Journals >Chinese Journal of Lasers
Contents
2004
Volume: 31 Issue 5
29 Article(s)
Export citation format
Research Article
Experimental Investigation on Ablation Character of Capillary Discharge
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A capillary discharge setup, consisting of a Marx generator system, main switch, Blumlein transmission line and pre-pulse circuit, has been developed . This device is designed to excite electron-collision pumping scheme XUV laser in Ne-like Ar at 46.9 nm. The ablation characteristics of the discharged capillary are expA capillary discharge setup, consisting of a Marx generator system, main switch, Blumlein transmission line and pre-pulse circuit, has been developed . This device is designed to excite electron-collision pumping scheme XUV laser in Ne-like Ar at 46.9 nm. The ablation characteristics of the discharged capillary are experimentally investigated by measuring VUV emission from the capillary discharged. The ablation of capillary wall for polythene and alumina material is studied at inherent pre-pulse (7 kA) of the Blumlein transition line (BIL) and at pre-pulse of 20～30 A respectively under the same main current of 30 kA having a rising time of 30 ns. The reason of the plentiful ablation is that there exist high electric fields for inherent pre-pulse, which cause an inhomogenous channel spark near the wall. The experiment results indicate that the inherent pre-pulse of BTL on grounding inductance is too large to create uniform plasma columns. In the case of 20 A-pre-pulse the background emission decreased remarkably and the radiations is discriminable. In the experiments, only when the pre-pulse is less than 100 A, for alumina capillary, can the ablation be greatly reduced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 538 (2004)
Tolerance Optimizing Design and Analysis for Power Conditioning System Circuit of High Power Laser Facility
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Circuit tolerance design for circuit systems is an important technology for system reliability analysis, it can make the output of the circuit stably and reliable. Being one important part of high power laser facility, power conditioning system should be designed with high reliability. Circuit tolerance design of powerCircuit tolerance design for circuit systems is an important technology for system reliability analysis, it can make the output of the circuit stably and reliable. Being one important part of high power laser facility, power conditioning system should be designed with high reliability. Circuit tolerance design of power conditioning system is an important part of reliability analysis of high power laser facility. In this paper, the function and circuit diagram of power conditioning system are presented. Then based on the general model of circuit tolerance design, by the use of stochastic optimizing design method, a mathematical model is set up which will be used in the tolerance analysis of power condition system circuit and explain the design variable, random parameter, design rule and constraint of the model. In the end, the flow chart of computer simulation solution for stochastic optimizing model and the set of feasible result are represented..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 543 (2004)
Research on Fiber Amplifier of Many Position Side Pump Coupling
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, based on the micro-prism coupling of side pump, the fiber is wound into a coil around a object of racetrack shape to make the micro-prism couple the pump light in many positions. Based on population rate equation, pump and signal propagation equation, a numerical simulation has been done. In the case of In this paper, based on the micro-prism coupling of side pump, the fiber is wound into a coil around a object of racetrack shape to make the micro-prism couple the pump light in many positions. Based on population rate equation, pump and signal propagation equation, a numerical simulation has been done. In the case of end pump and side pump, pump power of different position is same and the hole pump power is same, the fiber gain change with the fiber length has been discussed. It is found that the side pump coupling in many positions increases the fiber gain. The influence of the bending loss and the residual pump power on the fiber gain has been discussed too, the result showed that the fiber bending can′t be too small and the residual pump power can be neglected. In this way, it can not only offer a simple way to design the micro prism and operate conveniently, but increase the signal output gain effectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 547 (2004)
