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RSS2006 Vol. 30, No. 1
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2006, 30(1): 1-4.
[Abstract]
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Abstract:
With the fast development of the new subject of biomedical optics/photonics,an investigation into laser triangulation for its biomedical application is presented by discussing,classifying and summarizing,which will be instructive for the further research and development of laser triangulation in biomedical application.
With the fast development of the new subject of biomedical optics/photonics,an investigation into laser triangulation for its biomedical application is presented by discussing,classifying and summarizing,which will be instructive for the further research and development of laser triangulation in biomedical application.
2006, 30(1): 5-8.
Abstract:
The change of the cavity length and single-pass loss in ring-down cavity is deduced from the misalignment angle of cavity mirrors.Based on the matrix method of misalignment resonator and experimental parameters,a theoretical model is proposed to simulate measurement of reflectivity for cavity mirrors'tilt in ring-down cavity.Applying this model,the waveform of ring-down signal can be simulated and its change reason is analyzed.Then the relation between measurement precision and cavity mirrors'tilt is studied.The analysis shows that the measurement precision drops rapidly with length misadjustment and spot offset brought by cavity mirrors'tilt.To improve measurement precision,it is suggested that ring-down signal on the oscillograph should be applied to adjust the cavity mirror.
The change of the cavity length and single-pass loss in ring-down cavity is deduced from the misalignment angle of cavity mirrors.Based on the matrix method of misalignment resonator and experimental parameters,a theoretical model is proposed to simulate measurement of reflectivity for cavity mirrors'tilt in ring-down cavity.Applying this model,the waveform of ring-down signal can be simulated and its change reason is analyzed.Then the relation between measurement precision and cavity mirrors'tilt is studied.The analysis shows that the measurement precision drops rapidly with length misadjustment and spot offset brought by cavity mirrors'tilt.To improve measurement precision,it is suggested that ring-down signal on the oscillograph should be applied to adjust the cavity mirror.
2006, 30(1): 9-12,30.
Abstract:
The development of optical feedback technology of LD pumped microchip Nd:YAG lasers is reviewed.At first its research background and basic theoretical model are introduced.Then its applications such as ultrahigh sensitivity self-mixing laser Doppler velocimeters,nanometer vibrometers and laser optical feedback tomography are described in detail.Finally some predictions of its future development are also presented.
The development of optical feedback technology of LD pumped microchip Nd:YAG lasers is reviewed.At first its research background and basic theoretical model are introduced.Then its applications such as ultrahigh sensitivity self-mixing laser Doppler velocimeters,nanometer vibrometers and laser optical feedback tomography are described in detail.Finally some predictions of its future development are also presented.
2006, 30(1): 13-15.
Abstract:
The object is to measure the amplitude and phase of femtosecond pulses,based on the spectral phase interferometry for direct electric-field reconstruction(SPIDER) of the numerical analysis methods.The spectral phases and intensity of the typical femtosecond pulses were numerical calculated,the spectral phases of these pulses are reconstructed.The reconstructed spectral phases are basically in agreement with the original ones.
The object is to measure the amplitude and phase of femtosecond pulses,based on the spectral phase interferometry for direct electric-field reconstruction(SPIDER) of the numerical analysis methods.The spectral phases and intensity of the typical femtosecond pulses were numerical calculated,the spectral phases of these pulses are reconstructed.The reconstructed spectral phases are basically in agreement with the original ones.
2006, 30(1): 20-22.
Abstract:
A high-repetition-rate CW laser diode pumped acousto-optically(AO) Q-switched eye-safe intracavity optical parametric oscillator at 1.57μm with a type-Ⅱ non-critically phase-matched X-cut KTP is experimentally studied.Using a CW laser diode three-side-pumping Nd:YAG module and a QSGSU-6 AO Q-switch,with a single oscillator 1.57μm OPO placed inside the resonator of a Q-switched 1.06μm Nd:YAG laser,the maximum power of 480mW and the maximum peak power of 58.8kW at 1.57μm are obtained with pulse duration about 2.72ns at 3kHz the opto-electronic efficiency is up to 2.6‰.CW laser diode pumped AO Q-switched intracality optical parametric oscillator is a good chice for high-repetition-rate eye-safe laser.
