Journals >Chinese Journal of Lasers
Contents
2005
Volume: 32 Issue 7
30 Article(s)
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Research Article
Experimental Study of Coupling Coefficients for Air-Breathing Mode Laser Propulsion
[in Chinese], [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 order to study the effect of the air pressure on the coupling coefficients for laser propulsion, a vacuum chamber was designed in which the air pressure can be changed from 4.6×103 Pa to 101.3×103 Pa. The pendulum with light-craft model was propelled by TEA CO2 laser. It was found in the experiment that whIn order to study the effect of the air pressure on the coupling coefficients for laser propulsion, a vacuum chamber was designed in which the air pressure can be changed from 4.6×103 Pa to 101.3×103 Pa. The pendulum with light-craft model was propelled by TEA CO2 laser. It was found in the experiment that when the laser pulse energy was 20 J, the coupling coefficients increased gradually with the increase of air pressure, reached the summit at the air pressure of 34.6 kPa, then began to decrease. When the laser pulse energy was reduced to the 10 J, the air pressure value at which the coupling coefficients reached the summit fell. According to the theory of shockwave and laser plasma, the paper gives a preliminary analysis to this phenomenon and predicted the effect of the laser pulse energy on the peak value of coupling coefficients..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 889 (2005)
Study on Voltage Measurement System for the Table-Top Capillary Fast Discharge X-Ray Laser Facility
[in Chinese], and Kim Dong-Eon
Table-top capillary fast discharge X-ray experiment facility is used to study the X-ray laser amplification by directly fast electric pulse excitation of gases. Due to the characteristics of high voltage, large current, fast pulse, strong disturb and small space available, it is difficult to carry out the high voltage Table-top capillary fast discharge X-ray experiment facility is used to study the X-ray laser amplification by directly fast electric pulse excitation of gases. Due to the characteristics of high voltage, large current, fast pulse, strong disturb and small space available, it is difficult to carry out the high voltage pulse measurement in this setup by a general high voltage non-inductance resistor and single grade voltage-division measuring system. A voltage sensor composed of a kind of high-voltage new insulation structure non-inductance resistor by making slots on the surface of an insulating rod and a two-grade voltage-divider measuring system were developed to accomplish the measurement of the high voltage pulse. The principle of insulation structure of the voltage sensor, the measurement system and the experiment results have been introduced, and the error of the measurement system has also been discussed in detail. Application results indicated that the new voltage-sensor has an advantage of higher potential gradient and smaller inductance simultaneously in air dielectric, and the measurement system has a good anti-disturb ability and smaller firstly-peak measuring error..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 894 (2005)
General Analysis on Phase Locked External Cavity Laser Diode Arrays
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Without referring to specific devices, a universal discussion has been made on the high power laser diode arrays (LDAs) phase locked with external cavities (ECs). For a phase locked LDA based on the diffraction coupling between the nearest neighbor emitters, the coupling parameters have been expressed by module and argWithout referring to specific devices, a universal discussion has been made on the high power laser diode arrays (LDAs) phase locked with external cavities (ECs). For a phase locked LDA based on the diffraction coupling between the nearest neighbor emitters, the coupling parameters have been expressed by module and argument, and the threshold conditions for different supermodes are analyzed, including the finite reflection of the front facet of the LDA facing the EC. Even though the thresholds of the super modes of LDA are affected by the residual reflection at the front facet, it can still be analytically proved that the favored mode of the LDA is either the lowest or highest order super mode. There exist some isolated EC lengths favoring the lowest order or highest order super modes, which are in consistent with the mode coupling theory..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 899 (2005)
Side Coupler of Double-Cladding Fiber
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new method for side-pumping double-cladding fiber is researched. A column of 3 mm length is cut off from D-shape double-cladding fiber which has a transverse sectional dimension of 350 μm×400 μm. Then the column-fiber coupler is formed by gluing the column onto the side of inner cladding. The pumping light is coA new method for side-pumping double-cladding fiber is researched. A column of 3 mm length is cut off from D-shape double-cladding fiber which has a transverse sectional dimension of 350 μm×400 μm. Then the column-fiber coupler is formed by gluing the column onto the side of inner cladding. The pumping light is coupled into the inner cladding from the end of column. When the output power is 1.3 W from the forward end of the coupler, the optimum efficiency is 85%. This method suits for pumping the fiber laser and amplifier of several watts output power..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 953 (2005)
