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RSS2013 Vol. 37, No. 2
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2013, 37(2): 139-142.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.001
[Abstract]
[PDF 568KB]
Abstract:
In order to study the accuracy of determination for elastic modulus of WC/Cu composites by digital image correlation method, WC/Cu composites with different WC content were prepared by powder metallurgy method. On the surface of specimens speckles were made by white paint with carbon powder. The tensile tests of these specimens were made in the universal material testing machine. Meanwhile the speckle figures were recorded by CCD camera. Correlation calculation was performed for the recorded speckle figures. And the calculation results were corrected according to the distortion correction theory. Then the stress-strain curve and elastic modulus of WC/Cu composites under small strain were given. The experimental results are in accordance with the results got by traditional electrical measurement. That means the measurement of elastic modulus of WC/Cu composites by digital image correlation applied to the small samples is correct and reliable.
In order to study the accuracy of determination for elastic modulus of WC/Cu composites by digital image correlation method, WC/Cu composites with different WC content were prepared by powder metallurgy method. On the surface of specimens speckles were made by white paint with carbon powder. The tensile tests of these specimens were made in the universal material testing machine. Meanwhile the speckle figures were recorded by CCD camera. Correlation calculation was performed for the recorded speckle figures. And the calculation results were corrected according to the distortion correction theory. Then the stress-strain curve and elastic modulus of WC/Cu composites under small strain were given. The experimental results are in accordance with the results got by traditional electrical measurement. That means the measurement of elastic modulus of WC/Cu composites by digital image correlation applied to the small samples is correct and reliable.
2013, 37(2): 143-146.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.002
Abstract:
To obtain data about position, size and velocity of droplets in the electrostatic spray, a device based on in-line digital microscopic holography for spray measurement was devised and established, which has lateral measurement scope of Ø12.5mm, utmost spatial resolution of 90.5LP/mm, and the capacity of measuring the droplet in 8μm diameter. Spray measurements under the Talyor-cone mode with single metal capillary and multiple metal capillaries were carried out respectively on the established device, and the relations between average diameter, average velocity of droplets and flow rate were obtained. Results show that position, size and velocity of droplets can be obtained simultaneously during a single-shot measurement by the device, which is of great significance to the measurement on spray and the research of electrostatic spray.
To obtain data about position, size and velocity of droplets in the electrostatic spray, a device based on in-line digital microscopic holography for spray measurement was devised and established, which has lateral measurement scope of Ø12.5mm, utmost spatial resolution of 90.5LP/mm, and the capacity of measuring the droplet in 8μm diameter. Spray measurements under the Talyor-cone mode with single metal capillary and multiple metal capillaries were carried out respectively on the established device, and the relations between average diameter, average velocity of droplets and flow rate were obtained. Results show that position, size and velocity of droplets can be obtained simultaneously during a single-shot measurement by the device, which is of great significance to the measurement on spray and the research of electrostatic spray.
2013, 37(2): 147-150.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.003
Abstract:
In order to design a crystal with special optical characteristics, the characteristics of 1-D ternary photonic crystal containing gain medium defects layer was studied with transfer matrix method without considering dispersion relation, and its band structure and optical amplification characteristics were analyzed and discussed. There is strong optical amplification in the passband edge 0.242μm. The thickness and optical constants of the gain medium at 0.242μm was studied, and the characteristics of the optical amplification were discussed when changing the central wavelength of light. The results indicate that there is corresponding forbidden band on the both sides of center wavelength when the center wavelength is 0.3μm. The influence of the band gap structures is small when changing the thickness and optical constants of the defect layer, and there is strong optical amplificatiom in passband edge 0.242μm. This simulated data provides a theoretical guidance for photonic crystal of the desired characteristics.
In order to design a crystal with special optical characteristics, the characteristics of 1-D ternary photonic crystal containing gain medium defects layer was studied with transfer matrix method without considering dispersion relation, and its band structure and optical amplification characteristics were analyzed and discussed. There is strong optical amplification in the passband edge 0.242μm. The thickness and optical constants of the gain medium at 0.242μm was studied, and the characteristics of the optical amplification were discussed when changing the central wavelength of light. The results indicate that there is corresponding forbidden band on the both sides of center wavelength when the center wavelength is 0.3μm. The influence of the band gap structures is small when changing the thickness and optical constants of the defect layer, and there is strong optical amplificatiom in passband edge 0.242μm. This simulated data provides a theoretical guidance for photonic crystal of the desired characteristics.
2013, 37(2): 151-154.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.004
Abstract:
In order to reduce the "S-W effect" of amorphous silicon thin film solar cells and increase its photoelectric conversion efficiency, intrinsic amorphous silicon thin films prepared by plasma enhanced chemical vapov deposition were crystallized with KrF excimer laser. The crystalline effect of the crystallized films under different laser energy density and repeated frequency was characterized with Raman spectroscopy, the morphologies of the samples before and after the crystallization was studied by means of scanning electron microscope. It is shown that the crystallization effect became better with the increase of laser energy density, maximum value of crystallization rate was 76.34% when the energy density reached 268.54mJ/cm2 and the optimum energy density range was from 204.99mJ/cm2 to 268.54mJ/cm2 in which the surface of film was crystallized well. In the range of 1Hz~10Hz, the crystallization effect got better with the increase of laser repeation frequency. Microcrystalline and polycrystal particles appeared obviously after the crystallization so that a good crystallization effect was achieved.
