Journals >Chinese Journal of Lasers
Contents
2006
Volume: 33 Issue 7
29 Article(s)
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Research Article
Technique for Forming a Rotator by Retarders and Its Application
[in Chinese], [in Chinese], and [in Chinese]
A technique for forming a rotator by retarders is presented. The principle to form the rotator and its application are analyzed with Mueller matrix. When a retarder is placed between two quarter-wave plates whose fast axes are perpendicular to each other and the angles between fast axes of the retarder and the two quarA technique for forming a rotator by retarders is presented. The principle to form the rotator and its application are analyzed with Mueller matrix. When a retarder is placed between two quarter-wave plates whose fast axes are perpendicular to each other and the angles between fast axes of the retarder and the two quarter-wave plates are ±45° respectively, the rotator is formed. Based on the technique, a phase modulator can be applied for the modulation of polarization direction. In the experiments, principle of forming the rotator and application of the phase modulator to modulation of polarization direction are verified..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 889 (2006)
Design and Experiment of 8-Pass Laser Pulse Stretcher
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In a chirped pulse amplification (CPA) laser facility, the output capability can be increased if the pulse can be stretched wider. Adopting the design of “single-grating and single-lens”, a 8-pass laser pulse stretcher is developed, and analytical formulae about the design are presented, with which the stretcher has beIn a chirped pulse amplification (CPA) laser facility, the output capability can be increased if the pulse can be stretched wider. Adopting the design of “single-grating and single-lens”, a 8-pass laser pulse stretcher is developed, and analytical formulae about the design are presented, with which the stretcher has been optimized to some extend. With the stretcher which has been developed, a pulse of 93 fs is stretched to 4.35 ns. Additionally, by controlling the reflection of the mirror in the focal plate (or controlling transmission of an optical component before the mirror), a shaped pulse can be obtained, which is similar to the pulse gotten from an acoustic-optic programmable dispersion filter (AOPDF)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 895 (2006)
Dynamical Laser Beams Steering with Phase-Only Spatial Light Modulator
[in Chinese], and [in Chinese]
A non-mechanical beam steering system is proposed and designed to resolve the problem of approaching the far-field diffractive pattern with laser beams. A beam steering method based on the phase only modulation with a liquid crystal spatial light modulator (LCSLM) is studied and described to control the light beams proA non-mechanical beam steering system is proposed and designed to resolve the problem of approaching the far-field diffractive pattern with laser beams. A beam steering method based on the phase only modulation with a liquid crystal spatial light modulator (LCSLM) is studied and described to control the light beams programmably. The Fourier iterative optimal algorithm is adopted to design the optimal phases approaching the expected far-field diffractive pattern. The schematic diagram and the experimental set-up are given. Results show that the method can generate 2-D spots arrays with the intensity error rate less than 8%. The response time of generating the dynamical diffractive pattern is less than 100 ms. With the merits of lightness, precision and quick response, this scanning system is of value in the fields of multi-object tracing, laser guiding and multi-object defense..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 899 (2006)
Output-Ability Analysis of High-Intensity Third Harmonic Generation System for ICF Driver
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By basing on the study and manufacture of the technical integration experiment line (TIL) prototype laser facility, and using the method that theoretical simulations guide experiments and experiment results check programs, the actors affecting third harmonic generation (THG) efficiency for large-aperture, high-intensitBy basing on the study and manufacture of the technical integration experiment line (TIL) prototype laser facility, and using the method that theoretical simulations guide experiments and experiment results check programs, the actors affecting third harmonic generation (THG) efficiency for large-aperture, high-intensity inertial confinement fusion (ICF) laser facility have been analyzed and studied in detail. Furthermore, the output-ability of THG system for ICF driver has been discussed adequately. As shown through experiment results, when average drive irradiance of fundamental light, I1ω is 2.7 GW/ cm2, measured value of THG efficiency is 50%～55% and the theory value is 60%, which indicates that the experiment result can be agreed with the theory value well. The experiment results will provide experiment proofs and calculation tools for eight beam eligibility and power balance of prototype laser facility..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 903 (2006)