Spoke-Type Fiber Grating Sensor of Measuring Force with Temperature Active Compensation
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Adopting the design of spoke-type sensing structure, the sensing head is composed of two Bragg gratings, which have different wavelengths and are bonded to the middle of two symmetrical spoke side surfaces with same angles along the direction of the spoke neutral axis. Using the characteristic of fiber grating absolateAdopting the design of spoke-type sensing structure, the sensing head is composed of two Bragg gratings, which have different wavelengths and are bonded to the middle of two symmetrical spoke side surfaces with same angles along the direction of the spoke neutral axis. Using the characteristic of fiber grating absolate code, the spoke-type fiber grating sensor of measuring force with temperature active compensation is designed and manufactured. The theoretical analysis and experimental results indicate that this sensor has the function of temperature active compensation, it can be used in high precision sensing and measuring of pressure and pull, the maximal force measurment value is up 3 kN and the temperature active compensation range is between -20 ℃ and 75 ℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 956 (2005)
Optical Fiber Bragg Grating Load Sensing with High Primary Resolution
[in Chinese], [in Chinese], and [in Chinese]
In this paper, a new scheme to measure the difference of two resonance wavelengths of a fiber Bragg grating (FBG) load sensor is presented. In order to acquire high primary resolution of the fiber grating transverse load sensing, a beam splitter and a Michelson interferometer with two Faraday rotation mirrors (FRM) areIn this paper, a new scheme to measure the difference of two resonance wavelengths of a fiber Bragg grating (FBG) load sensor is presented. In order to acquire high primary resolution of the fiber grating transverse load sensing, a beam splitter and a Michelson interferometer with two Faraday rotation mirrors (FRM) are adopted to compose the detecting system, the instability caused by birefringence of the fibers in the interferometer is considerably reduced. This new FBG load senor is demonstrated and the primary resolution of 0.025 N/mm is obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 961 (2005)
Beam Transmission
Transfer Matrix Method for Analyzing the Characteristics of Multiple-Ring Higher Order Microring Resonators
[in Chinese], [in Chinese], and [in Chinese]
The microring resonator coupled with the input/output channel waveguides can be applied in filter due to its compactness, functionality, and the possibility of dense integration. In order to achieve flatter tops and sharper rolloff in the passband, the multiple-ring higher order structure is employed. Both the transferThe microring resonator coupled with the input/output channel waveguides can be applied in filter due to its compactness, functionality, and the possibility of dense integration. In order to achieve flatter tops and sharper rolloff in the passband, the multiple-ring higher order structure is employed. Both the transfer functions of “series-coupled” and “parallel-coupled” multi-ring high order filters are derived using the transfer matrix method. For the “parallel-coupled” structure, the symmetric spectral response is achieved by optimizing the ring distance, while for the “series-coupled” structure, the performance is determined by the coupling coefficients between the ring and ring. In order to obtain maximally flat response passbands, the numerical results show that the proper coupling coefficients should be symmetric and smaller in the middle of the structure..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 929 (2005)
Experimental Research on Little-Size Serrated Aperture
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The experimental demonstration of the little-size serrated aperture instead of circular aperture in the laser system is given. The intensity distributing and the contributing range for using the serrated aperture are analyzed based on Fresnel diffraction theory. The pictures are recorded by charge coupled device (CCD) The experimental demonstration of the little-size serrated aperture instead of circular aperture in the laser system is given. The intensity distributing and the contributing range for using the serrated aperture are analyzed based on Fresnel diffraction theory. The pictures are recorded by charge coupled device (CCD) system. The intensity ripples of Fresnel diffraction are suppressed and the filling factor is improved by using the serrated aperture..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 933 (2005)
Laser Manufacturing
Research on Structure Property of Thick-Film Conductive Lines Fabricated by Laser Micro-Fine Cladding and Flexibly Direct Writing
