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RSS2012 Vol. 36, No. 3
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2012, 36(3): 293-297.
[Abstract]
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Abstract:
Laser dicing semiconductor wafer has advantages of narrow kerf,non-contact processing and high dicing velocity etc.However,there still exist some problems,such as redeposition of melting material,large heat affected zone and cracking easily.In order to overcome these problems,the causes were analyzed and a series of newly-developed methods were introduced in detail from three aspects,i.e.,lasers,optical systems and processing mediums.Simultaneously,the basic principles were described.Furthermore,advantages,disadvantages and applications of laser dicing technique were analyzed,which provides valuable technical references for further research and industrial applications.
Laser dicing semiconductor wafer has advantages of narrow kerf,non-contact processing and high dicing velocity etc.However,there still exist some problems,such as redeposition of melting material,large heat affected zone and cracking easily.In order to overcome these problems,the causes were analyzed and a series of newly-developed methods were introduced in detail from three aspects,i.e.,lasers,optical systems and processing mediums.Simultaneously,the basic principles were described.Furthermore,advantages,disadvantages and applications of laser dicing technique were analyzed,which provides valuable technical references for further research and industrial applications.
2012, 36(3): 298-300.
Abstract:
In order to meet the need of micro forming technology industrialization,a new method,micro-forming spallation delamination micro-forming of substrate/metal thin films under laser driven flyer,was discussed.Combining with laser radiation effect and wave reflection,spallation delamination micro-forming mechanism was expounded.The spallation process of substrate/metal thin film was optimized and strain rate of layers lobes and peak pressure of laser-induced shock wave were estimated according to the principle of conservation of energy.It was found that the spallation of phenomenon of workpieces became apparent with increase of pulse energy,until metal thin films appeared the same structure characteristics as micro-structure of the template,but the substrate remained intact without cracks or deformation.It shows that it's available to achieve spallation and micro-forming of substrate/thin film under laser driven flyer loading.
In order to meet the need of micro forming technology industrialization,a new method,micro-forming spallation delamination micro-forming of substrate/metal thin films under laser driven flyer,was discussed.Combining with laser radiation effect and wave reflection,spallation delamination micro-forming mechanism was expounded.The spallation process of substrate/metal thin film was optimized and strain rate of layers lobes and peak pressure of laser-induced shock wave were estimated according to the principle of conservation of energy.It was found that the spallation of phenomenon of workpieces became apparent with increase of pulse energy,until metal thin films appeared the same structure characteristics as micro-structure of the template,but the substrate remained intact without cracks or deformation.It shows that it's available to achieve spallation and micro-forming of substrate/thin film under laser driven flyer loading.
2012, 36(3): 301-306,311.
Abstract:
In order to investigate the feasibility of direct manufacturing customized lingual brackets by selective laser melting,firstly,a 3-D scanner was used to acquire and reconstruct teeth model,which was based on the customized lingual brackets designing with 3-D software;then customized metal lingual brackets were directly manufactured with a self-developed selective laser melting apparatus;finally the slot width of the bracket on front teeth was measured.The analysis shows that the teeth model obtained from the three dimensional laser scanner can meet the requirements for customized lingual brackets designing,and customized metal lingual brackets that can well fitted with teeth model can be produced precisely by selective laser melting process.Compared with the designed value 0.460mm on CAD model,the slot width of the front teeth was measured 0.471mm±0.009mm.The research proves it is feasible to manufacture precise and well fitted customized metal lingual brackets by means of selective laser melting technique.
In order to investigate the feasibility of direct manufacturing customized lingual brackets by selective laser melting,firstly,a 3-D scanner was used to acquire and reconstruct teeth model,which was based on the customized lingual brackets designing with 3-D software;then customized metal lingual brackets were directly manufactured with a self-developed selective laser melting apparatus;finally the slot width of the bracket on front teeth was measured.The analysis shows that the teeth model obtained from the three dimensional laser scanner can meet the requirements for customized lingual brackets designing,and customized metal lingual brackets that can well fitted with teeth model can be produced precisely by selective laser melting process.Compared with the designed value 0.460mm on CAD model,the slot width of the front teeth was measured 0.471mm±0.009mm.The research proves it is feasible to manufacture precise and well fitted customized metal lingual brackets by means of selective laser melting technique.
2012, 36(3): 307-311.
Abstract:
In order to solve the "mosaic" problem in plateau histogram enhancement algorithms,a novel method was proposed based on statistics,reuse of accumulated space and lossless compression.After theoretical analysis and simulation,the new algorithm reduces memory requirement more than 85%,but the time complexity keeps the same level as the original plateau histogram equalization.As a result,the processing space of plateau histogram equalization is greatly compressed by this improved algorithm,the difficulty of algorithm realization caused by the shortage of running memory of operating chips in infrared real time imaging system is solved and the requirements of practical application are achieved.
In order to solve the "mosaic" problem in plateau histogram enhancement algorithms,a novel method was proposed based on statistics,reuse of accumulated space and lossless compression.After theoretical analysis and simulation,the new algorithm reduces memory requirement more than 85%,but the time complexity keeps the same level as the original plateau histogram equalization.As a result,the processing space of plateau histogram equalization is greatly compressed by this improved algorithm,the difficulty of algorithm realization caused by the shortage of running memory of operating chips in infrared real time imaging system is solved and the requirements of practical application are achieved.
2012, 36(3): 312-314,329.
Abstract:
Considering graded-index reflective coating with high surface electric field and low surface damage threshold,a compensation process of reflection-induced retardance is applied for reducing the surface electric field of graded-index reflective coating.To achieve this compensation,without generating another interface,a uniform thin layer should be added on the surface of graded-index reflectance coating.This method obviously reduces the surface electric field.But it makes the central wavelength of reflective coating appreciably drift.However,comparing to reflectance bandwidth,this drift is so little that it can be ignored.This study will play an important role in designing graded-index reflectance coating with high damage threshold.