Experimental Study on Improving Axial Resolution of Scan Microscope
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, several methods are put forward, by which axial resolution of scan microscope could be improved. One is that detecting method of ordinary laser feedback is improved, the orthogonal polarized lights split by Wollaston prism are detected separately, comparing to the ordinary feedback, the axial resolution In this paper, several methods are put forward, by which axial resolution of scan microscope could be improved. One is that detecting method of ordinary laser feedback is improved, the orthogonal polarized lights split by Wollaston prism are detected separately, comparing to the ordinary feedback, the axial resolution is improved about 2.9 times. Another is that the orthogonal polarized lights, o-light and e-light, generated by dual frequency laser, is used instead of ordinary feedback light, the axial resolution is improved about 2 times. The last is that o-light or e-light is as the feedback light, the axial resolution is improved about 2.5 times. The experimental results indicate that mode competitive effects of orthogonal polarized lights can effectively improve axial resolution of scan microscope..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 551 (2004)
A Novel High Power and Ultra Bandwidth Superfluorescence Source with Reflected Structure
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel structure high power and ultra bandwidth superfluorescence source is reported in this paper. With bi-directional pump of 980 nm LD and 1480 nm LD, C+L band ASE reflected by fiber loop mirror is got. By adjusting the power of LDs, 76.6 nm bandwidth from 1524.0 to 1600.6 nm is acquired where the ASE power is highA novel structure high power and ultra bandwidth superfluorescence source is reported in this paper. With bi-directional pump of 980 nm LD and 1480 nm LD, C+L band ASE reflected by fiber loop mirror is got. By adjusting the power of LDs, 76.6 nm bandwidth from 1524.0 to 1600.6 nm is acquired where the ASE power is higher than -18.8 dBm, and from 1539.2 nm to 1600.6 nm (61.4 nm), the flatten of ASE is within 2.8 dB. The total ASE power is 22.1 mW and the power conversion rate is 18.8%. Without the fiber loop mirror, only C band ASE from 1525 to 1565 nm is got while the pump condition remains the same. The total ASE power is 7.1 mW and the power conversion rate is only 6%. From the experiment, the best ultra bandwidth superfluorescence source with the ASE power of 28.5 mW and the power conversion rate of 22.3% is acquired by adjusting the bi-directional pump power of LDs and using fiber loop mirror..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 591 (2004)
Effect of Quintic Nonlinearity on Modulational Instability in the Anomalous-Dispersion Regime of Fiber
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, the effect of quintic nonlinearity on modulational instability in the anomalous-dispersion regime of self-focusing fiber from extended nonlinear Schrodinger equation is considered. The result showsIn this paper, the effect of quintic nonlinearity on modulational instability in the anomalous-dispersion regime of self-focusing fiber from extended nonlinear Schrodinger equation is considered. The result shows.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 595 (2004)
Impact of Pump Saturation and SRS between Channels on B-DFRA Gain Spectrum
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In broad-band density wavelength dense multiplexing (DWDM) systems, there are two effects impacting the gain spectrum of backward pumped distributed fiber Raman amplifier (B-DFRA)In broad-band density wavelength dense multiplexing (DWDM) systems, there are two effects impacting the gain spectrum of backward pumped distributed fiber Raman amplifier (B-DFRA).