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Nowadays, the electronic components are developing towards to high density compaction and miniaturization, which needs higher line densities and narrower line widths for interior interconnected conductive lines. However, the conventional technologies can not meet the rapidly growing need for their inherent limits. In tNowadays, the electronic components are developing towards to high density compaction and miniaturization, which needs higher line densities and narrower line widths for interior interconnected conductive lines. However, the conventional technologies can not meet the rapidly growing need for their inherent limits. In this paper, based on the technique of laser micro-fine cladding and flexibly direct writing, micro-fine conductive lines of high quality and high property are fabricated on glass substrates. The properties and quality of conductive lines are adjusted by structure change with different processing parameters, so as to optimize parameters and make use of these parameters to fabricate the case patterns. The results showed that the conductive and welding properties of the conductive lines are high as well as bond strength and surface finish quality, therefore they are fit for fabrication and repair of products′ intellectual large-lot production and fine or micro-fine patterns..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 1001 (2005)
Substructural Modification of Austenitic Stainless Steel Induced by Laser Shock
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In current study, the laser shock processing (LSP) technique of high energy and short pulse duration is adopted. The substructural transformation characteristics and mechanisms of 2Cr17Mn15Ni2N austenitic stainless steel, subjected to ultra-high strain-rate and impact stress in excess of dynamic yield strength of the tIn current study, the laser shock processing (LSP) technique of high energy and short pulse duration is adopted. The substructural transformation characteristics and mechanisms of 2Cr17Mn15Ni2N austenitic stainless steel, subjected to ultra-high strain-rate and impact stress in excess of dynamic yield strength of the target, are investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) technology. It is found that the crystallinity in the treated zone is declined, and the size of subgrains ranging from 0.1 to 0.5 μm and the regular arrangement of chapped substructures are formed in the treated region. The hardness in the impacted zone increases apparently and the deformation depth reaches 0.25 mm. Meanwhile, the deformation-lagged annealing twins, microbands, dislocation blocks, streak-like subgrains, slip-type stacking faults, and so on, have been observed in the subsurface of the treated regions. No deformation twin and ε(α) martensite phase are identified. It shows that the ultra-high strain rate induced by LSP plays the crucial role accounting for the unique substructures of the impacted austenitic stainless steel..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 1006 (2005)
Effects of La2O3 on Microstructure and Properties of Laser Clad γ/Cr7C3/TiC Composite Coatings on TiAl Intermetallic Alloy
[in Chinese], and [in Chinese]
The effects of La2O3 addition on microstructure, wear and oxidation properties of laser clad composite coatings on TiAl intermetallic alloy substrates with NiCr-Cr3C2 precursor mixed powders have been investigated. The corresponding wear and oxidation mechanisms are also discussed based on the experimental results. TheThe effects of La2O3 addition on microstructure, wear and oxidation properties of laser clad composite coatings on TiAl intermetallic alloy substrates with NiCr-Cr3C2 precursor mixed powders have been investigated. The corresponding wear and oxidation mechanisms are also discussed based on the experimental results. The results show that no evident new crystallographic phases are formed except a rapidly solidified microstructure consisting of the primary hard Cr7C3 and TiC carbides and the γ/Cr7C3 eutectics distributed in the tough γ nickel solid solution matrix. The additions of rare earth oxide La2O3 can refine and purify the microstructure of the coatings, relatively decrease the volume fraction of primary blocky Cr7C3 to Cr7C3/γ eutectics and increase the microhardness of the coatings. The refinement of the microstructure is beneficial to improving the microhardness, strength and toughness of the coatings, the purification and compactness of the coatings is in favor of the wear and oxidation resistance. The composite coating with 4 wt.-% La2O3 addition can result the best enhancement of wear and oxidation resistance. However, too less or excessive addition amount of La2O3 have no better influence on wear and oxidation properties of the composite coatings..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 1011 (2005)
Laser Physics
Diode End-Pumped Kerr-Lens Mode-Locked Yb∶YAG Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A diode end-pumped Kerr-lens mode-locking in Yb∶YAG is got without using saturable absorber and hard diaphragm inside the cavity, instead five-mirror cavity is used. The moke-locking′s power is 20 mW, and the wavelength centers at 1038 nm, the repetition is 94 MHz, and full width at half maximum of spectrum bandwith isA diode end-pumped Kerr-lens mode-locking in Yb∶YAG is got without using saturable absorber and hard diaphragm inside the cavity, instead five-mirror cavity is used. The moke-locking′s power is 20 mW, and the wavelength centers at 1038 nm, the repetition is 94 MHz, and full width at half maximum of spectrum bandwith is lager than 9 nm (FWHM), corresponding to a transform limited pulse width of <124 fs..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 878 (2005)