Beam Transmission
Double Half-Cylindrical Lens Collimate the Beam of Laser Diode
[in Chinese], [in Chinese], and [in Chinese]
Cylindrical lenses have been widely used for collimating laser diode beam, but the collimating performance is usually not high. A new collimating element-double half-cylindrical lens (DHCL) was proposed. The theoretical expressions of the collimated beam of a DHCL are derived by transmission theory, and the numerical rCylindrical lenses have been widely used for collimating laser diode beam, but the collimating performance is usually not high. A new collimating element-double half-cylindrical lens (DHCL) was proposed. The theoretical expressions of the collimated beam of a DHCL are derived by transmission theory, and the numerical results are also given. Both theoretical and numerical results indicate that a DHCL can be made from the high refractive index material but a normal cylindrical lens cannot, and the collimating performance of a DHCL is much better than that of a normal cylindrical lens. The divergence angle of the collimated beam could be as small as 0.1 mrad..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 937 (2006)
Biomedical Photonics and Laser Medicine
Dependence of Optical Clearing Effect on Tissue Structure
[in Chinese], and [in Chinese]
The dependence of optical clearing on properties of the different tissue structures is investigated in order to better know the clearing mechanisms and effective clearing approach. Two typical tissues, muscle and epithelial, have been chosen as the targets and the effect of optical clearing has been comparatively studiThe dependence of optical clearing on properties of the different tissue structures is investigated in order to better know the clearing mechanisms and effective clearing approach. Two typical tissues, muscle and epithelial, have been chosen as the targets and the effect of optical clearing has been comparatively studied by optical coherence tomography (OCT) and near infrared spectroscopy (NIR) with the clearing agent glycerol used. The results show that the improved imaging depth and contrast among different layers in the porcine skeletal muscle and stomach mucosa are visualised with the OCT assessment. The overall increases in light transmittance in the muscle tissue and the stomach mucosal tissue after 30 min treatment are observed to be approximate 21% and 16%, decreases in diffuse reflectance are 33% and 21%, respectively, with the quantitative measurement of NIR. The clearing progress of each tissue type as a function of time corresponds very well with the respective loss in water dynamics shown by the near infrared spectra: early rapid transport, mid-linear and slow exponential diffusion for muscle tissue, and contrarily for stomach mucosa with an early very slow transport and later linear increasing efflux. The different permeabilities of muscle tissue and mucosal tissue are thought to be accountable for the difference in clearing effect between the two tissues. These observations confirm expectation that optical clearing is dependent on tissue structure in an explainable manner..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 998 (2006)
Fiber-Optic Measurement System for Pesticides Residua Based on Fluorescence Mechanism
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A measurement system is introduced using the technologies of fiber-optic sensing, dispersion of grating and multi-channel image sensing based on fluorescence mechanism of pesticides. The system adopts a pulsed xenon lamp as an excitation light source, chooses optical fibers to transmit and detect fluorescence, implemenA measurement system is introduced using the technologies of fiber-optic sensing, dispersion of grating and multi-channel image sensing based on fluorescence mechanism of pesticides. The system adopts a pulsed xenon lamp as an excitation light source, chooses optical fibers to transmit and detect fluorescence, implements dispersion of fluorescence with a small-sized flat field grating spectrometer and conducts data gathering and conversion with a high speed signal processing module. A full fluorescence spectrum of pesticides within a single exposure can be gotten. Moreover, it is used to conduct the measurement of fluorescence characteristics of carbaryl and carbofuran. The results show that the pesticides can emit fluorescence of 340～750 nm as excited by ultraviolet (UV) light of 319 nm,and the system has a good linear relationship in the range of 0.003～0.1 mg/L and the minimum detecting limit is 0.003 mg/L. At the same time, the instrument is also be applied to detect concentration of the trace pesticides in Chinese cabbages,the recovery may be closed to 100%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 1003 (2006)
Laser Manufacturing
On Laser Absorptivity of Ductile Iron