Considering graded-index reflective coating with high surface electric field and low surface damage threshold,a compensation process of reflection-induced retardance is applied for reducing the surface electric field of graded-index reflective coating.To achieve this compensation,without generating another interface,a uniform thin layer should be added on the surface of graded-index reflectance coating.This method obviously reduces the surface electric field.But it makes the central wavelength of reflective coating appreciably drift.However,comparing to reflectance bandwidth,this drift is so little that it can be ignored.This study will play an important role in designing graded-index reflectance coating with high damage threshold.
2012, 36(3): 315-317,432.
Abstract:
Image-converter tube streak cameras are commonly used in study on ultra-high speed physical phenomena.The sweep speed and its nonlinearity are main parameters of an image-converter tube streak camera and its accuracy has great effect on experimental results of ultra-high speed physical phenomena.The cause of nonlinearity was explained in theory.A method was introduced to calibrate the sweep speed and its nonlinearity,in which a picosecond light pulse source,an etalon and a high precision time delay device was used.Better experimental results were obtained with ±3.52% maximum nonlinearity of the sweep speed and its relative error of measurement was ±1.4%,which improved the reliability of experimental data processing and analysis effectively.
Image-converter tube streak cameras are commonly used in study on ultra-high speed physical phenomena.The sweep speed and its nonlinearity are main parameters of an image-converter tube streak camera and its accuracy has great effect on experimental results of ultra-high speed physical phenomena.The cause of nonlinearity was explained in theory.A method was introduced to calibrate the sweep speed and its nonlinearity,in which a picosecond light pulse source,an etalon and a high precision time delay device was used.Better experimental results were obtained with ±3.52% maximum nonlinearity of the sweep speed and its relative error of measurement was ±1.4%,which improved the reliability of experimental data processing and analysis effectively.
2012, 36(3): 318-321,325.
Abstract:
In order to compress 905nm semiconductor laser for remote distance measurement,based on geometrical optical theory,an alignment system composed of two vertical elliptical cylindrical lens was designed,then simulation was carried out in the non-sequential mode of ZEMAX software.Initial divergent angles of a semiconductor laser at fast axis and slow axis are 30° and 15° respectively.After passing through the cylindrical lens,these divergent angles became greatly compressed in both directions.After collimation,the divergent angles became 4.4mrad and 3.6mrad at fast axis and slow axis respectively,meeting the requirement of a remote distance detection lidar.The results show that the elliptical cylindrical lenses have good effect on semiconductor laser collimation.
In order to compress 905nm semiconductor laser for remote distance measurement,based on geometrical optical theory,an alignment system composed of two vertical elliptical cylindrical lens was designed,then simulation was carried out in the non-sequential mode of ZEMAX software.Initial divergent angles of a semiconductor laser at fast axis and slow axis are 30° and 15° respectively.After passing through the cylindrical lens,these divergent angles became greatly compressed in both directions.After collimation,the divergent angles became 4.4mrad and 3.6mrad at fast axis and slow axis respectively,meeting the requirement of a remote distance detection lidar.The results show that the elliptical cylindrical lenses have good effect on semiconductor laser collimation.
2012, 36(3): 322-325.
Abstract:
A series of nano-crystalline silicon films were deposited maintaining the same distance between the target and substrate by means of a pulse laser deposition system.The crystalline volume fraction of films and the average grain size were calculated based on Raman scattering and X-ray diffraction spectra.The results show that with the increase of the pulse energy,the average grain size becomes larger at first,and then goes smaller.The largest average grain size is 8.58nm when the pulse laser energy is 300mJ.The results have positive significance to the preparation of nano-crystalline silicon thin film.
A series of nano-crystalline silicon films were deposited maintaining the same distance between the target and substrate by means of a pulse laser deposition system.The crystalline volume fraction of films and the average grain size were calculated based on Raman scattering and X-ray diffraction spectra.The results show that with the increase of the pulse energy,the average grain size becomes larger at first,and then goes smaller.The largest average grain size is 8.58nm when the pulse laser energy is 300mJ.The results have positive significance to the preparation of nano-crystalline silicon thin film.
2012, 36(3): 326-329.
Abstract:
For responding to the weak signal and narrow pulse width feature of echo signals in pulse laser fuze and getting enough no distortion information of objectives,the feature of photodiode detector and the bandwidth of amplifier circuit were analyzed,and then an practical photoelectric conversion system was designed,including the PIN detector circuit,pre-amplifier circuit and main amplifier circuit.Through the actual experiments and simulation with the TINA and MULTISIM softwares,the bandwidth was 61.089MHz and the gain was 72.14dB.The result shows that the echo signal with pulse width more than 10ns was amplified with low noise and no distortion,which meets the designed requirements.The processed signals match the need of the following control system.
For responding to the weak signal and narrow pulse width feature of echo signals in pulse laser fuze and getting enough no distortion information of objectives,the feature of photodiode detector and the bandwidth of amplifier circuit were analyzed,and then an practical photoelectric conversion system was designed,including the PIN detector circuit,pre-amplifier circuit and main amplifier circuit.Through the actual experiments and simulation with the TINA and MULTISIM softwares,the bandwidth was 61.089MHz and the gain was 72.14dB.The result shows that the echo signal with pulse width more than 10ns was amplified with low noise and no distortion,which meets the designed requirements.The processed signals match the need of the following control system.
2012, 36(3): 330-333,345.