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 599 (2004)
Galerkin Algorithm for Investigating the Photonic Crystal Fibers
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The photonic crystal fiber is a kind of microstructured optical fiber with a 2-D periodial dielectric profile constructed by air/silica. There are a few models to investigate the mode characteristics. For the TIR PCF, as an example, the index profile can be considered as the construction of a pure center defect and a pThe photonic crystal fiber is a kind of microstructured optical fiber with a 2-D periodial dielectric profile constructed by air/silica. There are a few models to investigate the mode characteristics. For the TIR PCF, as an example, the index profile can be considered as the construction of a pure center defect and a perfect 2-D photonic crystal with the periodic air-hole lattice, which can be expanded with the normalized Hermite-Gaussian basis set and cosine function respectively. From the electromagnetic wave equation, the mode eigen equation can be obtained with the algorithm when the transverse electric field is also expanded as the series of the Hermite-Gaussian basis. All elements in the eigen equation are evaluated analytically based on the orthonormality and some identities of the Hermite-Gaussian function. The propagation constant and the mode field distribution of the PCF can be calculated, hence the mode characteristics, the dispersion properties and the polarization properties can also be investigated with this algorithm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 604 (2004)
Biomedical Photonics and Laser Medicine
Study on Photothermal Transfer and Thermal Damage of Bio-tissues
[in Chinese], [in Chinese], and [in Chinese]
Thermal interaction of bio-tissues laser heated presents sorts of thermal effects such as coagulation, vaporization, carbonization. Both the thermal effects and thermal damage produce due to the continuously accumulation and diffusion of the laser energy in tissue. Based on the analysis of the mechanism of the thermal Thermal interaction of bio-tissues laser heated presents sorts of thermal effects such as coagulation, vaporization, carbonization. Both the thermal effects and thermal damage produce due to the continuously accumulation and diffusion of the laser energy in tissue. Based on the analysis of the mechanism of the thermal propagation and equilibrium, the relationship among temperature rise, thermal damage and exposure duration was deeply discussed. With increasing of the laser energy and thermal source diffuse to the ambient tissue, the distribution of temperature rise changes from a shape δ function to normal function, the higher temperature makes the thermal damage to some extent. It is theoretically proved temperature rise is one of the most important factors in laser surgery. Clinically, with the shortage of the setup to trace the actual temperature of the target tissue, one is only to adjust the laser output or the duration time in order to get better curative effect, which could tend to bring excessive thermal damage or insufficient irradiation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 631 (2004)
Holography and Information Processing
Some Quantitative Analysis about Digital Holographic Reconstructed Image
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By use of Fresnel diffraction and traditional holographic theory, this paper gives some quantitative analysis of the object-image relation and the resolution of digital holography by computer simulation and corresponding experiment. The results showsBy use of Fresnel diffraction and traditional holographic theory, this paper gives some quantitative analysis of the object-image relation and the resolution of digital holography by computer simulation and corresponding experiment. The results shows.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 570 (2004)
Laser Manufacturing
Numerical Simulation of Laser-Generated Ultrasounic by Finite Element Method in the Plate Material
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A laser pulse incident on a material generates the transient temperature field. As rapid and localized thermal expansion occurs, energy is released in the form of propagating ultrasound in all directions. Laser-generated ultrasound is non-contact, broadband, and multiple propagation modes. Considering the temperature dA laser pulse incident on a material generates the transient temperature field. As rapid and localized thermal expansion occurs, energy is released in the form of propagating ultrasound in all directions. Laser-generated ultrasound is non-contact, broadband, and multiple propagation modes. Considering the temperature dependence of material properties, the transient temperature distribution is simulated using the finite element method in the plate material; a finite element is developed to simulate the laser thermo-elastic generation and propagation of laser ultrasound. The numerical results indicate that the heat-affected zone is very localized, such a distribution of the transient temperature is considered as a body source in the generation of ultrasound; analyze the propagation features of surface waveforms in the near and far field; Discuss the relation between the laser input parameters and the generated ultrasonic wave characteristics; establish a quantitative basis for the thermo-elastic mechanism in nondestructive evaluation of the material properties..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 621 (2004)