High Efficient CW Tm,Ho∶YLF Laser Pumped by Fiber-Coupled Diodes
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, a high power of cryogenic Tm(8 at.-%),Ho(1.4 at.-%)∶YLF end-pumped by a fiber-coupled laser diode (LD) with number aperture of 0.3, core diameter of 0.4 mm, and central wavelength of 792 nm at 20 ℃ temperature is reported. The highest continuous-wave (CW) power of 5.2 W at 2.05 μm is achieved under pump In this paper, a high power of cryogenic Tm(8 at.-%),Ho(1.4 at.-%)∶YLF end-pumped by a fiber-coupled laser diode (LD) with number aperture of 0.3, core diameter of 0.4 mm, and central wavelength of 792 nm at 20 ℃ temperature is reported. The highest continuous-wave (CW) power of 5.2 W at 2.05 μm is achieved under pump power of 14.8 W, corresponding to optical-optical conversion efficiency of 35%, and the slope efficiency is greater than 40%. The threshold power is only about 0.48 W because of the long lifetime, large effective emission cross section, and low reabsorption loss in Tm,Ho∶YLF crystal. Under pumping power of 29.6 W with dual-end pumping configuration, the highest CW power of 10.2 W at 2.051 μm is attained, corresponding to optical-optical conversion efficiency of 33%, and the slope efficiency is greater than 36%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 881 (2005)
A New Picosecond Pulse Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new picosecond pulse laser consists of a resonator, a single pulse laser selector, two amplifiers, frequency doubling, and so on. A Nd∶YAG rod is used as active medium of laser and two Glan prisms are separately used as polarizer and analyzer of polarized light. In order to generate a series of mode-locked pulse laseA new picosecond pulse laser consists of a resonator, a single pulse laser selector, two amplifiers, frequency doubling, and so on. A Nd∶YAG rod is used as active medium of laser and two Glan prisms are separately used as polarizer and analyzer of polarized light. In order to generate a series of mode-locked pulse laser lights, a passive mode-locked dye cell is used in the resonator. A single pulse laser light is obtained from the series of mode-locked pulse laser lights after they have passed the selector. Finally, after the pulse laser light has been amplified and doubled in frequency, an output of laser light beam with energy of 120 mJ and duration of laser light of 100 ps at wavelength of 532 nm is realized. It is equal about 1.2×109 W of pulse power or 4.2 ×109 W/cm2 of power density. An out-triggering synchro-precision of better than 2 μs is obtained from the laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 885 (2005)
Photovoltaic Gray Spatial Solitons in Photorefractive Crystal
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Plane waves are absolutely stable against small modulations in self-defocusing media, the dark spatial solitons exist only in the form localized dark hole on the plane wave background. Based on such modulation stability, the evolution equations for one-dimensional gray spatial solitons supported by the photovoltaic selPlane waves are absolutely stable against small modulations in self-defocusing media, the dark spatial solitons exist only in the form localized dark hole on the plane wave background. Based on such modulation stability, the evolution equations for one-dimensional gray spatial solitons supported by the photovoltaic self-defocusing nonlinearity are presented and its stationary solution in photovoltaic photorefractive crystal LiNbO3∶Fe is given. The properties associated with these gray solitons are investigated numerically, such as soliton profile and its phase distribution for different values of soliton grayness, and the normalized transverse velocity and the normalized full width at half maximum (FWHM) of photovoltaic gray soliton as functions of normalized intensity and degree of grayness. These properties can be steered by adjusting the relative phase difference on either side of the soliton wave. Both similarities and differences between photovoltaic gray solitons and screening gray solitons are emphasized..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 903 (2005)
Fractional Fourier Transforms for Cosh-Gaussian Beams
[in Chinese], and [in Chinese]
The analytical formulae of the beam width and the intensity distribution for fractional Fourier transform (FRFT) of cosh-Gaussian (ChG) beams are derived based on the characteristic of the equality between the rotation of the Wigner distribution function (WDF) and the FRFT. By using the derived formulae, the influencesThe analytical formulae of the beam width and the intensity distribution for fractional Fourier transform (FRFT) of cosh-Gaussian (ChG) beams are derived based on the characteristic of the equality between the rotation of the Wigner distribution function (WDF) and the FRFT. By using the derived formulae, the influences of the fractional order and the decentered parameter on the transformation properties of ChG beams in the fractional Fourier plane are studied in detail. Numerical calculation examples have been presented to illustrate the propagation properties of ChG beams through FRFT optical system. It was shown that for given decentered parameter, a flatted beams can be obtained by FRFT with suitable order. The derived formulae provide a simple and convenient way to study the FRFT of ChG beams..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 908 (2005)
