Journals >Chinese Journal of Lasers
Contents
2007
Volume: 34 Issue 12
28 Article(s)
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Research Article
[in Chinese]
[in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1737 (2007)
[in Chinese]
[in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1752 (2007)
Large-Mode-Area Photonic Crystal Fiber Laser Output High Average Power Femtosecond Pulses
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Many experiments have proven the potential of power scaling of Yb-doped fibers when they are used in lasers and amplifiers. Recently, photonic crystal fibers have pushed the output parameters of femtosecond fiber laser to compare to the solid-state laser system. Our recently work on this field is presented in this papeMany experiments have proven the potential of power scaling of Yb-doped fibers when they are used in lasers and amplifiers. Recently, photonic crystal fibers have pushed the output parameters of femtosecond fiber laser to compare to the solid-state laser system. Our recently work on this field is presented in this paper. A mode-locking high energy photonic crystal fiber laser operating in the dispersion compensation free regime generates positively-chirped pulses with an average power 2 W of 51 MHz in a stable and self-starting operation. The energy of the pulse is up to 40 nJ and the pulse duration is 450 fs. A domestic Yb-doped double-cladding large-mode-area fiber was used for amplication experiment. With the milliwatt seed laser pulse inputting, 103 gain was obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1603 (2007)
Optimization Design for Aspheric Collimation System of High-Power Semiconductor Laser Beam
[in Chinese], [in Chinese], and [in Chinese]
Based on the law of refraction in vector form, the laser beam propagation in an aspheric and asymmetrical laser beam collimation system from high-power semiconductor laser has been researched for spatial laser beam long-distance propagation. The matrixes transfer formulas for spatial rays have been obtained. For the hiBased on the law of refraction in vector form, the laser beam propagation in an aspheric and asymmetrical laser beam collimation system from high-power semiconductor laser has been researched for spatial laser beam long-distance propagation. The matrixes transfer formulas for spatial rays have been obtained. For the high-power semiconductor laser with line emitting source, the divergent angle of the converted laser beam has been diminished by the optimization design of high precision collimation system. Cassegrain optical antenna has been designed by optical design software CODE-V to collimate the laser beam further. Based on the two-point algorithm, the divergent angle for the collimation system has been measured. The measured results indicate that the divergent angle of the optimization collimation system is less than 1.924 mrad, and the divergent angle collimated by the optical antenna is less than 96.2 μrad. The spatial rays method possesses reference meaning for accurate counting of complex optical systems. The collimation system designed for high-power semiconductor laser with line emitting source can be widely used in long-distance spatial laser communication..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1607 (2007)
Spectrum-Width Stability of All Solid-State Frequency-Shifted Feedback Laser
[in Chinese], and [in Chinese]
The continuous-wave output of the frequency-shifted feedback (FSF) laser with Nd∶YVO4 crystal was analyzed, with laser rate equations by dividing the gain spectrum of laser crystal into many bands in unit of round-trip frequency shift and frequency-shifting. The output spectrum width and spectrum shift with varied pumpThe continuous-wave output of the frequency-shifted feedback (FSF) laser with Nd∶YVO4 crystal was analyzed, with laser rate equations by dividing the gain spectrum of laser crystal into many bands in unit of round-trip frequency shift and frequency-shifting. The output spectrum width and spectrum shift with varied pumping power level, diffraction efficiency of acousto-optical modulator (AOM), round-trip frequency shift and gain spectrum width of laser crystal were given in details. Based on a resonator structure of end-pumping and frequency-shifter of AOM, an all solid-state FSF laser with Nd∶YVO4 crystal was constructed. The experimental results were in consistent with the simulated ones, and output power higher than 1 W is also obtained. The result proves the spectrum-width stability of the FSF laser at variant pumping levels..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1612 (2007)
Mode Selection of a Tapered Large-Mode-Area Fiber Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