Abstract:
In order to study the nonlinear optical properties of C60 derivative,a new bridged C60 derivative was prepared through the interaction between 5-(2-methylthio-4-methyl-5-pyrimidinyl)-2,4-pentadiyne-1-olsorbate and C60.The molecular structure was identified and characterized by MALDI-TOF-MS,IR,UV-vis,1H NMR,DEPT and 13C NMR spectra.The optical nonlinear properties were investigated by z-scan technique and optical limiting experiment with Q-switched,double frequency ns/ps Nd:YAG laser pulse.The experimental results show that the values of third-order optical nonlinear susceptibilities (3) and nonlinear absorption coefficient .The lower value of optical limiting clamp of C60 derivative were also found.It has a good optical limiting performance.
In order to study the nonlinear optical properties of C60 derivative,a new bridged C60 derivative was prepared through the interaction between 5-(2-methylthio-4-methyl-5-pyrimidinyl)-2,4-pentadiyne-1-olsorbate and C60.The molecular structure was identified and characterized by MALDI-TOF-MS,IR,UV-vis,1H NMR,DEPT and 13C NMR spectra.The optical nonlinear properties were investigated by z-scan technique and optical limiting experiment with Q-switched,double frequency ns/ps Nd:YAG laser pulse.The experimental results show that the values of third-order optical nonlinear susceptibilities (3) and nonlinear absorption coefficient .The lower value of optical limiting clamp of C60 derivative were also found.It has a good optical limiting performance.
2012, 36(3): 334-337,389.
Abstract:
Performance of optical wireless communication system based on binary pulse position modulation(BPPM) and low-density parity-check(LDPC) code through atmospheric turbulence channel was investigated in the both situations of perfect channel state information(CSI) and non-channel state information(NCSI)compared with LDPC coded optical wireless communication system based on on-off keying(OOK)with the same bite rate and the same average transmission power.Simulation results show that in the both situations of CSI and NCSI,optical wireless communication systems based on LDPC code and BPPM have more excellent bit error rate performance than that of LDPC coded optical wireless communication systems based on OOK,and when decoded with the average fading amplitude as an estimate of the NCSI channel,performance of optical wireless communication system based on LDPC and BPPM are not degraded too much compared to the CSI channel,and it was also found that LDPC coded optical wireless communication systems based on BPPM are less sensitive to turbulent intensity than the systems based on OOK.Therefore,in the situation of NCSI,LDPC coded optical wireless communication systems based on BPPM have excellent error correction capabilities and access to a larger coding gains,and the above scheme is well suited for optical wireless communication systems.
Performance of optical wireless communication system based on binary pulse position modulation(BPPM) and low-density parity-check(LDPC) code through atmospheric turbulence channel was investigated in the both situations of perfect channel state information(CSI) and non-channel state information(NCSI)compared with LDPC coded optical wireless communication system based on on-off keying(OOK)with the same bite rate and the same average transmission power.Simulation results show that in the both situations of CSI and NCSI,optical wireless communication systems based on LDPC code and BPPM have more excellent bit error rate performance than that of LDPC coded optical wireless communication systems based on OOK,and when decoded with the average fading amplitude as an estimate of the NCSI channel,performance of optical wireless communication system based on LDPC and BPPM are not degraded too much compared to the CSI channel,and it was also found that LDPC coded optical wireless communication systems based on BPPM are less sensitive to turbulent intensity than the systems based on OOK.Therefore,in the situation of NCSI,LDPC coded optical wireless communication systems based on BPPM have excellent error correction capabilities and access to a larger coding gains,and the above scheme is well suited for optical wireless communication systems.
2012, 36(3): 338-341.
Abstract:
In order to study effect of different parameters on coupling efficiency between a semiconductor laser and a single-mode fiber with a ball lens,its optical transmission model was established.Based on ABCD matrix and the coupling theory of Gaussian beam to a single-mode fiber,its coupling efficiency was calculated.The parameter tolerances were obtained when the coupling efficiency decreased 0.5dB and the ball lens was in 0.5mm radius.Combined with coupling efficiency calculation model,the coupling efficiency distribution was simulated with Monte Carlo method when the parameters met the normal distribution.The result shows that maximum efficiency reaches 0.616 and the maximum likely efficiency is 0.585.The efficiency improves significantly as the parameters' tolerances reduce by half.But further narrowing of tolerances can't enhance the efficiency obviously.The research approach is instructive for selection of alignment units and estimation of coupling efficiency in laser device package.
In order to study effect of different parameters on coupling efficiency between a semiconductor laser and a single-mode fiber with a ball lens,its optical transmission model was established.Based on ABCD matrix and the coupling theory of Gaussian beam to a single-mode fiber,its coupling efficiency was calculated.The parameter tolerances were obtained when the coupling efficiency decreased 0.5dB and the ball lens was in 0.5mm radius.Combined with coupling efficiency calculation model,the coupling efficiency distribution was simulated with Monte Carlo method when the parameters met the normal distribution.The result shows that maximum efficiency reaches 0.616 and the maximum likely efficiency is 0.585.The efficiency improves significantly as the parameters' tolerances reduce by half.But further narrowing of tolerances can't enhance the efficiency obviously.The research approach is instructive for selection of alignment units and estimation of coupling efficiency in laser device package.
2012, 36(3): 342-345.
Abstract:
In order to analyze the phase matching of extreme ultraviolet high harmonics in the process of attosecond pulses generation,the analytic expressions were achieved based on the three-step analysis model for optical field ionization high-harmonic generation(HHG),and the harmonic spectral phase in the process of attosecond pulse generation was analyzed.It was found that,except the highest order harmonic,the spectral phase contribution of each harmonic consists of two sources of long trajectory electrons and short ones,and that,unlike the generated harmonics by the former,the spectral phase of those harmonics from the latter has regular phase relation among each other.The final conclusion is drawn that suppressing the long trajectory electrons can reduce the pulse width of attosecond pulses,which is of great significance to the issue of high harmonic phase matching in generation of attosecond pulses.
