when the length of sensing fiber was 34.793km.The system is feasible for long intrusion location and helpful to intrusion detection.
In order to locate the long distance perimeter intrusion, an optical fiber intrusion detection system was promoted based on Fox-Smith interferometer with 33 coupler as the main component. Theoretical analysis and experimental verification were carried out on the system and its location method. When the impact force acts on the sensor fiber, the optical wave is modulated by the phase. There is phase difference because of the modulation time difference between both the beams. A series of trap points are gained after the fast Fourier transform of the demodulated phase signal. The results showed the average location error was 83m when the length of sensing fiber was 34.793km.The system is feasible for long intrusion location and helpful to intrusion detection.
2014, 38(4): 484-487.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.011
Abstract:
In order to measure the wet steam parameters with laser scattering method, monitor the steam humidity at the final stage and guide the safe operation of turbine, the multi-population genetic algorithm was adopted, cubic spline interpolation was used in stead of scattering theory, the least squares of theoretical value and measured value were adopted as the objective functions and the appropriate control parameters were set up for searching the optimization among the simulation data added Gaussian white noise and the experimental data of analog cylinder. The experimental results show that multi-population genetic algorithm can effectively restraint premature convergence, locate the global optimal solution accurately and inverse every parameter of wet steam prominently among some hereditary algebras. The study is helpful for the measurement of wet steam parameters with laser scattering method and the inversion of particle size distribution.
In order to measure the wet steam parameters with laser scattering method, monitor the steam humidity at the final stage and guide the safe operation of turbine, the multi-population genetic algorithm was adopted, cubic spline interpolation was used in stead of scattering theory, the least squares of theoretical value and measured value were adopted as the objective functions and the appropriate control parameters were set up for searching the optimization among the simulation data added Gaussian white noise and the experimental data of analog cylinder. The experimental results show that multi-population genetic algorithm can effectively restraint premature convergence, locate the global optimal solution accurately and inverse every parameter of wet steam prominently among some hereditary algebras. The study is helpful for the measurement of wet steam parameters with laser scattering method and the inversion of particle size distribution.
2014, 38(4): 488-493.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.012
Abstract:
To reduce the number of binary random phase mask used in an image encryption system and simplify the effect of hidden encryption images on decryption process, an optical multiple-image encryption and hiding scheme was put forward based on Fourier transform holography under spherical wave illumination. Theoretical analysis and numerical simulation of image encryption and hiding encryption image and image decryption were made. The results show that correlation coefficient between encryption image and original image approaches 0, correlation coefficient between host image and hiding encryption image approaches 1 when superposition coefficient between host image and hiding encryption image is less than 0.3, correlation coefficient between decryption image and original image approaches 1. The encryption method can obtain good encryption effect.
To reduce the number of binary random phase mask used in an image encryption system and simplify the effect of hidden encryption images on decryption process, an optical multiple-image encryption and hiding scheme was put forward based on Fourier transform holography under spherical wave illumination. Theoretical analysis and numerical simulation of image encryption and hiding encryption image and image decryption were made. The results show that correlation coefficient between encryption image and original image approaches 0, correlation coefficient between host image and hiding encryption image approaches 1 when superposition coefficient between host image and hiding encryption image is less than 0.3, correlation coefficient between decryption image and original image approaches 1. The encryption method can obtain good encryption effect.
2014, 38(4): 494-503.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.013
Abstract:
The high power laser energy research (HiPER) project is initiated by the Council for the Central Laboratory of the Research Councils in United Kingdom and dedicated to the development of carbon-free thermonuclear energy source on base of high power laser driven inertial confinement fusion. The design purpose of HiPER is not only to develop laser-driven inertial confinement fusion technology and make Europe a leading position in the research field of inertial fusion energy, but also to achieve an internationally unique capability in the field of extreme physical state scientific research by means of the extreme experimental conditions provided by HiPER laser device. HiPER, starting from a Pan-European project, has now been becoming an example of global fusion energy research cooperation, which offers us many references. An overall description of current HiPER development status in various aspects such as research background, project planning management, technical progress, external cooperation is presented. A conclusion is made in the end with expectation for providing useful information to the researchers in large laser facilities and fusion energy development.
