Journals >Chinese Journal of Lasers
Contents
2005
Volume: 32 Issue 2
36 Article(s)
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Research Article
Research on Frequency Stabilization of Modulation Transfer Spectroscopy
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Iodine-stabilization lasers are becoming important wavelength standards and optical frequency standards. The frequency value of Iodine R (56) 32-0 transition was recommended as the standard frequency for practical realization of the meter by CIPM in 2001. Molecular iodine has rich strong absorption lines near 532 nm thIodine-stabilization lasers are becoming important wavelength standards and optical frequency standards. The frequency value of Iodine R (56) 32-0 transition was recommended as the standard frequency for practical realization of the meter by CIPM in 2001. Molecular iodine has rich strong absorption lines near 532 nm that can provide the absolute references for frequency stabilization. A monolith solid laser was tuned at the spectrum of transition R (56) 32-0 of iodine molecule with new modulation frequency 375 kHz. And 15 hyperfine components of this spectrum were observed using modulation transfer spectroscopy. The sensitivity of frequency detecting with 375 kHz modulation frequency was higher than that with 312 kHz modulation frequency by broadening one hyperfine component. The laser frequency was successfully locked at a10 component for no less than 10 hours. The frequency stability was estimated about level of 10-13, and the exact value of frequency stability is under measurement by frequency beating between two same kind of lasers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 164 (2005)
Experimental Research on Hard X-Ray Phase-Contrast Imaging
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The principle and experimental results of hard X-ray phase-contrast imaging are presented in the paper. The wavelength of the X-ray is 0.08860 nm and the specimen is a natural moth. The obtained image was readout by optical microscope, using Kodak high-resolution X-ray films as recording medium. It is demonstrated thatThe principle and experimental results of hard X-ray phase-contrast imaging are presented in the paper. The wavelength of the X-ray is 0.08860 nm and the specimen is a natural moth. The obtained image was readout by optical microscope, using Kodak high-resolution X-ray films as recording medium. It is demonstrated that some fine structures of the moth were recognized, especially in the boundary areas of the specimen. Contrarily, no absorption-contrast images were observed under the same conditions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 167 (2005)
Analysis of Misalignment and Spectrum Bandpass of Pulse Stretcher
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, an analytical pulse stretcher model for the single-grating stretcher based on ray-tracing is presented. By this model, the effect of misalignment of optical element of stretcher on the second dispersion and on the deviation angle of the output pulse is analyzed. When the misalignment angle for the plane In this paper, an analytical pulse stretcher model for the single-grating stretcher based on ray-tracing is presented. By this model, the effect of misalignment of optical element of stretcher on the second dispersion and on the deviation angle of the output pulse is analyzed. When the misalignment angle for the plane reflective mirror M1 is 0.2 degree, the second order dispersion of the stretcher reaches the maximum. Increasing or decreasing misalignment angle, the second order dispersion of the stretcher decreases. That indicates that the misalignment of optical element of stretcher increases deviation angle of output pulse. The finite size of the diffraction grating and the concave mirror in the stretcher has constrain effect on spectrum bandwidth. A new way of increasing second order dispersion by misaligning reflective mirror, and improving bandwidth by increasing size of the diffraction grating and the concave mirror in the stretcher is proposed. It is important to the design of the stretcher..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 170 (2005)
Vibrating Mirror for Smoothing of High Power Laser Beam
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In order to acquire uniform and flatten Gaussian beam, a new resonator is designed. The beam intensity distribution is modified to obtain greater temporal uniformity by reflector′s periodically vibrating. The theoretical model of this beam shaping was built and analyze. Simulated and experimental results are presented In order to acquire uniform and flatten Gaussian beam, a new resonator is designed. The beam intensity distribution is modified to obtain greater temporal uniformity by reflector′s periodically vibrating. The theoretical model of this beam shaping was built and analyze. Simulated and experimental results are presented that the high-power CO2 laser beam intensity distribution uniformization can be achieved using the new resonator. The novel method avoided some shortcoming in high power CO2 laser beam shaping and simplified the whole system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 175 (2005)
Elliptical Crystal Spectrometer Designed for Laser-Produced Plasma X-Ray