For large-mode-area (LMA) fiber laser, the beam quality is not as good as that of single mode fiber laser. A tapered section was introduced to a LMA fiber. The core diameter of the smallest part was 9 μm, which was located 5 mm away from the output end of the fiber and about three times smaller than the conventional fiFor large-mode-area (LMA) fiber laser, the beam quality is not as good as that of single mode fiber laser. A tapered section was introduced to a LMA fiber. The core diameter of the smallest part was 9 μm, which was located 5 mm away from the output end of the fiber and about three times smaller than the conventional fiber core with the diameter of 26 μm. The experimental results show that the beam quality factor M2 is reduced from 3.50 to 1.81, with the slope efficiency from 63.6% to 51.1%. Although the tapering induces 19.8% power loss, the brightness of the tapered fiber laser is 3 times as much as that of the untapered..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1625 (2007)
Performance Improvement of Nd∶GdVO4Laser under 879 nm Direct Pumping
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Thermal effect in the laser diode (LD) high-power pumped solid-state lasers will reduce the efficiency of output power, decrease the output beam quality, deteriorate the resonator stability and so on. The novel 879 nm LD instead of 808 nm LD was used to pump Nd∶GdVO4 crystal rod directly, driving Nd3+ ions into the lasThermal effect in the laser diode (LD) high-power pumped solid-state lasers will reduce the efficiency of output power, decrease the output beam quality, deteriorate the resonator stability and so on. The novel 879 nm LD instead of 808 nm LD was used to pump Nd∶GdVO4 crystal rod directly, driving Nd3+ ions into the laser emitting level, avoiding useless heat generation during no-radiation transition and reducing the thermal effects efficiently. In the same experimental conditions, the comparison on performances of Nd∶GdVO4 laser between under 808 nm LD pumping and under 879 nm LD pumping was demonstrated, and showed that the performances of the former were superior to that of the latter. In the 879 nm LD pumped Nd∶GdVO4 plane-plane cavity laser, the maximum TEM00 1063 nm output power of 9.8 W is obtained at an absorbed pump power of 16.3 W, an optical-optical efficiency of 60.1% and a slope efficiency of 68.4% are achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1629 (2007)
High Power All-Solid-State Blue-Green Laser Based on Quadrature Frequency Conversion
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effect of multi transversal mode on quadrature frequency conversion in a solid-state laser was analyzed, and the relation between the conversion efficiency and the divergent angle was conducted. A quadrature frequency conversion scheme using two KTP crystals was implemented in an all-solid-state Nd∶YAG laser with hThe effect of multi transversal mode on quadrature frequency conversion in a solid-state laser was analyzed, and the relation between the conversion efficiency and the divergent angle was conducted. A quadrature frequency conversion scheme using two KTP crystals was implemented in an all-solid-state Nd∶YAG laser with high-order transverse mode. An energy-conversion efficiency of 75.5% is obtained when the fundamental laser intensity is 121 MW/cm2. This experiment indicates that when the parameters of nonlinear crystals are properly optimized, high-efficiency frequency doubling can be achieved using quadrature frequency-conversion scheme even in a multimode solid-state laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1634 (2007)
A Novel Coupling Technique of Optical Fiber for High Peak Power Pulse Laser
[in Chinese], and [in Chinese]
The guiding and coupling principles of light cone are analyzed, and the design parameters are calculated by the ray theory. Some parameters of light cone, such as a transmitting ratio and coupling efficiency were tested: the transmitting ratio is 99%, the coupling efficiency is beyond 73%, the laser-induced damage threThe guiding and coupling principles of light cone are analyzed, and the design parameters are calculated by the ray theory. Some parameters of light cone, such as a transmitting ratio and coupling efficiency were tested: the transmitting ratio is 99%, the coupling efficiency is beyond 73%, the laser-induced damage threshold energy density of front face of cone is 56 J/cm2, and the threshold of power density is 2.25 GW/cm2, output laser energy reaches 50 mJ before the light cone is damaged. Finally, it is proved that high peak power pulse laser can be coupled into fibers through light cone, which can increase the capacity of laser power..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1639 (2007)
Micromachining of an in-Fiber Extrinsic Fabry-Perot Interferometric Sensor by Using a Femtosecond Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The fabrication of a micromachining extrinsic Fabry-Perot (F-P) interferometer (MEFPI) within a conventional single-mode fiber (SMF) by using a 800 nm femtosecond laser was reported in this paper. The strain and temperature characteristics of the MEFPI are investigated. The experimental results show that the strain senThe fabrication of a micromachining extrinsic Fabry-Perot (F-P) interferometer (MEFPI) within a conventional single-mode fiber (SMF) by using a 800 nm femtosecond laser was reported in this paper. The strain and temperature characteristics of the MEFPI are investigated. The experimental results show that the strain sensitivity is 0.006 nm/με, and linearity is 99.69% at the range of 0 to 350 με. Furthermore, the interference fringe of the MEFPI shifts about 0.15 nm to the short wavelength while the temperature rises from 20 ℃ to 100 ℃. Such kind of in-fiber interference sensors has many advantages, such as compact size, good reliability, low cost, easy fabrication and mass-production, which offers great potential for sensing applications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1660 (2007)