Protection and Simulation of the Boundaries of a Workpiece of Laser Heat Treatment
[in Chinese], [in Chinese], and [in Chinese]
In the application of laser heat treatment, when a laser beam is nearthe boundaries of a workpiece, it is important to avoid the melting dissolutionof the boundaries and obtain the satisfactory heat treatment. The experimentalresults indicates that designing the diaphragm in terms of boundaries′ shape ofa treated workpIn the application of laser heat treatment, when a laser beam is nearthe boundaries of a workpiece, it is important to avoid the melting dissolutionof the boundaries and obtain the satisfactory heat treatment. The experimentalresults indicates that designing the diaphragm in terms of boundaries′ shape ofa treated workpiece and then putting the diaphragm in the proper place, may avoidinjuring of boundaries effectively and obtain the treatment result with highquality. In order to simplify the research of heating action, treated material isusually regarded as the continuous medium whose thermal physical parameter isconstant. Moreover, when the boundaries of the treated workpiece are composed of the boundaries of intersectant planes, the appropriate image heat source can beused to deal with the problem of boundary. Therefore, instantaneous temperaturefield near the boundaries can be obtained satisfactorily by a semi-analyticnumeration of temperature field of laser heat treatment. To sum up, a simplemethod for boundary protection is proposed and proved by a semi-analyticnumeration of field of laser heat treatment in this paper. Results indicates thatchoosing the proper protective width of the boundaries properly, not only canprotect the boundaries effectively, but also can obtain the hardening band witheven depth near the boundaries..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 626 (2004)
Laser Physics
Watt Level CW Frequency-Stabilized Nd:YAP/KTP Laser with Dual Wavelength Outputs
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A continuous laser-diode end-pumped Nd:YAP/KTP laser with dual wavelength outputs at 0.54 μm and 1.08 μm has been achieved. The ring laser resonator consists of five mirrors and a piece of frequency-doubling crystal KTP is placed between two concave mirrors. After calculating and comparing the waist-sizes of the fundamA continuous laser-diode end-pumped Nd:YAP/KTP laser with dual wavelength outputs at 0.54 μm and 1.08 μm has been achieved. The ring laser resonator consists of five mirrors and a piece of frequency-doubling crystal KTP is placed between two concave mirrors. After calculating and comparing the waist-sizes of the fundamental wave and the astigmatism at different incident angles to the concave mirrors, the curvature radii of the concave mirrors as 100 millimeter are chosen and the incident angles of infrared light are less than 3 degree. The cooler and temperature controller of Nd:YAP rod are improved and the lower dopant concentration of the Nd:YAP (0.6 at.-%) is chosen, thus the thermal effect of the laser rod is decreased. Under a pump power of 10 W, the output powers for the second-harmonic wave and the fundamental wave of 1.02 W and 700 mW are simultaneously obtained with the intensity fluctuations less than ±0.65% and ±0.5%, respectively. With the frequency-stabilizing servo system on, the frequency stabilities for 0.54 μm and 1.08 μm wavelengths are better than ±484 kHz and ±240 kHz, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 513 (2004)
Transient Thermal Characteristic Analysis of Tunnel Regeneration High-Power Semiconductor Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Heat source of tunnel regeneration high power semiconductor laser has been discussed. Two-dimension transient thermal distribution of this kind of laser diode at pulse work is simulated by using the finite element method, and the wavelength shift is measured and converted to temperature rising value at different time, Heat source of tunnel regeneration high power semiconductor laser has been discussed. Two-dimension transient thermal distribution of this kind of laser diode at pulse work is simulated by using the finite element method, and the wavelength shift is measured and converted to temperature rising value at different time, the calculated results are in agreement with the measured data. It is found that the temperature rising of the active region close to the substrate is higher than that of the active region close to the heat sink, and using the diamond-copper heat sink to replace the copper heat sink could reduce the inner temperature rising of laser diode greatly, and make tunnel regeneration high-power semiconductor laser working with high efficiency..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 518 (2004)