In order to reduce the "S-W effect" of amorphous silicon thin film solar cells and increase its photoelectric conversion efficiency, intrinsic amorphous silicon thin films prepared by plasma enhanced chemical vapov deposition were crystallized with KrF excimer laser. The crystalline effect of the crystallized films under different laser energy density and repeated frequency was characterized with Raman spectroscopy, the morphologies of the samples before and after the crystallization was studied by means of scanning electron microscope. It is shown that the crystallization effect became better with the increase of laser energy density, maximum value of crystallization rate was 76.34% when the energy density reached 268.54mJ/cm2 and the optimum energy density range was from 204.99mJ/cm2 to 268.54mJ/cm2 in which the surface of film was crystallized well. In the range of 1Hz~10Hz, the crystallization effect got better with the increase of laser repeation frequency. Microcrystalline and polycrystal particles appeared obviously after the crystallization so that a good crystallization effect was achieved.
2013, 37(2): 155-157.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.005
Abstract:
In order to get a high power and solid-state UV laser, based on a plane-plane cavity, with laser diode double-end pumping Nd:YVO4 crystal, fundamental pulse at 1064nm was output under modulation of a acousto-optic Q-switch. Then the laser at 355nm was generated by the second harmonic generation and the third harmonic generation with two LBO crystals. Under the pump power of 54W, 6.67W, average output power at 355nm was obtained at 40kHz with the pulse width of 20ns and M2=1.1. The results show that the design of intra-cavity third harmonic generation lasers can give high conversion efficiency and good beam quality.
In order to get a high power and solid-state UV laser, based on a plane-plane cavity, with laser diode double-end pumping Nd:YVO4 crystal, fundamental pulse at 1064nm was output under modulation of a acousto-optic Q-switch. Then the laser at 355nm was generated by the second harmonic generation and the third harmonic generation with two LBO crystals. Under the pump power of 54W, 6.67W, average output power at 355nm was obtained at 40kHz with the pulse width of 20ns and M2=1.1. The results show that the design of intra-cavity third harmonic generation lasers can give high conversion efficiency and good beam quality.
2013, 37(2): 158-164.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.006
Abstract:
In order to select proper space-time coding mode according to the time-varying channel, a 4×4 adaptive multi-layer space-time coding scheme was proposed in free space optical-multiple input multiple output(FSO-MIMO) based on the multi-layer space-time coding theory of antenna groups, which concludes the advantages of both orthogonal space-time block codes(OSTBC)and layered space-time code(LSTC). Simulation was carried out with Monte Carlo method. The simulation shows within a certain signal-to-noise ratio(SNR) range, the data rate can maximized at specific level of bit error rate(BER) with adaptive multi-layered space-time coding scheme.
In order to select proper space-time coding mode according to the time-varying channel, a 4×4 adaptive multi-layer space-time coding scheme was proposed in free space optical-multiple input multiple output(FSO-MIMO) based on the multi-layer space-time coding theory of antenna groups, which concludes the advantages of both orthogonal space-time block codes(OSTBC)and layered space-time code(LSTC). Simulation was carried out with Monte Carlo method. The simulation shows within a certain signal-to-noise ratio(SNR) range, the data rate can maximized at specific level of bit error rate(BER) with adaptive multi-layered space-time coding scheme.
2013, 37(2): 165-168.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.007
Abstract:
To reveal the mechanism that laser discrete pre-quenching substrate could increase the lifetime of a certain model chromium-plated gun barrel, the substrate behavior between laser treated and untreated the end Cr-plating barrel were compared in experiments. The results show that there is no obvious ablation pits in the gun barrel; the ablation value of laser-treated gun barrel is decreased by 10% than that of untreated one, which is because the main-cracks of Cr-coating with larger distance between a main crack and nearby other Cr-coating are propagated to the ablation layer, the distance of main crack affecting ablation layer spallation is increased, and then the spallation time of ablation layer is delayed. The result is helpful to further analysis of laser discrete pre-processing substrate to improve service life of chromium plated gun barrels.
To reveal the mechanism that laser discrete pre-quenching substrate could increase the lifetime of a certain model chromium-plated gun barrel, the substrate behavior between laser treated and untreated the end Cr-plating barrel were compared in experiments. The results show that there is no obvious ablation pits in the gun barrel; the ablation value of laser-treated gun barrel is decreased by 10% than that of untreated one, which is because the main-cracks of Cr-coating with larger distance between a main crack and nearby other Cr-coating are propagated to the ablation layer, the distance of main crack affecting ablation layer spallation is increased, and then the spallation time of ablation layer is delayed. The result is helpful to further analysis of laser discrete pre-processing substrate to improve service life of chromium plated gun barrels.
2013, 37(2): 169-173.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.008
Abstract:
In order to reduce the error caused by manual operation in test process,improve testing efficiency and accuracy,a new automatic erbium-doped optical fiber amplifier(EDFA) calibration and test system was developed. The optical switch in the testing system was designed according to the factors affecting the optical performance. The automatic device was controlled through general-purpose interface bus(GPIB) interface. The automatic control and test was realized by VC++, the software was designed in modular pattern with high cohesion and low coupling characteristics. Major sub-modules were encapsulated as a dynamic link library so that the compatibility and expansibility of software was enhanced, and it's also easier to maintain and modify the software. The efficiency was improved by 60% in the experiments. The result indicates that the testing system is full of practical value for its high test efficiency and accuracy.
