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RSS2017 Vol. 41, No. 4
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2017, 41(4): 463-466.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.001
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Abstract:
In order to measure the frequency doubling characteristics of powder materials, according to the theory of Kurtz-Perry powder frequency doubling effect and the theory of optical parametric oscillation, dual wavelength Q-switched laser output of 130mJ@1064nm and 20mJ@1570nm was obtained. After theoretical analysis and experimental verification, the 1064nm and 1570nm dual wavelength frequency doubling test of powder sample was realized. The problem, that the absorption of crystal powder material to the wavelength of frequency doubling signal makes it difficult to measure the frequency doubling signal when testing the single wavelength, was solved. The results show that the test sensitivity of effective nonlinear coefficient reaches 0.46pm/V. the variation trend of frequency doubling signal of KTP powder samples is consistent with the theory. The system is stable, simple, convenient and reliable for nonlinear detection of crystals.
In order to measure the frequency doubling characteristics of powder materials, according to the theory of Kurtz-Perry powder frequency doubling effect and the theory of optical parametric oscillation, dual wavelength Q-switched laser output of 130mJ@1064nm and 20mJ@1570nm was obtained. After theoretical analysis and experimental verification, the 1064nm and 1570nm dual wavelength frequency doubling test of powder sample was realized. The problem, that the absorption of crystal powder material to the wavelength of frequency doubling signal makes it difficult to measure the frequency doubling signal when testing the single wavelength, was solved. The results show that the test sensitivity of effective nonlinear coefficient reaches 0.46pm/V. the variation trend of frequency doubling signal of KTP powder samples is consistent with the theory. The system is stable, simple, convenient and reliable for nonlinear detection of crystals.
2017, 41(4): 467-472.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.002
Abstract:
In order to understand spatial distribution of H2+ molecular harmonics, the spatial distribution of H2+ molecular harmonic spectra in spatial homogeneous and inhomogeneous fields was studied through solving non-Bohn-Oppenheimer time-dependent Schr dinger equation. The results show that in spatial homogeneous field, harmonic intensity from positive-H nucleus is higher than that from negative-H nucleus. In spatial inhomogeneous field, due to plasma resonance on metallic nanostructure surface, harmonic cutoff is extended, and harmonic intensity from negative-H nucleus is higher than that from positive-H nucleus. Furthermore, spatial distribution of the harmonics can be explained by ionization probability, electron localization in two nuclei, time-dependent wave function and time-frequency analyses of harmonic spectra. Finally, by superposing a selected harmonics properly, an isolated ultrashort 36as pulse can be obtained. The investigation is helpful for understanding spatial distribution of molecular harmonics and producing attosecond pulses.
In order to understand spatial distribution of H2+ molecular harmonics, the spatial distribution of H2+ molecular harmonic spectra in spatial homogeneous and inhomogeneous fields was studied through solving non-Bohn-Oppenheimer time-dependent Schr dinger equation. The results show that in spatial homogeneous field, harmonic intensity from positive-H nucleus is higher than that from negative-H nucleus. In spatial inhomogeneous field, due to plasma resonance on metallic nanostructure surface, harmonic cutoff is extended, and harmonic intensity from negative-H nucleus is higher than that from positive-H nucleus. Furthermore, spatial distribution of the harmonics can be explained by ionization probability, electron localization in two nuclei, time-dependent wave function and time-frequency analyses of harmonic spectra. Finally, by superposing a selected harmonics properly, an isolated ultrashort 36as pulse can be obtained. The investigation is helpful for understanding spatial distribution of molecular harmonics and producing attosecond pulses.
2017, 41(4): 473-478.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.003
Abstract:
Traditional algorithm of in-plane displacement measurement by speckle photography is based on the power spectrum of Fourier transform directly. However, the measured minimum displacement is limited by speckle size. In order to solve this problem, a novel algorithm based on the phase angle of Fourier transform was proposed. Theoretical analysis showed that the minimum and maximum displacement measured by this new algorithm was determined by the photoelectric converter, such as charge-coupled device or complementary metal oxide semiconductor. The size of speckle patterns had no effect on displacement. The result shows that the minimum and maximum displacement measured by new method can achieve 2pixel spacings and the half of photo-sensitive area width of photoelectric conversion device respectively. The actual measurement is in agreement with the theoretical analysis.
Traditional algorithm of in-plane displacement measurement by speckle photography is based on the power spectrum of Fourier transform directly. However, the measured minimum displacement is limited by speckle size. In order to solve this problem, a novel algorithm based on the phase angle of Fourier transform was proposed. Theoretical analysis showed that the minimum and maximum displacement measured by this new algorithm was determined by the photoelectric converter, such as charge-coupled device or complementary metal oxide semiconductor. The size of speckle patterns had no effect on displacement. The result shows that the minimum and maximum displacement measured by new method can achieve 2pixel spacings and the half of photo-sensitive area width of photoelectric conversion device respectively. The actual measurement is in agreement with the theoretical analysis.
2017, 41(4): 479-483.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.004
Abstract:
In order to improve the coupling efficiency and increase the tolerance range of grating coupling packaging structure on silicon substrate, the characteristics of grating coupling structure were analyzed theoretically and verified by simulation based on finite-difference time-domain method. After studying the main influence factors of the coupling efficiency, the basic grating coupling structure was improved without changing the parameters of the grating. A grating coupling structure with lenses was proposed. The results show that, after the lenses are added, coupling efficiency, angle tolerance and bandwidth are optimized through simulation. The coupling efficiency is increased to 73.809% with an incident wavelength in 1550nm when adding the reflectors on the substrate. The analysis results provide a reference for the design of the packaging structure of the grating coupling.
In order to improve the coupling efficiency and increase the tolerance range of grating coupling packaging structure on silicon substrate, the characteristics of grating coupling structure were analyzed theoretically and verified by simulation based on finite-difference time-domain method. After studying the main influence factors of the coupling efficiency, the basic grating coupling structure was improved without changing the parameters of the grating. A grating coupling structure with lenses was proposed. The results show that, after the lenses are added, coupling efficiency, angle tolerance and bandwidth are optimized through simulation. The coupling efficiency is increased to 73.809% with an incident wavelength in 1550nm when adding the reflectors on the substrate. The analysis results provide a reference for the design of the packaging structure of the grating coupling.