A high-repetition-rate CW laser diode pumped acousto-optically(AO) Q-switched eye-safe intracavity optical parametric oscillator at 1.57μm with a type-Ⅱ non-critically phase-matched X-cut KTP is experimentally studied.Using a CW laser diode three-side-pumping Nd:YAG module and a QSGSU-6 AO Q-switch,with a single oscillator 1.57μm OPO placed inside the resonator of a Q-switched 1.06μm Nd:YAG laser,the maximum power of 480mW and the maximum peak power of 58.8kW at 1.57μm are obtained with pulse duration about 2.72ns at 3kHz the opto-electronic efficiency is up to 2.6‰.CW laser diode pumped AO Q-switched intracality optical parametric oscillator is a good chice for high-repetition-rate eye-safe laser.
2006, 30(1): 23-26.
Abstract:
At some process condition,the weld fusion area increase linearly with heat input,and for the two common parameters of laser power and weld speed,laser power has more influence on penetration while weld speed has more influence on weld width.The plasma optic signal at 400nm~600nm corresponds to variation of the weld penetration,and the signal's RMS value increases with the penetration in a quadratic curve mode.The inherent relation between plasma optic signal and penetration is also analyzed.The results provide theoretical and practical guidance for real-time penetration monitor and prediction in partial-penetration laser welding.
At some process condition,the weld fusion area increase linearly with heat input,and for the two common parameters of laser power and weld speed,laser power has more influence on penetration while weld speed has more influence on weld width.The plasma optic signal at 400nm~600nm corresponds to variation of the weld penetration,and the signal's RMS value increases with the penetration in a quadratic curve mode.The inherent relation between plasma optic signal and penetration is also analyzed.The results provide theoretical and practical guidance for real-time penetration monitor and prediction in partial-penetration laser welding.
2006, 30(1): 27-30.
Abstract:
In case of co-existence of cubic and quintic nonlinearity,the condition and power gain spectra of modulation instability induced by the cross-phase modulation for two optical waves in loss,single-mode optical fibers are studied.In the normal dispersion region of the decreasing dispersion fibers,the effects of the quintic nonlinear coefficients,the dispersion longitudinal varying parameters,and the size relation of the two perturbation frequencies on the power gain spectra of modulation instability are analyzed in detail.The results indicate that,in case of quintic nonlinearity,the longitudinal decreasing of dispersion is still benefit to broaden the gain spectra of modulation instability.The positive quintic nonlinearity will make the width and the peak value of the gain spectra larger,and make the position of peak value be far away from the frequency of the main wave,while the negative quintic nonlinearity will do the opposite.If the size relation of the two perturbation frequencies is different,the dispersion longitudinal varying parameters will influence the position and value of the spectrum peak in different ways,and the quintic nonlinearity will intensify or suppress the modulation instability to different degrees.
In case of co-existence of cubic and quintic nonlinearity,the condition and power gain spectra of modulation instability induced by the cross-phase modulation for two optical waves in loss,single-mode optical fibers are studied.In the normal dispersion region of the decreasing dispersion fibers,the effects of the quintic nonlinear coefficients,the dispersion longitudinal varying parameters,and the size relation of the two perturbation frequencies on the power gain spectra of modulation instability are analyzed in detail.The results indicate that,in case of quintic nonlinearity,the longitudinal decreasing of dispersion is still benefit to broaden the gain spectra of modulation instability.The positive quintic nonlinearity will make the width and the peak value of the gain spectra larger,and make the position of peak value be far away from the frequency of the main wave,while the negative quintic nonlinearity will do the opposite.If the size relation of the two perturbation frequencies is different,the dispersion longitudinal varying parameters will influence the position and value of the spectrum peak in different ways,and the quintic nonlinearity will intensify or suppress the modulation instability to different degrees.
2006, 30(1): 31-33,49.
Abstract:
The working theory and optical criterion for the CD optical system is introduced,then some main issues for the design and assembling are discussed.A kind of CD lens for practical use and mass production have been designed.Based on the calculation of the lens,the optical performance curves affected by the LD astigmatism,manufacturing errors and system errors are presented.The design can endure various manufacture errors.Even the focusing error and disk tilt occur,excellent optical performance can be obtained within the whole tracking area,which shows the design is practical.