In order to reduce the error caused by manual operation in test process,improve testing efficiency and accuracy,a new automatic erbium-doped optical fiber amplifier(EDFA) calibration and test system was developed. The optical switch in the testing system was designed according to the factors affecting the optical performance. The automatic device was controlled through general-purpose interface bus(GPIB) interface. The automatic control and test was realized by VC++, the software was designed in modular pattern with high cohesion and low coupling characteristics. Major sub-modules were encapsulated as a dynamic link library so that the compatibility and expansibility of software was enhanced, and it's also easier to maintain and modify the software. The efficiency was improved by 60% in the experiments. The result indicates that the testing system is full of practical value for its high test efficiency and accuracy.
2013, 37(2): 174-177.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.009
Abstract:
In order to measure the range accurately and calculate the transmittance precisely with infrared spectrum passive ranging technology,baseline was fitted with interpolation method. Taking oxygen A band as an example, baseline fitting was completed through a variety of interpolation fitting methods making use of both sides of the absorption data from line-by-line radiative transfer model. Meanwhile, detail theoretical analysis and simulation verification were carried out, after comparing several algorithms, the accuracy of polynomial interpolation fitting is the best. The implementation of baseline fitting algorithm provides method for establishing a database of transmittance, distance and other conditions and provides a solid foundation for realization of passive ranging.
In order to measure the range accurately and calculate the transmittance precisely with infrared spectrum passive ranging technology,baseline was fitted with interpolation method. Taking oxygen A band as an example, baseline fitting was completed through a variety of interpolation fitting methods making use of both sides of the absorption data from line-by-line radiative transfer model. Meanwhile, detail theoretical analysis and simulation verification were carried out, after comparing several algorithms, the accuracy of polynomial interpolation fitting is the best. The implementation of baseline fitting algorithm provides method for establishing a database of transmittance, distance and other conditions and provides a solid foundation for realization of passive ranging.
2013, 37(2): 178-181.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.010
Abstract:
In order to study the relation between the scale factor and temperature of small low cost ring laser gyroscopes (RLG) deeply, and improve its performance without increasing cost on hardware, theoretical analysis and experiments were carried out. Data of scale factor both in given temperature and in slowly changing temperature were obtained. Those experimental data conformed to the theoretical data approximately. The equation between scale factor and temperature was built and thus the scale factor error caused by temperature was apparently reduced.
In order to study the relation between the scale factor and temperature of small low cost ring laser gyroscopes (RLG) deeply, and improve its performance without increasing cost on hardware, theoretical analysis and experiments were carried out. Data of scale factor both in given temperature and in slowly changing temperature were obtained. Those experimental data conformed to the theoretical data approximately. The equation between scale factor and temperature was built and thus the scale factor error caused by temperature was apparently reduced.
2013, 37(2): 182-186.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.011
Abstract:
In order to study the evolution of separate spatial soliton pairs in a biased series centrosymmetric two-photon photorefractive crystal circuit, separate spatial soliton screening pairs solitons were proved to stay in a series circuit of two-photon photorefractive crystals based on the centrosymmetric two-photon photorefractive effect. The spatial envelope, dynamical evolution and stability of separate dark-dark and bright-dark soliton pairs were investigated numerically. The results show that only the dark soliton can affect the other soliton by light-induced current, but the bright soliton cannot.
In order to study the evolution of separate spatial soliton pairs in a biased series centrosymmetric two-photon photorefractive crystal circuit, separate spatial soliton screening pairs solitons were proved to stay in a series circuit of two-photon photorefractive crystals based on the centrosymmetric two-photon photorefractive effect. The spatial envelope, dynamical evolution and stability of separate dark-dark and bright-dark soliton pairs were investigated numerically. The results show that only the dark soliton can affect the other soliton by light-induced current, but the bright soliton cannot.
2013, 37(2): 187-190.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.012
Abstract:
In order to analyze the dependence of the nonlinear coefficient and dispersion property on the structural parameters of the inner air hole size and the changing of the air hole fraction, by using the full vector finite element method, the nonlinear coefficient and dispersion property as a function of frequency and design parameters were investigated. According to the analysis results, the nonlinear coefficient of photonic crystal fiber with hexagonal structure is significantly increased and the dispersion is flat. It is shown from numerical results that it is possible to design photonic crystal fiber of hexagonal structure with single mode transmission during 400nm~1160nm and high nonlinear coefficient achieves 172km-1·W-1, dispersion becomes flattened between 0.65μm~1.0μm. This result is helpful to the research of optical communication.
In order to analyze the dependence of the nonlinear coefficient and dispersion property on the structural parameters of the inner air hole size and the changing of the air hole fraction, by using the full vector finite element method, the nonlinear coefficient and dispersion property as a function of frequency and design parameters were investigated. According to the analysis results, the nonlinear coefficient of photonic crystal fiber with hexagonal structure is significantly increased and the dispersion is flat. It is shown from numerical results that it is possible to design photonic crystal fiber of hexagonal structure with single mode transmission during 400nm~1160nm and high nonlinear coefficient achieves 172km-1·W-1, dispersion becomes flattened between 0.65μm~1.0μm. This result is helpful to the research of optical communication.