In order to analyze the phase matching of extreme ultraviolet high harmonics in the process of attosecond pulses generation,the analytic expressions were achieved based on the three-step analysis model for optical field ionization high-harmonic generation(HHG),and the harmonic spectral phase in the process of attosecond pulse generation was analyzed.It was found that,except the highest order harmonic,the spectral phase contribution of each harmonic consists of two sources of long trajectory electrons and short ones,and that,unlike the generated harmonics by the former,the spectral phase of those harmonics from the latter has regular phase relation among each other.The final conclusion is drawn that suppressing the long trajectory electrons can reduce the pulse width of attosecond pulses,which is of great significance to the issue of high harmonic phase matching in generation of attosecond pulses.
2012, 36(3): 346-348.
Abstract:
In order to analyze the impact of tracking error on the satellite-ground optical communication link,the received optical signal was collected with the LabVIEW.The time-domain characteristics of optical signals at the receiving end were obtained under different tracking conditions according to theoretical analysis and experiment.The experiment results show that the system can be stable when the tracking error is 10μrad and the output power is 23dBm.By contrast,the system becomes unstable when the tracking error is up to 8 0μrad or servo system starts to shake.
In order to analyze the impact of tracking error on the satellite-ground optical communication link,the received optical signal was collected with the LabVIEW.The time-domain characteristics of optical signals at the receiving end were obtained under different tracking conditions according to theoretical analysis and experiment.The experiment results show that the system can be stable when the tracking error is 10μrad and the output power is 23dBm.By contrast,the system becomes unstable when the tracking error is up to 8 0μrad or servo system starts to shake.
2012, 36(3): 349-352,356.
Abstract:
In order to study the rebound phenomenon of mechanical properties in the spot center of metallic material induced by laser shock processing,Ni42CrTiAl,a Fe-Ni elastic alloy material,was processed by high-energy neodymium glass pulse laser.Then the distribution of the residual stress on the elastic alloy surface was tested with an X-ray strain gauge.The results showed that there was a high distribution of residual compressive stress in the shocked region and there was a rebound phenomenon of mechanical properties in the spot center region where the residual stress values slightly less than its surrounding area.And then for the purpose of further studying the distribution of the residual stress induced by laser shock processing,the finite elementsimulation software was introduced to simulate the shocking experiment.The simulation results showed that there was also a high distribution of residual compressive stress in the shocked region and a rebound phenomenon of mechanical properties in the spot center region.The simulation results are in good agreement with the measurement.Finally the formation mechanism of rebound phenomenon of the material mechanical properties in the center region was explored from the angle of the movement,the reflection and the reverse effect of the shock wave.This study result is benefit to optimize the process of the laser shock processing and laser parameter selection.
In order to study the rebound phenomenon of mechanical properties in the spot center of metallic material induced by laser shock processing,Ni42CrTiAl,a Fe-Ni elastic alloy material,was processed by high-energy neodymium glass pulse laser.Then the distribution of the residual stress on the elastic alloy surface was tested with an X-ray strain gauge.The results showed that there was a high distribution of residual compressive stress in the shocked region and there was a rebound phenomenon of mechanical properties in the spot center region where the residual stress values slightly less than its surrounding area.And then for the purpose of further studying the distribution of the residual stress induced by laser shock processing,the finite elementsimulation software was introduced to simulate the shocking experiment.The simulation results showed that there was also a high distribution of residual compressive stress in the shocked region and a rebound phenomenon of mechanical properties in the spot center region.The simulation results are in good agreement with the measurement.Finally the formation mechanism of rebound phenomenon of the material mechanical properties in the center region was explored from the angle of the movement,the reflection and the reverse effect of the shock wave.This study result is benefit to optimize the process of the laser shock processing and laser parameter selection.
2012, 36(3): 353-356.
Abstract:
When the rail wear measurement is carried out in the wild,the interference from outside strong sunlight is inevitable.In order to eliminate the interference effect of sunlight effectively,a laser lock-in imaging technology was utilized.An external controlling circuit triggered the lasers and CCD image acquisition synchronously,and high quality image was achieved by means of laser lock-in imaging method.Lots of experiments verified that laser lock-in imaging makes the output of the rail wear more stable and adapt to a wide range interference of outside complicated background light.Experimental results show that laser lock-in imaging can guarantee stability of the measurement system,fundamentally eliminating the random measurement errors.
When the rail wear measurement is carried out in the wild,the interference from outside strong sunlight is inevitable.In order to eliminate the interference effect of sunlight effectively,a laser lock-in imaging technology was utilized.An external controlling circuit triggered the lasers and CCD image acquisition synchronously,and high quality image was achieved by means of laser lock-in imaging method.Lots of experiments verified that laser lock-in imaging makes the output of the rail wear more stable and adapt to a wide range interference of outside complicated background light.Experimental results show that laser lock-in imaging can guarantee stability of the measurement system,fundamentally eliminating the random measurement errors.
2012, 36(3): 357-360,378.
Abstract:
In the detection of trace gas based on tunable diode laser absorption spectroscopy(TDLAS),residual amplitude modulation(RAM) might happen simultaneously when wavelength modulation is performed directly by input current.This RAM will affect line-shape of measurement signal and system noise.In order to study the influences of RAM on the line-shape of the second harmonic signal of wavelength modulation spectroscopy(WMS),a calculation method of the second harmonic signal was put forward simultaneously considering amplitude modulation and frequency modulation(AM-FM) factor.After analyzing the method,the corresponding expression was derived.Quantitative calculation results were compared between AM-FM method and traditional FM method.The baseline,positive and negative peak of the second harmonic signal were obtained.The results show that the RAM has direct influences on detection signal line shape and signal baseline.The signal line shape calculated with the AM-FM method more close to detected results.
