Journals >Chinese Journal of Lasers
Contents
2006
Volume: 33 Issue 9
30 Article(s)
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Research Article
A New Airborne Laser Bathymetry System and Survey Result
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new airborne laser bathymetry system is developed. Compared with the previous one, the new system is improved in data-acquisition rate, accuracy of measuring point position, ability of shallower water detecting and automatic operating. 1000 Hz laser is used to improve density of points gird, backward signals are sepaA new airborne laser bathymetry system is developed. Compared with the previous one, the new system is improved in data-acquisition rate, accuracy of measuring point position, ability of shallower water detecting and automatic operating. 1000 Hz laser is used to improve density of points gird, backward signals are separated into two channels of deep water and shallow water to enhance the ability of detecting signal from shallow water, high accuracy inertial measurement unit (IMU) and global positioning system (GPS) are equipped to improve the measuring point accuracy of orientation and depth. In addition, tide correcting and wave correcting are applied to improve the depth accuracy in data processing. The new system has been tested several times over a sea.The obtained results show that the new system can be practical in ocean survey with good depth accuracy and efficiency..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1163 (2006)
Principles and Experiments of Uniform Scattering Waveguide Multilayer Memory
[in Chinese], [in Chinese], and [in Chinese]
The structure and principles of the uniform scattering waveguide multilayer memory are introduced. To read the information in the waveguide multilayer memory, an optoelectronic detector is used to detect the scattering beams emitted from the information dots on the waveguide surface. But the scattering light intensity The structure and principles of the uniform scattering waveguide multilayer memory are introduced. To read the information in the waveguide multilayer memory, an optoelectronic detector is used to detect the scattering beams emitted from the information dots on the waveguide surface. But the scattering light intensity distribution on the waveguide multilayer memory surface is not uniform which leads to low signal to noise ratio (SNR). Uniform scattering waveguide multilayer memory can cover this defect by changing the information dots depths in each position. It has been proved that one of the methods to realize the uniform scattering is to change the depths of the information dots in each position. And a function about the depths distribution of information dots is deduced in the paper. Furthermore, experimental setup is designed to prove the feasibility of the theories above, An experimental storage device is fabricated and some good experimental results are demonstrated , including two photos contrasting the performance of the uniform scattering waveguide multilayer memory with that of the ordinary waveguide multilayer memory..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1168 (2006)
New Tube-Plate Electrodes for High-Power Transverse Flow CO2Lasers
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new type of tube-plate electrodes more suitable for low order transverse electric (TE) modes output in fields like laser welding has been developed. It has a bigger size in the direction of the laser beam, so that more uniform discharge and longer discharge length can be obtained. Its width in the direction of gas flA new type of tube-plate electrodes more suitable for low order transverse electric (TE) modes output in fields like laser welding has been developed. It has a bigger size in the direction of the laser beam, so that more uniform discharge and longer discharge length can be obtained. Its width in the direction of gas flow is determined by the output laser mode, so that the active volume can be fully used. Its stable and even discharge makes the ballast resistor smaller which reduces extra power consumption. Compared with the former electrodes, it has greatly increased the input power density, the maximum output power and efficiency of mode-selecting lasers. As a result, high electro-optic conversion efficiency of 20% for multimode output, 15% and laser total efficiency of 8% for low order TEM11 output are obtained. It is suitable for home made transversal CO2 lasers, making them capable of acquiring high efficiency for different TE modes output and more suitable for low order TE modes output in fields like laser welding..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1172 (2006)