2013, 37(2): 191-194.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.013
Abstract:
In order to improve the beam characteristics of high-power laser diode, whose beam quality is quite different in fast axis and slow axis, a set of emitting shaping system was designed through theoretical analysis and software simulation based on geometrical optics of refraction. As beam divergence of fast axis and slow axis is changed by cylindrical lens separately, the beams radiate in the meridional direction to the narrow field of view, and cover the field of view of ±30° in the sagittal direction. Meanwhile, a prism of special structure was added in the shaping system to mix light. Consequently, the uniformity of energy distribution of the output beam became greater than 75% within the target area, and the energy utilization rate reached to 80% or more. The results show that a single emitting system can complete the detection of ±30° field of view within the work distance of 15m, and six emission systems constitute a 360° field of view to complete panorama detection. This result is helpful for improving the accuracy of the laser active detection and increasing its scope.
In order to improve the beam characteristics of high-power laser diode, whose beam quality is quite different in fast axis and slow axis, a set of emitting shaping system was designed through theoretical analysis and software simulation based on geometrical optics of refraction. As beam divergence of fast axis and slow axis is changed by cylindrical lens separately, the beams radiate in the meridional direction to the narrow field of view, and cover the field of view of ±30° in the sagittal direction. Meanwhile, a prism of special structure was added in the shaping system to mix light. Consequently, the uniformity of energy distribution of the output beam became greater than 75% within the target area, and the energy utilization rate reached to 80% or more. The results show that a single emitting system can complete the detection of ±30° field of view within the work distance of 15m, and six emission systems constitute a 360° field of view to complete panorama detection. This result is helpful for improving the accuracy of the laser active detection and increasing its scope.
2013, 37(2): 195-197.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.014
Abstract:
To achieve efficient all fiber laser at 2μm, a Tm-Ho co-doped single mode fiber was pumped by a dual double-cladding Er-Yb co-doped fiber amplifier. An all fiber ring laser was formed with a 1550nm/2000nm wavelength-division multiplexier and a fiber coupler. When the drive current of 915nm LD was 6.9A, the maximum laser output power was about 57.23mW, the slope efficiency was measured to be about 12% with the linewidth of 4.5nm, the threshold pump power was about 180mW. The experimental results demonstrate that the laser shows high performance and it is prospective in fields of optical fiber sensing and laser medical treatment.
To achieve efficient all fiber laser at 2μm, a Tm-Ho co-doped single mode fiber was pumped by a dual double-cladding Er-Yb co-doped fiber amplifier. An all fiber ring laser was formed with a 1550nm/2000nm wavelength-division multiplexier and a fiber coupler. When the drive current of 915nm LD was 6.9A, the maximum laser output power was about 57.23mW, the slope efficiency was measured to be about 12% with the linewidth of 4.5nm, the threshold pump power was about 180mW. The experimental results demonstrate that the laser shows high performance and it is prospective in fields of optical fiber sensing and laser medical treatment.
2013, 37(2): 198-203.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.015
Abstract:
Optical parameter oscillator (OPO) based on periodically poled lithium niobate(PPLN) crystal and quasi phase matching (QPM) are suitable for generating continuous wave (CW) and tunable coherent radiation in mid-infrared wavelength range 3μm~5μm, which has important applications in atmosphere pollution monitoring, remote sensing, laser radar, spectroscopy analysis, and military infrared countermine. The recent development and advantages of CW mid-infrared optical parameter oscillator base on PPLN crystal was introduced. Specifically, the progress of techniques to increase the output power, lower the pump threshold, widen the tunable range and narrow the linewidth was addressed. Currently, the researches of optical parameter oscillator based on PPLN crystal are focus on the four areas mentioned above. Along with the development of the pump laser and nonlinear crystal, it will make further progresses toward the direction of higher power, lower threshold, wider tuning range, and the narrower line width as well.
Optical parameter oscillator (OPO) based on periodically poled lithium niobate(PPLN) crystal and quasi phase matching (QPM) are suitable for generating continuous wave (CW) and tunable coherent radiation in mid-infrared wavelength range 3μm~5μm, which has important applications in atmosphere pollution monitoring, remote sensing, laser radar, spectroscopy analysis, and military infrared countermine. The recent development and advantages of CW mid-infrared optical parameter oscillator base on PPLN crystal was introduced. Specifically, the progress of techniques to increase the output power, lower the pump threshold, widen the tunable range and narrow the linewidth was addressed. Currently, the researches of optical parameter oscillator based on PPLN crystal are focus on the four areas mentioned above. Along with the development of the pump laser and nonlinear crystal, it will make further progresses toward the direction of higher power, lower threshold, wider tuning range, and the narrower line width as well.
2013, 37(2): 204-206.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.016
Abstract:
Aiming at completely eliminating the influence of CCD's noise and scattered background light on the reconstructed image of digital hologram, based on the hologram subtracting reference light intensity and object light intensity(HRO) subtraction method and hologram subtracting reference light intensity, object light intensity and CCD's noise(HRON) subtraction method, the background intensity compensation method(BICM) was proposed. The quality of the experimentally reconstructed images of the original hologram and holograms processed by BICM was compared. Results show that BICM could effectively improve the quality of reconstructed image and relax the requirement on digital hologram recording environment.
