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RSS2010 Vol. 34, No. 1
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2010, 34(1): 1-4.
doi: 10.3969/j.issn.1001-3806.2010.01.001
[Abstract]
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Abstract:
To evaluate the feasibility of designing and fabricating crowns and fixed bridge by means of the digital reverse engineering and selective laser melting rapid prototyping technology, an optical scanning system, Laserdenta was used to measure the dental cast and reconstruct its three-dimension digital profile. The shape of crowns and fixed bridge was designed by computer based on the digital dental cast. By using the Dimetal-280 selective laser melting rapid prototyping system, the crowns and fixed bridge of 316L stainless steel was made through orthogonal experiments for parameter optimization. The results show that the crowns and fixed bridge of 316L stainless steel have good surface quality, high accuracy of ±0.15mm in dimension, good roughness of about 20μm. The technology of reverse engineering and direct manufacturing of complex customized metallic crowns and fixed bridge by selective laser melting shows obvious superiority with high speed, precise profile and good accuracy in size comparing with the traditional one so as to offer some evidence for its application in CAD/CAM of oral prosthesis.]
To evaluate the feasibility of designing and fabricating crowns and fixed bridge by means of the digital reverse engineering and selective laser melting rapid prototyping technology, an optical scanning system, Laserdenta was used to measure the dental cast and reconstruct its three-dimension digital profile. The shape of crowns and fixed bridge was designed by computer based on the digital dental cast. By using the Dimetal-280 selective laser melting rapid prototyping system, the crowns and fixed bridge of 316L stainless steel was made through orthogonal experiments for parameter optimization. The results show that the crowns and fixed bridge of 316L stainless steel have good surface quality, high accuracy of ±0.15mm in dimension, good roughness of about 20μm. The technology of reverse engineering and direct manufacturing of complex customized metallic crowns and fixed bridge by selective laser melting shows obvious superiority with high speed, precise profile and good accuracy in size comparing with the traditional one so as to offer some evidence for its application in CAD/CAM of oral prosthesis.]
2010, 34(1): 5-7,29.
doi: 10.3969/j.issn.1001-3806.2010.01.002
Abstract:
In order to acquire high power, single-frequency, single-polarization narrow-linewidth laser beam, a single-frequency erbium doped loop fiber laser and its amplification configuration were studied. With an un-pumped erbium-doped fiber as saturable absorber, with a high-reflectivity fiber Bragg grating as wavelength selector, a super narrow band filter was constructed. Fiber polarization controller and polarization-maintaining optical circulator with high extinction ratio were incorporated in the loop cavity to obtain single polarization output. A single stage amplifier was used outside the loop cavity to increase the output power. 206mW output laser was obtained, and the power stability reached 1.4%. The linewidth of output laser was less than 500Hz measured through fiber delayed self-heterodyne method. The degree of polarization was stable at 99.7%. The result shows that un-polarization-maintaining saturable absorber with fiber Bragg grating together with partially polarization-maintaining structure can lead to single-polarization narrow-linewidth laser,and laser amplification will broaden the linewidth.
In order to acquire high power, single-frequency, single-polarization narrow-linewidth laser beam, a single-frequency erbium doped loop fiber laser and its amplification configuration were studied. With an un-pumped erbium-doped fiber as saturable absorber, with a high-reflectivity fiber Bragg grating as wavelength selector, a super narrow band filter was constructed. Fiber polarization controller and polarization-maintaining optical circulator with high extinction ratio were incorporated in the loop cavity to obtain single polarization output. A single stage amplifier was used outside the loop cavity to increase the output power. 206mW output laser was obtained, and the power stability reached 1.4%. The linewidth of output laser was less than 500Hz measured through fiber delayed self-heterodyne method. The degree of polarization was stable at 99.7%. The result shows that un-polarization-maintaining saturable absorber with fiber Bragg grating together with partially polarization-maintaining structure can lead to single-polarization narrow-linewidth laser,and laser amplification will broaden the linewidth.
2010, 34(1): 8-12.
doi: 10.3969/j.issn.1001-3806.2010.01.003
Abstract:
In order to study the nonuniform temperature rise and thermal effect in the Yb:YAG crystal, based on the theory of semi-analytical thermal analysis and working characteristic analysis of Yb:YAG microchip with super-Gaussian beam end-pumping and back-face cooling, a new solution of heat conduction equation was introduced and the general expressions of temperature field, thermal distortion field and additional optical path differences (OPD) of Yb:YAG microchip were obtained respectively. Some factors affecting the temperature distribution and thermal distortion of Yb:YAG microchip, such as the super-Gaussian beam with different orders,different spot radius, were quantitatively analyzed. If a Yb:YAG microchip with 0.08 atom fraction of ytterbium is end-pumped by the fifth order super-Gaussian beam with power of 50W in 300μm radius, its maximal temperature raise was up to 52.18℃ and its maximum thermal distortion was 0.1195μm and maximum additional OPD was 0.2152μm. The results can provide theoretical instruction for the heat insensitivity cavity design of microchip laser.
In order to study the nonuniform temperature rise and thermal effect in the Yb:YAG crystal, based on the theory of semi-analytical thermal analysis and working characteristic analysis of Yb:YAG microchip with super-Gaussian beam end-pumping and back-face cooling, a new solution of heat conduction equation was introduced and the general expressions of temperature field, thermal distortion field and additional optical path differences (OPD) of Yb:YAG microchip were obtained respectively. Some factors affecting the temperature distribution and thermal distortion of Yb:YAG microchip, such as the super-Gaussian beam with different orders,different spot radius, were quantitatively analyzed. If a Yb:YAG microchip with 0.08 atom fraction of ytterbium is end-pumped by the fifth order super-Gaussian beam with power of 50W in 300μm radius, its maximal temperature raise was up to 52.18℃ and its maximum thermal distortion was 0.1195μm and maximum additional OPD was 0.2152μm. The results can provide theoretical instruction for the heat insensitivity cavity design of microchip laser.
2010, 34(1): 13-16.
doi: 10.3969/j.issn.1001-3806.2010.01.004
Abstract:
In order to solve the problems that absolute temperature compensation for strain sensing of single line optical fiber sensors based on Brillouin and fiber Bragg grating encounters, e.g. high cost and difficulty of installation, a novel temperature inter-compensation method was presented. Based on a sensor, i.e,a dual fiber reinforced polymer-fiber Bragg grating rebar, experiments were carried out under room and outdoor environments. The results show that the temperature inter-compensation can be easily realized with a practically acceptable error less than 8%. Moreover this method can also give the dual parameters of strain and temperature values simultaneously. The system based on optical fiber sensors is suitable for practical applications for its simple structure and low cost.
In order to solve the problems that absolute temperature compensation for strain sensing of single line optical fiber sensors based on Brillouin and fiber Bragg grating encounters, e.g. high cost and difficulty of installation, a novel temperature inter-compensation method was presented. Based on a sensor, i.e,a dual fiber reinforced polymer-fiber Bragg grating rebar, experiments were carried out under room and outdoor environments. The results show that the temperature inter-compensation can be easily realized with a practically acceptable error less than 8%. Moreover this method can also give the dual parameters of strain and temperature values simultaneously. The system based on optical fiber sensors is suitable for practical applications for its simple structure and low cost.