Influence of the Main-Switch of the Capillary Discharge Setup on Soft X-ray Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The current in the capillary can affect the state of the plasma in pinch process and affect the soft X-ray laser. The inductance of the main switch can change the current waveform. Therefore the scheme of changing current waveform is put forward with different main switches to find the best current waveforms, which areThe current in the capillary can affect the state of the plasma in pinch process and affect the soft X-ray laser. The inductance of the main switch can change the current waveform. Therefore the scheme of changing current waveform is put forward with different main switches to find the best current waveforms, which are fit for soft X-ray pumped by capillary discharge. In the experiment, three kinds of main switches are used to observe the effect of inductance on the current duration and amplitude. The inductance of main switch is estimated and the current amplitude and duration are calculated with pulse power theory. The theoretical results are compared with the experimental data. With three different main-switches, the influence of current waveforms on soft X-ray laser spike is observed. The experimental results show that the ring-disk-shaped main switch, discharge distance of which is 3 cm, is fit for soft X-ray laser best..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1176 (2006)
Improved Method of Calculating Thermal Lens Focal Length in “Top-Hat” End-Pumped Solid-State Lasers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The thermal effect is one of the factors that must be considered in designing the fiber coupled laser diode (LD) end-pumped solid-state lasers. The most convenient way of studying the thermal effect is using an ideal lens with equivalent thermal focal length. The old expression of the thermal lens (TL) focal length givThe thermal effect is one of the factors that must be considered in designing the fiber coupled laser diode (LD) end-pumped solid-state lasers. The most convenient way of studying the thermal effect is using an ideal lens with equivalent thermal focal length. The old expression of the thermal lens (TL) focal length gives values smaller than the actual one. The cause leading to the difference is studied and a new more precise method is given. Numerical calculation is done and curve fitting equations are presented. The results show that the focal length is not only a function of the pump power but also a function of the ratio of the laser radius to the pump radius. When the laser radius is about the same as the pump radius, the ratio of the new value of the focal length to the old one is about 1.6. And at the same condition, the new value of the diffraction loss is much smaller than the one calculated by the old value of the focal length, and is also a function of the pump radius and the laser radius. Experiments show that the new values are closer to the measured results than the old ones..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1180 (2006)
Optical Controlled Microwave Time Delay Technology Based on Broad Band Optical Source
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel optical controlled beam forming network (OCBFN) scheme based on broad band optical source and dispersion device is presented and compared with traditional scheme based on laser diode (LD). The principle of this scheme is illustrated by theoretical analysis and the feasibility is validated by experiment. In expeA novel optical controlled beam forming network (OCBFN) scheme based on broad band optical source and dispersion device is presented and compared with traditional scheme based on laser diode (LD). The principle of this scheme is illustrated by theoretical analysis and the feasibility is validated by experiment. In experiment, Er-doped fiber amplifier (EDFA) is used as broad band optical source, 10 km single mode fiber (SMF) is used as dispersion device for time delay, tuneable optical filter is used to choose operation wavelength, and vector network analyzer is used to generate microwave signal and measure the time delay performance. In 9.25～10.25 GHz microwave band, system time delay range, time delay precision and true time delay performance are measured, and the feasibility of the OCBFN scheme based on broad band optical source is verified by the experiment results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1239 (2006)
Study on Fiber Grating Petroleum Pressure Sensor and Its Reliability
[in Chinese], [in Chinese], and HSU Luke
A high pressure and temperature fiber grating sensor was presented. The sensor was implemented by using three metal tubes. The central elastic metal tube was used to convert pressure into longitudinal strain. The outer tube was only affected by temperature. Fiber grating was fixed on both end of central and outer tube,A high pressure and temperature fiber grating sensor was presented. The sensor was implemented by using three metal tubes. The central elastic metal tube was used to convert pressure into longitudinal strain. The outer tube was only affected by temperature. Fiber grating was fixed on both end of central and outer tube, so as to sense the wavelength increment introduced by the pressure. Temperature compensation scheme was studied, and two fiber Bragg gratings (FBGs) (pressure sensing grating and temperature sensing grating) with similar temperature coefficient were designed. High pressure and high temperature/humidity storage tests were carried out. Results showed that the sensor during the condition of 0～50 MPa had a pressure sensitivity up to 31.7 pm/MPa. After storage of 16 hours under 200 ℃ and immersion into 100 ℃ water for 6 hours, the fiber grating wavelength showed no obviously decay..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1243 (2006)