Aiming at completely eliminating the influence of CCD's noise and scattered background light on the reconstructed image of digital hologram, based on the hologram subtracting reference light intensity and object light intensity(HRO) subtraction method and hologram subtracting reference light intensity, object light intensity and CCD's noise(HRON) subtraction method, the background intensity compensation method(BICM) was proposed. The quality of the experimentally reconstructed images of the original hologram and holograms processed by BICM was compared. Results show that BICM could effectively improve the quality of reconstructed image and relax the requirement on digital hologram recording environment.
2013, 37(2): 207-210.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.017
Abstract:
In order to avoid the impact of image registration precision on detection accuracy, a novel approach for circuit defect inspection on liquid crystal displary(LCD)panel was adopted based on image contour analysis. The contours were found by depth first search(DFS), and their areas were calculated according to Green formula. In order to ascertain whether there are any defects such as short, open, hole and island on this LCD, the circuit contours' areas of the LCD to be detected are compared with the areas of standard template. This method needs no image registration, therefore, precision requirement for algorithm is reduced and detection accuracy is improved. Through the experiment on 200 small LCDs, the accuracy comes up to 99%. The results show that all contours are found and their areas are calculated correctly and rapidly. With comparison of areas instead of images, the accuracy of detecting defects such as short and open circuit is improved. This method has great application future in the field of defect detection for LCD circuits.
In order to avoid the impact of image registration precision on detection accuracy, a novel approach for circuit defect inspection on liquid crystal displary(LCD)panel was adopted based on image contour analysis. The contours were found by depth first search(DFS), and their areas were calculated according to Green formula. In order to ascertain whether there are any defects such as short, open, hole and island on this LCD, the circuit contours' areas of the LCD to be detected are compared with the areas of standard template. This method needs no image registration, therefore, precision requirement for algorithm is reduced and detection accuracy is improved. Through the experiment on 200 small LCDs, the accuracy comes up to 99%. The results show that all contours are found and their areas are calculated correctly and rapidly. With comparison of areas instead of images, the accuracy of detecting defects such as short and open circuit is improved. This method has great application future in the field of defect detection for LCD circuits.
2013, 37(2): 211-215.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.018
Abstract:
To test the divergence angle of a glass bead Scotchlite retroreflector, after utilizing a CMOS high-speed camera to take photos of laser spots imaged on a piece of parchment paper reflected by the glass bead Scotchlite retroreflector, the images of laser spots were processed and the divergence angle was calculated according to a certain geometric proportion. The divergence range of the retroreflector was 0.907°~0.956°.Results show that the test method is reasonable and has certain practical value.
To test the divergence angle of a glass bead Scotchlite retroreflector, after utilizing a CMOS high-speed camera to take photos of laser spots imaged on a piece of parchment paper reflected by the glass bead Scotchlite retroreflector, the images of laser spots were processed and the divergence angle was calculated according to a certain geometric proportion. The divergence range of the retroreflector was 0.907°~0.956°.Results show that the test method is reasonable and has certain practical value.
2013, 37(2): 216-218.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.019
Abstract:
To study effect of pump power deployment on bi-directional pumping fibre Raman amplifiers(FRA), the gain, gain saturation and power conversion efficiency under different pump power deployment were calculated based on the known coupling equations. The simulation results show that the gain, gain saturation and power conversion efficiency are all between the values of forward-pumped and backward-pumped FRAs and they increase when forward pump power is larger. The phenomenon becomes evident with all the pump power and initial signal power increases. The conclusion gives some advice for the work of FRA and fibre laser.
To study effect of pump power deployment on bi-directional pumping fibre Raman amplifiers(FRA), the gain, gain saturation and power conversion efficiency under different pump power deployment were calculated based on the known coupling equations. The simulation results show that the gain, gain saturation and power conversion efficiency are all between the values of forward-pumped and backward-pumped FRAs and they increase when forward pump power is larger. The phenomenon becomes evident with all the pump power and initial signal power increases. The conclusion gives some advice for the work of FRA and fibre laser.
2013, 37(2): 223-226.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.021
Abstract:
Baseline correction is an important preprocessing step before subsequent data processing of Fourier transform infrared (FTIR) spectra. Polynomial iterative fitting is one of the methods of baseline correction. In order to improve the speed of baseline correction, taking CO2 spectrum as example, an improved polynomial iterative fitting algorithm was used for theoretical analysis and experimental verification and the same correction result was achieved with polynomial iterative fitting algorithm.The algorithm automatically identify the range of peaks for baseline correction, reducing the number of iterations in the process of baseline correction. The number of iterations decreased from 39 to 11, the elapsed time reduced from 4.78s to 1.12s. The result is great significant for real-time gas monitoring systems.
Baseline correction is an important preprocessing step before subsequent data processing of Fourier transform infrared (FTIR) spectra. Polynomial iterative fitting is one of the methods of baseline correction. In order to improve the speed of baseline correction, taking CO2 spectrum as example, an improved polynomial iterative fitting algorithm was used for theoretical analysis and experimental verification and the same correction result was achieved with polynomial iterative fitting algorithm.The algorithm automatically identify the range of peaks for baseline correction, reducing the number of iterations in the process of baseline correction. The number of iterations decreased from 39 to 11, the elapsed time reduced from 4.78s to 1.12s. The result is great significant for real-time gas monitoring systems.