Effect of Deviation Distance to Focal Spot on Nanosecond-Pulsed-Laser Drilling Rates in Air
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effects of deviation distance from the focal spot to the target surface (d) on nanosecond-pulsed-laser drilling rates under different pulse energy were experimentally studied. The laser operated at a wavelength of 1.06 μm and pulse width of 10 ns (full width at half maximum). Pulse energy of 26, 52, 85, 204 and 274The effects of deviation distance from the focal spot to the target surface (d) on nanosecond-pulsed-laser drilling rates under different pulse energy were experimentally studied. The laser operated at a wavelength of 1.06 μm and pulse width of 10 ns (full width at half maximum). Pulse energy of 26, 52, 85, 204 and 274 mJ was used respectively. The drilling rate was measured under different pulse energy and d value. The experimental results show that d is one of the important aspects affecting laser drilling rate, and that it is a reasonable choice of using relatively low intensity laser pulses and d at +3～+4 mm. When d<0, the drilling rate is mainly determined by laser-induced thrermal ablation and shielding of plasma. And when d>0, the drilling rate is mainly determined by thermal ablation, shielding of plasma and promoting absorption induced by irradiation from the plasma at the beam waist..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 6121 (2007)
Biomedical Photonics and Laser Medicine
A Real-Time Energy Meter for Medical Excimer Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A laser power/energy meter which is designed based on laser induced thermoelectric voltage (LITV) effect was reported. The laser power/energy meter can not only measure and record the energy of every input laser pulse and the total real-time energy, but also can record the response waveform of every input laser pulse. A laser power/energy meter which is designed based on laser induced thermoelectric voltage (LITV) effect was reported. The laser power/energy meter can not only measure and record the energy of every input laser pulse and the total real-time energy, but also can record the response waveform of every input laser pulse. It realize the real-time controlling for laser energy. It was used to simulating experiment for 248 nm excimer laser. The result show that the relative standard deviation (RSD) of the laser output energy is 8.6%～10.7% with repetition frequency. And under the simulating setup parameters of refractive surgery, 193 nm excimer laser was measured, and its RSD is 8.3%. This kind of laser power/energy meter would be very significant in cornea refraction operation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1732 (2007)
Holography and Information Processing
A Holographic Display Screen Based on Laser Speckle Structure
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A method of designing and fabricating display screen based on the planar holography is proposed. The holographic screen is composed of many pixels, and every pixel is produced by the speckle image holography. The input illumination is diffracted by the gratings in each pixel and directionally diffracted to reconstruct A method of designing and fabricating display screen based on the planar holography is proposed. The holographic screen is composed of many pixels, and every pixel is produced by the speckle image holography. The input illumination is diffracted by the gratings in each pixel and directionally diffracted to reconstruct image observed on the holographic plane. The reconstructed speckle image, which is influenced by both incident angle of reference beam and the width of slot, is demonstrated by numerical simulation. A holographic projection screen sample with a size of 600 mm×800 mm (about 40 inch diagonal) and thickness of 1.5 mm is fabricated. The corresponding fabrication details are given .The proposed holographic screen has the advantages of high brightness and achromatism. Furthermore, the surface-relief micro-structure can be manufactured by the nano-imprint technology efficiently and cost-effectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1665 (2007)
Imaging Resolution Analysis of Digital Holographic Microscopy
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