In the detection of trace gas based on tunable diode laser absorption spectroscopy(TDLAS),residual amplitude modulation(RAM) might happen simultaneously when wavelength modulation is performed directly by input current.This RAM will affect line-shape of measurement signal and system noise.In order to study the influences of RAM on the line-shape of the second harmonic signal of wavelength modulation spectroscopy(WMS),a calculation method of the second harmonic signal was put forward simultaneously considering amplitude modulation and frequency modulation(AM-FM) factor.After analyzing the method,the corresponding expression was derived.Quantitative calculation results were compared between AM-FM method and traditional FM method.The baseline,positive and negative peak of the second harmonic signal were obtained.The results show that the RAM has direct influences on detection signal line shape and signal baseline.The signal line shape calculated with the AM-FM method more close to detected results.
2012, 36(3): 361-363.
Abstract:
When the strip steel is rolled by the cone rollers,in order to strengthen the friction force between the cone roller surface and the strip steel,the laser texturing(LT) technology on the cone roller surface is adopted.The LT technology on cone roller surface was introduced.The composition of the LT equipment was presented.The control principle of the LT equipment was given.Because the processing process of LT on the cone roller surface is a process of changing diameter,in order to gain the same distance between two adjoining LT dots on the same processed circle,the computational formulas of the diameter,the number of LT dots and the frequency division coefficient on every processed circle must be worked out.The formulas were provided which can solve the problem that the distance between the last LT dot and the first LT dot is larger than the usual.The practical application shows that the LT on cone roller surface enhances the friction force between the cone roller surface and the strip steel and extends the life of the cone roller.
When the strip steel is rolled by the cone rollers,in order to strengthen the friction force between the cone roller surface and the strip steel,the laser texturing(LT) technology on the cone roller surface is adopted.The LT technology on cone roller surface was introduced.The composition of the LT equipment was presented.The control principle of the LT equipment was given.Because the processing process of LT on the cone roller surface is a process of changing diameter,in order to gain the same distance between two adjoining LT dots on the same processed circle,the computational formulas of the diameter,the number of LT dots and the frequency division coefficient on every processed circle must be worked out.The formulas were provided which can solve the problem that the distance between the last LT dot and the first LT dot is larger than the usual.The practical application shows that the LT on cone roller surface enhances the friction force between the cone roller surface and the strip steel and extends the life of the cone roller.
2012, 36(3): 364-367.
Abstract:
In order to improve the surface hardness and toughness of dies,several typical die materials,such as 7CrSiMnMoV,Cr12MoV,CrMo cast iron,were hardened with a high power diode laser and the optimal laser parameters were obtained.Results show that the optimal laser parameters can meet the requirement of the hardness of dies and provide a guarantee to the hardness and toughness of dies in future application.
In order to improve the surface hardness and toughness of dies,several typical die materials,such as 7CrSiMnMoV,Cr12MoV,CrMo cast iron,were hardened with a high power diode laser and the optimal laser parameters were obtained.Results show that the optimal laser parameters can meet the requirement of the hardness of dies and provide a guarantee to the hardness and toughness of dies in future application.
2012, 36(3): 368-371.
Abstract:
In order to study the optical characteristics of ternary layer 1-D photonic crystal with defect as gain medium,they were analyzed based on the optical transfer matrix.The thickness of gain defect layer and the optical constant change have little effect on the prohibited-band structure in the infrared region,and that the gain medium layer mainly affects the band-edge amplification effect of the transmission band at central wavelength of 1.8μm.The effect of the thickness of gain medium layer,optical constant change on the amplification effect at infrared transmission band edge(2.1969μm) wavelength was also studied.When the gain medium is 0.0101μm thick,n=5.03+0.124i,the transmission coefficient at the wavelength 2.1869μm is up to 428 optical amplification.In the infrared band,optical amplification changes with the central wavelength,but the central wavelength is always at the edges of the wavelength band where the central wavelength is located.The results provide theoretical guidance for the photonic crystal as a laser gain medium.
In order to study the optical characteristics of ternary layer 1-D photonic crystal with defect as gain medium,they were analyzed based on the optical transfer matrix.The thickness of gain defect layer and the optical constant change have little effect on the prohibited-band structure in the infrared region,and that the gain medium layer mainly affects the band-edge amplification effect of the transmission band at central wavelength of 1.8μm.The effect of the thickness of gain medium layer,optical constant change on the amplification effect at infrared transmission band edge(2.1969μm) wavelength was also studied.When the gain medium is 0.0101μm thick,n=5.03+0.124i,the transmission coefficient at the wavelength 2.1869μm is up to 428 optical amplification.In the infrared band,optical amplification changes with the central wavelength,but the central wavelength is always at the edges of the wavelength band where the central wavelength is located.The results provide theoretical guidance for the photonic crystal as a laser gain medium.
2012, 36(3): 379-381.
Abstract:
In order to study the application of laser direct writing technology in the fabrication of thin platinum film resistors,platinum resistors in 2m thick were manufactured by means of laser direct writing.The fabrication mechanism of thin platinum film resistors was discussed.Taking strip platinum resistors as an example,the effect of the laser parameters on the figures of platinum resistors was studied.A 0.37 strip thin platinum film resistor was manufactured under the condition that the optimal laser pulse repetition frequency was 18kHz and the laser scanning speed was 100mm/s.Finally,the resistance of the platinum resistors was tested.The results indicate that the width of platinum resistor increases with the increase of laser pulse frequency and the increase of laser scan frequency independently.The edge of the manufactured resistor is neat and the surface is smooth.The relative deviation of the actual resistance to the theoretical one is only 0.8%.
In order to study the application of laser direct writing technology in the fabrication of thin platinum film resistors,platinum resistors in 2m thick were manufactured by means of laser direct writing.The fabrication mechanism of thin platinum film resistors was discussed.Taking strip platinum resistors as an example,the effect of the laser parameters on the figures of platinum resistors was studied.A 0.37 strip thin platinum film resistor was manufactured under the condition that the optimal laser pulse repetition frequency was 18kHz and the laser scanning speed was 100mm/s.Finally,the resistance of the platinum resistors was tested.The results indicate that the width of platinum resistor increases with the increase of laser pulse frequency and the increase of laser scan frequency independently.The edge of the manufactured resistor is neat and the surface is smooth.The relative deviation of the actual resistance to the theoretical one is only 0.8%.