2013, 37(2): 227-230.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.022
Abstract:
To improve the positioning accuracy of small objects, a direct positioning scheme was proposed based on machine vision. Besides, relevant theoretical analysis and experimental verification were carried out. By analyzing the optical features of ruby bearings, a vision automatic positioning system was designed, and image algorithms were used to get the center of the hole. The top of the probe on coordinate measuring machine was used as an ideal target for camera calibration, so the coefficients of coordinate transformation between camera system and the coordinate measuring machine was calculated. Experiments show that the positioning accuracy of the system is up to 0.01mm, which fulfills the requirement of positioning.
To improve the positioning accuracy of small objects, a direct positioning scheme was proposed based on machine vision. Besides, relevant theoretical analysis and experimental verification were carried out. By analyzing the optical features of ruby bearings, a vision automatic positioning system was designed, and image algorithms were used to get the center of the hole. The top of the probe on coordinate measuring machine was used as an ideal target for camera calibration, so the coefficients of coordinate transformation between camera system and the coordinate measuring machine was calculated. Experiments show that the positioning accuracy of the system is up to 0.01mm, which fulfills the requirement of positioning.
2013, 37(2): 231-234.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.023
Abstract:
In order to improve the facular-shaping effect of the microcylinders and lens duct, a new duct with changing elliptical cross section was proposed. The long axis of the ellipse on the front surface is located in horizontal direction, which matches the light emitting distribution pattern, The long axis of the ellipse on the back surface gradually become in vertical direction. The 3-D ray-tracing simulation indicates that the irregular duct can achieve relatively good circular symmetric pumping energy distribution. The energy transferring efficiency of microcylinders and the duct is calculated to be 90.84% and 91.98% respectively, corresponding to the total efficiency of 83.55%. The contrast indicates that the irregular duct possesses some advantages in facular shaping and energy transferring efficiency over common ducts.
In order to improve the facular-shaping effect of the microcylinders and lens duct, a new duct with changing elliptical cross section was proposed. The long axis of the ellipse on the front surface is located in horizontal direction, which matches the light emitting distribution pattern, The long axis of the ellipse on the back surface gradually become in vertical direction. The 3-D ray-tracing simulation indicates that the irregular duct can achieve relatively good circular symmetric pumping energy distribution. The energy transferring efficiency of microcylinders and the duct is calculated to be 90.84% and 91.98% respectively, corresponding to the total efficiency of 83.55%. The contrast indicates that the irregular duct possesses some advantages in facular shaping and energy transferring efficiency over common ducts.
2013, 37(2): 235-238.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.024
Abstract:
In order to effectively describe the relationship between beam splitting ratio, extra loss of polarization-maintainning fiber and polarization state, a new concept of intensity transmission matrix was proposed. The new theory can refine the expression equation including intensity transmission matrix parameters, extra loss and beam splitting ratio with different polarization. The curves of extra loss, beam splitting ratio with 45°circularly polarized light and eight intensity transmission matrix parameters was included and the correctness of intensity transmission matrix was validated. The results show intensity transmission matrix has important influence for the description of polarization characteristics of polarization-maintaining fiber couplers.
In order to effectively describe the relationship between beam splitting ratio, extra loss of polarization-maintainning fiber and polarization state, a new concept of intensity transmission matrix was proposed. The new theory can refine the expression equation including intensity transmission matrix parameters, extra loss and beam splitting ratio with different polarization. The curves of extra loss, beam splitting ratio with 45°circularly polarized light and eight intensity transmission matrix parameters was included and the correctness of intensity transmission matrix was validated. The results show intensity transmission matrix has important influence for the description of polarization characteristics of polarization-maintaining fiber couplers.
2013, 37(2): 239-242.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.025
Abstract:
In order to study the terahertz radiation process through InSb photoconduction, the terahertz near field radiation formulas was deduced. Considering the effect of auger relaxation on the photoconduction process, the change of the carrier density, the scattering ratio and the reflection ratio of InSb photoconduction were analyzed in detail. It can be illustrated the validity of this research as the simulation results can fit well with the experimental data in the references.
In order to study the terahertz radiation process through InSb photoconduction, the terahertz near field radiation formulas was deduced. Considering the effect of auger relaxation on the photoconduction process, the change of the carrier density, the scattering ratio and the reflection ratio of InSb photoconduction were analyzed in detail. It can be illustrated the validity of this research as the simulation results can fit well with the experimental data in the references.
2013, 37(2): 243-246.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.026
Abstract:
In order to study the effect of the antiresonant core-surround ring interface on the confinement loss and scatter loss, the given hollow-core photonic crystal fibers(HC-PCFs) with different antiresonant core-surround rings and core radius were simulated by means of full-vector finite element method, and the curves among the effective index, confinement loss and power-percentage in core with change of wavelength were obtained. The numerical simulation shows that, when the antiresonant core-surround ring is designed as T=3 annular or elliptic geometry, the confinement loss reduces 2 order of magnitude and the power-percentage in core increases 13% in communication wave band which demonstrate both the designs in this paper can reduce the confinement loss and scatter loss in HC-PCFs effectively.