2010, 34(1): 17-19,40.
doi: 10.3969/j.issn.1001-3806.2010.01.005
Abstract:
In order to obtain the width-tunable 355nm pulses,a 1064nm laser-induced plasma shutter was used to control the pulse width of 355nm pulses. The width tunable from 2.8ns to 10ns was obtained under the interaction of ionization of the Cu pinhole and the atmospheric breakdown. Firstly,the effect of 1064nm pulse energy on pulse compression was discussed, and the shortest output pulse with a width of 2.8ns was obtained without delay time between two laser paths. Subsequently, adopting the device for delay-time to vary the optical differences between two paths, the width-tunable 355nm laser pulses were obtained. Experimental results indicate that laser-induced plasma shutter is a better pulse-shaping means with simple configuration, convenient operation, and widespread applications.
In order to obtain the width-tunable 355nm pulses,a 1064nm laser-induced plasma shutter was used to control the pulse width of 355nm pulses. The width tunable from 2.8ns to 10ns was obtained under the interaction of ionization of the Cu pinhole and the atmospheric breakdown. Firstly,the effect of 1064nm pulse energy on pulse compression was discussed, and the shortest output pulse with a width of 2.8ns was obtained without delay time between two laser paths. Subsequently, adopting the device for delay-time to vary the optical differences between two paths, the width-tunable 355nm laser pulses were obtained. Experimental results indicate that laser-induced plasma shutter is a better pulse-shaping means with simple configuration, convenient operation, and widespread applications.
2010, 34(1): 20-21,44.
doi: 10.3969/j.issn.1001-3806.2010.01.006
Abstract:
For the sake of research of producing method, light spectrum and laser characteristics of Nd-doped inorganic liquid, Nd-POCl3-SnO2 was compound in the laboratory. The absorption and fluorescent characteristics of the liquid was tested. With flashlamp pumping and traveling wave amplification, the gain of the liquid was studied. Stable Nd-doped inorganic laser liquid was achieved,whose gain coefficient was 1%/cm at 1051nm central wavelength with 83.33μs pulse width. It is indicated that stable Nd-doped inorganic liquid can be compounded under dry condition and at proper Lewis acid and Nd concentration, its light spectrum was similar to that of Nd glass, stable laser can be output at single pulse mode.
For the sake of research of producing method, light spectrum and laser characteristics of Nd-doped inorganic liquid, Nd-POCl3-SnO2 was compound in the laboratory. The absorption and fluorescent characteristics of the liquid was tested. With flashlamp pumping and traveling wave amplification, the gain of the liquid was studied. Stable Nd-doped inorganic laser liquid was achieved,whose gain coefficient was 1%/cm at 1051nm central wavelength with 83.33μs pulse width. It is indicated that stable Nd-doped inorganic liquid can be compounded under dry condition and at proper Lewis acid and Nd concentration, its light spectrum was similar to that of Nd glass, stable laser can be output at single pulse mode.
2010, 34(1): 22-25.
doi: 10.3969/j.issn.1001-3806.2010.01.007
Abstract:
To meet the cobalt-free requirement for a certain valve, thicker coating with gradient hardness distribution was prepared on 0Cr18Ni10Ti stainless steel by laser cladding two kinds of cobalt-free nickel-based alloy powder. The microstructure, hardness and the interface bonding strength of the coating were analyzed. The results showed that using nickel-based alloy with lower hardness as a transition layer, the problem of cracking for nickel-based alloy coating with higher hardness could be resolved. The interfaces between the coating and the substrate as well as these two nickel-based alloy coatings were smoothly transited. The hardness was also gradient along the cross-section of the coating. The hardness of the coating surface was about HRC47. The coating was metallurgically bonded with the substrate. And the interface bonding strength of the coating was higher than 565MPa. There was no de-bonding and cracking after bending and thermal shock test, indicating the good anti-thermal shock property of the coating.
To meet the cobalt-free requirement for a certain valve, thicker coating with gradient hardness distribution was prepared on 0Cr18Ni10Ti stainless steel by laser cladding two kinds of cobalt-free nickel-based alloy powder. The microstructure, hardness and the interface bonding strength of the coating were analyzed. The results showed that using nickel-based alloy with lower hardness as a transition layer, the problem of cracking for nickel-based alloy coating with higher hardness could be resolved. The interfaces between the coating and the substrate as well as these two nickel-based alloy coatings were smoothly transited. The hardness was also gradient along the cross-section of the coating. The hardness of the coating surface was about HRC47. The coating was metallurgically bonded with the substrate. And the interface bonding strength of the coating was higher than 565MPa. There was no de-bonding and cracking after bending and thermal shock test, indicating the good anti-thermal shock property of the coating.
2010, 34(1): 26-29.
doi: 10.3969/j.issn.1001-3806.2010.01.008
Abstract:
In order to optimize the performance of an integrated optics gyroscope (IOG), effect on the gyroscope sensitivity resulting from resonant characteristics and structural parameters of a passive ring resonator (PRR), a gyroscope's critical component, was studied based on frequency modulation spectroscopy theory and multi-beams interference method. Because of much more serious light attenuation in waveguides than that in fibers, there were bidirectional function in the design of an IOG while PRR's cavity length and coupling coefficient were changed,being distinguished with the situation in fiber-optic gyroscopes. Finally, a conclusion was drawn that there were optimum parameters determined by the attenuation in waveguides.
In order to optimize the performance of an integrated optics gyroscope (IOG), effect on the gyroscope sensitivity resulting from resonant characteristics and structural parameters of a passive ring resonator (PRR), a gyroscope's critical component, was studied based on frequency modulation spectroscopy theory and multi-beams interference method. Because of much more serious light attenuation in waveguides than that in fibers, there were bidirectional function in the design of an IOG while PRR's cavity length and coupling coefficient were changed,being distinguished with the situation in fiber-optic gyroscopes. Finally, a conclusion was drawn that there were optimum parameters determined by the attenuation in waveguides.
2010, 34(1): 30-33,98.
doi: 10.3969/j.issn.1001-3806.2010.01.009
Abstract:
To detect pipeline leakage and locate leakage point in real-time,a long distance distributed optical fiber sensor based on interferometer principle was introduced to detect leak signals dynamically. The measuring principle and the leaking source locating method for the detection system were analyzed, and an experiment was designed to study the influence of the carrier on the performance of the system. It is observed from the experiment results that the sensor can obtain optimal performance when the absolute value of one order Bessel is max; the leak signal can not be detected when the absolute value of one order Bessel is far less than the max. The results verify that the sensor can locate the leaking source accurately when the optimal carrier parameters are selected,and the positioning error is 0.99%.
To detect pipeline leakage and locate leakage point in real-time,a long distance distributed optical fiber sensor based on interferometer principle was introduced to detect leak signals dynamically. The measuring principle and the leaking source locating method for the detection system were analyzed, and an experiment was designed to study the influence of the carrier on the performance of the system. It is observed from the experiment results that the sensor can obtain optimal performance when the absolute value of one order Bessel is max; the leak signal can not be detected when the absolute value of one order Bessel is far less than the max. The results verify that the sensor can locate the leaking source accurately when the optimal carrier parameters are selected,and the positioning error is 0.99%.