2012, 36(3): 382-385.
Abstract:
A pinhole is one of the key components in a phase-shifting point diffraction interferometer(PS-PDI).In order to study the effect of the size of pinhole,material of pinhole and thickness of material on the quality of diffraction wave-front,and determine the measurement accuracy of the PS-PDI,near-field data was obtained by means of the finite-difference time-domain method,and then the data of far field based on Rayleigh-Sommerfeld vector diffraction theory could be acquired from near field data.The quality of diffractive wave-front was analyzed under the uniform incident light with TE and TM polarization,and the corresponding curve was achieved.The results show that in order to obtain perfect wave-front,the thickness of material should not be less than 300nm.Appropriate aperture size can reduce the error of wave-front.When the size of pinhole is 300nm,the root mean square wave-front error is below λ/1000(λ=632.8nm).It is of great help to design and application of a PS-PDI.
A pinhole is one of the key components in a phase-shifting point diffraction interferometer(PS-PDI).In order to study the effect of the size of pinhole,material of pinhole and thickness of material on the quality of diffraction wave-front,and determine the measurement accuracy of the PS-PDI,near-field data was obtained by means of the finite-difference time-domain method,and then the data of far field based on Rayleigh-Sommerfeld vector diffraction theory could be acquired from near field data.The quality of diffractive wave-front was analyzed under the uniform incident light with TE and TM polarization,and the corresponding curve was achieved.The results show that in order to obtain perfect wave-front,the thickness of material should not be less than 300nm.Appropriate aperture size can reduce the error of wave-front.When the size of pinhole is 300nm,the root mean square wave-front error is below λ/1000(λ=632.8nm).It is of great help to design and application of a PS-PDI.
2012, 36(3): 386-389.
Abstract:
In order to obtain stable laser beam,random deviations of light beams should be corrected.Taking the progress of adjusting direction drifts of pulse laser beam with fast steering mirrors in the beam delivery system as an example,an algorithm based on moving average(MA) correction mechanism was used to simulate the correction outcomes with or without ground jitters.MA and moving standard deviation(MSD) are used to evaluate the correction effects.The results indicate that this algorithm can control the position excursions on the plane of beam delivery system caused by the direction drifts of laser beam effectively,and the MA corrected has a big jump between n~2n pulses,for example,the optimal MA can be reduced to n-1/2 times(n is pulse numbers in a window).At the same time,there is a sudden decline in MSD between n~2n pulses,and soon afterwards,MSD is going to be sticking.Meanwhile,the drifts can be restrained while loading the ground jitters,and the dropping amplitude is bigger than without the ground jitters.The results show that the key of applications lies in construction of the appropriate corrections.What is more,this algorithm which is practical can achieve real-time control of direction drifts.
In order to obtain stable laser beam,random deviations of light beams should be corrected.Taking the progress of adjusting direction drifts of pulse laser beam with fast steering mirrors in the beam delivery system as an example,an algorithm based on moving average(MA) correction mechanism was used to simulate the correction outcomes with or without ground jitters.MA and moving standard deviation(MSD) are used to evaluate the correction effects.The results indicate that this algorithm can control the position excursions on the plane of beam delivery system caused by the direction drifts of laser beam effectively,and the MA corrected has a big jump between n~2n pulses,for example,the optimal MA can be reduced to n-1/2 times(n is pulse numbers in a window).At the same time,there is a sudden decline in MSD between n~2n pulses,and soon afterwards,MSD is going to be sticking.Meanwhile,the drifts can be restrained while loading the ground jitters,and the dropping amplitude is bigger than without the ground jitters.The results show that the key of applications lies in construction of the appropriate corrections.What is more,this algorithm which is practical can achieve real-time control of direction drifts.
2012, 36(3): 390-393,397.
Abstract:
In the study of calculation method of atmospheric trace gas detection limit based on wavelength modulation spectroscopy,it is extremely important to describe the magnitude of the absorption signal and noise objectively and accurately.In order to study the effect of residual amplitude modulation noise on the detection limit when the wavelength of a semiconductor diode laser is modulated directly,the second harmonic signal analysis and extraction method were used in theoretical derivation taking into account the frequency modulation and amplitude modulation simultaneously.The difference value between the peak and valley of the second harmonic signal was utilized as detection signal.The signal-to-noise ratio(SNR) and detection limit of the tunable diode laser absorption spectroscopy detection system were theoretically analyzed.Under the condition of Lorentzian absorption lineshape,accurate calculation data of the impact of the residual amplitude modulation noise on the SNR and the detection limit were obtained.The results show that the residual amplitude modulation noise is an important factor affecting the detection limit under the condition of large absorption linewidth.
In the study of calculation method of atmospheric trace gas detection limit based on wavelength modulation spectroscopy,it is extremely important to describe the magnitude of the absorption signal and noise objectively and accurately.In order to study the effect of residual amplitude modulation noise on the detection limit when the wavelength of a semiconductor diode laser is modulated directly,the second harmonic signal analysis and extraction method were used in theoretical derivation taking into account the frequency modulation and amplitude modulation simultaneously.The difference value between the peak and valley of the second harmonic signal was utilized as detection signal.The signal-to-noise ratio(SNR) and detection limit of the tunable diode laser absorption spectroscopy detection system were theoretically analyzed.Under the condition of Lorentzian absorption lineshape,accurate calculation data of the impact of the residual amplitude modulation noise on the SNR and the detection limit were obtained.The results show that the residual amplitude modulation noise is an important factor affecting the detection limit under the condition of large absorption linewidth.
2012, 36(3): 394-397.