The working theory and optical criterion for the CD optical system is introduced,then some main issues for the design and assembling are discussed.A kind of CD lens for practical use and mass production have been designed.Based on the calculation of the lens,the optical performance curves affected by the LD astigmatism,manufacturing errors and system errors are presented.The design can endure various manufacture errors.Even the focusing error and disk tilt occur,excellent optical performance can be obtained within the whole tracking area,which shows the design is practical.
2006, 30(1): 34-36.
Abstract:
The output characteristics of the Er/Yb co-doped fiber superfluorescent source,pumped by six CW laser diodes operating at 976nm through six pigtails of the tapered fiber bundle in order to obtain higher output power,are investigated.With SPB configuration,when the pump power is 957mW,the superfluorescent output power is 120.4mW,and the slope efficiency is 17.5%.In DPB configuration,the 3dB bandwidth can be spread to 88nm efficiently with additional 4m Er-doped fibers.
The output characteristics of the Er/Yb co-doped fiber superfluorescent source,pumped by six CW laser diodes operating at 976nm through six pigtails of the tapered fiber bundle in order to obtain higher output power,are investigated.With SPB configuration,when the pump power is 957mW,the superfluorescent output power is 120.4mW,and the slope efficiency is 17.5%.In DPB configuration,the 3dB bandwidth can be spread to 88nm efficiently with additional 4m Er-doped fibers.
2006, 30(1): 37-39,55.
Abstract:
A novel plastic optical fiber(POF) power coupler manufactured with the ultrasonic welding method is investigated.The manufacture process is feasible and convenient.The relation is discussed between the coupling ratio and its main work variables,including the length and thickness of the coupling section and the distance between two fiber axes.The experimental result is identical with the computer simulation result basically.Some measures are provided to reduce the excess loss.The manufactured plastic fiber coupler can satisfy the demand of short-distance communication in coupling ratio and excess loss.
A novel plastic optical fiber(POF) power coupler manufactured with the ultrasonic welding method is investigated.The manufacture process is feasible and convenient.The relation is discussed between the coupling ratio and its main work variables,including the length and thickness of the coupling section and the distance between two fiber axes.The experimental result is identical with the computer simulation result basically.Some measures are provided to reduce the excess loss.The manufactured plastic fiber coupler can satisfy the demand of short-distance communication in coupling ratio and excess loss.
2006, 30(1): 40-42,46.
Abstract:
Lithium silicate photosensitive glass doped silver is fabricated by means of high temperature melt in silica crucible.After irradiation of Ti-sapphire femtosecond laser followed by a thermo development which is photo-thermo-refractive(PTR) process,Li2O·Al2O3·3SiO2micro crystalline phase structure is observed and confirmed in the glass matrix with the help of optical microscope and X-ray diffraction.The above micro crystal is white and hexagonal structure.Variation of the refractive index in exposed parts of glass happens while almost no apparent variation occurrs in unexposed parts.So this is a process of structure change with spatial selectivity.Based on photo-indued refractive index change of glass and spatial selectivity of femtosecond lasers,it is expected that micro grating,optical waveguide,MEMS devices,optical mask,etc,can be fabricated in the glass matrix.
Lithium silicate photosensitive glass doped silver is fabricated by means of high temperature melt in silica crucible.After irradiation of Ti-sapphire femtosecond laser followed by a thermo development which is photo-thermo-refractive(PTR) process,Li2O·Al2O3·3SiO2micro crystalline phase structure is observed and confirmed in the glass matrix with the help of optical microscope and X-ray diffraction.The above micro crystal is white and hexagonal structure.Variation of the refractive index in exposed parts of glass happens while almost no apparent variation occurrs in unexposed parts.So this is a process of structure change with spatial selectivity.Based on photo-indued refractive index change of glass and spatial selectivity of femtosecond lasers,it is expected that micro grating,optical waveguide,MEMS devices,optical mask,etc,can be fabricated in the glass matrix.
2006, 30(1): 43-46.
Abstract:
Backscattered laser energy profile is very important parameter in a cone-shaped laser energy meter because it affects the measurement precision of the instrument.From the reflection rule of laser in the surface of energy meter obeyed,the distribution function of power of laser beam in energy meter surface is deduced.Using the Simpson numerical calculation method,the distribution of laser power density in the opening of absorption body and the total backscattered laser power are obtained when the reflective index is fixed but the ratio of laser diameter and absorption cavity diameter is changed.The calculation results show that the backscattered energy loss is up to 0.5%~2.5% for a large caliber high energy laser.According to the backscattered laser power density profile,total backscattered laser energy can be gotten to compensate the measurement result,which will greatly improve the accuracy of high energy laser energy measurement.