Compensating Group Velocity Mismatch in BBO Type-Ⅱ Collinear Phase-Matched Configuration
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In order to avoid adverse effect arisen from group velocity mismatch in femtosecond optical parametric amplification (OPA), a method that compensates completely the group velocity mismatch among three waves is presented, by tilting simultaneously wave fronts of pump and signal pulses, for femtosecond OPA in β-BaB2O4 (BIn order to avoid adverse effect arisen from group velocity mismatch in femtosecond optical parametric amplification (OPA), a method that compensates completely the group velocity mismatch among three waves is presented, by tilting simultaneously wave fronts of pump and signal pulses, for femtosecond OPA in β-BaB2O4 (BBO) type-Ⅱ collinear phase-matched configuration. When the group velocities of three waves are matched, the variations of the phase-matched angle and the wave front tilting angles of pump and signal pulses with the signal wavelength are calculated theoretically, and the effects on the pump beam size and the parametric bandwidth are analyzed. The results indicate that this method not only can match completely group velocities among three waves, but also can achieve maximal parametric bandwidth for continuous tunable femtosecond BBO OPA. In addition, for increasing parametric gain, it is very importance to appropriately choose the pump beam size..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 913 (2005)
Analysis on the Bistable Dynamic Characteristics of Nonuniform Distributed Feedback Semiconductor Optical Amplifiers
[in Chinese], [in Chinese], and [in Chinese]
Distribution feedback semiconductor optical amplifiers (DFB-SOAs) have potential applications in optical signal processing because of lower switching-on threshold of bistability. By introducing spatial phase-shift and chirp, its bistable performance can be improved. If the amplifier operates at pulse state, signal tranDistribution feedback semiconductor optical amplifiers (DFB-SOAs) have potential applications in optical signal processing because of lower switching-on threshold of bistability. By introducing spatial phase-shift and chirp, its bistable performance can be improved. If the amplifier operates at pulse state, signal transmission rate would be affected by the falling-edge distortion of output pulse and turn-on delay, so it is necessary to study its dynamic properties. In this paper, based on the coupled mode equation and carrier rate equation, the bistable dynamic characteristics of phased-shifted and chirped distributed-feedback semiconductor optical amplifiers have been investigated numerically. The results show that, the phase-shifted DFB-SOAs make the shape distortion of falling edge and turn-on delay of output pulse worsened firstly and then weakened with the decreased initial detuning, which can be suppressed by introducing chirp but being accompanied by the enhanced input peak overdrive..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 917 (2005)
Thermal Effect Research of End-pumped Rectangle Nd∶GdVO4 Crystals
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Temperature field and pump-face thermal distortion field of a rectangle Nd∶GdVO4 crystal end-pumped by the diode laser with Gauss mode was researched by the analytical theory. Through work characteristic analysis of Nd∶GdVO4 crystal by a diode laser end-pumped, a thermal model was built according to the actual working Temperature field and pump-face thermal distortion field of a rectangle Nd∶GdVO4 crystal end-pumped by the diode laser with Gauss mode was researched by the analytical theory. Through work characteristic analysis of Nd∶GdVO4 crystal by a diode laser end-pumped, a thermal model was built according to the actual working state. A new solution of the heat conduct equation was introduced, and the general solution of temperature field and pump-face thermal distortion field of rectangle Nd∶GdVO4 crystal were obtained. Some relevant parameters, which would influence temperature field distribution, were analyzed simultaneously. The result shows that when the output power of diode laser is 15 W, the pump-face centre of 1.2 at.-% neodymium-doped Nd∶GdVO4 crystal can get 189 ℃ maximal temperature rise and has 1.37 μm thermal distortion. The method can also be applied to analyze thermal problems of other laser crystals..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 923 (2005)
Materials and Thin Films
Co2+-Doped LiNbO3 Crystals Grown by the Bridgman Method and Their Optical Spectra
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The growth of LiNbO3 (LN) crystals doped with Co2+ ions in 0.1 and 0.3 mol% concentrations by the Bridgman method in congruent composition (Li2O: 48.6mol%, Nb2O5: 51.4mol%) and CoO as dopant under the conditions of temperature gradient around 20～40 ℃/cm for solid-liquid interface and growth rate of 1～3 mm/h was reporteThe growth of LiNbO3 (LN) crystals doped with Co2+ ions in 0.1 and 0.3 mol% concentrations by the Bridgman method in congruent composition (Li2O: 48.6mol%, Nb2O5: 51.4mol%) and CoO as dopant under the conditions of temperature gradient around 20～40 ℃/cm for solid-liquid interface and growth rate of 1～3 mm/h was reported. The X-ray diffraction (XRD) and differential thermal analysis (DTA) were used to characterize the crystals. The absorption spectra of different parts of crystals from 350 to 2500 nm were recorded. The three split absorption peaks at 520, 549 and 612 nm, and a wide band centered at 1358 nm were observed. The absorption results indicated that the Co ions presented +2 valence in crystal and located within the distorted oxygen octahedrons. The concentration of Co2+ ion in crystal reduced along growing direction, and the effective distribution coefficient of Co2+ in LiNbO3 crystal was more than 1. The emission spectra under 900-nm wavelength were studied. The band at 750 nm was observed and the peak was red-shifted as the increase of exciting wavelength..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 965 (2005)