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new space and time resolved focusing elliptical curved crystal spectrometer has been developed and applied to diagnose X-ray of laser-produced plasma in 0.2～2 nm region. Twin channels collocated symmetrically are utilized for simultaneous measurement of space and time resolved spectra. The design parameters of the spA new space and time resolved focusing elliptical curved crystal spectrometer has been developed and applied to diagnose X-ray of laser-produced plasma in 0.2～2 nm region. Twin channels collocated symmetrically are utilized for simultaneous measurement of space and time resolved spectra. The design parameters of the spectrometer are presented, a novel aligning method is adopted, and the error due to off-axis of source is analyzed. The spectrometer has been calibrated for experiment on Shengguang-Ⅱ target chamber in Shanghai. Photographs of spectra have been recorded by using X-ray CCD camera. It is demonstrated experimentally that the measured wavelength is accorded with the theoretical value..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 180 (2005)
Temperature and Pressure Responsive Characteristics of Polymer Packaged Fiber Bragg Grating with Large Dynamic Range
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The pressure and temperature response characteristics of polymer packaged fiber Bragg grating (FBG) sensor are analyzed. The experimental results show that the pressure sensitivity is not a constant but a variable because of the effect of temperature on elastic modulus of polymer when the change range of temperature isThe pressure and temperature response characteristics of polymer packaged fiber Bragg grating (FBG) sensor are analyzed. The experimental results show that the pressure sensitivity is not a constant but a variable because of the effect of temperature on elastic modulus of polymer when the change range of temperature is large. The pressure sensitivity is 0.036 nm/MPa at 30℃ and 0.175 nm/MPa at 180℃ and the change of sensitivity is piecewise linear at different temperature range. So elastic modulus should be treated as the function of temperature when using polymer to packaged FBG, the pressure coefficient in the coefficient matrix of FBG should also be the function of temperature in order to eliminate the error induced by the change of elastic modulus caused by large range temperature change..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 224 (2005)
Fiber Optic Temperature Sensor Based on F-P Cavity Interferometric/Intensity Modulation Mechanism
[in Chinese], [in Chinese], and [in Chinese]
A fiber optic temperature sensor based on extrinsic Fabry-Perot (F-P) cavity interferometric/intensity modulation mechanism is described. The light from a light-emitting diode (LED) is coupled into a 2×2 multimode fiber coupler C1 and propagates to the F-P sensor head. The light reflected from the F-P cavity is reA fiber optic temperature sensor based on extrinsic Fabry-Perot (F-P) cavity interferometric/intensity modulation mechanism is described. The light from a light-emitting diode (LED) is coupled into a 2×2 multimode fiber coupler C1 and propagates to the F-P sensor head. The light reflected from the F-P cavity is recoupled into C1, and then through another fiber coupler C2 the light is divided into two beams. One propagates to optoelectronic detector D1 and another through narrow filter propagates to detector D2. The two signals are transported to the computer through the optoelectronic conversion and amplifier circuit. A theoretical model for the temperature calculation and self-compensation has been worked out, which gives out the compensated intensity expression on the F-P cavity length, spectral width of the light source and band pass filter. The temperature calibration curve was obtained by fitting the experiment data to the theoretical model with Levenberg-Marquardt algorithm. A minimum temperature resolution of 0.1℃ and long term accuracy of ±0.2℃ were obtained over a temperature measurement range of 20～200℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 228 (2005)
Separately Measurement of Strain and Temperature Using a Single Fiber Bragg Grating
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new practical technology for separately sensing of strain and temperature using a single fiber Bragg grating (FBG) is proposed and demonstrated. The FBG can be think to be a grating composed of two inner FBGs with the same period but different diameter when a part cladding diameter of the FBG is decreased. TheoreticaA new practical technology for separately sensing of strain and temperature using a single fiber Bragg grating (FBG) is proposed and demonstrated. The FBG can be think to be a grating composed of two inner FBGs with the same period but different diameter when a part cladding diameter of the FBG is decreased. Theoretical analysis and experiment data show that the two inner FBGs have the same temperature response but different strain response. So the strain and temperature responses can be measured separately and the span between the two inner FBGs can be used to measure the temperature-independent strain. In experiment, a part of cladding diameter of a FBG is decreased to 82 μm by etching it in HF acid. The strain responses of two inner FBGs are 0.00201 nm/με and 0.000858 nm/με, respectively, the strain response of the span between two inner FBGs is 0.00116 nm/με, and the temperature responses of two inner FBGs both are 0.01 nm/℃. Based on these experiment data, the strain and temperature can be simultaneously measured using a single FBG..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 232 (2005)
Holography and Information Processing
Optical Erasure Characteristic of Batch Thermal Fixing for Photorefractive Multiplexing Holograms