Backscattered laser energy profile is very important parameter in a cone-shaped laser energy meter because it affects the measurement precision of the instrument.From the reflection rule of laser in the surface of energy meter obeyed,the distribution function of power of laser beam in energy meter surface is deduced.Using the Simpson numerical calculation method,the distribution of laser power density in the opening of absorption body and the total backscattered laser power are obtained when the reflective index is fixed but the ratio of laser diameter and absorption cavity diameter is changed.The calculation results show that the backscattered energy loss is up to 0.5%~2.5% for a large caliber high energy laser.According to the backscattered laser power density profile,total backscattered laser energy can be gotten to compensate the measurement result,which will greatly improve the accuracy of high energy laser energy measurement.
2006, 30(1): 47-49.
Abstract:
A high-aspect-ration hole with line width of 32μm,height of 2000μm are drilled on PMMA by excimer laser,then it is used as mould in electroform as well as another structure made by lithographic.Through experiments,the parameters are optimined to fit the high-aspect-ration structure electroform,two main difficulties including the surface tension and polarization of concentration are resolved and the micro-structure with line width of 10μm is obtained.
A high-aspect-ration hole with line width of 32μm,height of 2000μm are drilled on PMMA by excimer laser,then it is used as mould in electroform as well as another structure made by lithographic.Through experiments,the parameters are optimined to fit the high-aspect-ration structure electroform,two main difficulties including the surface tension and polarization of concentration are resolved and the micro-structure with line width of 10μm is obtained.
2006, 30(1): 50-52,59.
Abstract:
Based on the Huygens-Fresnel diffraction integral,the diffraction of laser beams with amplitude modulations passing serrated apertures is studied and compared with hard-edged circular apertures numerically.Furthermore,the effect of aperture parameters on the diffraction characteristics of laser beams with amplitude modulations is also analyzed.It is shown that,while maintaining a relatively large fill factor,the use of serrated apertures can suppress the diffraction modulations of axial intensity and reduce the nonuniformity of transversal intensity distributions.
Based on the Huygens-Fresnel diffraction integral,the diffraction of laser beams with amplitude modulations passing serrated apertures is studied and compared with hard-edged circular apertures numerically.Furthermore,the effect of aperture parameters on the diffraction characteristics of laser beams with amplitude modulations is also analyzed.It is shown that,while maintaining a relatively large fill factor,the use of serrated apertures can suppress the diffraction modulations of axial intensity and reduce the nonuniformity of transversal intensity distributions.
2006, 30(1): 53-55.
Abstract:
The acousto-optic switch based on optical-fiber fused null coupler is studied experimentally,a null coupler is fabricated,and a fiber acousto-optic switch with insertion loss,less than 0.2dB at 1550nm and coupled efficiency of 98% is realized.Because of its advantages,it is applicable in fiber telecommunication and detection.
The acousto-optic switch based on optical-fiber fused null coupler is studied experimentally,a null coupler is fabricated,and a fiber acousto-optic switch with insertion loss,less than 0.2dB at 1550nm and coupled efficiency of 98% is realized.Because of its advantages,it is applicable in fiber telecommunication and detection.
2006, 30(1): 56-59.
Abstract:
The effect of laser surface strengthening is determined by the thermal circular principle.In order to obtain the reasonable quenching depth and distribution of the micro-hardness,the temperature field resulted from the laser strengthening must be analyzed exactly.The influence of the scanning parameters on the temperature field induced by the laser can be analyzed through the FEM.At the same time,the result form the simulation can be verified with the infrared measuring method.Finally,the conclusion can be drawn that the microstructure of the material surface can be improved effectively by the laser strengthening technology and the thermal circular principle can be affected by the change of the process parameters.
The effect of laser surface strengthening is determined by the thermal circular principle.In order to obtain the reasonable quenching depth and distribution of the micro-hardness,the temperature field resulted from the laser strengthening must be analyzed exactly.The influence of the scanning parameters on the temperature field induced by the laser can be analyzed through the FEM.At the same time,the result form the simulation can be verified with the infrared measuring method.Finally,the conclusion can be drawn that the microstructure of the material surface can be improved effectively by the laser strengthening technology and the thermal circular principle can be affected by the change of the process parameters.