2017, 41(4): 484-488.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.005
Abstract:
In order to prevent the strong electromagnetic interference produced by an electric excitation excimer laser system, the electromagnetic radiation mechanism of excimer laser was analyzed according to the principle of electromagnetic radiation and the main radiation sources were determined, i.e., the main discharge circuit, the light outlet and hydrogen thyratron. The key parts were tested by using a near-field probe respectively. Electromagnetic shielding design was implemented and shielding effectiveness was tested by combining the test results with the principle of electromagnetic shielding. And then, other several measures was also put forward to restrain electromagnetic interference in view of the excimer laser system. The results show that the effectiveness of the shielding box can reach 40dB and the excimer laser system is stable and reliable after the introduction of electromagnetic interference suppression measures. This study satisfies the practical requirement in engineering.
In order to prevent the strong electromagnetic interference produced by an electric excitation excimer laser system, the electromagnetic radiation mechanism of excimer laser was analyzed according to the principle of electromagnetic radiation and the main radiation sources were determined, i.e., the main discharge circuit, the light outlet and hydrogen thyratron. The key parts were tested by using a near-field probe respectively. Electromagnetic shielding design was implemented and shielding effectiveness was tested by combining the test results with the principle of electromagnetic shielding. And then, other several measures was also put forward to restrain electromagnetic interference in view of the excimer laser system. The results show that the effectiveness of the shielding box can reach 40dB and the excimer laser system is stable and reliable after the introduction of electromagnetic interference suppression measures. This study satisfies the practical requirement in engineering.
2017, 41(4): 489-493.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.006
Abstract:
In order to determine the antibiotic mixture more quickly, conveniently and accurately at the same time, synchronous fluorescence spectra of 3 kinds of fluoroquinolones (ciprofloxacin, levofloxacin lactate, levofloxacin hydrochloride) were studied based on synchronous fluorescence spectroscopy combined with radial basis function neural network. The 3-D synchronous fluorescence spectrum for the 3-component mixed solution with concentration of 1.67ng/mL was measured. Then, simultaneous fluorescence spectra of 39 mixed solutions with different concentrations were measured. 35 of them were selected as the training group, and the other 4 were used as the prediction group. The spectral data corresponding to the training samples were taken as input to build and train the radial basis function neural network. The results show that, when Δλ=194nm, the concentration of each component in the prediction group is predicted by the trained neural network. The average relative errors of intensity prediction of 3 components were 3.59%, 3.47% and 3.09%, respectively. The method provides rapid, simple and accurate method for simultaneous determination of multiple antibiotic mixtures.
In order to determine the antibiotic mixture more quickly, conveniently and accurately at the same time, synchronous fluorescence spectra of 3 kinds of fluoroquinolones (ciprofloxacin, levofloxacin lactate, levofloxacin hydrochloride) were studied based on synchronous fluorescence spectroscopy combined with radial basis function neural network. The 3-D synchronous fluorescence spectrum for the 3-component mixed solution with concentration of 1.67ng/mL was measured. Then, simultaneous fluorescence spectra of 39 mixed solutions with different concentrations were measured. 35 of them were selected as the training group, and the other 4 were used as the prediction group. The spectral data corresponding to the training samples were taken as input to build and train the radial basis function neural network. The results show that, when Δλ=194nm, the concentration of each component in the prediction group is predicted by the trained neural network. The average relative errors of intensity prediction of 3 components were 3.59%, 3.47% and 3.09%, respectively. The method provides rapid, simple and accurate method for simultaneous determination of multiple antibiotic mixtures.
2017, 41(4): 494-497.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.007
Abstract:
In order to study optical properties of an optical fiber probe in scanning near-field optical microscopy (SNOM), simulation experiment was carried out by using the optical software VirtualLab Fusion based on field tracing method. The distribution of external optical field at the tip of SNOM optical probe was obtained. The results show along z axis, the distributions of optical field on different sections show the pattern of small aperture diffraction, the center intensity of center sample decreases exponentially with the increase of z value, and is almost attenuated to 0 at the position of z=100nm. With the increase of z value, full width at half maximum of center speckle contour remains stable at first and then increases. Its inflection point is at the position of z=20nm. The corresponding center strength value is 7.2V/m2 at this point. If calculated by the exponential function, this strength is at exactly e-2 of the position of z=0nm. The study shows the optical properties of SNOM optical probe. It confirms that it is necessary for SNOM probe to keep the distance of around 10nm from the sample surface.
In order to study optical properties of an optical fiber probe in scanning near-field optical microscopy (SNOM), simulation experiment was carried out by using the optical software VirtualLab Fusion based on field tracing method. The distribution of external optical field at the tip of SNOM optical probe was obtained. The results show along z axis, the distributions of optical field on different sections show the pattern of small aperture diffraction, the center intensity of center sample decreases exponentially with the increase of z value, and is almost attenuated to 0 at the position of z=100nm. With the increase of z value, full width at half maximum of center speckle contour remains stable at first and then increases. Its inflection point is at the position of z=20nm. The corresponding center strength value is 7.2V/m2 at this point. If calculated by the exponential function, this strength is at exactly e-2 of the position of z=0nm. The study shows the optical properties of SNOM optical probe. It confirms that it is necessary for SNOM probe to keep the distance of around 10nm from the sample surface.
2017, 41(4): 498-502.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.008
Abstract:
In order to improve machining efficiency and the surface quality of laser surface texturing for metal surface, the W-71s type spray gun was used to spray black paint, water glass, yellow material, zinc phosphate and graphite on the surface of GCr15 bearing steels respectively. Then, the samples were processed by Nd:YAG laser. Finally, the morphology of material was measured by 3-D morphology analyzer. The experimental results show that compared with uncoated specimens, the removing volume and slag volume around the dimple of specimen surface coated with water glass and yellow material increase and decrease respectively. The removing volume of the sample coated with yellow material increases by 29.4% and the slag volume of specimen surface coated with water glass decreases by 64.9%. Compared with single coating, some composite coating has better laser surface texturing performance. The composite coating with water glass and yellow material has great laser surface texturing performance. Compared with uncoated specimens, the removing volume increases by 47.1%, the slag volume decreases by 43.2%. The result is very instructive to improve the machining efficiency and surface quality of laser surface texturing.