Beam Transmission
Hybrid Refractive-Diffractive Coupler for Image Fiber Bundle
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
According to the third order aberration theory of binary optical element, the optical coupler system with one diffractive surface, telecentric optical path structure in the object space is shown with calculation and optimization of optical design software ZEMAX, whose operating wavelength is 0.4～0.7 μm, focal length isAccording to the third order aberration theory of binary optical element, the optical coupler system with one diffractive surface, telecentric optical path structure in the object space is shown with calculation and optimization of optical design software ZEMAX, whose operating wavelength is 0.4～0.7 μm, focal length is 27 mm, and optical length is 62.9 mm. The result is available for the image fiber bundle, whose single core diameter is 16 μm and section diameter is 6 mm. Compared with the conventional optical coupler, the hybrid refractive-diffractive system offers considerable reduction in the apparent size, weight, and improves the image quality. The simulation results of optical design software are proved well by the experiments on scenic imaging both indoors and outdoors..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1210 (2006)
Numerical Simulation for Transformation of Annular Laser Beam in Cassegrain Multi-Pass Amplifier
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Taking account of the transmission characteristics of the diaphragm and the saturation of the gain in the process of light amplifying, the evolution of the beam inside the Cassegrain multi-pass amplifier is numerically simulated by using the ray-tracing and split-step fast Fourier-Bessel transform (SSFFT) methods, the Taking account of the transmission characteristics of the diaphragm and the saturation of the gain in the process of light amplifying, the evolution of the beam inside the Cassegrain multi-pass amplifier is numerically simulated by using the ray-tracing and split-step fast Fourier-Bessel transform (SSFFT) methods, the annular beam is coming from Q-switched Nd∶glass laser with ring cavity. Preliminary experimental verification has been carried out. Analysis indicates that the staircase-like features of the input and output mirror reflections are responsible for the poor quality of the output annular beam, and special attention has been paid on optimizing amplifier configuration. As a result, a new type of amplifier configuration is proposed, whose input mirror has an anti-super Gaussian reflection distribution and output mirror has a super-Gaussian reflection distribution. The simulated results indicate that the use of the mirror couple can improve the quality of the output annular beam considerably..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1214 (2006)
Propagation Property of Gaussian Beams Passing through Spatial Filter
[in Chinese], and [in Chinese]
Based on the method of matrix decomposition and expanding the rectangular function into a sum of complex Gaussian functions and the Collins diffraction integral formulae, the propagation characteristics of a Gaussian beams passing through spatial filter are studied. As a result, corresponding analytical formulae are obBased on the method of matrix decomposition and expanding the rectangular function into a sum of complex Gaussian functions and the Collins diffraction integral formulae, the propagation characteristics of a Gaussian beams passing through spatial filter are studied. As a result, corresponding analytical formulae are obtained respectively. By using the numerical method, the analytical formulae are numerically simulated and the results can be got from the simulated figure. Numerical calculations have shown the dependence of the optimum pinhole size on the truncation parameters of the beams. As further extension , numerical calculations are performed for Gaussian beams and flattened Gaussian beams (N=12) propagating in spatial filter of B=0. The relation of truncation parameter and intensity distribution of Gaussian beams passing through filter is obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1220 (2006)
Transverse Mode Distribution of THz Wave by THz Imaging Technology