The high power laser energy research (HiPER) project is initiated by the Council for the Central Laboratory of the Research Councils in United Kingdom and dedicated to the development of carbon-free thermonuclear energy source on base of high power laser driven inertial confinement fusion. The design purpose of HiPER is not only to develop laser-driven inertial confinement fusion technology and make Europe a leading position in the research field of inertial fusion energy, but also to achieve an internationally unique capability in the field of extreme physical state scientific research by means of the extreme experimental conditions provided by HiPER laser device. HiPER, starting from a Pan-European project, has now been becoming an example of global fusion energy research cooperation, which offers us many references. An overall description of current HiPER development status in various aspects such as research background, project planning management, technical progress, external cooperation is presented. A conclusion is made in the end with expectation for providing useful information to the researchers in large laser facilities and fusion energy development.
2014, 38(4): 504-508.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.014
Abstract:
One of the most challenges in optical burst switching (OBS) networks is the resolution of burst conflict. In order to decrease the packet loss probability when bust conflict, a novel conflict resolution algorithm was proposed based on channel grading and back-off channel mechanism. The algorithm takes the priority of the unexpected business into account. The channels were divided into two levels of high and low priority to be treated differently. And then, the back-off channels were increased for the protection and the retransmission of conflict packet to guarantee the transmission reliability of high priority. The results show that, when conflicts occur, the network could adjust the number of two levels adaptively according to the proportion of the priority traffic. Taking into account the low packet loss rate of the low priority, small time delay rate is guaranteed. The algorithm can reduce the packet loss rate and the time delay in OBS networks effectively compared with the other conflict resolution algorithms.
One of the most challenges in optical burst switching (OBS) networks is the resolution of burst conflict. In order to decrease the packet loss probability when bust conflict, a novel conflict resolution algorithm was proposed based on channel grading and back-off channel mechanism. The algorithm takes the priority of the unexpected business into account. The channels were divided into two levels of high and low priority to be treated differently. And then, the back-off channels were increased for the protection and the retransmission of conflict packet to guarantee the transmission reliability of high priority. The results show that, when conflicts occur, the network could adjust the number of two levels adaptively according to the proportion of the priority traffic. Taking into account the low packet loss rate of the low priority, small time delay rate is guaranteed. The algorithm can reduce the packet loss rate and the time delay in OBS networks effectively compared with the other conflict resolution algorithms.
2014, 38(4): 509-514.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.015
Abstract:
In order to study the coherent combination of fiber lasers, coherent combination method of dual-beam fiber laser was simulated by means of the mathematical model of coherent combination of fiber laser, the power distribution of the combined Gaussian beam was studied under different conditions, the effect of different parameters on the coherent combination was analyzed. After simulation and experimental verification, the results show that the best effect of coherent combination can be obtained when the space distance is 0mm, the beam angle is 0° and the polarization is identical.
In order to study the coherent combination of fiber lasers, coherent combination method of dual-beam fiber laser was simulated by means of the mathematical model of coherent combination of fiber laser, the power distribution of the combined Gaussian beam was studied under different conditions, the effect of different parameters on the coherent combination was analyzed. After simulation and experimental verification, the results show that the best effect of coherent combination can be obtained when the space distance is 0mm, the beam angle is 0° and the polarization is identical.
2014, 38(4): 515-521.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.016
Abstract:
To demonstrate the function of random polarization mask in an optical encryption system, the influence of parameters in random polarization mask on encryption effect and decryption error in double random polarization optical encoding system was analyzed by means of theoretical analysis and numerical simulation. The different effects of random phase encoding algorithm and random polarization encoding algorithm on encryption effect and decryption error were compared and presented. The results indicate that a satisfying white-noise liked encrypted image can be obtained when using random phase mask or random polarization mask. But a larger key space is observed with random polarization mask due to its two structured parameters. From decryption point of view, the key sensitivities are different among the different parameters in random polarization mask or random phase mask. The random polarization encoding algorithm has the favorable feasibility for practical application. The results are significant not only for the understanding on the intrinsic of random phase and polarization optical encoding system but also for the design of optical encryption system with high security level.