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Ductile iron has been as the materials for stamping and drawing dies due to its good mechanical properties. In recent years, laser surface modification of dies of ductile iron has been an important method to improve its wear resistance and useful life. With laser surface modification, absorptivity influences the surfacDuctile iron has been as the materials for stamping and drawing dies due to its good mechanical properties. In recent years, laser surface modification of dies of ductile iron has been an important method to improve its wear resistance and useful life. With laser surface modification, absorptivity influences the surface modification straightly under certain laser parameters. So it is necessary to determine the laser absorptivity of ductile iron. The temperature is measured by thermal couple and treated by computer data-acquisition system. Meanwhile, the numerical simulation is to determine the absorptivity. The simulative temperature response at a certain point can be obtained through predictive absorptivity and compared with that of experiments until the simulated one is coincidence with experimental one. In the result, the absorptivities of ductile iron under atmosphere is 23.3%. It provides some reference for the selection and optimization of technical parameters during the laser material processing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 977 (2006)
Temperature Field of Laser Scanning Line Facula
[in Chinese], [in Chinese], and [in Chinese]
In order to describe scanning facula temperature field and its characteristic exactly, the forming progress of scanning facula temperature field is analyzed in this paper, and the math model of the temperature field of point heat source scanning and superposing in the facula of laser repeating scanning line is built byIn order to describe scanning facula temperature field and its characteristic exactly, the forming progress of scanning facula temperature field is analyzed in this paper, and the math model of the temperature field of point heat source scanning and superposing in the facula of laser repeating scanning line is built by applying the superposing principle of the temperature field,and the value simulation and figure description are given. The relationship between parameter and temperature distribution is studied, the result shows that the temperature field of scanning facula has obvious speciality similar to skin effect. The speciality is the theoretical basis for that wide band surface treatment can be done on material by laser scanning rotating mirror with lower laser power. The research method used is applicable to other temperature field that has the character of scanning and superposing process..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 981 (2006)
In Situ Synthesized NbC Particulate Reinforced Ni-Based Composite Coatings by Laser Cladding
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laser cladding is the one of the efficient methods for the surface hardening and modifying of metal material. Using this technology, NbC particulate reinforced Ni-based composite coating has been successfully in situ synthesized on steel A3 substrate by prior to pasting. The microstructure observation and hardness testLaser cladding is the one of the efficient methods for the surface hardening and modifying of metal material. Using this technology, NbC particulate reinforced Ni-based composite coating has been successfully in situ synthesized on steel A3 substrate by prior to pasting. The microstructure observation and hardness test on the cross-section of the laser clad layer were performed. And that X-ray diffraction (XRD) analysis and tribotesting on the surface of the coatings were also accomplished. The microstructural and metallographic analyses by a scanning electron microscope (SEM), energy-dispersive spectrometer (EDS) and X-ray diffractometer reveal that the coating epitaxial growing from the substrate with excellent bonding between the coating and substrate is ensured by the strong metallurgical interface and suggest the presence of the in situ synthesized NbC particles in the clad layer. These NbC particles together with the carbide dendrites present as reinforcements of the composite coatings and are homogenously dispread in the γ(Ni Fe) matrix. The experimental results show that the composite coating gives high average hardness of HV0.31200 and excellent wear resistance, which is 2.5 times as high as that of pure Ni60 coatings. The improvement of wear resistance is due to the presence of the substantive in situ synthesized NbC particles and their homogenous distribution in the coatings..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 987 (2006)
Experimental Measurement of Metal Powder Stream Concentration Field in Laser Manufacturing