2006, 30(1): 60-63.
Abstract:
The bandwidth of the vertical-cavity semiconductor optical amplifiers(VCSOAs) is commonly narrow.A VCSOAs using a coupled-cavity design to broaden the bandwidth is proposed.The coupled-cavity is made by changing the structure of the distributed Bragg reflector(DBRs) on one side of the active region to construct the passive cavity coupled with the active region.Based on this model and under the reflection mode,the characters of the gain bandwidth of the two cavities and three cavities structure are calcucated.With the transfers matrix method.It is found that the bandwidth is increased to above 3nm at the 10dB peak gain level.It has a great improvement compared to simple cavity structure.
The bandwidth of the vertical-cavity semiconductor optical amplifiers(VCSOAs) is commonly narrow.A VCSOAs using a coupled-cavity design to broaden the bandwidth is proposed.The coupled-cavity is made by changing the structure of the distributed Bragg reflector(DBRs) on one side of the active region to construct the passive cavity coupled with the active region.Based on this model and under the reflection mode,the characters of the gain bandwidth of the two cavities and three cavities structure are calcucated.With the transfers matrix method.It is found that the bandwidth is increased to above 3nm at the 10dB peak gain level.It has a great improvement compared to simple cavity structure.
2006, 30(1): 64-66,69.
Abstract:
A CW THz waveguide discharge-pumped high-power DCN laser operating at 1.54THz(195μm) and 1.58THz(190μm) is developed.With 3m discharge length and 3.4m resonator length.The resonator cavity consists of a pyrex tube of(54mm) diameter and two plane reflectors against its ends.One end is a plane mirror,the other is a metal mesh.The mixture gas of N2,CD4and He(or D2) is used in DCN laser.The laser output power is 0.2W at the 1.54THz.Optimization of various parameters,such as the pressure,the discharge current and the wall temperature are studied in experiments.The free space propagation of the EH11mode of DCN laser is observed.Our experimental study has shown the feasibility of THz high-power CW discharge-pumped DCN waveguide laser with new mixture gas:N2,CD4and D2.The beam profile is found to be qualitatively Gaussian in the far-field(z4m).After optimization of various parameters,this laser delivers 0.15W and 0.16W on the 190μm and 195μm lines,respectively,for EH11mode.It fits the requirements of interferometric measurements on superconducting tokamaks for long time operation.
A CW THz waveguide discharge-pumped high-power DCN laser operating at 1.54THz(195μm) and 1.58THz(190μm) is developed.With 3m discharge length and 3.4m resonator length.The resonator cavity consists of a pyrex tube of(54mm) diameter and two plane reflectors against its ends.One end is a plane mirror,the other is a metal mesh.The mixture gas of N2,CD4and He(or D2) is used in DCN laser.The laser output power is 0.2W at the 1.54THz.Optimization of various parameters,such as the pressure,the discharge current and the wall temperature are studied in experiments.The free space propagation of the EH11mode of DCN laser is observed.Our experimental study has shown the feasibility of THz high-power CW discharge-pumped DCN waveguide laser with new mixture gas:N2,CD4and D2.The beam profile is found to be qualitatively Gaussian in the far-field(z4m).After optimization of various parameters,this laser delivers 0.15W and 0.16W on the 190μm and 195μm lines,respectively,for EH11mode.It fits the requirements of interferometric measurements on superconducting tokamaks for long time operation.
2006, 30(1): 67-69.
Abstract:
The effect of processing parameters on the microstructure and wear property of laser cladding γ/Cr7C3/TiC composite coatings on TiAl intermetallic alloy substrates with NiCr-50%Cr3C2precursor mixed powder is investigated.The results show that the microstructure of the laser cladding composite coatings is refined and the microhardness increases with the increasing of the laser beam scan-rate,but the thickness of the clad coating decreases.The laser cladding coating with the moderate(2.0mm/s) scan-rate exhibits the best wear-resistance under the full dry sliding wear test condition.
The effect of processing parameters on the microstructure and wear property of laser cladding γ/Cr7C3/TiC composite coatings on TiAl intermetallic alloy substrates with NiCr-50%Cr3C2precursor mixed powder is investigated.The results show that the microstructure of the laser cladding composite coatings is refined and the microhardness increases with the increasing of the laser beam scan-rate,but the thickness of the clad coating decreases.The laser cladding coating with the moderate(2.0mm/s) scan-rate exhibits the best wear-resistance under the full dry sliding wear test condition.