To demonstrate the function of random polarization mask in an optical encryption system, the influence of parameters in random polarization mask on encryption effect and decryption error in double random polarization optical encoding system was analyzed by means of theoretical analysis and numerical simulation. The different effects of random phase encoding algorithm and random polarization encoding algorithm on encryption effect and decryption error were compared and presented. The results indicate that a satisfying white-noise liked encrypted image can be obtained when using random phase mask or random polarization mask. But a larger key space is observed with random polarization mask due to its two structured parameters. From decryption point of view, the key sensitivities are different among the different parameters in random polarization mask or random phase mask. The random polarization encoding algorithm has the favorable feasibility for practical application. The results are significant not only for the understanding on the intrinsic of random phase and polarization optical encoding system but also for the design of optical encryption system with high security level.
2014, 38(4): 522-526.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.017
Abstract:
In order to meet the beam homogenization application requirements of laser diodes, a beam homogenization shaping system was designed with ZEMAX optical design software. A collimation system composed of aspheric lenses and inverted cylindrical lenses telescope system was used to get a circular Gaussian beam. On the basis of deducing homogenization projection radius of fundamental mode Gaussian beams, the two-aspheric lens homogenization system was optimized with ZEMAX. The whole system can obtain a circular spot with energy uniformity over 96% at a large range. Meanwhile, the beam homogenization of high power optical fiber couple module was realized, which satisfied the needs of high uniformity in applications. This research provides an effective way for the homogenization applications of laser diodes.
In order to meet the beam homogenization application requirements of laser diodes, a beam homogenization shaping system was designed with ZEMAX optical design software. A collimation system composed of aspheric lenses and inverted cylindrical lenses telescope system was used to get a circular Gaussian beam. On the basis of deducing homogenization projection radius of fundamental mode Gaussian beams, the two-aspheric lens homogenization system was optimized with ZEMAX. The whole system can obtain a circular spot with energy uniformity over 96% at a large range. Meanwhile, the beam homogenization of high power optical fiber couple module was realized, which satisfied the needs of high uniformity in applications. This research provides an effective way for the homogenization applications of laser diodes.
2014, 38(4): 527-532.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.018
Abstract:
In order to study the performance of circular array light source in underwater wireless light-emitting diode (LED) optical communication, the mathematical model of the relative intensity of illumination distribution was deduced choosing a circular array light source composed of 6 LEDs as the research object and based on the distribution model of a single LED illumination in the air. The actual underwater illumination distribution was measured with an illuminometer based on the dot matrix measurement method. The experimental data were analyzed. The results show that the intensity of illumination in the output port of the light source increases with the increase of the carrier signal frequency. The whole underwater illumination distribution of the light source is asymmetry. When the optical signal was transmitted to a certain distance, the illumination intensity tends to distribute more evenly in the light receiving plane.
In order to study the performance of circular array light source in underwater wireless light-emitting diode (LED) optical communication, the mathematical model of the relative intensity of illumination distribution was deduced choosing a circular array light source composed of 6 LEDs as the research object and based on the distribution model of a single LED illumination in the air. The actual underwater illumination distribution was measured with an illuminometer based on the dot matrix measurement method. The experimental data were analyzed. The results show that the intensity of illumination in the output port of the light source increases with the increase of the carrier signal frequency. The whole underwater illumination distribution of the light source is asymmetry. When the optical signal was transmitted to a certain distance, the illumination intensity tends to distribute more evenly in the light receiving plane.
2014, 38(4): 533-537.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.019
Abstract:
In order to study the dynamic characteristics of self-similar pulse-pairs in dispersion decreasing fiber, the evolution and compression of pulse-pairs were simulated theoretically with nonlinear Schrdinger equation. In addition, the interactions between the pulses in the neighboring region were analyzed. The results show that without considering the third-order dispersion, the symmetrical oscillation is created in the overlap region while the evolution of pulses is unaffected outside the overlap region. After dispersion compensation, the compressed pulse-pairs are obtained with the temporal width of 128.4fs and the compression factor of 7.8. When considering the third-order dispersion, the evolution of pulses is distorted and created asymmetrical oscillation in the overlap region. The compressed pulse-pairs have a temporal width of 211.6fs and the corresponding compression factor of 4.7. It is worthy of noticing that the pedestals of compression pulse due to asymmetrical oscillation do not affect the quality of the pulses severely. The results provide references for the evolution of self-similar pulse-pairs.