Abstract:
To study the slant path scattering characteristics of aerosols in atmosphere,the slant path scattering model of 1.064μm laser was built based on Mie scattering theory.The distribution characteristics of radiative parameters were analyzed with the help of MATLAB.Combined with ground surface detection,the effect of detection azimuth and angle of a detector on the scattering intensity was discussed.As a result,the model is a credible method for the tactical training of airborne designator system and ground laser detection.
To study the slant path scattering characteristics of aerosols in atmosphere,the slant path scattering model of 1.064μm laser was built based on Mie scattering theory.The distribution characteristics of radiative parameters were analyzed with the help of MATLAB.Combined with ground surface detection,the effect of detection azimuth and angle of a detector on the scattering intensity was discussed.As a result,the model is a credible method for the tactical training of airborne designator system and ground laser detection.
2012, 36(3): 398-401.
Abstract:
In order to study the effect of isotopes except for 52Cr on the transverse position distribution of Cr atomic beam,simulation was carried out for 1-D transverse laser cooling with a three-aperture pre-collimating slit by means of Monte Carlo method.The results show that isotopes except for 52Cr can make the background increased and affect characteristics of each part of the atomic beam: the central maximum value decreases 9.5% and its full width at half maximum(FWHM)increases 2.9% in the center;while the maximum value increases 25% with little increase of the FWHM in either side.It concludes that the existence of the isotopes except for 52Cr has little effect on the center maximum value and FWHM of the center part atomic beam.
In order to study the effect of isotopes except for 52Cr on the transverse position distribution of Cr atomic beam,simulation was carried out for 1-D transverse laser cooling with a three-aperture pre-collimating slit by means of Monte Carlo method.The results show that isotopes except for 52Cr can make the background increased and affect characteristics of each part of the atomic beam: the central maximum value decreases 9.5% and its full width at half maximum(FWHM)increases 2.9% in the center;while the maximum value increases 25% with little increase of the FWHM in either side.It concludes that the existence of the isotopes except for 52Cr has little effect on the center maximum value and FWHM of the center part atomic beam.
Calculation and analysis of spherical aberration on Gaussian image plane based on diffraction theory
2012, 36(3): 405-407,412.
Abstract:
In order to study how to analyze spherical aberration based on the diffraction theory of wave optics,theoretical analysis and simulation were carried out.Firstly,the light intensity distribution of the image point was calculated and then the spherical aberration was further analyzed and processed.Starting from the imaging principle a circular aperture irradiated by a point source,referring to relevant documents,analytical expression of the intensity distribution of the image point only with spherical aberration on the Gaussian image plane was deduced.The diffraction mechanism and calculation and correction of spherical aberration on Gaussian image plane were analyzed and discussed.The method can handle spherical aberration more accurately.It is helpful for balancing and correction of spherical aberration in optical design and the detection and correction of spherical aberration in optical processing and electronic correction of spherical aberration in digital imaging,and conducive to promote the development of laser technology and micro-optics and micro-optoelectro mechanical systems.
In order to study how to analyze spherical aberration based on the diffraction theory of wave optics,theoretical analysis and simulation were carried out.Firstly,the light intensity distribution of the image point was calculated and then the spherical aberration was further analyzed and processed.Starting from the imaging principle a circular aperture irradiated by a point source,referring to relevant documents,analytical expression of the intensity distribution of the image point only with spherical aberration on the Gaussian image plane was deduced.The diffraction mechanism and calculation and correction of spherical aberration on Gaussian image plane were analyzed and discussed.The method can handle spherical aberration more accurately.It is helpful for balancing and correction of spherical aberration in optical design and the detection and correction of spherical aberration in optical processing and electronic correction of spherical aberration in digital imaging,and conducive to promote the development of laser technology and micro-optics and micro-optoelectro mechanical systems.
2012, 36(3): 408-412.
Abstract:
In order to improve the reliability of wavelength division multiplexing(WDM),the segmented shared path protection(SSPP) algorithm is usually adopted.It requires equal length segmentation in WDM optical networks and it must obey the shared risk link group(SRLG) constraint.When searching protection path,the SRLG constraint will lead the call blocking probability of the networks to rise.In order to reduce the call blocking probability,a new path protection algorithm,so-called preferential shared path protection(PSPP) was proposed.The simulation of SSPP and PSPP algorithms was done in the discrete event emulation system.The result shows the call blocking probability of the PSPP algorithm is better than that of the SSPP algorithm,and the resource reservation ratio of PSPP is also relatively better.
In order to improve the reliability of wavelength division multiplexing(WDM),the segmented shared path protection(SSPP) algorithm is usually adopted.It requires equal length segmentation in WDM optical networks and it must obey the shared risk link group(SRLG) constraint.When searching protection path,the SRLG constraint will lead the call blocking probability of the networks to rise.In order to reduce the call blocking probability,a new path protection algorithm,so-called preferential shared path protection(PSPP) was proposed.The simulation of SSPP and PSPP algorithms was done in the discrete event emulation system.The result shows the call blocking probability of the PSPP algorithm is better than that of the SSPP algorithm,and the resource reservation ratio of PSPP is also relatively better.
2012, 36(3): 413-415.
Abstract:
In order to improve achromatism of rhomb-type retarders,it is necessary to expand selection of materials.According to the principle that the light arising total reflection has a phase transformation in the medium surface,rhomb-type achromatism retarders were analyzed,and relation between the refractive index n and structural angle θ was deduced.Although dn/dλ increases with enlargement of the refractive index ,n,dδ/dn decreases rapidly,so high refractive index materials probably have better achromatism.It was shown that the maximal delay errors of low refractive index materials were smaller than 1.32°,and the maximal delay errors of high refractive index materials were smaller than 0.95° within the range of 350nm~1240nm.Comparing with low refractive index materials,high refractive index materials have better achromatism.