In order to improve machining efficiency and the surface quality of laser surface texturing for metal surface, the W-71s type spray gun was used to spray black paint, water glass, yellow material, zinc phosphate and graphite on the surface of GCr15 bearing steels respectively. Then, the samples were processed by Nd:YAG laser. Finally, the morphology of material was measured by 3-D morphology analyzer. The experimental results show that compared with uncoated specimens, the removing volume and slag volume around the dimple of specimen surface coated with water glass and yellow material increase and decrease respectively. The removing volume of the sample coated with yellow material increases by 29.4% and the slag volume of specimen surface coated with water glass decreases by 64.9%. Compared with single coating, some composite coating has better laser surface texturing performance. The composite coating with water glass and yellow material has great laser surface texturing performance. Compared with uncoated specimens, the removing volume increases by 47.1%, the slag volume decreases by 43.2%. The result is very instructive to improve the machining efficiency and surface quality of laser surface texturing.
2017, 41(4): 503-506.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.009
Abstract:
In order to determine carmine concentration in the mixed pigment solution, normalization method was used to preprocess the fluorescence spectra. The processed data were combined with radial basis function neural network to establish the prediction model of carmine content. The average relative error of the prediction results of 3-D synchronous fluorescence spectrometry and 3-D ordinary fluorescence spectrometry were 2.86% and 11.12% respectively. The results showed that the 3-D synchronous fluorescence spectrometry was superior for the determination of the mixed pigment solution. The research provides the help for the prediction of the pigment concentration in the mixed pigment solution.
In order to determine carmine concentration in the mixed pigment solution, normalization method was used to preprocess the fluorescence spectra. The processed data were combined with radial basis function neural network to establish the prediction model of carmine content. The average relative error of the prediction results of 3-D synchronous fluorescence spectrometry and 3-D ordinary fluorescence spectrometry were 2.86% and 11.12% respectively. The results showed that the 3-D synchronous fluorescence spectrometry was superior for the determination of the mixed pigment solution. The research provides the help for the prediction of the pigment concentration in the mixed pigment solution.
2017, 41(4): 507-510.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.010
Abstract:
In order to remove data redundancy of hyperspectral images, and improve the accuracy and efficiency of hyperspectral image processing, a band selection algorithm was proposed based on band index of hyperspectral images. Wavelet transform was used to deal with the noise of hyperspectral image data. Bands are divided into groups by using joint skewness-kurtosis figure, and the band was removed as a redundant band which was determined based on the size of band index. The set of the minimum bands was obtained in this way. The experimental results show that the endmember set selected by using the above bands is consistent with that selected by using all bands. The redundancy band is removed to the greatest extent without affecting the endmember extraction. The classification accuracy of the band set is close to that of all bands. The band selection algorithm is feasible and effective. The study provides help to reduce the dimension of hyperspectral images.
In order to remove data redundancy of hyperspectral images, and improve the accuracy and efficiency of hyperspectral image processing, a band selection algorithm was proposed based on band index of hyperspectral images. Wavelet transform was used to deal with the noise of hyperspectral image data. Bands are divided into groups by using joint skewness-kurtosis figure, and the band was removed as a redundant band which was determined based on the size of band index. The set of the minimum bands was obtained in this way. The experimental results show that the endmember set selected by using the above bands is consistent with that selected by using all bands. The redundancy band is removed to the greatest extent without affecting the endmember extraction. The classification accuracy of the band set is close to that of all bands. The band selection algorithm is feasible and effective. The study provides help to reduce the dimension of hyperspectral images.
2017, 41(4): 511-514.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.011
Abstract:
In order to overcome the shortcomings of traditional subpixel location algorithm, such as weak anti-jamming ability, poor positioning accuracy, and difficulty in software realization, and improve the center location accuracy of laser spot, the method of curve fitting was used and a high-precision positioning measurement method of small spot size was proposed. After theoretical analysis and experimental verification, the error of center-of-mass extraction is controlled within 0.1pixel. The results show that the image centroid measurement method reduces the noise interference effectively and enhances the anti-noise performance. Compared with the traditional algorithm, the error is smaller.
In order to overcome the shortcomings of traditional subpixel location algorithm, such as weak anti-jamming ability, poor positioning accuracy, and difficulty in software realization, and improve the center location accuracy of laser spot, the method of curve fitting was used and a high-precision positioning measurement method of small spot size was proposed. After theoretical analysis and experimental verification, the error of center-of-mass extraction is controlled within 0.1pixel. The results show that the image centroid measurement method reduces the noise interference effectively and enhances the anti-noise performance. Compared with the traditional algorithm, the error is smaller.
2017, 41(4): 515-520.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.012
Abstract:
In order to improve calibration accuracy of liquid crystal spatial light modulator (LC-SLM), high bit depth phase gratings were proposed. Firstly, 16bit phase grating patterns were presented on LC-SLM, and diffraction spot was generated after the modulation of LC-SLM, the intensity of the diffracted spot was measured. Through calculation and analysis, the mapping relationship between gray level signal and phase modulation was obtained. Finally, calibration LUT file (LUT16) of LC-SLM for 488nm laser was obtained. The experimental results suggest that, hollow spot of good quality can be obtained when 0~2π vortex phase and LUT16 are presented on LC-SLM. Compared with LUT8, spot quality of LUT16 is improved 1.43 times of LUT8 from 0.53 to 0.76. The results show that aiming at specific wavelength, LUT file can be obtained by calibration of LC-SLM by means of high bit deep phase gratings and that beam can be modulated effectively by LC-SLM according to the loading phase. Modulation effect is better than that of LUT8 and calibration accuracy of LC-SLM is improved.
In order to improve calibration accuracy of liquid crystal spatial light modulator (LC-SLM), high bit depth phase gratings were proposed. Firstly, 16bit phase grating patterns were presented on LC-SLM, and diffraction spot was generated after the modulation of LC-SLM, the intensity of the diffracted spot was measured. Through calculation and analysis, the mapping relationship between gray level signal and phase modulation was obtained. Finally, calibration LUT file (LUT16) of LC-SLM for 488nm laser was obtained. The experimental results suggest that, hollow spot of good quality can be obtained when 0~2π vortex phase and LUT16 are presented on LC-SLM. Compared with LUT8, spot quality of LUT16 is improved 1.43 times of LUT8 from 0.53 to 0.76. The results show that aiming at specific wavelength, LUT file can be obtained by calibration of LC-SLM by means of high bit deep phase gratings and that beam can be modulated effectively by LC-SLM according to the loading phase. Modulation effect is better than that of LUT8 and calibration accuracy of LC-SLM is improved.