In order to study the dynamic characteristics of self-similar pulse-pairs in dispersion decreasing fiber, the evolution and compression of pulse-pairs were simulated theoretically with nonlinear Schrdinger equation. In addition, the interactions between the pulses in the neighboring region were analyzed. The results show that without considering the third-order dispersion, the symmetrical oscillation is created in the overlap region while the evolution of pulses is unaffected outside the overlap region. After dispersion compensation, the compressed pulse-pairs are obtained with the temporal width of 128.4fs and the compression factor of 7.8. When considering the third-order dispersion, the evolution of pulses is distorted and created asymmetrical oscillation in the overlap region. The compressed pulse-pairs have a temporal width of 211.6fs and the corresponding compression factor of 4.7. It is worthy of noticing that the pedestals of compression pulse due to asymmetrical oscillation do not affect the quality of the pulses severely. The results provide references for the evolution of self-similar pulse-pairs.
2014, 38(4): 538-541.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.020
Abstract:
In order to reveal the plating mechanism that the steel substrate pre-treated by laser quenching could refine the grain of the Cr-plating coating interface, theoretical analysis and experimental verification were carried out. Both sides of the interface between laser discrete pre-quenching substrate and Cr-coating were prepared by chemical etching method: Cr-plating coating interface and substrate interface. The grain morphology of Cr-plating coating interface was researched by scanning electron microscope and the roughness of substrate interface was measured by laser roughness instrument. Based on plating theory, the analytical model of the relationship between the grain size and the roughness was developed with the help of the over-potential. The test and theoretical results indicated that the roughness was proportional to the grain size. The results show that the plating mechanism of grain refinement of Cr-plating coating by laser pretreatment substrate is that the smaller roughness could increase the over potential, which is obtained by laser pre-quenching substrate. The increase of over-potential reduces the grain size. The result is helpful for further analysis of laser pre-processing substrate to improve the interfacial bonding strength.
In order to reveal the plating mechanism that the steel substrate pre-treated by laser quenching could refine the grain of the Cr-plating coating interface, theoretical analysis and experimental verification were carried out. Both sides of the interface between laser discrete pre-quenching substrate and Cr-coating were prepared by chemical etching method: Cr-plating coating interface and substrate interface. The grain morphology of Cr-plating coating interface was researched by scanning electron microscope and the roughness of substrate interface was measured by laser roughness instrument. Based on plating theory, the analytical model of the relationship between the grain size and the roughness was developed with the help of the over-potential. The test and theoretical results indicated that the roughness was proportional to the grain size. The results show that the plating mechanism of grain refinement of Cr-plating coating by laser pretreatment substrate is that the smaller roughness could increase the over potential, which is obtained by laser pre-quenching substrate. The increase of over-potential reduces the grain size. The result is helpful for further analysis of laser pre-processing substrate to improve the interfacial bonding strength.
2014, 38(4): 542-545.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.021
Abstract:
To study the characteristics of high energy pulse laser propagating through turbulent atmosphere, the propagation of high energy laser in atmosphere was numerically simulated, and the far-field beam quantity in terms of the power in the bucket was compared with the experiment performed by using an Nd∶glass laser at output of 800J. The error between the numerical simulation and experiment was analyzed in detail. The numerical simulation and experiments were studied under different conditions of visibility, output energy, and turbulence. It is shown that the numerical simulation can be used to predict the experimental results by a suitable choice of structure parameters of the phase screen. The results show the significance to guide the application and development of high energy pulse lasers.
To study the characteristics of high energy pulse laser propagating through turbulent atmosphere, the propagation of high energy laser in atmosphere was numerically simulated, and the far-field beam quantity in terms of the power in the bucket was compared with the experiment performed by using an Nd∶glass laser at output of 800J. The error between the numerical simulation and experiment was analyzed in detail. The numerical simulation and experiments were studied under different conditions of visibility, output energy, and turbulence. It is shown that the numerical simulation can be used to predict the experimental results by a suitable choice of structure parameters of the phase screen. The results show the significance to guide the application and development of high energy pulse lasers.