1.1 W CW Output, All-Solid-Stated Blue Laser at 473 nm
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A LD-pumped Nd:YAG, LBO (type-Ⅰ critical phase matching) intracavity frequency doubled, blue laser at 473 nm is reported in this paper. With the quasi-three-level model and a ordinary Nd:YAG rod as gain medium, by using a short three-folded-cavity resonator that is in sensitive to thermal effect, under the condition ofA LD-pumped Nd:YAG, LBO (type-Ⅰ critical phase matching) intracavity frequency doubled, blue laser at 473 nm is reported in this paper. With the quasi-three-level model and a ordinary Nd:YAG rod as gain medium, by using a short three-folded-cavity resonator that is in sensitive to thermal effect, under the condition of 14 W pump power, high power TEM00 mode blue laser at 473 nm of 1.1 W is obtained at last, with the light-light conversion efficiency up to 7.9%, the threshold value is just 2 W. Moreover, the possibility of improving the power is discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 523 (2004)
Research of Single-Longitudinal-Mode Main Oscillator Pumped by LD in MOPA System
[in Chinese], [in Chinese], and [in Chinese]
In the MOPA system, the smooth spatial and temporal shapes and a long coherent length of the output laser pulses are the essential requirement to the master-oscillator. With the development of DPSL, it becomes the first choice of the master- oscillator in the MOPA laser system. In this paper, a single-longitudinal-modeIn the MOPA system, the smooth spatial and temporal shapes and a long coherent length of the output laser pulses are the essential requirement to the master-oscillator. With the development of DPSL, it becomes the first choice of the master- oscillator in the MOPA laser system. In this paper, a single-longitudinal-mode DPSL with short length resonator and end-pumped Nd:YAG using LN Q-switching is presented. Through arranging the optical components in the resonator reasonably, controlling the depth of the focusing point in the Nd:YAG, decreasing the effects of the stationary waves to laser mode, and without using any special selecting-mode component, the single-longitudinal-mode output energies of 50～100 μJ are attained. On the repetition of 40 Hz, the following performance are achieved.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 527 (2004)
Stable and Simple Structure Passively Q-Switched Single-Longitudinal-Mode Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the ring-shaped laser-diode array side-pumped Nd:YLF high gain amplifier and the conventional plan-concave resonator, a simple structure single-longitudinal-mode single-pulse Q-switched oscillator is demonstrated by taking advantages of mode-selecting property of passive Q-switches (Cr4+:YAG crystal) and etaloBased on the ring-shaped laser-diode array side-pumped Nd:YLF high gain amplifier and the conventional plan-concave resonator, a simple structure single-longitudinal-mode single-pulse Q-switched oscillator is demonstrated by taking advantages of mode-selecting property of passive Q-switches (Cr4+:YAG crystal) and etalons (formed by two end of uncoated Nd:YLF rod). The average pulse width is 9.3 ns, the average energy is 1.218 mJ, the pulse width stability is 8% by RMS and the pulse energy stability is 3% by RMS and the output pulse reaches the peak-power of 0.13 MW. This kind of oscillator holds the excellent single-longitudinal mode probability great than 99% in long running time. Keep in mind of its simplicity and unsensible to the change of working condition, it is preferred to put this kind of oscillator into practical usage in these situations where accurate time sequence is not required..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 531 (2004)
940 nm High Power Semiconductor Laser
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
InGaAs/GaAs/AlGaAs material high power diode lasers with large optical cavity (LOC) have been reported. Based on the solution to the intrinsic equation of quantum well energy level, In content of the InGaAs quantum well layer was optimized; the output beam divergence and optical power density on facets were reduced effInGaAs/GaAs/AlGaAs material high power diode lasers with large optical cavity (LOC) have been reported. Based on the solution to the intrinsic equation of quantum well energy level, In content of the InGaAs quantum well layer was optimized; the output beam divergence and optical power density on facets were reduced effectively by using LOC structure for high power, low beam divergence output. The designed 940 nm wavelength laser structure has been obtained by successful molecular beam epitaxy (MBE) growth with a low threshold current. The finally prepared devices reached up to 2 W power output with a low threshould current of 300 mA. The beam divergence of θ∥ and θ⊥ is 10° and 30° respectively and the peak wavelength of the lasing devices is 939.4 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 535 (2004)
Squeezing Property of Coherent Light Coupled to a Nonlinear Medium of Inversion Symmetry
[in Chinese], and [in Chinese]