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The transverse mode distribution of THz wave near the position of focus point was studied in this paper. It is important to know the transverse distribution of THz wave, which can be referenced as an evidence of sample positioning in THz spectroscopy and THz imaging experiments. By using THz point-by-point imaging techThe transverse mode distribution of THz wave near the position of focus point was studied in this paper. It is important to know the transverse distribution of THz wave, which can be referenced as an evidence of sample positioning in THz spectroscopy and THz imaging experiments. By using THz point-by-point imaging technology, THz transverse mode distribution in the positions, where samples are usually placed, is analyzed qualitatively. By applying “slit method”, the beam width of THz wave was measured. The results show that the shapes of the transverse modes of THz wave in different positions around the focus have much difference. To the maximum wavelength of about 1.5 mm of THz wave in the system, the minimum diameter of THz beam at the focus point is around 1.0 mm. The results provide a basic reference for further application of THz Spectroscopy and THz Imaging..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1225 (2006)
Biomedical Photonics and Laser Medicine
Effects of Low Level Laser Irradiation on Delayed Rectifier Potassium Current in Neuron Membrane
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Acutely isolated rat hippocampal CA3 pyramidal neurons were irradiated with a semiconductor laser of 650 nm wavelengh and 5 mW power, and properties of delayed rectifier potassium (K+) channel were studied using the whole-cell patch clamp technique. The experiment indicated that low level laser reversibly reduced the aAcutely isolated rat hippocampal CA3 pyramidal neurons were irradiated with a semiconductor laser of 650 nm wavelengh and 5 mW power, and properties of delayed rectifier potassium (K+) channel were studied using the whole-cell patch clamp technique. The experiment indicated that low level laser reversibly reduced the amplitudes of IK in a time-dependent and voltage-dependent manner. The percentage of inhibition was up to 34.54%±3.22% (n=15) in irradiating 5 min. The maximum activated current densities of control group, irradiation group and restoration group respectively were 429.78±41.40 pA/pF, 283.26±39.62 pA/pF (n=10, P<0.01) and 397.22±36.81 pA/pF (n=10, P>0.05). Laser irradiation significantly affected the activation process of IK. The half-activation voltage and the slope factor of the activation curves were also changed by the laser′s exposure. The half-activation voltages of control group and irradiation group were 5.74±1.56 mV and 20.98±8.85 mV (n=10, P<0.01) respectively, and the slope factors were 16.51±6.67 mV and 17.44±5.19 mV (n=10, P>0.05) respectively. The results show that low level laser can change the properties of delayed rectifier K+ channel. Therefore, repolarization process of action potential is affected. Further, physiological functions of neurons are adjusted, which might contribute to the restoration and regeneration of injured neurons..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1288 (2006)
Laser Manufacturing
Theoretical Analysis And Experiment on Deformation of TA2 Sheet Under Laser Shock
[in Chinese], [in Chinese], and [in Chinese]
Laser shock forming of metal sheet is a novel technique by applying a compressive shock wave on the surface of the metal. It is a mechanical not a thermal process. In this paper, the deformation of TA2 sheet has been analyzed under single-time laser shock loading. By the theoretical analysis, a mathematical model of shLaser shock forming of metal sheet is a novel technique by applying a compressive shock wave on the surface of the metal. It is a mechanical not a thermal process. In this paper, the deformation of TA2 sheet has been analyzed under single-time laser shock loading. By the theoretical analysis, a mathematical model of sheet deformation has been constituted, the relationship between the sheet deformation and the various parameters such as laser energy, sheet thickness and so on has been discussed. This model can be used to optimize the manufacturing parameters, to effectively control sheet forming and can provide theoretical basis for carrying out the large-scale laser shock forming of metal sheet. Considering some factors of affecting sheet forming, three experimental projects have been actualized in virtue of the high-power Nd∶glass laser shock device. Experimental results show that the theoretical deformation amount is comparatively approximate to the experimental results, so the correctness and validity of the theory used to calculate the theoretical sheet-deformation amount under single-time laser shock loading have been validated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1282 (2006)
Laser Physics
Phase-Locking and High Coherent Power Output of Two Fiber Lasers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Phase-locking and coherent output of two fiber lasers are studied. Two fiber laser are coupled into a common self-imaging resonator with a spatial filter for mode selection. The resonator consists of two collimators with 8 mm focal length, a Fourier lens with 500 mm focal length, and a coupled output mirror. The filterPhase-locking and coherent output of two fiber lasers are studied. Two fiber laser are coupled into a common self-imaging resonator with a spatial filter for mode selection. The resonator consists of two collimators with 8 mm focal length, a Fourier lens with 500 mm focal length, and a coupled output mirror. The filter is made of two platinum wires with 20 μm diameter and is placed at the plane of the output mirror. The high-contrast interference strips of the beam profile are observed. Under the output mirror with the different reflectivity of 50% and 30% condition, the slope efficiencies of the individual laser and the laser array are analyzed. When the whole pump power is 60 W, a high coherent power output of 18.3 W is obtained. Steady phase-locking results from a self adjusting process of the laser array which adapts to changes in the optical path lengths. This experiment shows that the coherent power output can be improved greatly by means of this method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1153 (2006)