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The research on the distributions of metal powder stream from co-axial nozzle is very interested in laser manufacturing. The paper was focused in the concentration field of powder stream. Theoretic model of concentration field of powder stream from the co-axial nozzle has been established. A new digital particle image The research on the distributions of metal powder stream from co-axial nozzle is very interested in laser manufacturing. The paper was focused in the concentration field of powder stream. Theoretic model of concentration field of powder stream from the co-axial nozzle has been established. A new digital particle image measurement technique has been developed to measure the concentration field of powder stream. The system mainly consists of Nd+:YAG laser and charge coupled device (CCD) camera. It is shown that focus parameters and concentration distribution of powder stream can be measured by the technique. The system could be a useful device for laser manufacturing after further developed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 993 (2006)
Laser Physics
Ultraintense Solid-State Lasers and Applications to the Frontiers of Sciences
[in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 865 (2006)
Fabrication of Distributed Feedback Bragg Fiber Laser on Regular Er-Doped Fiber
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A 5 cm fiber Bragg grating distributed feedback Bragg (DFB) fiber laser is fabricated by using 248 nm KrF excimer laser, the fiber used is regular Er-doped fiber with peak absorption of 5 dB/m, the fiber laser has a output power of 50 μW and 50 dB sidelobe suppression ratio by a 100 mW 980 nm pump laser. Coupled-mode tA 5 cm fiber Bragg grating distributed feedback Bragg (DFB) fiber laser is fabricated by using 248 nm KrF excimer laser, the fiber used is regular Er-doped fiber with peak absorption of 5 dB/m, the fiber laser has a output power of 50 μW and 50 dB sidelobe suppression ratio by a 100 mW 980 nm pump laser. Coupled-mode theory was introduced to analyze DFB fiber laser output characteristics and transfer-matrix method was used to simulate a 5 cm phase shifted DFB fiber laser. From the analysis, it showed that the cavity loss is a very important factor affecting the output power, larger loss corresponds to lower grating coupling coefficient. Hence, when fabricating DFB fiber laser on regular Er-doped fiber, the cavity loss evaluation and coupling coefficient optimization could yield high output power..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 873 (2006)
Study on Characteristics of Acoustooptical Tunable Erbium-doped Fiber Ring Laser
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new-style single mode output tunable erbium-doped fiber ring laser employing advanced two-stage integrated acousto-optic tunable filter (IAOTF) is presented. It has simple structure and can be tuned conveniently, widely and rapidly by changing the acoustic frequency. Considering the conversion efficiency of this IAOTA new-style single mode output tunable erbium-doped fiber ring laser employing advanced two-stage integrated acousto-optic tunable filter (IAOTF) is presented. It has simple structure and can be tuned conveniently, widely and rapidly by changing the acoustic frequency. Considering the conversion efficiency of this IAOTF and neglecting amplified spontaneous emission (ASE) and excited-state absorption (ESA), the characteristics of the laser such as line width, output power, slope efficiency, and threshold power are discussed. When pumping power is 100 mW and radio frequency (RF) is 175 MHz, the center wavelength of the laser is 1550 nm, output power peak is about 6.34 mW, slope efficiency is 7.19%, and output peak with a full width at half maximum (FWMH) of 0.1 nm is obtained, the tuned peak gap is about 0.88 nm when changed the acoustic frequency by 0.1 MHz. Because the tunable range of the IAOTF is wide (about 180 nm when acoustic frequency changes in 20 MHz), the tunable range of the laser is only decided by the gain bandwidth of the erbium-doped fiber..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 877 (2006)
Double-Control Acousto-Optic Q-Switched All-Solid-State Infrared Laser
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new type of double-control acousto-optic (A-O) Q-switched all solid state laser has been developed. A special home-made double-control driver, instead of a laser diode (LD) driver and an unattached A-O Q-switcher driver as used in the normal A-O Q-switched solid-state lasers, is used in the laser. In the double-contrA new type of double-control acousto-optic (A-O) Q-switched all solid state laser has been developed. A special home-made double-control driver, instead of a laser diode (LD) driver and an unattached A-O Q-switcher driver as used in the normal A-O Q-switched solid-state lasers, is used in the laser. In the double-control driver, both LD and the A-O Q-switcher work periodically at the same repetition rate as the output laser pulses. In each period, LD lights in advance of the time of the output laser pulse occurrence and quenches behind the laser pulse. At the same period, A-O Q-switcher starts working before LD and stops working behind LD. The new type of solid state infrared laser has much better performance in compare with the normal A-O Q-switched solid-state lasers at the same repetition rates: electric power saving more than 50%, temperature rising at main parts of the laser set dropping down with more than 10 ℃, time taken for thermally stable state being reduced to 23%. Pumped by a 1 W LD, the non-spurious output pulses with peak power of about 4 kW and width of 16.8 ns are obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 882 (2006)