2010, 34(1): 34-36,52.
doi: 10.3969/j.issn.1001-3806.2010.01.010
Abstract:
In order to study the microstructure and property of butt joints of aluminum alloy 5A06,the butt joint of 2mm thick aluminum alloy 5A06 sheets was filled with SA1-Mg5 wire and welded with a 3kW Nd:YAG laser. The chemical elements in the welding seam were almost the same as those of the substrate. Its microstructure was fine,dense columnar crystals near to the fusion area and fine dendrites in the center, and the width of heat affected zone was only from 50μm to 100μm. The tensile strength and elongation were respective up to 93% and 58% of that of the substrate metal. The entire joint was broken in the heat affected zone, the scanning electron microscope observation showed that the fracture surface of 5A06 alloy and welded joint exhibited hybrid tough fracture of dimple and tear ridge. The results show that the butt laser welding aluminum alloy with appropriate component filler wire can erase the falling, undercut and sag which is inevitably with laser autogenous welding, and the property of joints is improved a lot.
In order to study the microstructure and property of butt joints of aluminum alloy 5A06,the butt joint of 2mm thick aluminum alloy 5A06 sheets was filled with SA1-Mg5 wire and welded with a 3kW Nd:YAG laser. The chemical elements in the welding seam were almost the same as those of the substrate. Its microstructure was fine,dense columnar crystals near to the fusion area and fine dendrites in the center, and the width of heat affected zone was only from 50μm to 100μm. The tensile strength and elongation were respective up to 93% and 58% of that of the substrate metal. The entire joint was broken in the heat affected zone, the scanning electron microscope observation showed that the fracture surface of 5A06 alloy and welded joint exhibited hybrid tough fracture of dimple and tear ridge. The results show that the butt laser welding aluminum alloy with appropriate component filler wire can erase the falling, undercut and sag which is inevitably with laser autogenous welding, and the property of joints is improved a lot.
2010, 34(1): 37-40.
doi: 10.3969/j.issn.1001-3806.2010.01.011
Abstract:
In order to study the factors affecting the confined state in a photonic quantum well (PQW) structure, the transmission characteristics of the PQW structure with different dielectric thickness and constants were studied by means of optical transfer matrix,then it was known that the frequency in the PQW structure changed with the dielectric constants and thickness. The frequency in a confined state can be changed linearly by changing the dielectric thickness and constants in wells and barriers a little. The dependence of the confined frequency on the dielectric thickness and dielectric constants in wells is more than that in barriers. The investigation results might be used to obtain the desired frequency in the confined state in a PQW structure.
In order to study the factors affecting the confined state in a photonic quantum well (PQW) structure, the transmission characteristics of the PQW structure with different dielectric thickness and constants were studied by means of optical transfer matrix,then it was known that the frequency in the PQW structure changed with the dielectric constants and thickness. The frequency in a confined state can be changed linearly by changing the dielectric thickness and constants in wells and barriers a little. The dependence of the confined frequency on the dielectric thickness and dielectric constants in wells is more than that in barriers. The investigation results might be used to obtain the desired frequency in the confined state in a PQW structure.
2010, 34(1): 41-44.
doi: 10.3969/j.issn.1001-3806.2010.01.012
Abstract:
In order to study the diffraction characteristics of blazed gratings and analyze the influence of grating parameters on diffraction efficiency, the dependence of diffraction efficiency on the different grating structure parameters and wavelengths was obtained based on the rigorous coupled-wave electromagnetic theory. Calculation results showed that the larger the slot angle, the smaller the blazed angle and the diffraction efficiency, and the bigger the wavelength, the smaller the diffraction efficiency and the bigger the blazed angle. Finally,the polarization phenomenon of a blazed grating was analyzed. The obtained results are helpful for the grating design.
In order to study the diffraction characteristics of blazed gratings and analyze the influence of grating parameters on diffraction efficiency, the dependence of diffraction efficiency on the different grating structure parameters and wavelengths was obtained based on the rigorous coupled-wave electromagnetic theory. Calculation results showed that the larger the slot angle, the smaller the blazed angle and the diffraction efficiency, and the bigger the wavelength, the smaller the diffraction efficiency and the bigger the blazed angle. Finally,the polarization phenomenon of a blazed grating was analyzed. The obtained results are helpful for the grating design.
2010, 34(1): 45-47,84.
doi: 10.3969/j.issn.1001-3806.2010.01.013
Abstract:
In order to study the difference of urine fluorescence spectroscopy from healthy female, excited by 200nm～390nm ultraviolet light,the urine specimens of healthy women aging from 20～55 were measured with SP-2558 multifunctional spectrometer system. According to the multi-peak fitting on the line shape of spectrum,the characteristics and mechanism for urine spectrum were found. The results show that the strong urine fluorescence is caused by three inclusions: nicotinamide ade-nine nucleotide (NAD+) which is the metabolic intermediate of kidney, riboflavin and coproporphyrin. Their corresponding peaks are at 458nm,520nm,612nm and 674nm,and the latter two are generated by coproporphyrin. The difference between samples of youth and elderly is the peak intensity at 458nm, for the elderly women's contends of NAD+ in the urine is higher than that of the young due to the degeneration of kidney metabolic function.
In order to study the difference of urine fluorescence spectroscopy from healthy female, excited by 200nm～390nm ultraviolet light,the urine specimens of healthy women aging from 20～55 were measured with SP-2558 multifunctional spectrometer system. According to the multi-peak fitting on the line shape of spectrum,the characteristics and mechanism for urine spectrum were found. The results show that the strong urine fluorescence is caused by three inclusions: nicotinamide ade-nine nucleotide (NAD+) which is the metabolic intermediate of kidney, riboflavin and coproporphyrin. Their corresponding peaks are at 458nm,520nm,612nm and 674nm,and the latter two are generated by coproporphyrin. The difference between samples of youth and elderly is the peak intensity at 458nm, for the elderly women's contends of NAD+ in the urine is higher than that of the young due to the degeneration of kidney metabolic function.
2010, 34(1): 48-52.
doi: 10.3969/j.issn.1001-3806.2010.01.014
Abstract:
In order to study the effect of Nd3+ concentration on the fluorescence property at 1.3μm, Nd2O3-doped 0.70TeO2-(30-x)WO3-xNd2O3(mole fraction x is 0.001,0.003,0.005,0.007,0.010) tellurite glass was prepared by means of the conventional melt-quenching method. The fluorescence spectra were obtained. The dependence of the effective bandwidth and the stimulated emission cross-sections of 4F(3/2)→4I(13/2) transition on Nd3+ concentration was studied. Based on the electric dipole-dipole interaction theory,the interaction parameters,C(d,d),for the energy migration rate 4F(3/2), 4I(9/2)→4I(9/2),4F(3/2) and C(d,a),for cross relaxation rate 4F(3/2),4I(9/2)→4I(15/2),4I(15/2),and/or 4F(3/2),4I(9/2)→4I(13/2),4I(15/2) in tellurite glass are about 10.6×10-40 cm6/s and 2.80×10-40 cm6/s,respectively. The result shows that the fluorescence intensity drastically increases and has a maximum around 0.005(mole fraction) Nd2O3 and decreases with increase of the Nd2O3 concentration.