According to optical imaging theory and the point spread function of digital holographic system, the imaging resolution of the digital holographic microscopy was investigated. The imaging resolution expressions of the digital holographic systems with and without pre-magnification were presented in details. With those fAccording to optical imaging theory and the point spread function of digital holographic system, the imaging resolution of the digital holographic microscopy was investigated. The imaging resolution expressions of the digital holographic systems with and without pre-magnification were presented in details. With those formulas, it is clearly shown that only when the imaging resolution of CCD is not below the resolution of the microscope objective (MO), the imaging resolution of the whole system is dependent on the numerical aperture (NA) of MO. Otherwise, it is dependent on the numerical aperture of the CCD. Experimental imaging of US air force-resolution test target is performed using the lensless Fourier transform configuration. The experimental results that ultimate resolution of reconstructed image in horizontal direction and vertical direction is 3.91 μm and 4.38 μm respectively. Finally, recording and reconstructing of holograms for stripe object are stimulated , and results are corresponding with theoretical analysis..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1670 (2007)
Laser Manufacturing
A15-Nb3Al/B2Laminated-Structure Intermetallic Composites Produced by Laser Deposition
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Niobium-based intemetallic composite is a kind of potential high temperature structural material. However, it is very brittle at room temperature. Laser deposition was used to synthesize A15-Nb3Al intemetallic brittle coating and B2 structure tough alloy coating by using Nb-12Ti-22Al and Nb-40Ti-15Al powder blends, resNiobium-based intemetallic composite is a kind of potential high temperature structural material. However, it is very brittle at room temperature. Laser deposition was used to synthesize A15-Nb3Al intemetallic brittle coating and B2 structure tough alloy coating by using Nb-12Ti-22Al and Nb-40Ti-15Al powder blends, respectively. By deposition technique optimization, the composite of the coating and layer thickness can be controlled. An A15-Nb3Al/B2 laminated-structural intermetallic composite material was then produced via layer by layer deposition method. The element composition, microstructure and microhardness of the laminated intermetallic composite show periodic variation,and gradual change at the interface between two neighboring layers. This material demonstrates good strength at room and elevated temperature. The yield strengths of laminated composites increased with the brittle/ductile layer thickness ratios. The horizontal yeild strengths reach up to 1030 MPa and 301 MPa at room temperature and 900 ℃, and the vertical yeild strengths reach up to 871 MPa and 267 MPa at room temperature and 900 ℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1694 (2007)
Model Manufacturing Process from Aluminum Alloys Using Selective Laser Melting
[in Chinese]
The paper focused on the technological research on model manufacturing using selective laser melting (SLM) process, materials under investigation were four kinds of aluminum alloys powder AlSi25, AlSi10Mg, AlMgSi0.5 and AlMg3. The results showed that different aluminum alloys have different laser process thresholds. WhThe paper focused on the technological research on model manufacturing using selective laser melting (SLM) process, materials under investigation were four kinds of aluminum alloys powder AlSi25, AlSi10Mg, AlMgSi0.5 and AlMg3. The results showed that different aluminum alloys have different laser process thresholds. When laser power was above this threshold, aluminum alloy powder melted and bonded with the under layer and fest metallurgical bonding formed, model with approx. 100% density can be achieved. Further research showed that the density of sample from all the four kinds of aluminum alloys varied with laser power and scanning velocity, at the same time they showed different sensitivity to the forming of holes and crack because of their different metallurgical properties. Tensile sample from AlSi10Mg was manufactured with optimized parameters. The tensile test showed that the sample of SLM possessed better mechanical properties than aged casting tensile sample. The research showed that SLM would be one of the effective methods of direct manufacturing for metallic models and parts..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1700 (2007)
Model and Control Technology for Machining Large-Diameter Optical Aspheric Mirror
[in Chinese], and [in Chinese]
Numerical control (NC) machining is an effective method for soluting the problem of aspheric machining. For the application of aspherical lens in large solid-state laser system , a novel method via ultra-precision grinding has been proposed to shape the hard-brittle material with high accuracy and efficiency. To improvNumerical control (NC) machining is an effective method for soluting the problem of aspheric machining. For the application of aspherical lens in large solid-state laser system , a novel method via ultra-precision grinding has been proposed to shape the hard-brittle material with high accuracy and efficiency. To improve the machining quality and efficiency, the machining experiments are carried out to find the influence of grinding depth and feeding speed on surface quality. The subsurface defects have been effectively restrained by adopting the larger grinding depth and smaller feeding speed. And the compensation machining is also investigated. The compensation machining with equal profile error curve can reach fine surface with less than 3-microns error in peak-valleyy (PV) values for 330 mm×330 mm aspherical lens..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1705 (2007)