InAlGaAs Quantum Well 808 nm Laser Diode with Low Threshold Current and High Efficiency
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In order to lower the threshold current and raise the efficiency of 808 nm laser diode, traditional no strain quantum well (QW) is replaced by Al0.3Ga0.7As/InAlGaAs/Al0.3Ga0.7As compression strain QW as the active region. The device structure is optimized firstly, then the structure is grown by metal organic chemical vIn order to lower the threshold current and raise the efficiency of 808 nm laser diode, traditional no strain quantum well (QW) is replaced by Al0.3Ga0.7As/InAlGaAs/Al0.3Ga0.7As compression strain QW as the active region. The device structure is optimized firstly, then the structure is grown by metal organic chemical vapor deposition (MOCVD). By using the proper MOCVD epitaxial condition, the uniformity of the QW photoluminescence (PL) peak wavelength reaches 0.1%. For devices of 50 μm strip width and 750 μm cavity length after facet coating, the threshold current is as low as 81 mA, the slope efficiency is 1.22 W/A, and the wall-plug efficiency reaches 53.7%. By fitting the external quantum efficiency and the cavity length, a cavity loss of 2 cm-1 and internal quantum efficiency of 90% are obtained. All results show that the compression strain laser diodes have better characteristics..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1159 (2006)
Design for Microwave Cavity in a Laser-Cooled Rb Fountain Clock
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The analysis and design for the microwave cavity in laser-cooled Rb fountain clock developed by ourselves were presented and the basic parameters of the microwave cavity developed were designed in this paper. Based on the analysis to the factors of affecting the resonant frequency of the microwave cavity, the laws of tThe analysis and design for the microwave cavity in laser-cooled Rb fountain clock developed by ourselves were presented and the basic parameters of the microwave cavity developed were designed in this paper. Based on the analysis to the factors of affecting the resonant frequency of the microwave cavity, the laws of the resonant frequency with surroundings factors were obtained, which are very important significance to improve the accuracy of the atom clock and to adjust the resonant frequency of the microwave cavity. Finally, the microwave cavity developed was tested and the test results indicated that the performance of microwave cavity met the requirements for laser-cooled Rb fountain clock. The transverse phase shift from the microwave cavity was evaluated by the test results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1185 (2006)
Investigation on Laser-Induced Breakdown Spectroscopy of AlCl3Water Solution
[in Chinese]
The laser-induced breakdown spectroscopy (LIBS) technique has been successfully employed for qualitative and semi-quantitative elemental analysis of trace heavy metal element in solid samples and gas samples. To make an analysis of the heavy metal trace element in liquid, the LIBS of the AlCl3 solution was measured witThe laser-induced breakdown spectroscopy (LIBS) technique has been successfully employed for qualitative and semi-quantitative elemental analysis of trace heavy metal element in solid samples and gas samples. To make an analysis of the heavy metal trace element in liquid, the LIBS of the AlCl3 solution was measured with the single pulse LIBS technique applied flexibly in experiment. The time revolution properties of the Al LIBS signal in the solution, the dependence of the LIBS signal on the laser energy, and the detection limit of the LIBS technique were also investigated. The experimental result showed that the laser energy suitable for this experiment is approximately 50 mJ and lower than that reported in previous experiments. With this easy realizable experiment, a higher detection limit of the LIBS in liquid samples was obtained. The result also showed that there are peculiar time revolution properties of the LIBS signal in liquid. The lifetime of LIBS signal in liquid samples was shorter than that in solid samples, about 30 ns. Meanwhile, the LIBS signal intensity increased and decreased quickly, only lasting several ns..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1190 (2006)
Numerical Research of Two-Dimensional Photonic Crystal Heterostructures with Order-N Method