2017, 41(4): 521-525.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.013
Abstract:
In order to solve the problem that the distance between laser port and calibration object couldn't be measured directly and accurately, a new method based on distance difference of calibration was presented. The moving distance of calibration object was used as the calibration input to improve the traditional calibration method of measurement system. Gaussian-Newton iterative method was used to calculate the parameters of measurement system. The extraction error and non-vertical error of laser image point were analyzed. The results show that the precision can reach 4.000mm. The method can be used to calibrate the distance between calibration object and laser port accurately.
In order to solve the problem that the distance between laser port and calibration object couldn't be measured directly and accurately, a new method based on distance difference of calibration was presented. The moving distance of calibration object was used as the calibration input to improve the traditional calibration method of measurement system. Gaussian-Newton iterative method was used to calculate the parameters of measurement system. The extraction error and non-vertical error of laser image point were analyzed. The results show that the precision can reach 4.000mm. The method can be used to calibrate the distance between calibration object and laser port accurately.
2017, 41(4): 526-530.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.014
Abstract:
In order to study effect of laser shock peening(LSP) on residual stress, micro-hardness and metallographic structure evolution of Ti-6Al-4V titanium alloy at different temperatures, Ti-6Al-4V alloy samples were treated by LSP using high power and short pulse Nd:YAG laser and then were annealed at the temperatures of 400℃, 500℃, 550℃ and 600℃ for 1h respectively. Residual stress was measured by X-ray diffraction (XRD) method and metallographic structures were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The correlations between strengthening effect and grain size, dislocation were studied based on microstructure observations. The results indicate that high amplitude of residual compressive stress is induced on the surface via laser shock peening and micro-hardness is increased significantly. After the 1h preheating of 550℃, the effect depth of residual stress is about 100μm. After the 1h preheating of 400℃ and 600℃, micro-hardness on the specimen surface declines 8.3HV and 20.1HV respectively. After heat processing, grain size has an increasing trend in general. LSP can effectively improve mechanical property of Ti-6Al-4V titanium alloy at different temperatures.
In order to study effect of laser shock peening(LSP) on residual stress, micro-hardness and metallographic structure evolution of Ti-6Al-4V titanium alloy at different temperatures, Ti-6Al-4V alloy samples were treated by LSP using high power and short pulse Nd:YAG laser and then were annealed at the temperatures of 400℃, 500℃, 550℃ and 600℃ for 1h respectively. Residual stress was measured by X-ray diffraction (XRD) method and metallographic structures were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The correlations between strengthening effect and grain size, dislocation were studied based on microstructure observations. The results indicate that high amplitude of residual compressive stress is induced on the surface via laser shock peening and micro-hardness is increased significantly. After the 1h preheating of 550℃, the effect depth of residual stress is about 100μm. After the 1h preheating of 400℃ and 600℃, micro-hardness on the specimen surface declines 8.3HV and 20.1HV respectively. After heat processing, grain size has an increasing trend in general. LSP can effectively improve mechanical property of Ti-6Al-4V titanium alloy at different temperatures.
2017, 41(4): 531-536.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.015
Abstract:
In order to realize the design of feedback control circuit of space micro gravity active vibration isolation system, 6 laser displacement sensors were used to measure the displacements of 3 orthogonal positioning surfaces of vibration isolation platform. 3-D position and attitude were solved. And the derivation process was also given. The method was verified by numerical simulation and experimental test. The source of error and its influence on the result of calculation were analyzed. The relationship between error influence factors and calculation error was given. The results show that this algorithm can accurately calculate the 3-D position and attitude of a vibration isolation platform. The theoretical calculation error is less than 30μm. This research has some practical value and prospects for the design of feedback control loop based on displacement measurement.
In order to realize the design of feedback control circuit of space micro gravity active vibration isolation system, 6 laser displacement sensors were used to measure the displacements of 3 orthogonal positioning surfaces of vibration isolation platform. 3-D position and attitude were solved. And the derivation process was also given. The method was verified by numerical simulation and experimental test. The source of error and its influence on the result of calculation were analyzed. The relationship between error influence factors and calculation error was given. The results show that this algorithm can accurately calculate the 3-D position and attitude of a vibration isolation platform. The theoretical calculation error is less than 30μm. This research has some practical value and prospects for the design of feedback control loop based on displacement measurement.
2017, 41(4): 537-544.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.016
Abstract:
Temperature effect is an important factor affecting photoelectric efficiency of laser power beaming. To analyze the impact of temperature effect on photoelectric efficiency, physical model and thermal model of photovoltaic cells were established based on numerical simulation combing COMSOL Multiphysics software and MATLAB software. The effects of irradiation time, power density, beam size, incident angle, thermal radiation and heat convection on temperature field were obtained. The results show that under power density of 2000W/m2, photovoltaic cell temperature rises rapidly at the first, increases slowly after 20s and tends to the constant value of 343K after 100s with thermal equilibrium. The greater the power density, the faster the cell temperature, the higher the temperature which reaches thermal equilibrium time. When the cell surface is covered by laser spot completely, the temperature difference on the surface is minimum. The influence of incident angle on temperature rise of cell is affected by the effective laser power density. Heat radiation and heat convection are very favorable for decreasing cell temperature. When laser incident angle is 0°, laser power density is about 2000W/m2, and laser spot area is approximately cell surface area, the photovoltaic cell can obtain the best photoelectric efficiency. The study provides theoretical reference for improving photoelectric efficiency.
Temperature effect is an important factor affecting photoelectric efficiency of laser power beaming. To analyze the impact of temperature effect on photoelectric efficiency, physical model and thermal model of photovoltaic cells were established based on numerical simulation combing COMSOL Multiphysics software and MATLAB software. The effects of irradiation time, power density, beam size, incident angle, thermal radiation and heat convection on temperature field were obtained. The results show that under power density of 2000W/m2, photovoltaic cell temperature rises rapidly at the first, increases slowly after 20s and tends to the constant value of 343K after 100s with thermal equilibrium. The greater the power density, the faster the cell temperature, the higher the temperature which reaches thermal equilibrium time. When the cell surface is covered by laser spot completely, the temperature difference on the surface is minimum. The influence of incident angle on temperature rise of cell is affected by the effective laser power density. Heat radiation and heat convection are very favorable for decreasing cell temperature. When laser incident angle is 0°, laser power density is about 2000W/m2, and laser spot area is approximately cell surface area, the photovoltaic cell can obtain the best photoelectric efficiency. The study provides theoretical reference for improving photoelectric efficiency.