Preparation and Properties Research of Reverse Saturable Absorption Materials of Alkoxy Phthalocyanine Pb
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Three derivatives of alkoxy phthalocyanine Pb were synthesized. The structures of products were characterized by means of infrared (IR), hydrogen nuclear magnetic resonance (HNMR) spectra and elementary analysis. The ultraviolet-visible spectra were measured between 200～800 nm when the derivatives were in polymethyl meThree derivatives of alkoxy phthalocyanine Pb were synthesized. The structures of products were characterized by means of infrared (IR), hydrogen nuclear magnetic resonance (HNMR) spectra and elementary analysis. The ultraviolet-visible spectra were measured between 200～800 nm when the derivatives were in polymethyl methacrylate (PMMA) solution. Three derivatives were mixed into PMMA solution independently, then the composite materials which had nonlinear optical properties were prepared. The nonlinear reverse saturable absorption measurements of composite materials were performed with a frequency-doubled Q switched Nd∶YAG laser with 8-ns laser pulse at 532 nm. The factors that affect the performance of reverse saturable absorption and optical limiting of the materials were discussed. A phenomenological model is used to describe optical limiting phenomena, it meets with the experiment results largely. The effect of saturable absorption of alkoxy phthalocyanine Pb is the best ones among these compounds. It is due to the improvement of its conjugate characteristics and avoiding low polymerization of molecules..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 969 (2005)
Investigations of Neutron-Induced Color Centers in Ti-Doped Sapphire Crystals
[in Chinese], [in Chinese], and [in Chinese]
Neutron-irradiation induced optical properties changes and defects formation in Ti-doped sapphire crystals were studied. Temperature gradient technique (TGT) grown Ti-doped sapphire crystals were irradiated by 1.5 MeV neutrons with a dose of 4.32×1016 neutrons/cm2. Absorption, emission and excitation spectra were Neutron-irradiation induced optical properties changes and defects formation in Ti-doped sapphire crystals were studied. Temperature gradient technique (TGT) grown Ti-doped sapphire crystals were irradiated by 1.5 MeV neutrons with a dose of 4.32×1016 neutrons/cm2. Absorption, emission and excitation spectra were presented. The 194-nm absorption band intensity enhanced and the 268-nm band weakened after irradiation. And the 420-nm luminescence band weakened and blue shifted to 414-nm. The results indicated that F+-type centers formed and the valence state of titanium switched from quadrivalent to trivalent during irradiation. Thermoluminescence (TL) was observed at 247℃ and assigned to irradiation-induced color centers. The thermoluminescence trap depth is 0.63 eV calculated with initial elevation method, and the lower thermoluminescence intensity is ascribed to the quenching effect of Ti ions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 973 (2005)
Optical Properties and the Minimal Continuous Thickness of Molybdenum Nano-Films
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Mo nano-films of different thicknesses have been prepared by ion beam sputtering. The reflectance and transmittance of Mo nano-films in the range of 310 nm to 1250 nm have been measured by Lambda-900 spectrophotometer. Relationships of the reflectance, transmittance, absorptance to the thickness of Mo nano-films in theMo nano-films of different thicknesses have been prepared by ion beam sputtering. The reflectance and transmittance of Mo nano-films in the range of 310 nm to 1250 nm have been measured by Lambda-900 spectrophotometer. Relationships of the reflectance, transmittance, absorptance to the thickness of Mo nano-films in the wavelengths selected 310 nm, 350 nm, 400 nm, 500 nm, 550 nm, 632 nm, 800 nm and 1200 nm have been discussed. The results showed that the optical properties of Mo nano-films have obvious size effect. There is a point of intersection, which is located in the curves of relationships of the reflectance, transmittance to the thickness of Mo nano-films at the wavelength of 550 nm. The corresponding thickness of this point of intersection can be thought of as the minimal continuous thickness of the growth of metal films from discontinuous to continuous in the optical properties. The topography image of Mo nano-film with thickness of 15.76 nm was obtained by using atomic force microscopy (AFM). This topography image is already the topography image of the continuous film..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 977 (2005)