An analytical approach is adopted for the calculation of squeezed property of coherent light interacting with a nonlinear medium of inversion symmetry. A medium is called inversion symmetric if the potential energy remains invariant under parity transformation. Thus the even order susceptibilities would vanish for the An analytical approach is adopted for the calculation of squeezed property of coherent light interacting with a nonlinear medium of inversion symmetry. A medium is called inversion symmetric if the potential energy remains invariant under parity transformation. Thus the even order susceptibilities would vanish for the medium and the leading contribution to the nolinear polarization due to the medium is the third order susceptibility. Therefore interaction Hamitonian of the single-mode light field with the medium is proportional to the fourth power of the annihilation operator plus creation operator. This means is to take care all the non-conserving energy terms for the calculation of the squeezing property of coherent light passing through the nonlinear medium of inversion symmetry. For a single-mode light, two dimensionless quadrature operators are defined which are proportional to the usual position and momentum operators respectively. Using the Heisenberg operator equation of motion, the differential equation of the quadrature operators and the approximate solutions to the equations are got. Then the quantum fluctuations of the two quadratures are calculated. The result shows that the squeezing property of the two quadrature operators is controllable through changing the following parameters.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 554 (2004)
Experimental Research on the Second Harmonic Generation of TEA CO2 Laser in AgGaSe2 Crystal
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, the second harmonic generation (SHG) of the TEA CO2 laser in an AgGaSe2 nonlinear crystal is realized. How energy of TEA CO2 laser, repetition frequency of pulse and focal position affect SHG is studied emphatically. The tuning curve upon incident angle is obtained and the maximal second harmonic energy In this paper, the second harmonic generation (SHG) of the TEA CO2 laser in an AgGaSe2 nonlinear crystal is realized. How energy of TEA CO2 laser, repetition frequency of pulse and focal position affect SHG is studied emphatically. The tuning curve upon incident angle is obtained and the maximal second harmonic energy 1.32 mJ is measured with the energy conversion efficiency 2.4% for total and 4% for main peak. Besides, the influence of pulse repetition rate (<10 Hz) on SHG conversion efficiency is analyzed. From the experimental results, it is found that the main factors restraining conversion efficiency are the crystal′s optical quality, the low power intensity tail of lasing pulse and the instability of pulse radiation. Specially, the thermal lens effect is intensified due to the long tail attached to pulse, which leads to decreasing of conversion efficiency if pulse repetition rate is enhanced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 559 (2004)
Incoherently Coupled Low-Amplitude Soliton Pairs in Biased Photorefractive-Photovoltaic Crystals
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A theory on incoherently coupled low-amplitude soliton pairs for screening-photovoltaic solitons in biased photorefractive-photovoltaic crystals is investigated that gives rise to the analytical solutions of bright-bright and dark-dark soliton pairs, which are due to both the spatially nonuniform screening of the exterA theory on incoherently coupled low-amplitude soliton pairs for screening-photovoltaic solitons in biased photorefractive-photovoltaic crystals is investigated that gives rise to the analytical solutions of bright-bright and dark-dark soliton pairs, which are due to both the spatially nonuniform screening of the external electric field and the photovoltaic effect. These soliton pairs, differ from screening soliton pairs originating from the spatially nonuniform screening of the external electric field and photovoltaic soliton pairs originating from the photovoltaic effect, are of interesting properties. When the photovoltaic effect is neglected, their nonlinear wave equations change into that for screening solitons, and these soliton pairs change into screening soliton pairs. When the external bias field is absent, their nonlinear wave equation change into that for photovoltaic solitons in closed and open circuits, and these soliton pairs change into photovoltaic soliton pairs in closed and open circuits. If the carrier beams share the same polarization, wavelength, and are mutually incoherent, these soliton pairs can be obtained. Relevant examples are provided where the photorefractive-photovoltaic crystal is lithium niobate (LiNbO3) crystal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 563 (2004)
Supercontinuum Generation and Transmission in a Random Distorted Microstructure Fiber