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The order-N method is used to study the transmission properties of heterostructures of two-dimensional (2D) photonic crystal. Three different heterostructures, i.e., refractive index, pole′s shape and lattice structure heterostructures are numerically calculated respectively. Numerical results show the property of singThe order-N method is used to study the transmission properties of heterostructures of two-dimensional (2D) photonic crystal. Three different heterostructures, i.e., refractive index, pole′s shape and lattice structure heterostructures are numerically calculated respectively. Numerical results show the property of single direction guidance of light, which is similar to that of the semiconductors of electronic type. Analogous analyzing between these two phenomena was made with a simple theory. It is further shown that guide modes appear not only in the case of lattice structure aberrance but also in the other two cases..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1195 (2006)
Modulation Instability Induced by Cross-Phase Modulation in Case of High-Order Dispersion and Quintic Nonlinearity
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Taking into account the second- to the fourth-order dispersion and the quintic nonlinearity of an optical fiber, the synthetical effects of the fourth-order dispersion, the quintic nonlinearity and the input optical power on modulation instability induced by cross-phase modulation of two optical waves are investigated.Taking into account the second- to the fourth-order dispersion and the quintic nonlinearity of an optical fiber, the synthetical effects of the fourth-order dispersion, the quintic nonlinearity and the input optical power on modulation instability induced by cross-phase modulation of two optical waves are investigated. The results show that, in case of high-order dispersion, the positive and negative quintic nonlinearity also intensifies and weakens the cross-phase modulation instability, respectively. The third-order dispersion does not influence the gain spectra of cross-phase modulation instability. When the fourth-order dispersion has the same sign as the second-order one, the existence of the fourth-order dispersion makes a new gain spectrum called the second one appear. And the second gain spectrum actually consists of two small spectra which are always linked togather. The first gain spectrum has nearly the same peak value as that of the small spectrum closing to the zero of the second gain spectrum. With the increase of the input optical power of one of the optical waves, from being separated from each other to drawing near, the two spectra merge into single one eventually, and the peak numbers of the gain spectra also become two from three. In the second gain spectrum, the peak value and the width of the small spectrum which is closing to (far away from) the zero are comparatively smaller in the normal (abnormal ) dispersion region. In the other dispersion regions, there exists only the first or the second spectral region..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1200 (2006)
M2Factor of Partially Coherent Ultrashort Pulsed Beams
[in Chinese]
The M2 factor of partially coherent ultrashort pulsed beams is studied. Starting from the space-time Wigner distribution function and taking the Gaussian Schell-model (GSM) pulsed beam as a typical example, the closed-form expressions for the M2 factor have been derived. The M2 factor of spatially fully coherent GaussiThe M2 factor of partially coherent ultrashort pulsed beams is studied. Starting from the space-time Wigner distribution function and taking the Gaussian Schell-model (GSM) pulsed beam as a typical example, the closed-form expressions for the M2 factor have been derived. The M2 factor of spatially fully coherent Gaussian pulsed beams and quasi-monochromatic GSM pulsed beams can be treated as special cases of the general expressions. Due to the effects of the bandwidth and the spatial correlation degree, the M2 factor of GSM pulsed beams is always greater than 1. It is shown that the M2 factor increases with increasing bandwidth and deceases with increasing spatial correlation degree. Furthermore for chirped pulse, the M2 factor increases as the chirp parameter increases..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1206 (2006)
Materials and Thin Films
AICF Laser Glasses
[in Chinese]
The composition and properties of neodymium-doped silicate, phosphate and fluorophosphates glasses used for inertial confinement fusion (ICF) research-simultaneous high energy and high peak power (1011～1015 W) are reviewed. Optical and spectroscopic properties of different glasses for ICF laser application are comparedThe composition and properties of neodymium-doped silicate, phosphate and fluorophosphates glasses used for inertial confinement fusion (ICF) research-simultaneous high energy and high peak power (1011～1015 W) are reviewed. Optical and spectroscopic properties of different glasses for ICF laser application are compared, the parameters considered include linear and nonlinear refractive indices, stimulated emission cross section, fluorescent lifetime of neodymium ion in 4F3/2→4I11/2 transition. Some special technologies include continuous melting process of phosphate laser glass, dehydroxylation, elimination of platinum inclusion on the large scale laser glasses are discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1165 (2006)