Size Dependence of Maximum Energy of Protons Produced in the Intense Femtosecond Laser Interaction with Hydrogen Clusters
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The dependence of the maximum energy of protons Emax produced in the interaction of an intense femtosecond laser pulse (60 fs, 790 nm, 2×1016 W/cm2) with hydrogen clusters in a gas jet on the square of the cluster radius r2c has been investigated experimentally. The results obtained have established a Emax～r2c relThe dependence of the maximum energy of protons Emax produced in the interaction of an intense femtosecond laser pulse (60 fs, 790 nm, 2×1016 W/cm2) with hydrogen clusters in a gas jet on the square of the cluster radius r2c has been investigated experimentally. The results obtained have established a Emax～r2c relation such as Emax(keV)=1.2+0.32r2c (nm2) with rc ranging from ～1 to 3 nm, in quite good agreement with the reported simulation results, demonstrating that the hydrogen clusters were purely Coulomb exploded under the present experimental conditions. The results also imply that the cluster size distribution in a gas jet should be taken into account in a further simulation study..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 910 (2006)
Clusters in Eu-Doped Polymer Optical Fibers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Eu(DBM)3Phen-doped polymer optical fibers (POFs) were prepared by thermal polymerization. The cross relaxation model of clustering Eu3+ ions was described, and the clusters in this kind of fibers were studied based on the above model. The percentages of clustering ions in different fibers were obtained by the rate equaEu(DBM)3Phen-doped polymer optical fibers (POFs) were prepared by thermal polymerization. The cross relaxation model of clustering Eu3+ ions was described, and the clusters in this kind of fibers were studied based on the above model. The percentages of clustering ions in different fibers were obtained by the rate equation combining with fiber transmission experiment. While concentrations in these fibers are 0.1 wt.-%, 0.2 wt.-%, 0.3 wt.-%, 0.4 wt.-%, 0.5 wt.-% and 1 wt.-%, the percentages of clustering ions are 0.045, 0.07, 0.07, 0.07, 0.07 and 0.08, respectively. The result shows that this kind of fibers has low percentage of clustering ions. With the increasing of Eu3+ concentration, the percentage of clustering ions almost not increases, the clustering of Eu3+ ions is not obvious..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 914 (2006)
Diffraction Self-Enhancement by Two Wave Mixing of Femtosecond Pulse in LiNbO3:Fe
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Writing a grating by femtosecond coherent pulses, there was an erasure of grating during the reading process, so it is important for research a self-enhancement method to restrain the erasure. In the configuration of femtosecond two waves mixing, two pulses wrote a grating in a LiNbO3:Fe, there was a self-enhancement eWriting a grating by femtosecond coherent pulses, there was an erasure of grating during the reading process, so it is important for research a self-enhancement method to restrain the erasure. In the configuration of femtosecond two waves mixing, two pulses wrote a grating in a LiNbO3:Fe, there was a self-enhancement effect by using a special method that controlled the sequence of femtosecond pulse′s writing: after the two pulse′s writing, single pulse wrote the old grating which made the self-enhancement continue 1 h. At the same time the other self-enhancement effect had been found when the grating was unsaturated and the input two pulses changed to a single pulse, and this self-enhancement continued 2 h. Then the research on the relationship between the writing ultrafast pulse and the writing time had been done, finally the reason analysis had been done with the modulation of femtosecond pulse. This study showed that the diffracted pulse light interacting with writing pulse increased the level of mixing, then a new grating had been written, which boosted up the old one, so that diffraction efficiency increased. The experiment proved that the grating erasure written by femtosecond pulse can be restrained, which was good news for a reading effect of hologram writing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 918 (2006)
Far Field Analysis after Chirped Pulse Passing through a Misalignment Tiled-Grating Compressor