In order to improve achromatism of rhomb-type retarders,it is necessary to expand selection of materials.According to the principle that the light arising total reflection has a phase transformation in the medium surface,rhomb-type achromatism retarders were analyzed,and relation between the refractive index n and structural angle θ was deduced.Although dn/dλ increases with enlargement of the refractive index ,n,dδ/dn decreases rapidly,so high refractive index materials probably have better achromatism.It was shown that the maximal delay errors of low refractive index materials were smaller than 1.32°,and the maximal delay errors of high refractive index materials were smaller than 0.95° within the range of 350nm~1240nm.Comparing with low refractive index materials,high refractive index materials have better achromatism.
2012, 36(3): 416-420.
Abstract:
In order to solve the defaults of the traditional binocular vision calibration method for constructing 3-D images,a binocular stereo vision system was designed based on self calibration algorithm of binocular vision,and the spatial objective points were determined.The essential matrix for two adjacent images was solved based on the matrix constructed according to calibration mathematical model.Four linear equations were obtained according to the 3-D spatial equations of projection matrix.Coordinates of image points in the world coordinate by means of external the epipolar constraint method.The results show that the outline of the objective space is clear without ghost,and the 3-D surface is more realistic,stereographic.
In order to solve the defaults of the traditional binocular vision calibration method for constructing 3-D images,a binocular stereo vision system was designed based on self calibration algorithm of binocular vision,and the spatial objective points were determined.The essential matrix for two adjacent images was solved based on the matrix constructed according to calibration mathematical model.Four linear equations were obtained according to the 3-D spatial equations of projection matrix.Coordinates of image points in the world coordinate by means of external the epipolar constraint method.The results show that the outline of the objective space is clear without ghost,and the 3-D surface is more realistic,stereographic.
2012, 36(3): 421-423,427.
Abstract:
In order to meet the application of the ultraviolet(UV) warning systems in military domain,an optical system of a solar-blind ultraviolet warning system was designed with binary diffractive elements and aspherical elements.Its working wavelength is 240nm～280nm,full field of view is 40°.It is composed only of five lenses with "negative-positive" reverted-telephoto type.The lens has simple structure,small size,and high energy concentration.The results show that this design is a good solution to the UV-axis lens aberration correction,the spot is less than pixel size of UV-CCD,making point diagram with high energy concentration,and satisfying the design requirement of UV warning systems.
In order to meet the application of the ultraviolet(UV) warning systems in military domain,an optical system of a solar-blind ultraviolet warning system was designed with binary diffractive elements and aspherical elements.Its working wavelength is 240nm～280nm,full field of view is 40°.It is composed only of five lenses with "negative-positive" reverted-telephoto type.The lens has simple structure,small size,and high energy concentration.The results show that this design is a good solution to the UV-axis lens aberration correction,the spot is less than pixel size of UV-CCD,making point diagram with high energy concentration,and satisfying the design requirement of UV warning systems.
2012, 36(3): 424-427.
Abstract:
In order to decrease system phase-shifting errors in light emitting diode based digital holography,achromatic phase shift was introduced.Both theoretical analysis and experimental results were displayed.First of all,the spectral distribution of the light emitting diode was studied and the phase shift error induced by micro-displacement pizeo-electric ceramic actuator was calculated.Then the principle of an achromatic phase-shifter based on a rotatable half wave-plate was studied and it was found that the phase difference between the two beams was,in principle,independent of wavelength.Digital holography by means of micro-displacement pizeo-electric ceramic actuators and achromatic phase-shifters was carried out respectively and the quality of the reconstructed fields was compared.The experimental results indicate that the reconstruction quality by means of achromatic phase-shift was greatly improved compared with that by means of microdisplacement pizeo-electric ceramic actuators.The results are helpful for the reconstruction quality of partial coherent source based digital holography.
In order to decrease system phase-shifting errors in light emitting diode based digital holography,achromatic phase shift was introduced.Both theoretical analysis and experimental results were displayed.First of all,the spectral distribution of the light emitting diode was studied and the phase shift error induced by micro-displacement pizeo-electric ceramic actuator was calculated.Then the principle of an achromatic phase-shifter based on a rotatable half wave-plate was studied and it was found that the phase difference between the two beams was,in principle,independent of wavelength.Digital holography by means of micro-displacement pizeo-electric ceramic actuators and achromatic phase-shifters was carried out respectively and the quality of the reconstructed fields was compared.The experimental results indicate that the reconstruction quality by means of achromatic phase-shift was greatly improved compared with that by means of microdisplacement pizeo-electric ceramic actuators.The results are helpful for the reconstruction quality of partial coherent source based digital holography.
2012, 36(3): 428-432.
Abstract:
In order to improve the homogeneity of pumping power in the slab,based on the designing scheme of LD dual-end-pumped Nd:YAG ceramic slab laser,the absorbed pump power density distribution of constant concentration dopant slab and gradient concentration dopant slab were theoretically analyzed respectively.After analysis,it is found that the pump absorption intensity distribution becomes non-uniform for constant concentration dopant slab when the pump absorption efficiency is improved.However,for gradient concentration dopant slab,high pumping efficiency and uniform pump absorption intensity distribution can be separately achieved,which can improve the homogeneity of pumping power absorbed in the slab.
In order to improve the homogeneity of pumping power in the slab,based on the designing scheme of LD dual-end-pumped Nd:YAG ceramic slab laser,the absorbed pump power density distribution of constant concentration dopant slab and gradient concentration dopant slab were theoretically analyzed respectively.After analysis,it is found that the pump absorption intensity distribution becomes non-uniform for constant concentration dopant slab when the pump absorption efficiency is improved.However,for gradient concentration dopant slab,high pumping efficiency and uniform pump absorption intensity distribution can be separately achieved,which can improve the homogeneity of pumping power absorbed in the slab.