β-FeSi2/Si(111) Thin Films Prepared by Pulsed Laser Deposition
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The even single phase β-FeSi2 thin films were prepared by femtosecond pulsed laser deposition (PLD) on Si(111) wafers at different temperature using an FeSi2 alloy target, and excimer (nanosecond) PLD was introduced to prepared β-FeSi2 thin films also. X-ray diffraction (XRD), field scanning electron microscopy (FSEM),The even single phase β-FeSi2 thin films were prepared by femtosecond pulsed laser deposition (PLD) on Si(111) wafers at different temperature using an FeSi2 alloy target, and excimer (nanosecond) PLD was introduced to prepared β-FeSi2 thin films also. X-ray diffraction (XRD), field scanning electron microscopy (FSEM), energy disperse spectroscopy (EDS), ultraviolet-visible spectra photometer were used to characterize the structure, composition and morphology of the films. The micro drop appeared in the both samples prepared by nanosecond PLD at 500 ℃ and 550 ℃, the maze surface appeared in the surface of the sample prepared at 550 ℃. The single phase β-FeSi2 thin films were gained by femtosecond PLD below 400 ℃, but the proper temperature of nanosecond PLD was 500 ℃; The β-FeSi2 thin films prepared by femtosecond PLD were free of micro drop, the deposition efficiency at unit average laser power in the process of depositing β-FeSi2 thin films by the femtosecond PLD system was 1000 times over that of the nanosecond PLD system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1277 (2006)
Measurement and Metrology
Continuous-Wave Cavity Ring-Down Technique for Accurate Measurement of High Reflectivity
[in Chinese], and [in Chinese]
A continuous-wave cavity ring-down spectroscopy (CW-CRDS) technique employing a broad-band diode laser is developed for the high reflectivity measurement. The theory of square-wave modulated CW-CRDS is presented. Both amplitude and phase shift of the first harmonic of the CRDS signal, measured at an appropriate frequenA continuous-wave cavity ring-down spectroscopy (CW-CRDS) technique employing a broad-band diode laser is developed for the high reflectivity measurement. The theory of square-wave modulated CW-CRDS is presented. Both amplitude and phase shift of the first harmonic of the CRDS signal, measured at an appropriate frequency range, are detected by a lock-in method and fitted to obtain the ring-down time and the reflectivity. The measurements are repeated with different cavity spacings and the reflectivities are determined by the frequency-domain fitting methods. The reflectivity of the cavity mirror is determined to be 99.70%±0.01%. The agreement among the reflectivities determined with the frequency-domain fitting techniques indicates the high reliability of the CW-CRDS technique. Compared with the pulsed CRDS approach, the CW-CRDS technique is simple, low-cost and highly precise due to the use of a CW diode laser with high beam quality..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1247 (2006)
Impact of Fiber Bragg Grating Direction upon Strain Measurement
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The strain measurement by the fiber Bragg grating (FBG) is achieved by the change of FBG′s wavelength upon axial strain. But in the complicated stress state, the FBG′s strain respond error occurs due to the transverse effect. The impact of direction of FBG on strain measurement is proved through theoretical analysis anThe strain measurement by the fiber Bragg grating (FBG) is achieved by the change of FBG′s wavelength upon axial strain. But in the complicated stress state, the FBG′s strain respond error occurs due to the transverse effect. The impact of direction of FBG on strain measurement is proved through theoretical analysis and experimental results. The relationship between direction of FBG and strain measurement error in the state of uniaxial stress was derived and tested. The results indicate that the error increases rapidly when the FBG angle is about 60°, the results of strain are distorted extremely. In order to remove the error, modified formulas for strain were derived..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1251 (2006)
Urban Planetary Boundary Layer Aerosol Monitoring by Lidar at Beijing
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Beijing outfield experiments have been conducted with a new planetary boundary layer (PBL) aerosol monitoring lidar in the summer. The relations of black carbon mass concentration and near ground wind speed to aerosol extinction coefficient are analyzed, and the space-time distributions of aerosol extinction coefficienBeijing outfield experiments have been conducted with a new planetary boundary layer (PBL) aerosol monitoring lidar in the summer. The relations of black carbon mass concentration and near ground wind speed to aerosol extinction coefficient are analyzed, and the space-time distributions of aerosol extinction coefficient are also presented in this paper. The results indicate that: the correlations of black carbon mass concentration and near ground wind speed to aerosol extinction coefficient are good; the near ground weather conditions can affect the space-time diffusion and distribution of aerosol; the aerosol pollution during wee hours and morning is serious than in the afternoon and late at night. The results can be referenced for environment management..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1255 (2006)