Laser Cladding Ni-Based Tribaloy 700 Coatings on TA2 Titanium Alloy
[in Chinese], [in Chinese], and [in Chinese]
Laser cladding coatings of TA2 titanium alloy with preplaced Tribaloy700(T700) powder to fabricate Ni-based tribaloy 700 coatings are experimentally studied for developing a hardfacing process of titanium alloy. Ni-based alloy coatings without cracks and pores on the boundary are obtained. The dilution of Ti will expedLaser cladding coatings of TA2 titanium alloy with preplaced Tribaloy700(T700) powder to fabricate Ni-based tribaloy 700 coatings are experimentally studied for developing a hardfacing process of titanium alloy. Ni-based alloy coatings without cracks and pores on the boundary are obtained. The dilution of Ti will expedite the separation and growth of laves phases. Microstructure of the coating consists of mainly γ-Ni phase in cell and dendrite structure with less dilution of Ti and matrix (TiNi + γ-Ni) +laves phases in large dimension with more dilution of Ti. The transition region between the coating and substrate is about 80～100 μm thick. Microhardness test results show that, with solution strengthening and grain refinement, the microhardness of T700 coatings is higher than that of routine methods. The dilution of Ti will increase the microhardness dramatically. The microhardness of the coatings ranges from 700HV to 1000HV according to dilution ratio of Ti, and the microhardness are four to five times higher than that of TA2 alloy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1710 (2007)
Characteristics of Laser-TIG Double-Side Welding for Aluminum Alloys
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laser-TIG double-side welding (LTDSW) for aluminum alloys was explored. The double-side welding for 4 mm and 10 mm thick 5A06 aluminum alloys was implemented, and the characteristics of LTDSW were investigated. The results show that the technology combines the advantages of laser and TIG. Stable process and good weldinLaser-TIG double-side welding (LTDSW) for aluminum alloys was explored. The double-side welding for 4 mm and 10 mm thick 5A06 aluminum alloys was implemented, and the characteristics of LTDSW were investigated. The results show that the technology combines the advantages of laser and TIG. Stable process and good welding appearance were obtained. Other remarkable advantages, such as increasing joint penetration, deceasing welding defects, enhancing productive efficiency, reducing welding cost, were also achieved. The reliable join for 4 mm thick aluminum alloys was realized with 1.0 kW laser power. Compared with laser welding, the pore amount of LTDSW is descreased. The pore distribution is mainly determined by the energy ratio of laser and arc. The amount and size of pore are mainly determined by the welding heat input. The average tensile strength of joints is 310 MPa, about 88% of base metal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1716 (2007)
Simulation on Influence of Scanning Passes during Laser Bending of Steel Plate
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The influence of scanning passes on laser bending process was studied for the plates with 6 mm and 9 mm thickness at different laser parameters. A three-dimensional coupled thermo-mechanical finite element method (FEM) model was developed to calculate the variation of temperature field, stress field and bending angle dThe influence of scanning passes on laser bending process was studied for the plates with 6 mm and 9 mm thickness at different laser parameters. A three-dimensional coupled thermo-mechanical finite element method (FEM) model was developed to calculate the variation of temperature field, stress field and bending angle during multiple-irradiation laser bending process. Real-time temperature and bending angle were measured. The simulation results were in agreement with the experimental results well. The simulation results showed that the temperature distribution was similar between each irradiation. Residual stresses and bending angle were increasing with the increase of laser scanning passes. The bending angle of 6 mm thickness plate decreased as the irradiation number increasing, while that of 9 mm thickness plate increased linearly. Laser parameters affected the extent of strain hardening on the underside of the steel plate. Under different laser parameters, the bending angle of various thickness plates has dissimilar relationship with the laser scanning passes..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1721 (2007)
CO2Laser Welding of Vehicle Body