Measurement and Metrology
Intra-Cavity Absorption Gas Measurement Network Based on the Fiber Lasers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
High sensitivity of the intra-cavity absorption gas sensor (ICAGS) measurement network based on the erbium doped fiber ring laser was demonstrated. It is found that the maximum sensitivity can be obtained when the laser is operating near the threshold. Wavelength modulation/second harmonic detection technique was used High sensitivity of the intra-cavity absorption gas sensor (ICAGS) measurement network based on the erbium doped fiber ring laser was demonstrated. It is found that the maximum sensitivity can be obtained when the laser is operating near the threshold. Wavelength modulation/second harmonic detection technique was used to improve the performance of intra-cavity absorption measurement. A 1×N wavelength division multiplexer (WDM) with one channel corresponding to the absorption line of acetylene within the transmission window of 1530 nm was used in the WDM active sensing network. The system is demodulated by scanning the wavelength of a tunable filter. The minimum detectable gas concentration of 0.044 mol/m3 was achieved in measuring the 8.31 mol/m3 acetylene gas..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 982 (2005)
Experimental Analysis of 40 Gb/s All Optical Switch Using Ultrafast Nonlinear Interferometer
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The technology of 40 Gb/s has developed very slowly because of many factors, such as the nonlinear characteristic of optical fiber. All-optical regeneration is the effective way to solve this problem and the key of it is all-optical-nonlinear switch. After analyzing the transmission functions of a kind of all-optical sThe technology of 40 Gb/s has developed very slowly because of many factors, such as the nonlinear characteristic of optical fiber. All-optical regeneration is the effective way to solve this problem and the key of it is all-optical-nonlinear switch. After analyzing the transmission functions of a kind of all-optical switch (ultrafast nonlinear interferometer (UNI)), the mathematical descriptions of the UNI switch window are got. As a result, the data rate of the experiment according to UNI achieves 40 Gb/s. Combined with the experimental conditions, the influencing factors of UNI switch are analyzed. By increasing the injection current of semiconductor optical amplifier (SOA), the average power of control pulse and adjusting the power of continuous light to the optimal value, the shape and extinction ratio of UNI switch are effectively improved. Based on the experiment, this phenomenon is elementarily explained in theory. It is utilized these results to do the experiments in order to optimize the UNI system to the best conditions, which will be the theoretical and experimental foundations to all-optical regeneration and many other fields..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 987 (2005)
Experimental Study on Beam Parameter Measurement System by Using Area Array CCD
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The technical problems concerning the determination of the laser beam parameters by using area array charge couple device (CCD) detector were studied. The beam parameters of Hermite-Gaussian modes generated from laser diode (LD) pumped CW Nd∶YAG laser with 1064 nm and a lamp pumped Q-switched Nd∶YAG laser with 10 ns puThe technical problems concerning the determination of the laser beam parameters by using area array charge couple device (CCD) detector were studied. The beam parameters of Hermite-Gaussian modes generated from laser diode (LD) pumped CW Nd∶YAG laser with 1064 nm and a lamp pumped Q-switched Nd∶YAG laser with 10 ns pulse width were experimentally measured. Comparing the measured beam quality factor M2 with theoretical one, the measuring deviation of M2 was less than 5%. The measuring error of the divergence was elso less than 5%. The influences of various factors on the measured beam parameters were discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 993 (2005)
Influence of Detector Responsibility on Its Metrical Result of Ring-Down Cavity
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Capability of the detector influences the figure of measured ring-down signal very much. According to propagation equation of Gaussian beam and overlap-add of signal, a theory model is set up to research the influence of detector on its ring-down signal and its metrical result by using data processing of only fitting. Capability of the detector influences the figure of measured ring-down signal very much. According to propagation equation of Gaussian beam and overlap-add of signal, a theory model is set up to research the influence of detector on its ring-down signal and its metrical result by using data processing of only fitting. The change of ring-down waveform is numerically simulated in different case by this model, and based on this, it is calculated that relation between capability of the detector and measured reflectivity of the cavity ring-down spectroscopy (CRDS). Results show that appropriate detector can improve repeating precise of measured reflectivity for the present data processing, but its metrical result of 0.990045 is different from the true reflectivity of cavity′s mirror, which is 0.999. In the end, it is studied that metrical result is changed with reflectivity of cavity′s mirror, and another data processing is analyzed. Two collating ways for measured reflectivity are put forward, one is correcting in theory according to the difference between simulated result and true reflectivity of cavity's mirror; the second is adding pretreatment of ring-down waveform before data processing of fitting, such as comb filter..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 997 (2005)