Spatial Fourier Fringe Analysis with Single Three-Surface Interferogram
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
To accurately measure transparent elements with parallel surfaces, a new simple and useful method using spatial Fourier analysis technique with single three-surface interferogram is presented. It can obtain the interferometric phase from three-surface inteferogram by extracting the corresponding spectra. Therefore, theTo accurately measure transparent elements with parallel surfaces, a new simple and useful method using spatial Fourier analysis technique with single three-surface interferogram is presented. It can obtain the interferometric phase from three-surface inteferogram by extracting the corresponding spectra. Therefore, the profiles of both surface and variation in thickness are calculated simultaneously. By comparing the spatial Fourier fringe analysis with phase-shifting interferometry (PSI), it can be found that the measured results are almost the same.The main errors which cause the measurement difference for the two method are given and analyzed, such as reflection from back surface, boundary problem, off-axial aberrations and homogeneity of the plate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1260 (2006)
Optical Communication
Demonstration of 1.6 Tbit/s (40×40 Gbit/s) Wavelength Division Multiplexing 160 km Straight Line Transmission Experiments
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A 40×40 Gbit/s multi-wavelength carrier-suppressed return-to-zero (CS-RZ) format optical transmitter is designed. Based on this transmitter and the experiment of one channel 400 km×40 Gbit/s optical transmission which was upgraded from the National Natural Science Foundation of China Net (NSFCNet, 400 km×A 40×40 Gbit/s multi-wavelength carrier-suppressed return-to-zero (CS-RZ) format optical transmitter is designed. Based on this transmitter and the experiment of one channel 400 km×40 Gbit/s optical transmission which was upgraded from the National Natural Science Foundation of China Net (NSFCNet, 400 km×10 Gbit/s), a 40×40 Gbit/s wavelength division multiplexing (WDM) optical transmission is also realized. The results show that it is feasible to upgrade a middle and short haul 10 Gbit/s WDM optical transmission system to 40 Gbit/s. However, the chromatic dispersion must be compensated precisely in every channel, since the dispersion tolerance of 40 Gbit/s system is lower than 60 ps/nm and the dispersion slope of the transmission optical fiber does not match well the dispersion slope of the dispersion compensation module. The results also show that the system optimization or the links renewal is necessary for 40 Gbit/s WDM system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1230 (2006)
Mode Coupling in Polymer Optical Fiber and Its Enhancement to Transmission Bandwidth
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
There existed strong mode coupling when light traveling in the polymer optical fiber (POF). Due to the mode coupling , the transmission bandwidth of POF was enhanced. The mode coupling of POF was studied based on the power-flow equation. The mode coupling coefficient of POF was measured experimentally, the measured couThere existed strong mode coupling when light traveling in the polymer optical fiber (POF). Due to the mode coupling , the transmission bandwidth of POF was enhanced. The mode coupling of POF was studied based on the power-flow equation. The mode coupling coefficient of POF was measured experimentally, the measured coupling coefficient was 7.61×10-4 rad2/m. The mode coupling process in POF was simulated numerically using measured coupling coefficient; a coupling length of 20 m was obtained. The real bandwidth of POF was revealed from the coupling length. The transmission bandwidth of POF was about 130 Mbit/s over 150 m. To testify the result, a 125 Mbit/s·150 m local area network (LAN) POF communication experiment was carried out, the transmission waveform and communication eye diagram were analyzed. The experiment results showed that the transmission bandwidth of POF was enhanced by mode coupling, the transmission distance of POF could reach 150 m at data rate 125 Mbit/s..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 9, 1234 (2006)
Rapid Communications
[in Chinese]
[in Chinese], [in Chinese], [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. 33, Issue 9, 1294 (2006)
[in Chinese]
[in Chinese], [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. 33, Issue 9, 1295 (2006)
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