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on experiments of CO2 laser welding to vehicle body, joint microstructure and mechanical property of specimen are analyzed. The deep punching performance of laser welding adopting Ar as protective gas is better than that acquired by adopting N2. Meanwhile the percentage of zinc in welding seam can be effectively Based on experiments of CO2 laser welding to vehicle body, joint microstructure and mechanical property of specimen are analyzed. The deep punching performance of laser welding adopting Ar as protective gas is better than that acquired by adopting N2. Meanwhile the percentage of zinc in welding seam can be effectively controlled by the side protective gas blowing. Welding depth and width varying with laser power and speed of welding were also investigated. The result indicates that it does not appear some flaws, such as gas hole, crack and softening of heat affect zone (HAZ) in laser welding seam of tailor-welded blanks through optimizing technology parameters. The deep punching performance of tailor-welded blanks is of very high quality. Forming property of tailor-welded board depends on strength ratio and thickness ratio of two materials, welding line mainly locates at high strength galvanized steel sheet, the offset of welding line tends toward thin general steel..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1726 (2007)
Laser Physics
Low-Threshold Widely-Tunable Intracavity Q-Switched Nd∶YVO4/PPLN Optical Parametric Generator
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A quasi-phase-matched intracavity optical parametric generator (QPM-IOPG) is demonstrated based on multi-grating periodically poled lithium niobate (PPLN) internal to an acousto-optically Q-switched Nd∶YVO4 laser. The PPLN crystal is 20 mm long and periodically poled along the z-axis by using external electric poling tA quasi-phase-matched intracavity optical parametric generator (QPM-IOPG) is demonstrated based on multi-grating periodically poled lithium niobate (PPLN) internal to an acousto-optically Q-switched Nd∶YVO4 laser. The PPLN crystal is 20 mm long and periodically poled along the z-axis by using external electric poling technique. While the Q-switch repetition rate is set at 19 kHz, the signal wavelength can be continuously tuned from 1384 nm to 1541 nm by combining temperature tuning and grating tuning. The measured signal pulse width is approximately 80 ns. While the PPLN crystal temperature is 140 ℃, the QPM-IOPG threshold is just 0.93 W with the 29 μm grating period and 3 W of laser diode (LD) pump power produces 140 mW signal output. With the 26.5 μm grating period, the QPM-IOPG threshold is increased to 1.36 W and at an incident LD pump of 3 W, 105 mW signal is obtained. The reason of the different thresholds and conversion efficiencies for various grating periods is analyzed and the theoretical calculation of the QPM-IOPG threshold is also presented..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1643 (2007)
Materials and Thin Films
Effect of Yb3+on Infrared and Upconversion Emission of Er3+-Doped Tellurite-Based Glasses
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Er3+/Yb3+ co-doped TeO2-ZnO-La2O3 glasses were prepared, and the absorption spectra, fluorescence spectra and upconversion emission spectra of Er3+ ions were measured. Effects of Yb3+ on the infrared fluorescence at 1.5 μm band and the visible upconversion luminescence of Er3+ in the glasses were investigated under theEr3+/Yb3+ co-doped TeO2-ZnO-La2O3 glasses were prepared, and the absorption spectra, fluorescence spectra and upconversion emission spectra of Er3+ ions were measured. Effects of Yb3+ on the infrared fluorescence at 1.5 μm band and the visible upconversion luminescence of Er3+ in the glasses were investigated under the excitation at 975 nm. With the increase of Yb2O3 concentration, the 1.5 μm band infrared fluorescence intensity and the visible upconversion luminescent intensity increase evidently due to the effective energy transfer from Yb3+ to Er3+, but the latter increases more efficiently. According to the simulation of rate equations, the theoretical result agrees well with the experiment, indicating that Er3+/Yb3+ co-doped tellurite-based glass is a promising gain media suitable for developing upconversion fiber lasers. And the analysis to upconversion emission shows that a two-photon upconversion process is assigned to the intense green and red emission, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1688 (2007)
Measurement and Metrology
Light Scattering Virtual Simulation of Red Blood Cell under Double Curve Symmetrical Model
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and Frank Wyrowski