Optical Communication
4×4 Crossbar Micro-Electro-Mechanical System Optical Matrix Switches
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Optical switches made with micro-electro-mechanical systems (MEMS) technology bear advantages of both MEMS and traditional optics. In this paper, 4×4 MEMS optical matrix switches are proposed, in which on-off micro-mirrors are arranged with crossbar switching network. Ball-lensed single-mode optical fiber collimatOptical switches made with micro-electro-mechanical systems (MEMS) technology bear advantages of both MEMS and traditional optics. In this paper, 4×4 MEMS optical matrix switches are proposed, in which on-off micro-mirrors are arranged with crossbar switching network. Ball-lensed single-mode optical fiber collimators are used as input and output ports. With theory of Gaussian beam coupling, the insertion loss (IL) of the optical matrix switches, and also its main origins, i.e. the position misalignments and the angular misalignments, are calculated and analyzed. Some useful conclusions are drawn to guide designing such devices. With the misalignment tolerances: 2 μm of input/output lateral positioning misalignment, 0.15° for input/output angular misalignment, and 0.15° for micro-mirror angular misalignment, the insertion loss of different channels in the pilot study is tested and the highest value of that is 2.77 dB..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 937 (2005)
Address Code and Interference Estimate Receiver of 2D-OCDMA
[in Chinese], [in Chinese], and [in Chinese]
The new construction scheme of two dimensional optical orthogonal codes (2D-OOCs), of which auto-correlation side lobes are 0 and the cross-correlation side lobes are at most 1, and the interference estimate receiver of asynchronous frequency-hopping time-spreading two-dimensional optical code division multiple access The new construction scheme of two dimensional optical orthogonal codes (2D-OOCs), of which auto-correlation side lobes are 0 and the cross-correlation side lobes are at most 1, and the interference estimate receiver of asynchronous frequency-hopping time-spreading two-dimensional optical code division multiple access (2D-OCDMA) system are presented. For constructing the 2D-OOCs, two unipolar codes are used as the frequency-hopping pattern and the time-spreading pattern, respectively. The unipolar codes used as frequency-hopping patterns are OOCs of which auto-correlation side lobes and the cross-correlation one are at most 1, for the unipolar codes used as the time-spreading patterns, the restriction is that their code lengths are a prime number or their code length and displacement difference between any two non-zero chips in the same code are co-prime number. By using one 2D-OOC as multi-user interference (MUI) estimation code, which is not assigned to any user, the asynchronous MUI estimate can be realized. According to the estimating of MUI, the optimum decision threshold can be obtained. The analysis of bit error rate (BER) indicates that the system with interference estimate receiver has advantage over traditional system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 942 (2005)
Study of Control Protocol in Optical Burst Switching Ring Network with Dynamic Wavelength Add-Drop Multiplexer
[in Chinese], and [in Chinese]
A kind of optical burst switching (OBS) ring access control protocol—delay optical burst with a fixed period (DBFP) protocol is proposed, which uses dynamic wavelength add-drop multiplexer (WADM), i.e. uses wavelength tunable transmitters and tunable receivers (TTTR) mechanism. The wavelength resource is reserved by thA kind of optical burst switching (OBS) ring access control protocol—delay optical burst with a fixed period (DBFP) protocol is proposed, which uses dynamic wavelength add-drop multiplexer (WADM), i.e. uses wavelength tunable transmitters and tunable receivers (TTTR) mechanism. The wavelength resource is reserved by the control packet transmitted in advance. And every optical burst is delayed a fixed period with a fixed length fiber delay line (FDL) at every intermediate node to let all reserved bursts accomplish transmitting, in order to avoid colliding with reserved local access bursts. The result of simulation shows that DBFP protocol can statistically multiplex wavelength efficiently, can allocate wavelengths during in required period on demand, and can reuse wavelength at space domain, and that the wavelength reuse efficiency is up to 160%. Therefore, the proposed DBFP protocol enhances network performance and increases the link utilization, which adapts for bursty traffic, specially. Meanwhile, the delay introduced by DBFP protocol is small, for example, is about 1 ms for optical burst multiplex ring network with 10 nodes. So the delay is neglectable..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 7, 948 (2005)
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