2006, 30(1): 70-72.
Abstract:
Based on the numerical simulation of double-cladding Er-doped lasers,experimental study is performed.The output power of 670mW at 1.56μm is obtained when the launched pump power is 4.5W and the fiber is 2.5m long.
Based on the numerical simulation of double-cladding Er-doped lasers,experimental study is performed.The output power of 670mW at 1.56μm is obtained when the launched pump power is 4.5W and the fiber is 2.5m long.
2006, 30(1): 76-77,81.
Abstract:
When TiO2/SiO2film is irradiated by difterent 1.06μm CW-Nd:YAG laser radiation,the time history of the signal reflected from the TiO2/SiO2film is measured till a number of foam and pull-off phenomenon on the TiO2/SiO2film surface is observed.The test results indicate the variation of the reflected signal is caused by thermal effect due to laser irradiation and during the laser irradiation,the difference of thermal deformation of the TiO2/SiO2film and substrate is the main cause of the foam and pull-off phenomenon.
When TiO2/SiO2film is irradiated by difterent 1.06μm CW-Nd:YAG laser radiation,the time history of the signal reflected from the TiO2/SiO2film is measured till a number of foam and pull-off phenomenon on the TiO2/SiO2film surface is observed.The test results indicate the variation of the reflected signal is caused by thermal effect due to laser irradiation and during the laser irradiation,the difference of thermal deformation of the TiO2/SiO2film and substrate is the main cause of the foam and pull-off phenomenon.
2006, 30(1): 78-81.
Abstract:
In order to study the mechanism of photodynamic therapy on malignant tumors,photosensitization of BPD-MA is activated by laser with red light(632.8nm) delivered at 10mW/cm2to give a total dose of 2.4J/cm2.Apoptosis of human bladder cancer BIU-87 cells is determined with flow cytometry with PI staining and terminal deoxyuridine nick end labeling(TUNEL) assays.Results show that photodynamic therapy with BPD-MA significantly increases the rate of apoptosis in BIU-87 cells.A lot of the positive cells in which their nucleus is brown-yellow fine particle shape or overflowing-dispersed are observed after treatment of cells with photodynamic therapy with BPD-MA.However,laser irradiation alone,BPD-MA alone and sham radiation without BPD-MA can not affect apoptosis of human bladder cancer BIU-87 cells.A conclusion can be made that treatment of cells with photodynamic therapy obviously induces human bladder cancer BIU-87 cells to apoptosis,which may be one of the important mechanism of photodynamic therapy on malignant tumors.
In order to study the mechanism of photodynamic therapy on malignant tumors,photosensitization of BPD-MA is activated by laser with red light(632.8nm) delivered at 10mW/cm2to give a total dose of 2.4J/cm2.Apoptosis of human bladder cancer BIU-87 cells is determined with flow cytometry with PI staining and terminal deoxyuridine nick end labeling(TUNEL) assays.Results show that photodynamic therapy with BPD-MA significantly increases the rate of apoptosis in BIU-87 cells.A lot of the positive cells in which their nucleus is brown-yellow fine particle shape or overflowing-dispersed are observed after treatment of cells with photodynamic therapy with BPD-MA.However,laser irradiation alone,BPD-MA alone and sham radiation without BPD-MA can not affect apoptosis of human bladder cancer BIU-87 cells.A conclusion can be made that treatment of cells with photodynamic therapy obviously induces human bladder cancer BIU-87 cells to apoptosis,which may be one of the important mechanism of photodynamic therapy on malignant tumors.
2006, 30(1): 82-85.
Abstract:
The gain of Er3+/Yb3+co-doped phosphate glass fiber amplifiers is discussed from the ion doped concentration of the phosphate glass fiber,quantum conversion efficiency(QCE),signal wavelength and power,pump wavelength and power,and fiber length.The development of oversea is also introduced.
The gain of Er3+/Yb3+co-doped phosphate glass fiber amplifiers is discussed from the ion doped concentration of the phosphate glass fiber,quantum conversion efficiency(QCE),signal wavelength and power,pump wavelength and power,and fiber length.The development of oversea is also introduced.