To meet the demands of precise measurement of cell profile, the VirtualLab system was applied and a processing function of interfaces transmission was chosen. First, a double curve symmetrical model is designed out based on the character of red blood cell (RBC) in its shape and light scattering. In addition to this, seTo meet the demands of precise measurement of cell profile, the VirtualLab system was applied and a processing function of interfaces transmission was chosen. First, a double curve symmetrical model is designed out based on the character of red blood cell (RBC) in its shape and light scattering. In addition to this, several RBC scattering imitations are made after spherical and no-spherical models under some different light source and situation. Finally, these forward scatting patterns, scattering distribution of amplitudes and distribution of phase are all obtained with the VirtualLab system. The phase distribution in the field shows the correlation between cell′s shape, framework and situation with them. The forward scattering phase distribution of RBC is expected to become a new tool to discriminate cells..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1676 (2007)
Measurement Performance of Simultaneous Phase-Shifting Interferometer
[in Chinese], [in Chinese], and [in Chinese]
The structure of a simultaneous phase-shifting interferometry system based on two-dimensional (2D) orthogonal grating diffraction is analyzed in detail, including components of interference, spatial beam splitting, polarizing phase-shifting element, and image sampling and processing. The four diffraction-order beams ofThe structure of a simultaneous phase-shifting interferometry system based on two-dimensional (2D) orthogonal grating diffraction is analyzed in detail, including components of interference, spatial beam splitting, polarizing phase-shifting element, and image sampling and processing. The four diffraction-order beams of the 2D orthogonal transmission grating are taken as the testing beams. Both the theory and the experiment show that the beam splitting of the system function well. A polarizing array, consists of four linear polarizing elements of which transmitting directions change 45° in turn, acts as the phase-shifter. According to the requirement of spatial consistency, the four independent interferograms with 90° phase shift are divided. High phase-shifting precision is obtained. The repetitive experimental results show that, when the amplitude-frequency product of environmental vibration does not exceed 100 Hz λ, the peak to valley of testing repeatability is less than 0.02λ, so the advanced system can be used in on-line testing and dynamic measurement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1682 (2007)
Optical Communication
A Path Protection Algorithm with Differentiated Reliability in Multi-Domain Optical Networks
[in Chinese], and [in Chinese]
Path protection with differentiated reliability is a very promising survivable scheme in optical networks. It can meet the requirement of network traffics with different reliability demand in a resource efficient manner. This issue has been researched mainly in single-domain optical networks, however, its achievement cPath protection with differentiated reliability is a very promising survivable scheme in optical networks. It can meet the requirement of network traffics with different reliability demand in a resource efficient manner. This issue has been researched mainly in single-domain optical networks, however, its achievement can not be applied to next generation optical network directly, which is accepted to be a multi-domain optical netwrok. Therefore a path protection algorithm with differentiated reliability in multi-domain optical networks is proposed in this paper. And its performance is evaluated through simulation, which verifies that the algorithm can not only meet the reliability demand of different traffics in multi-domain optical networks, but also improve the network resource efficiency and reduce the traffic blocking probability..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1648 (2007)
A Novel Fixed Length Digital Pulse Interval Modulation for Optical Wireless Communications
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new fixed-length digital pulse interval modulation (FDPIM) is presented on the basis of pulse position modulation (PPM) which needs symbol synchronization and digital pulse interval modulation (DPIM) with unfixed symbol length. After introducing symbol structure, average transmit power and bandwidth efficiency are stA new fixed-length digital pulse interval modulation (FDPIM) is presented on the basis of pulse position modulation (PPM) which needs symbol synchronization and digital pulse interval modulation (DPIM) with unfixed symbol length. After introducing symbol structure, average transmit power and bandwidth efficiency are studied. Based on weak turbulence channel model, the packet error rate is derived, and compared with on-off keying (OOK), PPM and DPIM. Simulations show that error rate of FDPIM is bigger than PPM and DPIM, but obviously less than OOK. Moreover, FDPIM, which do not need symbol synchronization and has fixed symbol length, can simplify the receiver and solve modulator waiting or buffer overflow in comparison with PPM and DPIM respectively. Hence, FDPIM has some advantages in wireless optical communications system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1655 (2007)
Rapid Communications
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 12, 1736 (2007)
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