In order to study the effect of the antiresonant core-surround ring interface on the confinement loss and scatter loss, the given hollow-core photonic crystal fibers(HC-PCFs) with different antiresonant core-surround rings and core radius were simulated by means of full-vector finite element method, and the curves among the effective index, confinement loss and power-percentage in core with change of wavelength were obtained. The numerical simulation shows that, when the antiresonant core-surround ring is designed as T=3 annular or elliptic geometry, the confinement loss reduces 2 order of magnitude and the power-percentage in core increases 13% in communication wave band which demonstrate both the designs in this paper can reduce the confinement loss and scatter loss in HC-PCFs effectively.
2013, 37(2): 247-250.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.027
Abstract:
In order to improve the accuracy of infrared detectors to detect the infrared weak signal, a preamplifier circuit was built with a constant current bias circuit and a low-noise high-speed operational amplifier. The equivalent noisy model was deduced based on the circuit theory. The output voltage noise of the 1st amplification circuit was calculated with the superposition method. In temperature blackbody furnace experiment, the circuit performance was tested, the voltage waveform at 500℃~700℃ was obtained, and signal-to-noise ratio of 7.25×103 was obtained. The results show that the preamplifier circuit of infrared detection achieves the application goal of high signal-to-noise ratio, response speed and strong anti-jamming performance, it can be used to amplify the weak infrared signal.
In order to improve the accuracy of infrared detectors to detect the infrared weak signal, a preamplifier circuit was built with a constant current bias circuit and a low-noise high-speed operational amplifier. The equivalent noisy model was deduced based on the circuit theory. The output voltage noise of the 1st amplification circuit was calculated with the superposition method. In temperature blackbody furnace experiment, the circuit performance was tested, the voltage waveform at 500℃~700℃ was obtained, and signal-to-noise ratio of 7.25×103 was obtained. The results show that the preamplifier circuit of infrared detection achieves the application goal of high signal-to-noise ratio, response speed and strong anti-jamming performance, it can be used to amplify the weak infrared signal.
2013, 37(2): 251-255.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.028
Abstract:
In order to decrease the energy consumption of wireless sensor network nodes, ultraviolet was utilized as the signal carrier of wireless sensor network. Firstly, the energy consumption of single hop and multiple hops were studied based on the energy model of UV light sensor nodes, then the mathematical expression for calculating optimum hops was obtained. The average energy consumption of single hop communication, multiple-hop communication and optimum communication were simulated, and the simulation results were consistent with theoretical analysis. Mobile sink node can resolve the uneven energy consumption problem resulting from multiple hop communication. The influence of network average energy consumption, loss packet ratio, and delay under different mobile velocity of sink node was simulated and analyzed. The simulation results indicate that the different mobile velocity of sink node have different influence on the network' performance, and that mobile sink node can decrease network average energy consumption by selecting suitable mobile velocity according to different scenes.
In order to decrease the energy consumption of wireless sensor network nodes, ultraviolet was utilized as the signal carrier of wireless sensor network. Firstly, the energy consumption of single hop and multiple hops were studied based on the energy model of UV light sensor nodes, then the mathematical expression for calculating optimum hops was obtained. The average energy consumption of single hop communication, multiple-hop communication and optimum communication were simulated, and the simulation results were consistent with theoretical analysis. Mobile sink node can resolve the uneven energy consumption problem resulting from multiple hop communication. The influence of network average energy consumption, loss packet ratio, and delay under different mobile velocity of sink node was simulated and analyzed. The simulation results indicate that the different mobile velocity of sink node have different influence on the network' performance, and that mobile sink node can decrease network average energy consumption by selecting suitable mobile velocity according to different scenes.
2013, 37(2): 256-260.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.029
Abstract:
In order to analyze the relationship between the minimum position (lwmin, lwmax) of the minor and major axes of the isophotes and the mutation point (lR1,lR2) of the radius of curvature R1, R2 of the generalized Gaussian beam, which never studied before, and find some new and special nature of the generalized Gaussian beam from their relationship, at first, using the abc parameter method to carry out theoretical derivation, a simple analytical solution expression between lwmin,lwmax, lR1,lR2 was obtained. Secondly, after numerical simulation, the relationship figures between lwmin,lwmax, lR1,lR2 and wmin,0,wmax,0,R1,0,R2,0, φR1 were obtained. The results show that lwmin,lwmax is always between lR1 and lR2,and lwmin,lwmax, lR1,lR2 is distributed near l=0.lwmin has serious non-continuous points other than the other three positions. This conclusion adapts to the generalized Gaussian beam in actual and general situations.
In order to analyze the relationship between the minimum position (lwmin, lwmax) of the minor and major axes of the isophotes and the mutation point (lR1,lR2) of the radius of curvature R1, R2 of the generalized Gaussian beam, which never studied before, and find some new and special nature of the generalized Gaussian beam from their relationship, at first, using the abc parameter method to carry out theoretical derivation, a simple analytical solution expression between lwmin,lwmax, lR1,lR2 was obtained. Secondly, after numerical simulation, the relationship figures between lwmin,lwmax, lR1,lR2 and wmin,0,wmax,0,R1,0,R2,0, φR1 were obtained. The results show that lwmin,lwmax is always between lR1 and lR2,and lwmin,lwmax, lR1,lR2 is distributed near l=0.lwmin has serious non-continuous points other than the other three positions. This conclusion adapts to the generalized Gaussian beam in actual and general situations.