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The batch thermal fixing scheme for multiplexed holograms is investigated. The dynamic behaviors of both electrons and ions in the case of light illumination and elevated temperature are theoretically analyzed, and hereby the optical erasure effect of subsequent recording light on ion-compensated electronic gratings isThe batch thermal fixing scheme for multiplexed holograms is investigated. The dynamic behaviors of both electrons and ions in the case of light illumination and elevated temperature are theoretically analyzed, and hereby the optical erasure effect of subsequent recording light on ion-compensated electronic gratings is presented. The inter-batch optical erasure time constant, τF, is theoretically introduced, to evaluate the optical erasure to electronic gratings compensated by ions. The special experiment for measuring the parameter τF is designed and performed. The experimental result shows that inter-batch optical erasure time constant, τF, is much longer than intra-batch optical erasure time constant, τE, which agrees well with the theoretical prediction. Owing to the difference between τF and τE, the batch thermal fixing is an effective technique to achieve nonvolatile high-capability holographic storage..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 236 (2005)
Holographic Optical Disk Storage of Fiber Coupling and Wavelength Multiplexing
[in Chinese], and [in Chinese]
The optical path structure of holographic storage with fiber coupling and wavelength multiplexing in the optical disk is detailed in this paper. Because of simple structure, less optical elements and higher ratio of capability to price, it will become a new core technology in the holographic optical disk drive. BecauseThe optical path structure of holographic storage with fiber coupling and wavelength multiplexing in the optical disk is detailed in this paper. Because of simple structure, less optical elements and higher ratio of capability to price, it will become a new core technology in the holographic optical disk drive. Because the performance of the short wavelength single mode optical fiber should be higher, a multi-model optical fiber is used to produce quasi-single mode output, and a beam prism employed instead of the optical fiber splitter. A photopolymer is made which is sensitive to two wavelengths as the storage material. Its sensitivity of spectrum is even, and the spectrum range is not overlapping. The experimental result indicates that the storage effect is better and the structure of optical path is reasonable..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 240 (2005)
Improvement of Correlation Veracity of the Volume Holographic Correlator Based on the Speckle Modulation
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Volume holographic correlator has advantages for the fast optical parallel recognition. However, because of the inter page crosstalk, the sidelobes occur seriously, which reduces the parallel-processing capacity of the correlator, resulting in the low accuracy of the correlator. To suppress the sidelobes, the traditionVolume holographic correlator has advantages for the fast optical parallel recognition. However, because of the inter page crosstalk, the sidelobes occur seriously, which reduces the parallel-processing capacity of the correlator, resulting in the low accuracy of the correlator. To suppress the sidelobes, the traditional correlation formula is analyzed to discuss the origin of sidelobes. It is proposed to modify the formula with the autocorrelation function of a random function, which can suppress the sidelobes in the horizontal direction as well as in the vertical direction, with no dependence on the thickness of the hologram. A diffuser is proposed to be placed in the object path to modulate the object beam with speckle. The theoretical analysis, numerical simulation and experimental results are presented and it is shown that this method can suppress the sidelobes, sharpen the correlation peaks and improve the correlation veracity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 244 (2005)
Optimal Dopant Composition Ratio during Nonvolatile Holographic Recording in LiNbO3∶Cu∶Ce Crystals
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effect of dopant composition ratio on nonvolatile holographic recording in LiNbO3∶Cu∶Ce crystals has been investigated experimentally. The results show that the dopant composition ratio affects the performance of nonvolatile holographic recording by altering the ultraviolet light absorption characteristics of the cThe effect of dopant composition ratio on nonvolatile holographic recording in LiNbO3∶Cu∶Ce crystals has been investigated experimentally. The results show that the dopant composition ratio affects the performance of nonvolatile holographic recording by altering the ultraviolet light absorption characteristics of the crystals. Increasing the dopant composition ratio of Cu and Ce leads to an increase in the absorption of ultraviolet light and further to an increase in the recording sensitivity and the fixed diffraction efficiency. The maximum values of the fixed diffraction efficiency ηf=32% and the recording sensitivity S=0.022 cm/J are measured from a weakly oxidized LiNbO3∶Ce∶Cu crystal doped with 0.085% CuO and 0.011% Ce2O3..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 248 (2005)
Application of Image Simulation to the Holographic CT Measurement for Refractive Index of the Gas in an Incandescence Lamp
[in Chinese], and [in Chinese]