2017, 41(4): 545-548.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.017
Abstract:
In order to confirm that surface enhanced Raman spectroscopy (SERS) with flocculent colloid as substrate, combined with chemometric methods, can effectively detect pesticide residues in oranges, rapid and nondestructive detection of phosmet pesticide residues in navel oranges was studied with the help of confocal laser Raman spectrometer of Germany Bruker Optik GmbH. Detection limit of 4.113mg/L was concluded by cross validation method, and 7 methods of pretreatment of SERS spectra were carried out. After comparison, pretreatment method is the best with baseline correction at first, and then convolution smoothing, combined with partial least squares modeling. Correlation coefficient of prediction set is 0.904 and root mean square error of prediction set is 4.890mg/L. Correlation coefficient of correction set is 0.919 and root mean square error of correction set is 3.990mg/L. The results prove that the scientificity and feasibility of quantitative analysis of SERS. The study has certain reference in pesticide residue detection of export fruit and industrial production of domestic fruit.
In order to confirm that surface enhanced Raman spectroscopy (SERS) with flocculent colloid as substrate, combined with chemometric methods, can effectively detect pesticide residues in oranges, rapid and nondestructive detection of phosmet pesticide residues in navel oranges was studied with the help of confocal laser Raman spectrometer of Germany Bruker Optik GmbH. Detection limit of 4.113mg/L was concluded by cross validation method, and 7 methods of pretreatment of SERS spectra were carried out. After comparison, pretreatment method is the best with baseline correction at first, and then convolution smoothing, combined with partial least squares modeling. Correlation coefficient of prediction set is 0.904 and root mean square error of prediction set is 4.890mg/L. Correlation coefficient of correction set is 0.919 and root mean square error of correction set is 3.990mg/L. The results prove that the scientificity and feasibility of quantitative analysis of SERS. The study has certain reference in pesticide residue detection of export fruit and industrial production of domestic fruit.
2017, 41(4): 549-553.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.018
Abstract:
In order to obtain the attenuated internal reflection spectroscopy and realize on-line detection of oil in terahertz, the core components of total internal reflection system——the attenuated total internal reflection prism was designed by using the refraction law of light. At first, single reflection prism was designed and was used in terahertz attenuated total internal reflection system. According to the absorption of different material on terahertz wave, test experiments of water and product oil were carried out. Spectral data of samples were obtained. And then, multiple reflection prism was designed to increase the absorption of oil in terahertz, and optical simulation was carried out. The experimental results show that the absorption of oil after single total internal reflection is very limited, and the detection of oil cannot be achieved. The study is helpful for detection of oil quality.
In order to obtain the attenuated internal reflection spectroscopy and realize on-line detection of oil in terahertz, the core components of total internal reflection system——the attenuated total internal reflection prism was designed by using the refraction law of light. At first, single reflection prism was designed and was used in terahertz attenuated total internal reflection system. According to the absorption of different material on terahertz wave, test experiments of water and product oil were carried out. Spectral data of samples were obtained. And then, multiple reflection prism was designed to increase the absorption of oil in terahertz, and optical simulation was carried out. The experimental results show that the absorption of oil after single total internal reflection is very limited, and the detection of oil cannot be achieved. The study is helpful for detection of oil quality.
2017, 41(4): 554-557.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.019
Abstract:
In order to measure and detect refractive index of solution, by using transfer matrix method, the coupling system of Ce:YIG/Ag/liquid three-layer structure and prism based on magneto optic surface plasma resonance was studied. Numerical calculation was carried out and finite element method was used to simulate. For the structure composed of low loss Ag and strong magneto optical Ce:YIG, its sensitivity is to 4.082/RIU, solution refractive index is 1.330~1.340 when incident light wavelength is 980nm. The results show that compared with other conventional surface plasma resonance sensing structures, the sensitivity of the refractive index sensor presented in this paper is greatly improved. The structure can be used to detect refractive index of the solution more easily.
In order to measure and detect refractive index of solution, by using transfer matrix method, the coupling system of Ce:YIG/Ag/liquid three-layer structure and prism based on magneto optic surface plasma resonance was studied. Numerical calculation was carried out and finite element method was used to simulate. For the structure composed of low loss Ag and strong magneto optical Ce:YIG, its sensitivity is to 4.082/RIU, solution refractive index is 1.330~1.340 when incident light wavelength is 980nm. The results show that compared with other conventional surface plasma resonance sensing structures, the sensitivity of the refractive index sensor presented in this paper is greatly improved. The structure can be used to detect refractive index of the solution more easily.
2017, 41(4): 558-561.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.020
Abstract:
In order to obtain good time and frequency domain quality of a fast steering mirror (FSM), a method based on improving root locus was used to design its control parameters. At first, the root locus of FSM driven by a voice coil motor was established according to the identificated dynamic model. Then the expected dominant pole position was calculated based on the performance specification of the control system. By configuring the zero position of the controller, the root locus of the system was expected to have the dominant pole. Finally, the gain of system and the pole position of controller were obtained according to the modulus value formula and phase angle formula. The results show that the FSM control system based on the improved root locus algorithm has good dynamic performance and can suppress the mechanical resonance efficiently. The method is feasible and versatile.
In order to obtain good time and frequency domain quality of a fast steering mirror (FSM), a method based on improving root locus was used to design its control parameters. At first, the root locus of FSM driven by a voice coil motor was established according to the identificated dynamic model. Then the expected dominant pole position was calculated based on the performance specification of the control system. By configuring the zero position of the controller, the root locus of the system was expected to have the dominant pole. Finally, the gain of system and the pole position of controller were obtained according to the modulus value formula and phase angle formula. The results show that the FSM control system based on the improved root locus algorithm has good dynamic performance and can suppress the mechanical resonance efficiently. The method is feasible and versatile.
2017, 41(4): 562-565.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.021
Abstract:
In order to construct a micro acousto-optic Q-switched Nd:YVO4 laser with narrow pulse width, based on active Q-switched rate equation, the influence of pump speed, repetition rate and output mirror transmittance on pulse width was analyzed.The laser was designed with the structure of simple flat-flat cavity. High gain Nd:YVO4 laser crystal was end pumped by LD. A micro acousto-optic Q-switched was inserted in the resonant cavity, with action length of 7mm, cavity length of 13mm, and output mirror transmittance of 70%.The results show that when the pump power is 4.21W and repetition rate is 20kHz, the output of 1064nm laser was obtained with single pulse energy of 20μJ, pulse width of 1.65ns and peak power of 12kW. It is feasible to use micro acousto-optic Q-switched to construct short cavity and obtain narrow pulse width output. The device can also be used as the seed source of high-power lasers.