2014, 38(4): 546-550.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.022
Abstract:
In order to avoid measuring the inherent frequency and the scanning vibration frequency of C-dynamic scanning system before measuring discontinuous film thickness of lithium battery with laser sensors, the 3-layer wavelet-threshold judgment-sparse decomposition signal processing de-noising method was used. Theoretical analysis and experimental verification were made. Without prior knowledge of the inherent frequency and the scanning vibration frequency and under different C-dynamic scanning mode, the best-matching atomic sequence was selected by iteration and the film thickness distribution of lithium battery was reserved, fluctuations of the local noise were filtered and sparse iterative de-noising was realized. The results show that comparing with the wavelet algorithm and in the absence of the prior knowledge, sparse decomposition algorithm has better de-noising performance and is a simple, practical and effective method. Mean square error of sparse decomposition algorithm is 5μm~7μm.
In order to avoid measuring the inherent frequency and the scanning vibration frequency of C-dynamic scanning system before measuring discontinuous film thickness of lithium battery with laser sensors, the 3-layer wavelet-threshold judgment-sparse decomposition signal processing de-noising method was used. Theoretical analysis and experimental verification were made. Without prior knowledge of the inherent frequency and the scanning vibration frequency and under different C-dynamic scanning mode, the best-matching atomic sequence was selected by iteration and the film thickness distribution of lithium battery was reserved, fluctuations of the local noise were filtered and sparse iterative de-noising was realized. The results show that comparing with the wavelet algorithm and in the absence of the prior knowledge, sparse decomposition algorithm has better de-noising performance and is a simple, practical and effective method. Mean square error of sparse decomposition algorithm is 5μm~7μm.
2014, 38(4): 551-555.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.023
Abstract:
In order to encrypt double color images in a single channel, firstly, two color images to be encrypted were converted to indexed images instead of RGB model and the color mapping matrix of the index images was reserved. Then, after the logarithm operation, fraction Fourier transformation and random modulation of the data matrix, both the images were encrypted. The theoretical analysis and experiment results indicate that two color images can be retrieved without distortion only when correct keys are used. The algorithm has high security.
In order to encrypt double color images in a single channel, firstly, two color images to be encrypted were converted to indexed images instead of RGB model and the color mapping matrix of the index images was reserved. Then, after the logarithm operation, fraction Fourier transformation and random modulation of the data matrix, both the images were encrypted. The theoretical analysis and experiment results indicate that two color images can be retrieved without distortion only when correct keys are used. The algorithm has high security.
2014, 38(4): 556-560.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.024
Abstract:
Al2O3 ceramic polished with 355nm ultraviolet laser could effectively reduce the heat affected zone in processing and prevent the formation of microcracks. In order to find the effects of different parameters (laser energy intensity,laser scanning velocity,laser scanning interval) on the surface roughness and the surface quality,a series of experiments were carried out with a single factor of the 355nm ultraviolet laser affecting the polishing result. The optimal technology parameters were obtained at last. The results show that relatively small surface roughness can be obtained under the conditions of 6J/cm2 laser fluence,60mm/s laser scanning velocity and 2μm laser scanning interval. The study is helpful for getting low roughness and high quality of Al2O3 ceramic.
Al2O3 ceramic polished with 355nm ultraviolet laser could effectively reduce the heat affected zone in processing and prevent the formation of microcracks. In order to find the effects of different parameters (laser energy intensity,laser scanning velocity,laser scanning interval) on the surface roughness and the surface quality,a series of experiments were carried out with a single factor of the 355nm ultraviolet laser affecting the polishing result. The optimal technology parameters were obtained at last. The results show that relatively small surface roughness can be obtained under the conditions of 6J/cm2 laser fluence,60mm/s laser scanning velocity and 2μm laser scanning interval. The study is helpful for getting low roughness and high quality of Al2O3 ceramic.
2014, 38(4): 561-564.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.025
Abstract:
In order to break the asymmetric optical image cryptosystem based on phase-truncated Fourier transforms, known-public key attack method was proposed. Through theoretical analysis and experimental simulation, an attacker can get the general decryption key, recover the plaintext of asymmetric optical image encryption system based on phase truncation Fourier transform and achieve the good crack effect under the known public key attack. During the whole attack process, the method needs anything except for the public keys and the difficulty of implementation is also reduced. The results show this method has the practical significance.