2006, 30(1): 86-89.
Abstract:
The theoretical analysis of thermal effects in corner-bumped slab solid-state lasers is presented.A new model of the heat distribution is proposed.Based on this model,the distribution of temperature and stress is calculated.The optical distortion induced by the temperature and stress is also analyzed.These results may provide the fundamental theory for the stable design of corner-bumped all solid-state lasers.
The theoretical analysis of thermal effects in corner-bumped slab solid-state lasers is presented.A new model of the heat distribution is proposed.Based on this model,the distribution of temperature and stress is calculated.The optical distortion induced by the temperature and stress is also analyzed.These results may provide the fundamental theory for the stable design of corner-bumped all solid-state lasers.
2006, 30(1): 90-92.
Abstract:
The analytical expression for the electron density induced by a hyperbolic secant pulse is deduced,and an explicit expression for the threshold pulse width in terms of the fluence density is derived.By means of these expressions,damage threshold of the fused silica irradiated by 1053nm femtosecond pulses is calculated which is in agreement with those reported by others.
The analytical expression for the electron density induced by a hyperbolic secant pulse is deduced,and an explicit expression for the threshold pulse width in terms of the fluence density is derived.By means of these expressions,damage threshold of the fused silica irradiated by 1053nm femtosecond pulses is calculated which is in agreement with those reported by others.
2006, 30(1): 93-95.
Abstract:
A modulated laser detection system is designed to measure the zero time of launching.The best way is to adopt the correlation detection to enhance the signal-noise ratio(SNR) and the adaptive threshold,which can detect laser echo in the worst environment.The relationship among the optimal threshold level,SNR and the dynamic separation K is deduced.At SNR is 5.803dB,>1.4,the detection probability and the false alarm probability are 0.988,10-6respectively.
A modulated laser detection system is designed to measure the zero time of launching.The best way is to adopt the correlation detection to enhance the signal-noise ratio(SNR) and the adaptive threshold,which can detect laser echo in the worst environment.The relationship among the optimal threshold level,SNR and the dynamic separation K is deduced.At SNR is 5.803dB,>1.4,the detection probability and the false alarm probability are 0.988,10-6respectively.
2006, 30(1): 96-98.
Abstract:
The power in the bucket(PIB),β parameter,astigmatic parameter,Strehl ratio and the center of beam gravity are reguarded as the characteristic parameters of the laser beam quality in the far field,the influence of absorption in the inner optical system on the laser beam quality is studied.Results are compared with and without the presence of the transversal wind.By using a four-dimension simulation code,a large number of numerical calculations are performed and the results are analyzed physically.It is shown that the peak intensity and focus ability of laser beams increase with decreasing absorption coefficient and increasing wind velocity.However the transversal wind results in an astigmatism.
The power in the bucket(PIB),β parameter,astigmatic parameter,Strehl ratio and the center of beam gravity are reguarded as the characteristic parameters of the laser beam quality in the far field,the influence of absorption in the inner optical system on the laser beam quality is studied.Results are compared with and without the presence of the transversal wind.By using a four-dimension simulation code,a large number of numerical calculations are performed and the results are analyzed physically.It is shown that the peak intensity and focus ability of laser beams increase with decreasing absorption coefficient and increasing wind velocity.However the transversal wind results in an astigmatism.
2006, 30(1): 99-100.
Abstract:
A new accurate method for measuring the birefringence of muscovite mica has been reported in terms of the dispersion relations of the indices and the variety relations between the phase delay and the wavelength.Through measuring the thickness of mica plates and the wavelengths at which they act as quarter wave phase retarders,the birefringence can be obtained in terms of the function relation between the phase delay,the wavelength and the thickness.This method is simple and the accuracy of the measurement is in the order of 10-5.
A new accurate method for measuring the birefringence of muscovite mica has been reported in terms of the dispersion relations of the indices and the variety relations between the phase delay and the wavelength.Through measuring the thickness of mica plates and the wavelengths at which they act as quarter wave phase retarders,the birefringence can be obtained in terms of the function relation between the phase delay,the wavelength and the thickness.This method is simple and the accuracy of the measurement is in the order of 10-5.
2006, 30(1): 101-103,106.