In order to study the effect of Nd3+ concentration on the fluorescence property at 1.3μm, Nd2O3-doped 0.70TeO2-(30-x)WO3-xNd2O3(mole fraction x is 0.001,0.003,0.005,0.007,0.010) tellurite glass was prepared by means of the conventional melt-quenching method. The fluorescence spectra were obtained. The dependence of the effective bandwidth and the stimulated emission cross-sections of 4F(3/2)→4I(13/2) transition on Nd3+ concentration was studied. Based on the electric dipole-dipole interaction theory,the interaction parameters,C(d,d),for the energy migration rate 4F(3/2), 4I(9/2)→4I(9/2),4F(3/2) and C(d,a),for cross relaxation rate 4F(3/2),4I(9/2)→4I(15/2),4I(15/2),and/or 4F(3/2),4I(9/2)→4I(13/2),4I(15/2) in tellurite glass are about 10.6×10-40 cm6/s and 2.80×10-40 cm6/s,respectively. The result shows that the fluorescence intensity drastically increases and has a maximum around 0.005(mole fraction) Nd2O3 and decreases with increase of the Nd2O3 concentration.
2010, 34(1): 53-55.
doi: 10.3969/j.issn.1001-3806.2010.01.015
Abstract:
A vector index effective model is used to analyze the effect of Er3+ on the nonlinear coefficient erbium-doped photonic crystal fibers. Through adjusting the structural parameters, including air hole radius r, hole-to-hole spacing Λ, refractive index of fiber core n and air-filling index ƒ, the nonlinear coefficient was simulated and analyzed and its change with structural parameters was obtained. The nonlinearity can be increased by doping rare-earth ion Er3+ in the fiber core, and it can changed at ease by varying the structural parameters so that it is feasible to obtain more applicable photonic crystal fibers.
A vector index effective model is used to analyze the effect of Er3+ on the nonlinear coefficient erbium-doped photonic crystal fibers. Through adjusting the structural parameters, including air hole radius r, hole-to-hole spacing Λ, refractive index of fiber core n and air-filling index ƒ, the nonlinear coefficient was simulated and analyzed and its change with structural parameters was obtained. The nonlinearity can be increased by doping rare-earth ion Er3+ in the fiber core, and it can changed at ease by varying the structural parameters so that it is feasible to obtain more applicable photonic crystal fibers.
2010, 34(1): 56-59.
doi: 10.3969/j.issn.1001-3806.2010.01.016
Abstract:
In order to improve the laser utilization and automation of high power laser processings new three-working-position automatic laser welding control system was designed based on programmable logic controller and movement controller. By means of queue by turns and time sharing method to use the output laser, the universal saw blades, helical tooth saw blades and the bits can be welded simultaneously. Every working position can finish the manual debugger or execute the laser processing. And the processing laser power will be controlled independently by the working position. The production efficiency was improved 50% when the control system was used on welding production line. The universal saw blades, helical tooth saw blades and the bits in Ø115mm～Ø600mm diameter and diamond drills in Ø20mm～Ø250mm diameter can be welded in the system. Furthermore, the system has full diagnosis and warning functions.
In order to improve the laser utilization and automation of high power laser processings new three-working-position automatic laser welding control system was designed based on programmable logic controller and movement controller. By means of queue by turns and time sharing method to use the output laser, the universal saw blades, helical tooth saw blades and the bits can be welded simultaneously. Every working position can finish the manual debugger or execute the laser processing. And the processing laser power will be controlled independently by the working position. The production efficiency was improved 50% when the control system was used on welding production line. The universal saw blades, helical tooth saw blades and the bits in Ø115mm～Ø600mm diameter and diamond drills in Ø20mm～Ø250mm diameter can be welded in the system. Furthermore, the system has full diagnosis and warning functions.
2010, 34(1): 60-62,66.
doi: 10.3969/j.issn.1001-3806.2010.01.017
Abstract:
In the technology of laser modulation, it is very difficult to produce bireflective symmetric beam splitting prism and parallel beam splitting prism with large shear difference because of technical and material restrictions. In order to improve the symmetry and parallelism of output beams of a polarization prism, two design schemes are presented from the perspective of the structure of bireflective prism. One scheme is to change angle parameters φ and β,which can not only ensure the symmetry of the splitting beam angle, but also broaden the splitting angle. Also, according to requirements, appropriate symmetric splitting angle can be obtained by choosing different angle parameters. Another scheme is to change one flat face of the exit facet into two convex faces,therefore,big shear difference can be obtained and the shear of the prism can be designed according to the customer's requirements. As a result, the application scope of the bireflective prism will be widened greatly. The calculated result is well in agreement with experiments.
In the technology of laser modulation, it is very difficult to produce bireflective symmetric beam splitting prism and parallel beam splitting prism with large shear difference because of technical and material restrictions. In order to improve the symmetry and parallelism of output beams of a polarization prism, two design schemes are presented from the perspective of the structure of bireflective prism. One scheme is to change angle parameters φ and β,which can not only ensure the symmetry of the splitting beam angle, but also broaden the splitting angle. Also, according to requirements, appropriate symmetric splitting angle can be obtained by choosing different angle parameters. Another scheme is to change one flat face of the exit facet into two convex faces,therefore,big shear difference can be obtained and the shear of the prism can be designed according to the customer's requirements. As a result, the application scope of the bireflective prism will be widened greatly. The calculated result is well in agreement with experiments.
2010, 34(1): 63-66.
doi: 10.3969/j.issn.1001-3806.2010.01.018
Abstract:
In order to study the probability distribution of counting signal amplitude in a laser airborne particle counter,the relationship between the probability distribution of counting signal amplitude,particles number density in the sampling air-flow, light-intensity uniformity of the sensitive volume and the speed distribution of the lamellar flow were theoretically analyzed. Then, the probability density distribution of the counting signal amplitudes was tested with a self-designed optical sensor with sheath-air inlet, and it matched well with the theoretical result. In a word, the results indicate that the probability distribution of counting signal amplitude is determined by both the intensity distribution of the sensitive volume and the space distribution of the particles number density, which proposes a theoretical basis for the design of the particle counter.
In order to study the probability distribution of counting signal amplitude in a laser airborne particle counter,the relationship between the probability distribution of counting signal amplitude,particles number density in the sampling air-flow, light-intensity uniformity of the sensitive volume and the speed distribution of the lamellar flow were theoretically analyzed. Then, the probability density distribution of the counting signal amplitudes was tested with a self-designed optical sensor with sheath-air inlet, and it matched well with the theoretical result. In a word, the results indicate that the probability distribution of counting signal amplitude is determined by both the intensity distribution of the sensitive volume and the space distribution of the particles number density, which proposes a theoretical basis for the design of the particle counter.
2010, 34(1): 67-70.
doi: 10.3969/j.issn.1001-3806.2010.01.019
Abstract:
In order to measure bubble diameter in transparent solid materials, the bubble diameter in the prism is measured by means of far-field interference. When parallel laser beam is irradiating the bubble in the prism, circular interference fringe is produced in the far-field. It is analyzed based on the far-field theoretical model. The interference fringes outside the prism is measured with spectrometer and a set of data of angle position of interference fringes is obtained and converted into the angle position of interference fringes inside the prism according to Snell's law and then bubble diameter is calculated with computing software MATHEMATICA. The results showed that the relative error is 0.2%,the measured diameter direction is incident laser beam direction and the demand for the bubble location over platform is not strict. When appropriate change in measurement method is made,the bubble diameter of transparent medium in other shape can also be measured. The result is helpful for studying the shape of the bubble in a transparent material.