2013, 37(2): 261-264.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.030
Abstract:
In order to measure the radius of hat spots and Gaussian spots, knife-edge method was adopted for the theoretical analysis and experimental verification. A new iterative algorithm was proposed. The distance of knife-edge is in direct proportion to the radius of spot. The corresponding scale factors were calculated. It is convenient to obtain the radius of spots by multiplying a corresponding scale factor to the distance of knife-edge. The result shows this iterative algorithm is also valid for any spot whose distribution of intensity is already known.
In order to measure the radius of hat spots and Gaussian spots, knife-edge method was adopted for the theoretical analysis and experimental verification. A new iterative algorithm was proposed. The distance of knife-edge is in direct proportion to the radius of spot. The corresponding scale factors were calculated. It is convenient to obtain the radius of spots by multiplying a corresponding scale factor to the distance of knife-edge. The result shows this iterative algorithm is also valid for any spot whose distribution of intensity is already known.
2013, 37(2): 265-269.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.031
Abstract:
In order to study the influence of the multiple feedback on the self-mixing interference in laser diodes, double feedback effect and double frequency fringes phenomena were analyzed based on the three-mirror F-P model. After simulation, it is found that when the relative intensity η of the second trip light to the first is big enough, the image of interference can be recognized, and the two interferential signals of two trips can be distinguished by differential coefficients. The sensitivity of system can reach the value of λ/4. The phase differences affect the interference pattern. Experimental results are in good agreement with the simulation results. Experiments also validate the double frequency fringes phenomena, caused by the misalignment external reflector, could coupling the second trip light into laser without first trip. These obtained conclusions are helpful for improving the sensitivity of the system and judging whether the external cavity is alignment.
In order to study the influence of the multiple feedback on the self-mixing interference in laser diodes, double feedback effect and double frequency fringes phenomena were analyzed based on the three-mirror F-P model. After simulation, it is found that when the relative intensity η of the second trip light to the first is big enough, the image of interference can be recognized, and the two interferential signals of two trips can be distinguished by differential coefficients. The sensitivity of system can reach the value of λ/4. The phase differences affect the interference pattern. Experimental results are in good agreement with the simulation results. Experiments also validate the double frequency fringes phenomena, caused by the misalignment external reflector, could coupling the second trip light into laser without first trip. These obtained conclusions are helpful for improving the sensitivity of the system and judging whether the external cavity is alignment.
2013, 37(2): 270-273.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.032
Abstract:
In order to understand the influence of the technological parameters on spalling, it was analyzed by means of the finite element simulation. The maximum tensile stress instantaneous fracture criterion was used to check spalling happened or not. Then, the experiment of laser shock forming was carried out. The shocked samples were surveyed with a scanning electron microscope. The emerging, developing and forming of the spalling were analyzed. The results show that the spalling is susceptible to the shock region, and then the spot edge. Spalling will never happen outside the shock region. The influence of pulse width, peak pressure and sheet thickness affect the position of spalling significantly. However, the spot diameter affects it little. These have guiding significance to the development of the laser shock forming.
In order to understand the influence of the technological parameters on spalling, it was analyzed by means of the finite element simulation. The maximum tensile stress instantaneous fracture criterion was used to check spalling happened or not. Then, the experiment of laser shock forming was carried out. The shocked samples were surveyed with a scanning electron microscope. The emerging, developing and forming of the spalling were analyzed. The results show that the spalling is susceptible to the shock region, and then the spot edge. Spalling will never happen outside the shock region. The influence of pulse width, peak pressure and sheet thickness affect the position of spalling significantly. However, the spot diameter affects it little. These have guiding significance to the development of the laser shock forming.
2013, 37(2): 274-276.
doi: 10.7510/jgjs.issn.1001-3806.2013.02.033
Abstract:
In order to study the effect of the pharmacy ratio of graphite to potassium on the reactive photoacoustic spectrum, the dynamic photoacoustic detection technology and differential scanning calorimetry(DSC)were used for analysis. When the samples were irradiated by an Nd:YAG pulse laser (wavelength of 1.06μm, pulse width of 54μs), the greater the laser energy, the stronger the photoacoustic signal. The photoacoustic signal changed when the ratio of samples were different. The photoacoustic signal became the strongest when the ratio of the sample (3# sample) was 25/75, while the ratio was 30/70(4# sample), the photoacoustic signal was weak. After studying the time needed to achieve the photoacoustic signal peak, it found that when laser energy increased, the time first increased and then decreased. The results show that the different proportion of C and KNO3 arousing different chemical reaction. Thermal analysis results conform to the photoacoustic experimental results.
In order to study the effect of the pharmacy ratio of graphite to potassium on the reactive photoacoustic spectrum, the dynamic photoacoustic detection technology and differential scanning calorimetry(DSC)were used for analysis. When the samples were irradiated by an Nd:YAG pulse laser (wavelength of 1.06μm, pulse width of 54μs), the greater the laser energy, the stronger the photoacoustic signal. The photoacoustic signal changed when the ratio of samples were different. The photoacoustic signal became the strongest when the ratio of the sample (3# sample) was 25/75, while the ratio was 30/70(4# sample), the photoacoustic signal was weak. After studying the time needed to achieve the photoacoustic signal peak, it found that when laser energy increased, the time first increased and then decreased. The results show that the different proportion of C and KNO3 arousing different chemical reaction. Thermal analysis results conform to the photoacoustic experimental results.