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A random distributed microstructure fiber is demonstrated, and supercontinuum light with a spectrum more than one octave (390～1050 nm) was generated in 60 cm microstructure fiber by the femtosecond pulse laser with a duration of 35 fs and a energy of several nanojoules per pulse. The large refractive-index step betweenA random distributed microstructure fiber is demonstrated, and supercontinuum light with a spectrum more than one octave (390～1050 nm) was generated in 60 cm microstructure fiber by the femtosecond pulse laser with a duration of 35 fs and a energy of several nanojoules per pulse. The large refractive-index step between silica and air allows light to be concentrated into a very small area and resulting in those enhanced nonlinear effects. Some new phenomena is observed when the supercontinuum light transmits in this fiber due to its incomplete photonic band gap, such as the color variation along the fiber..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 567 (2004)
Measurement and Metrology
Temperature Measurement in CH4/Air Flame by Single-Pulse USED CARS
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The unstable-resonator spatially enhanced detection (USED) coherent antistokes Raman scattering (CARS) measurement of temperature in CH4/air flame is reported. The USED CARS measurement system which has a high spatial solution of ～0.1 mm in diameter and ～3 mm in length is constructed and permits instantaneous thermometThe unstable-resonator spatially enhanced detection (USED) coherent antistokes Raman scattering (CARS) measurement of temperature in CH4/air flame is reported. The USED CARS measurement system which has a high spatial solution of ～0.1 mm in diameter and ～3 mm in length is constructed and permits instantaneous thermometry at a 10 Hz rate. The single-pulse N2 Q-branch CARS spectra have been obtained from CH4/air flame and the CARS data are analyzed by comparison with theoretical spectra generated at various temperature. The temperature distribution of CH4/air flame have been measured by broad-band USED CARS and the measurement results have been analyzed. The uncertainty of single-pulse temperature measurement is less than 5% for T=2038 K..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 609 (2004)
Experimental Research of 30 km Long Distance Distributed Optical Fiber Raman Temperature Sensor System
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and Insoo S. KIM
A 30 km long range distributed optical fiber Raman temperature sensor (DOFRTS) system has been made, it use new measuring temperature principle of optical fiber amplified anti-Stokes Raman spontaneous scattering. In the system, 1550 nm erbium-doped optical fiber laser, high speed data acquisition card and signal procesA 30 km long range distributed optical fiber Raman temperature sensor (DOFRTS) system has been made, it use new measuring temperature principle of optical fiber amplified anti-Stokes Raman spontaneous scattering. In the system, 1550 nm erbium-doped optical fiber laser, high speed data acquisition card and signal processing technique are used. By using these technique, the problem of weak signal detection is resolved and signal to noise ratio is increased. All components of system are put into an intellectualized constant temperature box and work in constant temperature condition. Stability and environment adaptability are improved. By appraisal, performance of the system is listed as follows.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 613 (2004)
Anti-Model of Ray-Path for Four Quadrant Photoelectric Detector
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, the problem about observation space of detector is discussed. A method of modeling the anti-models of ray-path from electric signal to parameter of ray-path using neural network is introduced. Making use of the special relations between the parameters of fitting lines at the crossover points of outputs oIn this paper, the problem about observation space of detector is discussed. A method of modeling the anti-models of ray-path from electric signal to parameter of ray-path using neural network is introduced. Making use of the special relations between the parameters of fitting lines at the crossover points of outputs of four-quadrant photodetecor and the three-dimensional free position, the distance between photosurface and focus of photodetector, the anti-model called model 1 of ray-path of four-quadrant photodetector is modeled. At the same time, a model called model 2 is modeled using the voltages of the output of photodetector at special time as observed quantities. Taking measuring for the distance between photosurface and focus of photodetector as an example, the measuring results are given, and the measuring results for repeatability of model 1 are also given. The measuring results for repeatability of model 1 show that the maximal measuring error is only 0.015 mm. And the measuring results show that the measuring accuracy of model 1 reaches micron level and that of model 2 reaches only millimeter level. Thus, that using the parameters of fitting lines at the crossover points of outputs of four-quadrant photodetecor as observation quantities is ahead of that using the voltages of outputs of photodetector at special time as observation quantities.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 617 (2004)