In order to measure bubble diameter in transparent solid materials, the bubble diameter in the prism is measured by means of far-field interference. When parallel laser beam is irradiating the bubble in the prism, circular interference fringe is produced in the far-field. It is analyzed based on the far-field theoretical model. The interference fringes outside the prism is measured with spectrometer and a set of data of angle position of interference fringes is obtained and converted into the angle position of interference fringes inside the prism according to Snell's law and then bubble diameter is calculated with computing software MATHEMATICA. The results showed that the relative error is 0.2%,the measured diameter direction is incident laser beam direction and the demand for the bubble location over platform is not strict. When appropriate change in measurement method is made,the bubble diameter of transparent medium in other shape can also be measured. The result is helpful for studying the shape of the bubble in a transparent material.
2010, 34(1): 75-77.
doi: 10.3969/j.issn.1001-3806.2010.01.021
Abstract:
The band gap structure of face-centered cubic lattice of 3-D photonic crystal with sphere scatter was studied with the plane wave expansion method. The energy bands of the air sphere in medium and the medium sphere in air with different parameters were calculated. The results obviously prove that the wholly band gap of air sphere in medium will never exist at any parameter, and the wholly band gap of medium sphere in air will exist when suitable parameters are chosen. The relation between the width of band gap and the air sphere's radius is similar to that of the substrate's dielectric constant, while the relation between the band gap's center position and the radius of air sphere is dissimilar to that of the dielectric constant of the substrate. The conclusion extends and renews the relative fields.
The band gap structure of face-centered cubic lattice of 3-D photonic crystal with sphere scatter was studied with the plane wave expansion method. The energy bands of the air sphere in medium and the medium sphere in air with different parameters were calculated. The results obviously prove that the wholly band gap of air sphere in medium will never exist at any parameter, and the wholly band gap of medium sphere in air will exist when suitable parameters are chosen. The relation between the width of band gap and the air sphere's radius is similar to that of the substrate's dielectric constant, while the relation between the band gap's center position and the radius of air sphere is dissimilar to that of the dielectric constant of the substrate. The conclusion extends and renews the relative fields.
2010, 34(1): 78-80.
doi: 10.3969/j.issn.1001-3806.2010.01.022
Abstract:
In order to study the dynamic evolution and self-deflection of matching Gaussian beam in two-photon photorefractive media in external electric field, numerical simulation was used to obtain the dynamic evolution process and self-deflection graphics. The obtained results indicate that matching Gaussian beam can evolve into steady-state solitary wave for a given two-photon photorefractive crystal and the diffusion effect can cause self-deflection for the matching Gaussian beam. At first, the degree of self-deflection of matching Gaussian beam increases with the external electric field, however it decreases with the external electric field after a certain point. The relation between the degree of self-deflection of matching Gauss beam and the intensity of incident light is similar to external electric field.
In order to study the dynamic evolution and self-deflection of matching Gaussian beam in two-photon photorefractive media in external electric field, numerical simulation was used to obtain the dynamic evolution process and self-deflection graphics. The obtained results indicate that matching Gaussian beam can evolve into steady-state solitary wave for a given two-photon photorefractive crystal and the diffusion effect can cause self-deflection for the matching Gaussian beam. At first, the degree of self-deflection of matching Gaussian beam increases with the external electric field, however it decreases with the external electric field after a certain point. The relation between the degree of self-deflection of matching Gauss beam and the intensity of incident light is similar to external electric field.
2010, 34(1): 81-84.
doi: 10.3969/j.issn.1001-3806.2010.01.023
Abstract:
For the purpose of producing a phase plate for phase-contrast experiments, firstly, controlling the exposure time and washing process of a holographic plate, the thickness or refractive index of the film was changed so as to adjust the phase change. Secondly, with the help of two-point light sources interference phase measurement, the required phase plate was.detected and screened and its two-dimension phase distribution was obtained. Finally, a π/2 phase plate with a certain absorptivity was selected as a phase filter located in the spectrum surface of the lens in the experiment, and the predicated image was obtained on the image plane. The results in the phase detection and the phase-contrast experiments show that it is feasible to produce a phase plate with a holographic plate,and the phase and absorptivity of the phase plate can be designed at will. This is a simple,cheap and fast process to design, manufacture and measure a phase plate.
For the purpose of producing a phase plate for phase-contrast experiments, firstly, controlling the exposure time and washing process of a holographic plate, the thickness or refractive index of the film was changed so as to adjust the phase change. Secondly, with the help of two-point light sources interference phase measurement, the required phase plate was.detected and screened and its two-dimension phase distribution was obtained. Finally, a π/2 phase plate with a certain absorptivity was selected as a phase filter located in the spectrum surface of the lens in the experiment, and the predicated image was obtained on the image plane. The results in the phase detection and the phase-contrast experiments show that it is feasible to produce a phase plate with a holographic plate,and the phase and absorptivity of the phase plate can be designed at will. This is a simple,cheap and fast process to design, manufacture and measure a phase plate.
2010, 34(1): 85-87.
doi: 10.3969/j.issn.1001-3806.2010.01.024
Abstract:
In order to improve the diffraction efficiency of read out light,reasonable parameters must be selected. Combining Kogelnik coupling wave theory with the Kukhtarev equations, the expression of the diffraction efficiency of the transmission grating in paraelectric KTN crystal was obtained. After analyzing the factors affecting the diffraction efficiency of a grating,it was found that the reading diffraction efficiency was sensitive to incident angle, crystal thickness and applied field. A high diffraction efficiency district existed in close vicinity of 45° incident angle. The influence of absorption of crystal on reading diffraction efficiency was negligible. The results provide useful guides to choose the optimal parameters for high reading diffraction efficiency in application.
In order to improve the diffraction efficiency of read out light,reasonable parameters must be selected. Combining Kogelnik coupling wave theory with the Kukhtarev equations, the expression of the diffraction efficiency of the transmission grating in paraelectric KTN crystal was obtained. After analyzing the factors affecting the diffraction efficiency of a grating,it was found that the reading diffraction efficiency was sensitive to incident angle, crystal thickness and applied field. A high diffraction efficiency district existed in close vicinity of 45° incident angle. The influence of absorption of crystal on reading diffraction efficiency was negligible. The results provide useful guides to choose the optimal parameters for high reading diffraction efficiency in application.
2010, 34(1): 88-90,94.
doi: 10.3969/j.issn.1001-3806.2010.01.025
Abstract:
In order to get a dual-wavelength tunable CO2 laser, a two-resonator laser was developed, which consists of an output coupler and two diffraction gratings. The output pulse characteristics and tuning range were also analyzed experimentally. The experimental results indicate that the two resonators can oscillate independently. Two widely tunable laser pulses are generated without spatial competition. The temporal synchronization of the lines is controlled by rotating the gratings within a narrow range for varying their losses.