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A model is proposed for the analysis of possible errors in a tiled-grating pair compressor. By using the method of Fourier optics, the process of a chirped pulse's passing through a misalignment tiled-grating pair compressor and an ideal lens is studied and the integral expression of light field on focal plane is oA model is proposed for the analysis of possible errors in a tiled-grating pair compressor. By using the method of Fourier optics, the process of a chirped pulse's passing through a misalignment tiled-grating pair compressor and an ideal lens is studied and the integral expression of light field on focal plane is obtained. The effects of possible errors on focal spot intensity distribution are analyzed in detail by the numerical simulation. The results indicate that possible errors must satisfy Δx-nd
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 922 (2006)
Materials and Thin Films
Prediction of Polymerization Efficiency for PDPhSM Matrix Nanocomposite Thin Film Prepared by Laser Ablation Based on Artificial Neural Networks
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In order to shorten the fussy experimental process in synthesizing polydiphenysilylenemethylene (PDPhSM) technology, a back propagation (BP) neural network model and a radial basis function (RBF) neural network model are developed to approach the complex nonlinear relationship between technology parameters and polymeriIn order to shorten the fussy experimental process in synthesizing polydiphenysilylenemethylene (PDPhSM) technology, a back propagation (BP) neural network model and a radial basis function (RBF) neural network model are developed to approach the complex nonlinear relationship between technology parameters and polymerization efficiency for synthesizing PDPhSM matrix nanocomposite thin film respectively. By using the constructed neural network model, the relationship between the technology parameters (laser fluence, ambient pressure, distance between target and substrate, deposition time) and polymerization efficiency is discussed, and the weakness that the nonlinear relationship could not be approached more accurately, effectively by using of single-factor-experiment method is overcomed. Predicted and test results showed that all the relative errors between the desired values and predicted outputs of the network are less than 10%, but the predicted data of RBF model are well acceptable when comparing them to the real test values, hence providing a effective, economical way for synthesizing PDPhSM matrix nanocomposite thin film..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 953 (2006)
New Measurement Method of Thickness and Refractive Index of the Film Grown on the Strong Absorption Substrate
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A measuremant method of thickness and refractive index of film grown on the strong absorption substrate is proposed. A thin metal layer is deposited on a transparent film which is grown on a strong absorption substrate. As a result, an analogue waveguide configuration of metal-transparent film-absorption substrate, whiA measuremant method of thickness and refractive index of film grown on the strong absorption substrate is proposed. A thin metal layer is deposited on a transparent film which is grown on a strong absorption substrate. As a result, an analogue waveguide configuration of metal-transparent film-absorption substrate, which can accommodate a series of resonant modes, is formed due to a bigger reflectivity on the absorption substrate for the small angle of incidence. Based on the free-space coupling technique and the eigenvalue equation of the resonant modes derived by the standard electromagnetic field theory, the thickness and refractive index of the transparent film are simultaneously determined with a relative error of 1×10-3. The proposed method is simple and reliable, and can be used for the film with different refractive indexes..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 959 (2006)
Finite Element Analysis for Substrate′s Initial Stress in Vacuum Deposition
[in Chinese], [in Chinese], and [in Chinese]
In vacuum deposition, the substrate deformation caused by sustentation and temperature grads can affect the final surface form of film-substrate system. By finite element analysis and calculation on initial stress of different substrates under different sustentation manner, and the thermal stress caused by the interiorIn vacuum deposition, the substrate deformation caused by sustentation and temperature grads can affect the final surface form of film-substrate system. By finite element analysis and calculation on initial stress of different substrates under different sustentation manner, and the thermal stress caused by the interior temperature grads of substrate, P-V values of the substrate surface deformation are gained, and the contours of substrate deformation in different situations are plotted. This analysis shows that the deformation induced by gravity and the thermal deformation are great when its size is over 200 mm, which become the important factor affecting the final film surface form; with the augmentation of substrate obliquity when fixed, the substrate deformation and the stress show decreasing trend; in the same situation, the deformation induced by gravity of the fused silica substrate is a little greater than that of the BK7 glass substrate, while the thermal deformation quantity of the former is further less than the latter; the thermal stress has made greater contribution on substrate′s initial stress..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 963 (2006)