Abstract:
The nonlinear coupled equations of fiber Bragg gratings in single-side boundary condition is solved by means of the finite difference method,and based on the result,influence of Kerr-like nonlinearity on the characteristics of the grating is analyzed.The transmission characteristics of the short pulses in the linear and nonlinear operation areas of the uniform and apodized grating are discussed respectively.The results show that at the proper condition,the fiber Bragg grating can be used as optical switch.
The nonlinear coupled equations of fiber Bragg gratings in single-side boundary condition is solved by means of the finite difference method,and based on the result,influence of Kerr-like nonlinearity on the characteristics of the grating is analyzed.The transmission characteristics of the short pulses in the linear and nonlinear operation areas of the uniform and apodized grating are discussed respectively.The results show that at the proper condition,the fiber Bragg grating can be used as optical switch.
2006, 30(1): 104-106.
Abstract:
For the 3μm~5μm angle-tuned ZnGeP2optical parametric oscillator,an theoretical design of the ZnGeP2parameters is presented.The angle-tuned curve,effective nonlinear coefficient curve and parametric gain curve are calculated respectively,phase-matching angle of the optical parametric oscillators(OPO) and cut angle of the crystal are determined.The walk-off angle and acceptance angle of the crystal are calculated too,which are of some reference value to the experiment research of the ZnGeP2optical parametric oscillator.
For the 3μm~5μm angle-tuned ZnGeP2optical parametric oscillator,an theoretical design of the ZnGeP2parameters is presented.The angle-tuned curve,effective nonlinear coefficient curve and parametric gain curve are calculated respectively,phase-matching angle of the optical parametric oscillators(OPO) and cut angle of the crystal are determined.The walk-off angle and acceptance angle of the crystal are calculated too,which are of some reference value to the experiment research of the ZnGeP2optical parametric oscillator.
2006, 30(1): 107-109.
Abstract:
A multiscale mode named neural networks scale autoregressive(NSA) is presented.The model uses neural networks to represent the map between the pixels residing at images of various resolutions;in stead of the assumption of linearity in linear scale autoregressive(LSA) model.Then back-propagation algorithm is used in the neural networks training to decide the map,finally,the identified map is used to estimate images at finer resolution from coarser versions.Similarity in contrast is used to gauge the degree of similarity between estimated images and target images.The model is applied in face recognition and image segmentation approach using gradient operator is proposed to increase the recognition accuracy.Experimental results show that similarity between image estimated by NSA model and target image is 95.3634%.The NSA-based face recognition system is robust to illumination.
A multiscale mode named neural networks scale autoregressive(NSA) is presented.The model uses neural networks to represent the map between the pixels residing at images of various resolutions;in stead of the assumption of linearity in linear scale autoregressive(LSA) model.Then back-propagation algorithm is used in the neural networks training to decide the map,finally,the identified map is used to estimate images at finer resolution from coarser versions.Similarity in contrast is used to gauge the degree of similarity between estimated images and target images.The model is applied in face recognition and image segmentation approach using gradient operator is proposed to increase the recognition accuracy.Experimental results show that similarity between image estimated by NSA model and target image is 95.3634%.The NSA-based face recognition system is robust to illumination.
2006, 30(1): 110-112.
Abstract:
Starting from the Maggi-Rubinowic theory of the boundary diffraction wave and Helmhotz-Kirchhoff integral theorem,the diffraction integral formula of plane waves diffracted at an annular aperture is derived.The diffraction at a circular aperture and a circular screen,as well as the axial field distribution is treated as the special cases of our general result.The characteristics of axial intensity distribution of the diffracted field are analyzed.Numerical examples show that the results obtained by means of the formula given in this paper are in good agreement with the direct numerical integration of the Kirchhoff integral formula.In the near field there are noticeable discrepancies between our formula and the Rayleigh diffraction integral.
Starting from the Maggi-Rubinowic theory of the boundary diffraction wave and Helmhotz-Kirchhoff integral theorem,the diffraction integral formula of plane waves diffracted at an annular aperture is derived.The diffraction at a circular aperture and a circular screen,as well as the axial field distribution is treated as the special cases of our general result.The characteristics of axial intensity distribution of the diffracted field are analyzed.Numerical examples show that the results obtained by means of the formula given in this paper are in good agreement with the direct numerical integration of the Kirchhoff integral formula.In the near field there are noticeable discrepancies between our formula and the Rayleigh diffraction integral.