In order to get a dual-wavelength tunable CO2 laser, a two-resonator laser was developed, which consists of an output coupler and two diffraction gratings. The output pulse characteristics and tuning range were also analyzed experimentally. The experimental results indicate that the two resonators can oscillate independently. Two widely tunable laser pulses are generated without spatial competition. The temporal synchronization of the lines is controlled by rotating the gratings within a narrow range for varying their losses.
2010, 34(1): 91-94.
doi: 10.3969/j.issn.1001-3806.2010.01.026
Abstract:
In order to study the influence of defect on the surface acoustic wave, based on the theory of elastodynamics, the interaction between elastic surface acoustic waves and surface-breaking defect was simulated numerically by means of the finite element method. The interaction between the surface acoustic wave and surface-breaking defects in different depth and width was calculated, and the reflected and transmitted surface acoustic waves were obtained. And then the reflection and transmission coefficients were obtained by means of fast Fourier transform. The results show that the reflected and transmitted surface acoustic waves are induced by the interaction of defect on the acoustic wave. The reflection coefficient gradually increases and transmission coefficient decreases with the depth and width increasing.
In order to study the influence of defect on the surface acoustic wave, based on the theory of elastodynamics, the interaction between elastic surface acoustic waves and surface-breaking defect was simulated numerically by means of the finite element method. The interaction between the surface acoustic wave and surface-breaking defects in different depth and width was calculated, and the reflected and transmitted surface acoustic waves were obtained. And then the reflection and transmission coefficients were obtained by means of fast Fourier transform. The results show that the reflected and transmitted surface acoustic waves are induced by the interaction of defect on the acoustic wave. The reflection coefficient gradually increases and transmission coefficient decreases with the depth and width increasing.
2010, 34(1): 95-98.
doi: 10.3969/j.issn.1001-3806.2010.01.027
Abstract:
In order to study the effect of laser power density on laser shock formability of aluminum alloy sheet, the forming limit, depth, thickness and stress distribution of the sheet were simulated under different laser power density and different number of laser shock. The results show that fracture is prone to happen in the centre of sheet and the forming limit is inversely proportional to the laser power density,but directly proportional to the number of laser shock. The formability of aluminum alloy sheet can be optimized through proper choice of laser energy and the number of laser shock.
In order to study the effect of laser power density on laser shock formability of aluminum alloy sheet, the forming limit, depth, thickness and stress distribution of the sheet were simulated under different laser power density and different number of laser shock. The results show that fracture is prone to happen in the centre of sheet and the forming limit is inversely proportional to the laser power density,but directly proportional to the number of laser shock. The formability of aluminum alloy sheet can be optimized through proper choice of laser energy and the number of laser shock.
2010, 34(1): 99-101.
doi: 10.3969/j.issn.1001-3806.2010.01.028
Abstract:
In order to study the polarization property of a laser radiation side-scattered by randomly distributed particles in different diameters, various concentrations of suspending liquid, consisting of distilled water and particles in diameters of 0.22μm or 0.494μm, was served as the scattering medium. Through theoretical analysis and experiments, the data of polarization degree in different depths and at different angles scattered by 0.22μm particles were acquired,and the data of horizontal polarization and vertical polarization scattered by 0.22μm and 0.494μm particles in three different concentrations of suspending liquid were also obtained respectively. The experiment results show that the de-polarization of radiation side-scattered by the particles is very sensitive to the variation of the diameters of the particles,i. e.,the horizontal polarization degree of the radiation scattered by the particles in smaller diameters is much higher than that scattered by the particles in larger diameters. However,it is inverse for the vertical polarization degree. The result is helpful to test the diameter of particles under the condition of multiple particles (especially for the particles'diameter less than 1μm).
In order to study the polarization property of a laser radiation side-scattered by randomly distributed particles in different diameters, various concentrations of suspending liquid, consisting of distilled water and particles in diameters of 0.22μm or 0.494μm, was served as the scattering medium. Through theoretical analysis and experiments, the data of polarization degree in different depths and at different angles scattered by 0.22μm particles were acquired,and the data of horizontal polarization and vertical polarization scattered by 0.22μm and 0.494μm particles in three different concentrations of suspending liquid were also obtained respectively. The experiment results show that the de-polarization of radiation side-scattered by the particles is very sensitive to the variation of the diameters of the particles,i. e.,the horizontal polarization degree of the radiation scattered by the particles in smaller diameters is much higher than that scattered by the particles in larger diameters. However,it is inverse for the vertical polarization degree. The result is helpful to test the diameter of particles under the condition of multiple particles (especially for the particles'diameter less than 1μm).
2010, 34(1): 102-104.
doi: 10.3969/j.issn.1001-3806.2010.01.029
Abstract:
In order to reduce sideband spectral energy and improve image lining of a quartz filter,a novel filter structure was designed and its characteristics were analyzed theoretically. Taking a three-level quartz filter for example, its sideband energy can be reduced efficiently by adding the same structure as the first or second level after the third level. Comparatively speaking,it is better to add a structure the same as the second level. The outcome provides academic gist to reduce sideband energy in spectral observation.
In order to reduce sideband spectral energy and improve image lining of a quartz filter,a novel filter structure was designed and its characteristics were analyzed theoretically. Taking a three-level quartz filter for example, its sideband energy can be reduced efficiently by adding the same structure as the first or second level after the third level. Comparatively speaking,it is better to add a structure the same as the second level. The outcome provides academic gist to reduce sideband energy in spectral observation.
2010, 34(1): 105-108.
doi: 10.3969/j.issn.1001-3806.2010.01.030
Abstract:
In order to study the characteristics of the frequency of acoustic waves induced by high power laser, the acoustic waves were received by a wide band acoustic sensor. Then they were imported to MATLAB and calculated to obtain the power spectral density (PSD). After the analysis of the PSD of the acoustic waves induced by Nd:glass laser with water or K9 optical glass under different conditions as overlay,the frequencies at the maximum peak of the PSD were obtained. It is discovered that the frequencies are strongly influenced by different overlay or the overlay under different conditions, instead of the laser power density. The outcome provides important guiding significance to the realization of the on-line monitoring of the laser shock processing.
In order to study the characteristics of the frequency of acoustic waves induced by high power laser, the acoustic waves were received by a wide band acoustic sensor. Then they were imported to MATLAB and calculated to obtain the power spectral density (PSD). After the analysis of the PSD of the acoustic waves induced by Nd:glass laser with water or K9 optical glass under different conditions as overlay,the frequencies at the maximum peak of the PSD were obtained. It is discovered that the frequencies are strongly influenced by different overlay or the overlay under different conditions, instead of the laser power density. The outcome provides important guiding significance to the realization of the on-line monitoring of the laser shock processing.
2010, 34(1): 109-111,119.
doi: 10.3969/j.issn.1001-3806.2010.01.031
Abstract:
In order to study the effect of Wollaston prism on the intensity of single-mode Gaussian beam,the transmitting o light and e light were studied respectively by analyzing interference in the prism cementing layer. For a given single-mode Gaussian beam merged with two polarizing modes,the transmission polarizing light intensity of o and e oscillates in period with the incident light angle at the interface of the cementing layer, the thickness of the cementing layer, and the refracting index of the transmitter in the cementing layer,and that the amplitude and frequency of the oscillation change with them too. But in general,the effect on the transmitted Gaussian beam is less than 0.65%. In practice,if the relative intensity is required larger than 0.65%, the effect of Wollaston prism on the transmitting characteristics of Gaussian beam can be neglected.