In order to construct a micro acousto-optic Q-switched Nd:YVO4 laser with narrow pulse width, based on active Q-switched rate equation, the influence of pump speed, repetition rate and output mirror transmittance on pulse width was analyzed.The laser was designed with the structure of simple flat-flat cavity. High gain Nd:YVO4 laser crystal was end pumped by LD. A micro acousto-optic Q-switched was inserted in the resonant cavity, with action length of 7mm, cavity length of 13mm, and output mirror transmittance of 70%.The results show that when the pump power is 4.21W and repetition rate is 20kHz, the output of 1064nm laser was obtained with single pulse energy of 20μJ, pulse width of 1.65ns and peak power of 12kW. It is feasible to use micro acousto-optic Q-switched to construct short cavity and obtain narrow pulse width output. The device can also be used as the seed source of high-power lasers.
2017, 41(4): 566-572.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.022
Abstract:
In order to improve the thermal stability of excitation sources and ensure the beam quality of 4kW axis fast flow CO2 laser, the thermal dissipation mechanism of heat sinks of laser excitation sources theoretically was analyzed by means of computational fluid dynamics method. The heat sink structure of the excitation source with heat flux of 106W/m2 and area of 16cm2 was optimized. The results show that the maximum temperature on the surface of the heat sink is lower than 340K after optimization. It can fully meet the requirements of the heat source of MOSFET which is the core power of the excitation source in the normal operation of the laser. At the same time, by numerical simulation, the optimal structure size of the microchannel heat sink is obtained. The channel spacing P is 0.6mm, microchannel groove angle θ is 45°, and channel spacing s is 0.1mm. When the Reynolds number is Re=546.9, the heat sink has the best cooling effect. And the stability of laser output power can be controlled within ±2%. This study provides the theoretical guidance for the design of microchannel heat sinks with high heat dissipation capability.
In order to improve the thermal stability of excitation sources and ensure the beam quality of 4kW axis fast flow CO2 laser, the thermal dissipation mechanism of heat sinks of laser excitation sources theoretically was analyzed by means of computational fluid dynamics method. The heat sink structure of the excitation source with heat flux of 106W/m2 and area of 16cm2 was optimized. The results show that the maximum temperature on the surface of the heat sink is lower than 340K after optimization. It can fully meet the requirements of the heat source of MOSFET which is the core power of the excitation source in the normal operation of the laser. At the same time, by numerical simulation, the optimal structure size of the microchannel heat sink is obtained. The channel spacing P is 0.6mm, microchannel groove angle θ is 45°, and channel spacing s is 0.1mm. When the Reynolds number is Re=546.9, the heat sink has the best cooling effect. And the stability of laser output power can be controlled within ±2%. This study provides the theoretical guidance for the design of microchannel heat sinks with high heat dissipation capability.
2017, 41(4): 573-577.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.023
Abstract:
In order to study quality control problem of wind profile data in time domain, a method of neural network was used to correct residual error of grey algorithm. Back propagation neural network was used to train grey residual error of historical wind profile data, and the quality control data of wind profile was obtained. After theoretical analysis and experimental verification, the results show that the algorithm can effectively reduce residual error and improve the accuracy of wind profile data. The result is helpful for quality control of wind profile.
In order to study quality control problem of wind profile data in time domain, a method of neural network was used to correct residual error of grey algorithm. Back propagation neural network was used to train grey residual error of historical wind profile data, and the quality control data of wind profile was obtained. After theoretical analysis and experimental verification, the results show that the algorithm can effectively reduce residual error and improve the accuracy of wind profile data. The result is helpful for quality control of wind profile.
2017, 41(4): 578-581.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.024
Abstract:
In order to optimize the parameters and improve the quality of laser drilling, the experiment and theoretical analysis of laser drilling on SUS304 stainless steel with 5mm thickness was conducted based on the orthogonal experiment method. The inlet aperture, outlet aperture and hole taper of laser drilling were measured and calculated respectively. The effect degree of the parameters, such as pulse width, pulse energy, repetition frequency, defocusing amount and pulse number, on the hole taper was gotten. And the optimal parameters combination of laser drilling on SUS304 were obtained. The results show that defocusing amount, pulse width and pulse number have a great effect on hole taper, while repetition rate and pulse energy have a little effect on hole taper. The optimized laser parameters are pulse width of 0.5ms, pulse energy of 2.5J, repetition frequency of 40Hz, defocusing amount of 0mm and pulse number of 200.The smallest taper can be obtained with the optimized laser parameters.
In order to optimize the parameters and improve the quality of laser drilling, the experiment and theoretical analysis of laser drilling on SUS304 stainless steel with 5mm thickness was conducted based on the orthogonal experiment method. The inlet aperture, outlet aperture and hole taper of laser drilling were measured and calculated respectively. The effect degree of the parameters, such as pulse width, pulse energy, repetition frequency, defocusing amount and pulse number, on the hole taper was gotten. And the optimal parameters combination of laser drilling on SUS304 were obtained. The results show that defocusing amount, pulse width and pulse number have a great effect on hole taper, while repetition rate and pulse energy have a little effect on hole taper. The optimized laser parameters are pulse width of 0.5ms, pulse energy of 2.5J, repetition frequency of 40Hz, defocusing amount of 0mm and pulse number of 200.The smallest taper can be obtained with the optimized laser parameters.
2017, 41(4): 582-585.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.025
Abstract:
In order to reduce the volume and weight of a satellite communication system and enhance its temperature stability and anti electromagnetic interference ability, a new method was adopted. A photoelectric oscillator was used as microwave local oscillator on the satellite. Microwave signal was transmitted by the fiber. The generation, distribution, transmission and frequency conversion of microwave signal were integrated into the system. After theoretical analysis and experimental verification, the results show that the method is feasible. Based on an optoelectric oscillator, the microwave signal of 11.5GHz was generated and distributed by low-loss optical fiber through multi-channel output experimentally. The first output signal has the same frequency with the local oscillator, with phase noise of -100.5dBc/Hz@10kHz. The second output signal's frequency is twice of local oscillator's frequency with phase noise of -86.6dBc/Hz@10kHz. Compared with the conventional electrical method, the new method to transmit microwave signal has significant effect in improving transmit efficiency, reducing volume, weight and cost, enhancing anti-jamming power and temperature stability, improving signal quality and bandwidth of the system.