In order to break the asymmetric optical image cryptosystem based on phase-truncated Fourier transforms, known-public key attack method was proposed. Through theoretical analysis and experimental simulation, an attacker can get the general decryption key, recover the plaintext of asymmetric optical image encryption system based on phase truncation Fourier transform and achieve the good crack effect under the known public key attack. During the whole attack process, the method needs anything except for the public keys and the difficulty of implementation is also reduced. The results show this method has the practical significance.
2014, 38(4): 565-568.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.026
Abstract:
To estimate the impact of high repetition frequency jamming on laser decoding,the normalized cross-correlation function method was adopted. The effect of high repetition frequency jamming on precise frequency code during the distinguishing process of decoding was quantified under two circumstances. One was that only the jammed signal entered into the time-gate, the other was that the jammed signal entered into the time-gate at a certain time before the guiding signal. Experimental results show that the jamming effects are different for different jamming ferquency and the jamming effect is the best when the high frequency comes to 100kHz. The simulation of the effect of different factors provides the basis to analyze the jamming effect of high frequency signal.
To estimate the impact of high repetition frequency jamming on laser decoding,the normalized cross-correlation function method was adopted. The effect of high repetition frequency jamming on precise frequency code during the distinguishing process of decoding was quantified under two circumstances. One was that only the jammed signal entered into the time-gate, the other was that the jammed signal entered into the time-gate at a certain time before the guiding signal. Experimental results show that the jamming effects are different for different jamming ferquency and the jamming effect is the best when the high frequency comes to 100kHz. The simulation of the effect of different factors provides the basis to analyze the jamming effect of high frequency signal.
2014, 38(4): 569-573.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.027
Abstract:
In order to study effect of error signal of a quadrant detector on detection positioning accuracy of a laser seeker, based on the detection and position principles of a quadrant detector, the influence of size of light spot, width of division line and intensity of background light on error signal was studied by means of computer simulation. The results show that bigger size of the light spot will decrease the sensitivity of a quadrant detector and extend the dynamic range. Narrower width of division line is optimal under the condition of good crosstalk performance. The background light will decrease the performance of detector. The study is helpful to improve the detection positioning accuracy of quadrant detectors in laser seekers.
In order to study effect of error signal of a quadrant detector on detection positioning accuracy of a laser seeker, based on the detection and position principles of a quadrant detector, the influence of size of light spot, width of division line and intensity of background light on error signal was studied by means of computer simulation. The results show that bigger size of the light spot will decrease the sensitivity of a quadrant detector and extend the dynamic range. Narrower width of division line is optimal under the condition of good crosstalk performance. The background light will decrease the performance of detector. The study is helpful to improve the detection positioning accuracy of quadrant detectors in laser seekers.
2014, 38(4): 574-578.
doi: 10.7510/jgjs.issn.1001-3806.2014.04.028
Abstract:
To avoid the problem that traditional Gerchberg-Saxton (GS) algorithm was easy to get into a partial extremum and could not achieve the desired accuracy, a simple circulatory GS algorithm was used by increasing the amount of information, in another words, increasing one plane so that the GS algorithm could get out of the partial extremum effectively. After the simulative calculation, the phase and amplitude distribution of pupil plane was recovered by the intensity information of the focal plane or nearby position although the amplitude of pupil plane was unknown. The results show that the new algorithm can reach higher accuracy of phase retrieval and lead to precise retrieval of optical field on any planes.
To avoid the problem that traditional Gerchberg-Saxton (GS) algorithm was easy to get into a partial extremum and could not achieve the desired accuracy, a simple circulatory GS algorithm was used by increasing the amount of information, in another words, increasing one plane so that the GS algorithm could get out of the partial extremum effectively. After the simulative calculation, the phase and amplitude distribution of pupil plane was recovered by the intensity information of the focal plane or nearby position although the amplitude of pupil plane was unknown. The results show that the new algorithm can reach higher accuracy of phase retrieval and lead to precise retrieval of optical field on any planes.