In order to study the effect of Wollaston prism on the intensity of single-mode Gaussian beam,the transmitting o light and e light were studied respectively by analyzing interference in the prism cementing layer. For a given single-mode Gaussian beam merged with two polarizing modes,the transmission polarizing light intensity of o and e oscillates in period with the incident light angle at the interface of the cementing layer, the thickness of the cementing layer, and the refracting index of the transmitter in the cementing layer,and that the amplitude and frequency of the oscillation change with them too. But in general,the effect on the transmitted Gaussian beam is less than 0.65%. In practice,if the relative intensity is required larger than 0.65%, the effect of Wollaston prism on the transmitting characteristics of Gaussian beam can be neglected.
2010, 34(1): 112-115.
doi: 10.3969/j.issn.1001-3806.2010.01.032
Abstract:
In order to improve the contrast of a reconstructed image and reduce the effect of directly transmitted light, conjugate image and defocused image on the focused image of the particle in the reconstruction of a 3-D particle digital holography,a numerical method was proposed in which the above effect can be reduced because of the subtraction of both the complex amplitudes of the particle in the focused and defocused planes. The theory of the method was presented. The simulated results and experimental examples were shown. This method is useful to slice in-line digital holograms to display only in-focus particles at a focused plane. Furthermore,in the reconstruction process,only a single hologram is needed without additional pre- or post- processing.
In order to improve the contrast of a reconstructed image and reduce the effect of directly transmitted light, conjugate image and defocused image on the focused image of the particle in the reconstruction of a 3-D particle digital holography,a numerical method was proposed in which the above effect can be reduced because of the subtraction of both the complex amplitudes of the particle in the focused and defocused planes. The theory of the method was presented. The simulated results and experimental examples were shown. This method is useful to slice in-line digital holograms to display only in-focus particles at a focused plane. Furthermore,in the reconstruction process,only a single hologram is needed without additional pre- or post- processing.
2010, 34(1): 116-119.
doi: 10.3969/j.issn.1001-3806.2010.01.033
Abstract:
In order to study the effect of technical parameters on the performance of high density polyethylene (HDPE) plastic welding pieces,with laser permeating a weld HDPE workpiece,mechanical tensile test was carried out and the morphology of the joint fracture was observed with a scanning electron microscopy. Results show that the joint intensity and elongation property accrete with smaller light spot and welding velocity and larger laser power. The welding joint is good and mechanical property is best with laser spot diameter in 2mm,laser power at 75W and welding velocity at 2mm/s. It is proved that laser welding HDPE is a feasible.
In order to study the effect of technical parameters on the performance of high density polyethylene (HDPE) plastic welding pieces,with laser permeating a weld HDPE workpiece,mechanical tensile test was carried out and the morphology of the joint fracture was observed with a scanning electron microscopy. Results show that the joint intensity and elongation property accrete with smaller light spot and welding velocity and larger laser power. The welding joint is good and mechanical property is best with laser spot diameter in 2mm,laser power at 75W and welding velocity at 2mm/s. It is proved that laser welding HDPE is a feasible.
2010, 34(1): 120-123.
doi: 10.3969/j.issn.1001-3806.2010.01.034
Abstract:
In order to study the red-shifted radiation generation in a photonic crystal fiber with two zero dispersion wavelengths in the anomalous dispersion region,the nonlinear propagation and red-shifted radiation generation of a femtosecond laser pulse in a photonic crystal fiber were simulated with the split-step Fourier algorithm. The effect of pulse width, center wavelength and input peak power of the pump pulse on the red-shifted radiation was analyzed. It is found the phenomenon of redshifted radiation of Raman soliton caused by higher-order dispersion occurs when the pump wavelength is located in the anomalous dispersion region nearby the second zero dispersion wavelength. The intensity of red-shifted radiation components can be enhanced with the input peak power or pulse width increased. In addition,the three-order dispersion effect also has an important effect on the red-shifted radiation. The intensity of red-shifted radiation components can be further enhanced by increasing the three-order dispersion coefficient.
In order to study the red-shifted radiation generation in a photonic crystal fiber with two zero dispersion wavelengths in the anomalous dispersion region,the nonlinear propagation and red-shifted radiation generation of a femtosecond laser pulse in a photonic crystal fiber were simulated with the split-step Fourier algorithm. The effect of pulse width, center wavelength and input peak power of the pump pulse on the red-shifted radiation was analyzed. It is found the phenomenon of redshifted radiation of Raman soliton caused by higher-order dispersion occurs when the pump wavelength is located in the anomalous dispersion region nearby the second zero dispersion wavelength. The intensity of red-shifted radiation components can be enhanced with the input peak power or pulse width increased. In addition,the three-order dispersion effect also has an important effect on the red-shifted radiation. The intensity of red-shifted radiation components can be further enhanced by increasing the three-order dispersion coefficient.
2010, 34(1): 124-127,131.
doi: 10.3969/j.issn.1001-3806.2010.01.035
Abstract:
Based on the expression of diffractive field distribution of the Gaussian beams restricted by a rectangular aperture and focalized by a lens, the relationship between the width of the rectangular aperture and the spot size of the restricted beam, as well as the relationship between the aperture width and the power in the bucket,was numerically calculated with MATLAB. It was illuminated that the width of the centre bright fringe decreased along with the increasing width of the rectangular aperture when the effect of the aperture on the beam couldn't be ignored, however, the width of centre bright fringe step changed with increase of the size of the aperture when the effect could be ignorable, the width of the half maximum intensity of the centre bright fringe decreased along with the accretion of the width of the aperture and then it tends to a constant. The piecewise function of the relationship between the full width at half maximum(FWHM) of the centre bright fringe and the rectangular aperture width was put forward as well. The conclusions are useful for the design of a laser facility.
Based on the expression of diffractive field distribution of the Gaussian beams restricted by a rectangular aperture and focalized by a lens, the relationship between the width of the rectangular aperture and the spot size of the restricted beam, as well as the relationship between the aperture width and the power in the bucket,was numerically calculated with MATLAB. It was illuminated that the width of the centre bright fringe decreased along with the increasing width of the rectangular aperture when the effect of the aperture on the beam couldn't be ignored, however, the width of centre bright fringe step changed with increase of the size of the aperture when the effect could be ignorable, the width of the half maximum intensity of the centre bright fringe decreased along with the accretion of the width of the aperture and then it tends to a constant. The piecewise function of the relationship between the full width at half maximum(FWHM) of the centre bright fringe and the rectangular aperture width was put forward as well. The conclusions are useful for the design of a laser facility.
2010, 34(1): 128-131.
doi: 10.3969/j.issn.1001-3806.2010.01.036
Abstract:
In order to optimize the output beam quality of a multimode fiber amplifier,a novel mode control method, gain-loss-management (GLM), was proposed. The mode discrimination for optimized gain distribution and additionally incorporated loss distribution was analyzed. The effect of the various dopant profiles was discussed, and the method to design GLM fiber was obtained. The results show that GLM method can efficiently suppress the power of higher-order modes in multimode cores and the output percentage of the fundamental mode can exceed 90%.