Optical Communication
Characterization of Time Parameter of Error Control Scheme in Optical Wireless Communication
[in Chinese], [in Chinese], and [in Chinese]
The paper proposes and analyzes two turbo-coded error control schemes to improve performance of optical wireless communication with long burst error by scintillation and attenuation. Characterization of time parameter of two error control schemes was provided to design. For turbo code + channel interleaving scheme, theThe paper proposes and analyzes two turbo-coded error control schemes to improve performance of optical wireless communication with long burst error by scintillation and attenuation. Characterization of time parameter of two error control schemes was provided to design. For turbo code + channel interleaving scheme, the paper shows performance of optical wireless communication under various channel interleaving depth. For turbo code + ARQ scheme, simulations show that the feedback delay don′t influence average link throughput, but the feedback delay changes average link delay and probability distribution of transmitting times..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 575 (2004)
A Novel Method of Calculating Transmission Equations for Multiwavelength-Pumped Fiber Raman Amplifiers
[in Chinese], [in Chinese], and [in Chinese]
The Runge-Kutta interative algorithm is used to solve the standard propagation equations of fiber Raman amplifiers (FRAs). The analysis includes all the interactions of pumps, signals and noise without any approximation. Applications of the numerical analysis to practical FRA-based systems show a great reduction in comThe Runge-Kutta interative algorithm is used to solve the standard propagation equations of fiber Raman amplifiers (FRAs). The analysis includes all the interactions of pumps, signals and noise without any approximation. Applications of the numerical analysis to practical FRA-based systems show a great reduction in computation time comparing with the direct integration approach based on ordinary coupled differential equations, while reproducing all the essential system performances precisely. In addition to enhanced computational efficiency, the derived equations can also give deeper insights into the detailed dynamics of FRAs. By making use of this method, flattened signal gains of a multiwavelength-pumping FRA with a bandwidth of over 100 nm are successfully calculated and pump power distributions along the transmission fiber are given. Futhermore, noise figures of the FRA are also presented. The method is very suitable to the engineering design of ultrabroad band FRAs with multiwavelength pumps..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 579 (2004)
155/622 Mb/s Multiple Transmitter Laser Communication Systems
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A wireless laser communication system with multiple transmitter and auto-tracking is reported in this paper. The overall design, key optical and mechanical components, and servo-control sub-system are described including three laser transmitters at 800 nm, a beacon laser at 980 nm, optical detector, position sensitive A wireless laser communication system with multiple transmitter and auto-tracking is reported in this paper. The overall design, key optical and mechanical components, and servo-control sub-system are described including three laser transmitters at 800 nm, a beacon laser at 980 nm, optical detector, position sensitive detector, step motor and micro processor for auto-tracking. In experiments over a span distance of 1.3 km, percentages of error-free-second were measured to be more than 98% for 155 Mb/s during 24 hour continuous operation, and 95% for 622 Mb/s in a period of 8 hours, and bit error rate of less than 10-9. It is shown that the scheme of multiple transmitter and auto-tracking will improve the reliability of wireless laser communication systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 583 (2004)
Study on the Output Polarization State of Non-PM Fiber Ring Lasers
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the theory of Jones matrix, a model for the analysis of non-PM fiber ring lasers polarization characteristics was developed. The model was further tested by experiments. From the numerically and experimentally analysis results, it was found that lasers composed of non-PM fiber can achieve stable output but itsBased on the theory of Jones matrix, a model for the analysis of non-PM fiber ring lasers polarization characteristics was developed. The model was further tested by experiments. From the numerically and experimentally analysis results, it was found that lasers composed of non-PM fiber can achieve stable output but its polarization varied with external perturbation. If polarizer was inserted into the laser cavity, the instability of output and polarization was even more serious. So special polarization control must be performed to obtain single polarization laser output using non-PM fiber..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 5, 588 (2004)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20