Spectral Properties of Tm:YAP Laser Crystal
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Tm:YAP crystals doped with 4 at.-% Tm3+ ions have been obtained by the Czochralski technique. Absorption and fluorescence spectra of the crystals have been measured at room temperature. The most intensive absorption peaks occur around at wavelengths of 689.5 nm and 795 nm, which are corresponding to the transitions of Tm:YAP crystals doped with 4 at.-% Tm3+ ions have been obtained by the Czochralski technique. Absorption and fluorescence spectra of the crystals have been measured at room temperature. The most intensive absorption peaks occur around at wavelengths of 689.5 nm and 795 nm, which are corresponding to the transitions of Tm3+ ions 3H6→3F3 and 3H6→3H4, respectively. The absorption cross sections are 1.89×10-20 cm2 and 1.35×10-20 cm2 with full width of half maximum (FWHM) of 22.5 nm and 30 nm respectively. The strong emission peak is centered at about 1.89 μm, the fluorescence lifetime is about 13.90 ms, and emission cross section is 1.58×10-19 cm2. According to Judd-Ofelt theory, the intensity parameters Ωt (t=2,4,6) of Tm3+ ion have been calculated as Ω2=1.4560×10-20 cm2, Ω4=2.0673×10-20 cm2, and Ω6=0.3181×10-20 cm2. Experimental results show that Tm:YAP crystal is a potential candidate for compact, efficient mid-infrared lasers at 2 μm output with laser diode (LD) pumping..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 968 (2006)
Temperature Gradient Technique Grown Nd:YAG Crystal for Heat Capacity Laser with Laser Output of 1200 W
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Large sized high quality Nd:YAG crystal was grown by the temperature gradient technique (TGT) method. The absorption spectra of Nd:YAG crystal at room temperature were measured. The distributions of Nd ions in Nd:YAG crystal were studied by using absorption spectra. Accordding to heat capacity laser theory, a heat capaLarge sized high quality Nd:YAG crystal was grown by the temperature gradient technique (TGT) method. The absorption spectra of Nd:YAG crystal at room temperature were measured. The distributions of Nd ions in Nd:YAG crystal were studied by using absorption spectra. Accordding to heat capacity laser theory, a heat capacity laser by using this Nd:YAG crystal was designed and fabricated with the laser output of 1200 W and the optical-optical conversion efficiency of 30%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 973 (2006)
Measurement and Metrology
Study on Pulsed Laser Range Finder Based on Digital Polarity Correlation Algorithm
[in Chinese], [in Chinese], and [in Chinese]
The real-time signal processing of laser pulses is one of the key technologies in the laser rangefinding. The increased ability of anti-jamming and detectable distance are the main problems to be solved. Comparing with the direct threshold detection method, digital correlation techniques offer a good possibility for imThe real-time signal processing of laser pulses is one of the key technologies in the laser rangefinding. The increased ability of anti-jamming and detectable distance are the main problems to be solved. Comparing with the direct threshold detection method, digital correlation techniques offer a good possibility for improving the sensitivity of pulsed laser ranging system. The digital polarity correlation function is introduced, which can effectively reduce the hardware expended and achieve the parallel correlation computations in a single very large scale integration (VLSI) chip to increase the data throughput. Based on this digital polarity correlation system, some simulations are presented to confirm the feasibility of estimating time-of-flight from the noisy echoes, and an analysis of the influences on correlation results caused by pulse repetition rate, arrival delay, interval jitter, pulse width and sampling frequency is carried out, which provides a theory basis for laser transmitter designs used in correlation-based measurement systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 941 (2006)
Pulsed Thermal Lens Technique with a Non-Gaussian Beam Excitation
[in Chinese]