In order to reduce the volume and weight of a satellite communication system and enhance its temperature stability and anti electromagnetic interference ability, a new method was adopted. A photoelectric oscillator was used as microwave local oscillator on the satellite. Microwave signal was transmitted by the fiber. The generation, distribution, transmission and frequency conversion of microwave signal were integrated into the system. After theoretical analysis and experimental verification, the results show that the method is feasible. Based on an optoelectric oscillator, the microwave signal of 11.5GHz was generated and distributed by low-loss optical fiber through multi-channel output experimentally. The first output signal has the same frequency with the local oscillator, with phase noise of -100.5dBc/Hz@10kHz. The second output signal's frequency is twice of local oscillator's frequency with phase noise of -86.6dBc/Hz@10kHz. Compared with the conventional electrical method, the new method to transmit microwave signal has significant effect in improving transmit efficiency, reducing volume, weight and cost, enhancing anti-jamming power and temperature stability, improving signal quality and bandwidth of the system.
2017, 41(4): 586-590.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.026
Abstract:
In order to study the effect of laser micro-modeling on the friction performance of mechanical parts, Nd:YAG pulsed laser was used to form a micro pit texture array with certain diameter, spacing and density on the surface of a steel plate. The tribological performance was tested on ring/disc friction tester. The results show that the depth and diameter of micro pits increase with the increase of pulse number. The texture arrays with different densities can be obtained by adjusting the parameters (diameter and spacing). The specimen with a density of 8%~10% has the lowest friction factor of 0.055~0.06 and the lowest wear rate of 5.2×10-16m3/(N·m). The trend of the friction and wear performance with the change of texture density is obtained by curve fitting. The study obtains the parameters of the best tribological properties and can improve the mechanical efficiency and service life.
In order to study the effect of laser micro-modeling on the friction performance of mechanical parts, Nd:YAG pulsed laser was used to form a micro pit texture array with certain diameter, spacing and density on the surface of a steel plate. The tribological performance was tested on ring/disc friction tester. The results show that the depth and diameter of micro pits increase with the increase of pulse number. The texture arrays with different densities can be obtained by adjusting the parameters (diameter and spacing). The specimen with a density of 8%~10% has the lowest friction factor of 0.055~0.06 and the lowest wear rate of 5.2×10-16m3/(N·m). The trend of the friction and wear performance with the change of texture density is obtained by curve fitting. The study obtains the parameters of the best tribological properties and can improve the mechanical efficiency and service life.
2017, 41(4): 591-595.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.027
Abstract:
In order to design a photonic crystal waveguide which can propagate slow light with wide band and low dispersion, on the basis of photonic crystal structure of triangular lattice dielectric cylinder, the periodic arrangement was carried out using circular scatterers and elliptic scatterers. Plane wave expansion method was used to simulate the designed coupled cavity waveguide. The results show that the maximum group velocity of guided mode decreases from 0.035c to 0.01c by changing long axis Ra of oval scatterers in defect line. The group velocity can be further decreased when short axis Rb in defect line is changed. Further study shows that by changing area ratio of two scatterers of the first row around the microcavity, the maximum group velocity is reduced to 0.0065c, and low dispersion slow light with wavelength range of 3.25nm was gotten. When the designed coupled cavity was used in optical buffer, cache time of 76.82ps and the maximum ache capacity of 15.56bit can be achieved. The research has reference value in the design and application of novel devices based on photonic crystal waveguides.
In order to design a photonic crystal waveguide which can propagate slow light with wide band and low dispersion, on the basis of photonic crystal structure of triangular lattice dielectric cylinder, the periodic arrangement was carried out using circular scatterers and elliptic scatterers. Plane wave expansion method was used to simulate the designed coupled cavity waveguide. The results show that the maximum group velocity of guided mode decreases from 0.035c to 0.01c by changing long axis Ra of oval scatterers in defect line. The group velocity can be further decreased when short axis Rb in defect line is changed. Further study shows that by changing area ratio of two scatterers of the first row around the microcavity, the maximum group velocity is reduced to 0.0065c, and low dispersion slow light with wavelength range of 3.25nm was gotten. When the designed coupled cavity was used in optical buffer, cache time of 76.82ps and the maximum ache capacity of 15.56bit can be achieved. The research has reference value in the design and application of novel devices based on photonic crystal waveguides.
2017, 41(4): 596-601.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.028
Abstract:
In order to improve surface performance of H13 steel, Ni-based coatings were fabricated on H13 steel surface with YLS-4000 fiber laser. On the basis of orthogonal test and analysis, superficial status, geometric parameters, dilution ratio, microstructure and hardness of coatings under different processing parameters were obtained and investigated. The results show that coating surface is uneven when laser power is minimum (1800W) and powder feeding rate is maximum (1.0g/s). Coating surface has cracks when laser power (2200W) and scanning speed (25mm/s) are maximunm. When dilution ratio is lower than 10%, average hardness of cladding zone is improved to more than 800HV and is more than 3 times of substrate hardness (246HV). Strengthening effect is remarkable. When dilution ratio is larger than 25%, hardness of bottom layer in cladding zone is low due to the dilution of substrate. With the increase of laser power and scan speed, dilution ratio of the coating increases while dilution ratio decreases with the increase of powder feeding rate. Coatings of good quality with smooth surface, compact texture, and remarkable strengthening effect can be obtained by adjusting processing parameters.
In order to improve surface performance of H13 steel, Ni-based coatings were fabricated on H13 steel surface with YLS-4000 fiber laser. On the basis of orthogonal test and analysis, superficial status, geometric parameters, dilution ratio, microstructure and hardness of coatings under different processing parameters were obtained and investigated. The results show that coating surface is uneven when laser power is minimum (1800W) and powder feeding rate is maximum (1.0g/s). Coating surface has cracks when laser power (2200W) and scanning speed (25mm/s) are maximunm. When dilution ratio is lower than 10%, average hardness of cladding zone is improved to more than 800HV and is more than 3 times of substrate hardness (246HV). Strengthening effect is remarkable. When dilution ratio is larger than 25%, hardness of bottom layer in cladding zone is low due to the dilution of substrate. With the increase of laser power and scan speed, dilution ratio of the coating increases while dilution ratio decreases with the increase of powder feeding rate. Coatings of good quality with smooth surface, compact texture, and remarkable strengthening effect can be obtained by adjusting processing parameters.