In order to optimize the output beam quality of a multimode fiber amplifier,a novel mode control method, gain-loss-management (GLM), was proposed. The mode discrimination for optimized gain distribution and additionally incorporated loss distribution was analyzed. The effect of the various dopant profiles was discussed, and the method to design GLM fiber was obtained. The results show that GLM method can efficiently suppress the power of higher-order modes in multimode cores and the output percentage of the fundamental mode can exceed 90%.
2010, 34(1): 132-134.
doi: 10.3969/j.issn.1001-3806.2010.01.037
Abstract:
In order to study the detection sensitivity of a starring laser detecting system, considering the features of the starring laser detecting system and the fact that the detected laser energy varying with different view field angle, based on the available measure condition in laboratory,an indirect method was presented to test the detection sensitivity in laboratory. Probable problems in each part of the design were analyzed, and their resolution methods were put forward accordingly. Based on the experimental setup, experiments were carried out and the detection sensitivity was obtained at seven view angles.the detection sensitivity in center view field reaches 0.259nJ/cm2 with a relative deviation of 3.4%～4.2%. The measurement error was also theoretically analyzed. The test results confirm that the method is feasible and practical, and the accuracy meets the requirement. This method is useful for the design of high precision test systems.
In order to study the detection sensitivity of a starring laser detecting system, considering the features of the starring laser detecting system and the fact that the detected laser energy varying with different view field angle, based on the available measure condition in laboratory,an indirect method was presented to test the detection sensitivity in laboratory. Probable problems in each part of the design were analyzed, and their resolution methods were put forward accordingly. Based on the experimental setup, experiments were carried out and the detection sensitivity was obtained at seven view angles.the detection sensitivity in center view field reaches 0.259nJ/cm2 with a relative deviation of 3.4%～4.2%. The measurement error was also theoretically analyzed. The test results confirm that the method is feasible and practical, and the accuracy meets the requirement. This method is useful for the design of high precision test systems.
2010, 34(1): 135-137,140.
doi: 10.3969/j.issn.1001-3806.2010.01.038
Abstract:
In order to develop laser modes in stable resonators, an analytical method was adopted to resolve the field distribution of the laser modes in stable optical resonators. The expressions for the laser modes were derived after seeking simple solutions to Maxwell's equations. The plots of the field intensity distribution corresponding to some laser modes in plan-concave Nd:YAG laser were shown. The theory of laser modes in stable resonators was enhanced.
In order to develop laser modes in stable resonators, an analytical method was adopted to resolve the field distribution of the laser modes in stable optical resonators. The expressions for the laser modes were derived after seeking simple solutions to Maxwell's equations. The plots of the field intensity distribution corresponding to some laser modes in plan-concave Nd:YAG laser were shown. The theory of laser modes in stable resonators was enhanced.
2010, 34(1): 138-140.
doi: 10.3969/j.issn.1001-3806.2010.01.039
Abstract:
In order to study spectral beam combining of a laser diode array (LDA) based on grating-cavity, coupling efficiency model with abaxial aberration was adopted to analyze the effect of the system parameters on the coupling efficiency. The coupling efficiency decreased when abaxial distance or the order of mode increased, and the linewidth of emitters could be compressed to 0.05nm. A LDA comprised of 19 emitters was spectrally combined by means of grating-cavity with 10.1W CW output power,0.45W/A slope efficiency and beam quality factor Mx2 of 17.6 along the slow axis. Spectrum width of the LDA was broaden to 15nm,and linewidth of a single emitter was compressed to 0.1nm. It is shown that spectral beam combining can improve beam quality of a LDA and narrow linewidth of emitters.
In order to study spectral beam combining of a laser diode array (LDA) based on grating-cavity, coupling efficiency model with abaxial aberration was adopted to analyze the effect of the system parameters on the coupling efficiency. The coupling efficiency decreased when abaxial distance or the order of mode increased, and the linewidth of emitters could be compressed to 0.05nm. A LDA comprised of 19 emitters was spectrally combined by means of grating-cavity with 10.1W CW output power,0.45W/A slope efficiency and beam quality factor Mx2 of 17.6 along the slow axis. Spectrum width of the LDA was broaden to 15nm,and linewidth of a single emitter was compressed to 0.1nm. It is shown that spectral beam combining can improve beam quality of a LDA and narrow linewidth of emitters.
2010, 34(1): 141-144.
doi: 10.3969/j.issn.1001-3806.2010.01.040
Abstract:
For studying the axial intensity distribution of limited Laguerre-Gaussian beams in turbulent atmosphere, the axial intensity expression of the Laguerre-Gaussian beams limited by a circular aperture in atmospheric turbulence was obtained based on expanding Huygens-Fresnel principle. The theoretical axial intensity under conditions of different intensity of turbulence, wavelength and transmit aperture was simulated by means of MAPLE. The results indicate the axial intensity increases obviously in the near-field, after it reach the largest and then begin to decrease obviously when the Laguerre-Gaussian beams in vacuum or low atmospheric turbulence. The axial intensity is attenuated rapidly as the Laguerre-Gaussian beams propagate close quarters in rather strong atmospheric turbulence under different intensity of turbulence, wavelength and transmit aperture. Which were compared with that in vacuum. This result is helpful in studying Laguerre-Gaussian beams.
For studying the axial intensity distribution of limited Laguerre-Gaussian beams in turbulent atmosphere, the axial intensity expression of the Laguerre-Gaussian beams limited by a circular aperture in atmospheric turbulence was obtained based on expanding Huygens-Fresnel principle. The theoretical axial intensity under conditions of different intensity of turbulence, wavelength and transmit aperture was simulated by means of MAPLE. The results indicate the axial intensity increases obviously in the near-field, after it reach the largest and then begin to decrease obviously when the Laguerre-Gaussian beams in vacuum or low atmospheric turbulence. The axial intensity is attenuated rapidly as the Laguerre-Gaussian beams propagate close quarters in rather strong atmospheric turbulence under different intensity of turbulence, wavelength and transmit aperture. Which were compared with that in vacuum. This result is helpful in studying Laguerre-Gaussian beams.
2010, 34(1): 71-74,144.
doi: 10.3969/j.issn.1001-3806.2010.01.020
Abstract:
The latest development of guided-mode resonance filters was reviewed. Then its mechanics, advantages and application fields were summarized. The design of single, double and triple-layer of sub-wavelength guided-mode resonance filters was described in detail. After discussing its fabrication principle, the fabrication difficulties and key technology of guided-mode resonance filters were presented. It is concluded that guided-mode resonance filters exhibit excellent characteristics with high reflectance, low sidebands, narrow band and controllable spectral width, which have important research meanings and application value.
The latest development of guided-mode resonance filters was reviewed. Then its mechanics, advantages and application fields were summarized. The design of single, double and triple-layer of sub-wavelength guided-mode resonance filters was described in detail. After discussing its fabrication principle, the fabrication difficulties and key technology of guided-mode resonance filters were presented. It is concluded that guided-mode resonance filters exhibit excellent characteristics with high reflectance, low sidebands, narrow band and controllable spectral width, which have important research meanings and application value.