A non-Gaussian beam excitation scheme was introduced to a mode-dismatched pulsed thermal lens technique. The advantages of the thermal lens approach with a non-Gaussian beam excitation were described. Experiment was performed to investigate the amplitude and temporal behaviors of the thermal lens signals excited by nonA non-Gaussian beam excitation scheme was introduced to a mode-dismatched pulsed thermal lens technique. The advantages of the thermal lens approach with a non-Gaussian beam excitation were described. Experiment was performed to investigate the amplitude and temporal behaviors of the thermal lens signals excited by non-Gaussian beams of different profiles, as well as their dependences on the experimental parameters. The experimental results showed that for different beam profiles, the measurement sensitivity of the thermal lens technique could be maximized by employing the near-field detection scheme and optimizing the geometric parameters (e.g., the detection distance) of the thermal lens configuration. On the other hand, the influence of these geometric parameters on the determination of thermal properties of a measured sample could be minimized by using a far-field detection scheme..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 945 (2006)
Study on Retardation Variation Behavior of Quartz Wave-plate Follows Temperature
[in Chinese], [in Chinese], and [in Chinese]
The variation behavior of phase retardation of wave-plate with temperature was introduced, and the electro-optic modulation method was put forward to measure the phase retardation. The variation of temperature has an effect on the phase retardation, thus influencing the useful precision of wave-plate. In order to reducThe variation behavior of phase retardation of wave-plate with temperature was introduced, and the electro-optic modulation method was put forward to measure the phase retardation. The variation of temperature has an effect on the phase retardation, thus influencing the useful precision of wave-plate. In order to reduce this negative effect and improve the precision under different temperature conditions, the properties of the wave-plate should be analyzed. The temperature properties were analyzed theoretically and mathematically, then relationship between coefficient of thermal expansion and temperature coefficient of refractive index was obtained. The relationship between temperature coefficient of refractive index and wavelength offered theoretical basis and parameter choice basis for correctly using and designing wave-plate, respectively. The retardation would reduce 1° when the temperature increased 1 ℃ for the wave-plate with thickness of 1.8 mm and wavelength of 632.8 nm. According to the application shortage of wave-plate in different temperatures, the electro-optic modulation method was presented to measure the phase retardation, if the voltage was controlled within the range of ±700 V, the precision of measuring would be within 1%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 949 (2006)
Optical Communication
2D Pattern Transfer Based on Multi-Beam Array in Air-Water Channe
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel optical communication scheme of 2D pattern transfer model based on multi-beam array in complex channel is proposed. The model makes full use of the strong scattering of channel. Spreading of the beams produces an overlapping area at the receiver plane. The reconstruction of the initial 2D pattern spatial positiA novel optical communication scheme of 2D pattern transfer model based on multi-beam array in complex channel is proposed. The model makes full use of the strong scattering of channel. Spreading of the beams produces an overlapping area at the receiver plane. The reconstruction of the initial 2D pattern spatial position information can be performed by an imaging optics system within the area. The introduction of apparent parameters reduces the complex beam propagation inside two kinds of mediums to a brief propagation only inside air medium, which simplifies the theoretical analysis. A proof-of-concept experiment employs a micro lens array each diameter of which is 15 mm and sea water and atmosphere channel with length of 12.65 m to simulate the strong scattering in real case. The results indicate good feasibility of the proposed model..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 928 (2006)
Experimental Study of Long-Period Moiré Gratings
[in Chinese], [in Chinese], and C. Paul
Two kinds of special long-period fiber gratings, phase-shift and apodised long-period gratings, were studied by many researchers, because of their special spectral characteristics. According to the theory of long-period moiré gratings, with the methods of step-by-step ultraviolet (UV) writing and double-exposure wTwo kinds of special long-period fiber gratings, phase-shift and apodised long-period gratings, were studied by many researchers, because of their special spectral characteristics. According to the theory of long-period moiré gratings, with the methods of step-by-step ultraviolet (UV) writing and double-exposure with different grating period, several kinds of long-period moiré gratings were fabricated in the hydrogened high-germanium-doped fiber by controlling the period and the first position of both exposure and the exposure-time of each step, which realized the effects of phase-shift and apodization. The results indicated that the moiré gratings technology can be well applied in fabricating the special kinds of long-period fiber gratings, such as phase-shifted and apodised gratings..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 7, 933 (2006)
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