Influence of biased signal and noise on characteristics of stochastic resonance in single mode laser
2017, 41(4): 602-605.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.029
Abstract:
In order to study characteristics of a laser system, the signal-to-noise ratio (SNR) of the output laser intensity for a single mode laser was analyzed theoretically by means of linear approximation based on the loss model for a single mode laser driven by the colored pump noise and quantum noise with correlation of the real and imaginary parts. Then, effects of amplitude, low frequency of modulation signal, high frequency of carrier signal, intensity of quantum and pump noise, correlation coefficient of quantum noise between the real and imaginary parts on stochastic resonance of a laser system were analyzed in detail. It is found that the SNR has stochastic resonance phenomenon because of the net gain coefficient of the laser system. The result will provide some theoretical basis to optimize laser dynamics.
In order to study characteristics of a laser system, the signal-to-noise ratio (SNR) of the output laser intensity for a single mode laser was analyzed theoretically by means of linear approximation based on the loss model for a single mode laser driven by the colored pump noise and quantum noise with correlation of the real and imaginary parts. Then, effects of amplitude, low frequency of modulation signal, high frequency of carrier signal, intensity of quantum and pump noise, correlation coefficient of quantum noise between the real and imaginary parts on stochastic resonance of a laser system were analyzed in detail. It is found that the SNR has stochastic resonance phenomenon because of the net gain coefficient of the laser system. The result will provide some theoretical basis to optimize laser dynamics.
2017, 41(4): 606-610.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.030
Abstract:
For airborne laser communication, optical axis stabilization is the premise to establish laser communication link. In order to overcome the negative effect of carrier disturbance and parameters change on optical axis stabilization of coarse tracking system effectively, a proportion-integral-derivative(PID) control algorithm based on fuzzy neural network was designed. The algorithm combines the nonlinear controllability of fuzzy theory with self-learning ability of the neural network, and can achieve the real-time online adjustment of PID parameters. The simulation experiment results show that compared with the traditional PID control method, the fuzzy neural network PID control method can improve dynamic response speed and reduce the overshoot of a system and that the system has strong adaptability and robustness when the carrier is disturbed and the parameters change.
For airborne laser communication, optical axis stabilization is the premise to establish laser communication link. In order to overcome the negative effect of carrier disturbance and parameters change on optical axis stabilization of coarse tracking system effectively, a proportion-integral-derivative(PID) control algorithm based on fuzzy neural network was designed. The algorithm combines the nonlinear controllability of fuzzy theory with self-learning ability of the neural network, and can achieve the real-time online adjustment of PID parameters. The simulation experiment results show that compared with the traditional PID control method, the fuzzy neural network PID control method can improve dynamic response speed and reduce the overshoot of a system and that the system has strong adaptability and robustness when the carrier is disturbed and the parameters change.
2017, 41(4): 611-613.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.031
Abstract:
In order to study the extinction ratio of a reverse Rochon prism, extinction ratios of forward direction and reverse direction of a Rochon prism were studied by analyzing photoelastic effect in the prism cement. The reason for the declining of extinction ratio when parallel laser beam passing a Rochon prism backward was studied both in theory and by experiment. The result shows that the extinction ratio is 1.14×10-5 when parallel laser beam passes through a Rochon prism forward, and extinction ratio is 2.93×10-3 when beam passes through the prism backward. Extinction ratio is 5.72×10-5 when beam backward with a λ/4 wave plate. When collimation beam passes through a Rochon prism backward, the extinction ratio of the beam whose propagation direction does not change is decreased because of photoelastic effect in the cementing layer. The experiment verifies the correctness of the theory. The research can provide necessary reference for the designing and the correct using of Rochon prisms.
In order to study the extinction ratio of a reverse Rochon prism, extinction ratios of forward direction and reverse direction of a Rochon prism were studied by analyzing photoelastic effect in the prism cement. The reason for the declining of extinction ratio when parallel laser beam passing a Rochon prism backward was studied both in theory and by experiment. The result shows that the extinction ratio is 1.14×10-5 when parallel laser beam passes through a Rochon prism forward, and extinction ratio is 2.93×10-3 when beam passes through the prism backward. Extinction ratio is 5.72×10-5 when beam backward with a λ/4 wave plate. When collimation beam passes through a Rochon prism backward, the extinction ratio of the beam whose propagation direction does not change is decreased because of photoelastic effect in the cementing layer. The experiment verifies the correctness of the theory. The research can provide necessary reference for the designing and the correct using of Rochon prisms.
2017, 41(4): 614-618.
doi: 10.7510/jgjs.issn.1001-3806.2017.04.032
Abstract:
In order to realize crosstalk optimization of 4×10Gbit/s parallel optical modules, by using the ABCD transfer matrix method, combining with the optical fiber coupling constraint and the theory of collimating lens, focus lens and fiber end surface of the ball lens, two sets of optimization schemes were designed. Beam characteristics of vertical cavity surface emitting lasers (VCSEL) were studied, the relationship between the spot radius and divergence angle was simulated by using MATLAB, and crosstalk situation was analyzed. Optical modeling in ZEMAX non-sequential mode was founded, the parameters of lens structure and the design of fiber end face were optimized. After theoretical analysis and experimental verification, the optimized coupling beam radius and coupling efficiency were obtained. The results show that in indirect coupling optimization structure, light spot at the end of fiber is 53.72μm, coupling efficiency is up to 72.59%. In direct coupling optimization structure, light spot at the end of fiber is 3.695μm, and coupling efficiency is up to 76.11%. The design effectively solves the problem of optical crosstalk between parallel optical modules. The study is helpful for the optimization of transmission quality of optical network signal.
In order to realize crosstalk optimization of 4×10Gbit/s parallel optical modules, by using the ABCD transfer matrix method, combining with the optical fiber coupling constraint and the theory of collimating lens, focus lens and fiber end surface of the ball lens, two sets of optimization schemes were designed. Beam characteristics of vertical cavity surface emitting lasers (VCSEL) were studied, the relationship between the spot radius and divergence angle was simulated by using MATLAB, and crosstalk situation was analyzed. Optical modeling in ZEMAX non-sequential mode was founded, the parameters of lens structure and the design of fiber end face were optimized. After theoretical analysis and experimental verification, the optimized coupling beam radius and coupling efficiency were obtained. The results show that in indirect coupling optimization structure, light spot at the end of fiber is 53.72μm, coupling efficiency is up to 72.59%. In direct coupling optimization structure, light spot at the end of fiber is 3.695μm, and coupling efficiency is up to 76.11%. The design effectively solves the problem of optical crosstalk between parallel optical modules. The study is helpful for the optimization of transmission quality of optical network signal.