Real-time holographic interference patterns of three-dimensional distribution of gas refractive index in an incandescence lamp during its lighting process are introduced here briefly. Based on the fundamental physical problems occurred in gas heating process by filament, a concise physical and mathematical model has beReal-time holographic interference patterns of three-dimensional distribution of gas refractive index in an incandescence lamp during its lighting process are introduced here briefly. Based on the fundamental physical problems occurred in gas heating process by filament, a concise physical and mathematical model has been developed. The forming processes of holographic interference pattern are studied numerically by using digital image processing technique. The obtained results have shown that when the refractive index outside of filament has a non-uniform distribution, the information of this non-uniform distribution can be reflected by the interference pattern in the projection of lamp, and the measurements of the fringes of interference pattern can be used to modify the real measurement data. Moreover, based on the result of study and the holographic computed temography (CT) technique, an example of the three-dimension distribution of gas refractive index inside an incandescence lamp is given without the influence of the change of refractive index outside of the lamp..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 252 (2005)
Application of Holographical-Speckle Method for Intervertebral Disc Measurement in Orientation of the Lumbar Facet
[in Chinese], [in Chinese], and [in Chinese]
Application experiments of holographical-speckle method for intervertebral disc measurement of offset variable and metamorphosis in orientation of the lumbar surface are performed. The instruction of specimen making, loading device, design of beam path and process of experiment are introduced. The results of experimentApplication experiments of holographical-speckle method for intervertebral disc measurement of offset variable and metamorphosis in orientation of the lumbar surface are performed. The instruction of specimen making, loading device, design of beam path and process of experiment are introduced. The results of experiment indicate that holographical-speckle method can obtain three dimensional (3D) offset variable field of intervertebral disc, and metamorphosis can be got by calculation. This method has high accuracy, full-field and noncontact. The results of experiment offer data for contrasting the stabilization of different spinal fixation method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 257 (2005)
Laser Manufacturing
Direct Fabrication of Resistor on Glass Board by Laser Micro-Fine Cladding
[in Chinese], [in Chinese], and [in Chinese]
Basic principle and technologies of direct fabrication of resistor on glass structure by micro-fine cladding were introduced in this paper. The effect of technologic parameters on resistance values was systemically studied. Based on the thermal analysis and interacting principle between laser and matters, formation of Basic principle and technologies of direct fabrication of resistor on glass structure by micro-fine cladding were introduced in this paper. The effect of technologic parameters on resistance values was systemically studied. Based on the thermal analysis and interacting principle between laser and matters, formation of esistance films and relation between structure and properties were theoretically analyzed. The optimal technologic parameters about direct writing resistance and the optimal testing method of high-precision and small-error resistance values were obtained. The results demonstrated that laser micro-fine cladding method by one-step can realize fabrication and repair of high-quality, high-precision and high-property resistance components without mask in virtue of shape, size and volume of resistance and laser processing parameters adjusted, and need not to trim resistances. With the simple and flexible technology, rapid velocity and low cost, the technique is possessed of wide applied prospect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 281 (2005)
Microhardness Distribution of Ductile Iron Modified by Laser with Space Array
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Pulsed laser beams with two-dimensional array distribution by binary optical elements was used to modify surface processing for ductile iron. The statistical method of microhardness distribution of modified area was proposed to evaluate reasonably the microhardness distribution character, in which the space is divided Pulsed laser beams with two-dimensional array distribution by binary optical elements was used to modify surface processing for ductile iron. The statistical method of microhardness distribution of modified area was proposed to evaluate reasonably the microhardness distribution character, in which the space is divided into a columns 30 μm×30 μm or 30 μm×50 μm grids in the transect of modified area. The microhardness is tested in the intersections of grids. As a result, the data obtained are processed by math statistical method and drawn the contour map. The application shows that the statistical method for microhardness test could reasonably describe modified layer depth and microhardness distribution in the case of multiphase in comparison with conventional method. On some extent, the statistical method may disclose the relation between laser modifying technology and results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 287 (2005)
Study on Interface Microstructure and Laser Re-melting NiCrBSi+TiN Coating
[in Chinese], [in Chinese], and [in Chinese]
The re-melting coating of NiCrBSi+TiN metal-ceramic powders sprayed on the surface of Ti6Al4V alloy was performed by CO2 laser. By means of scan electron microscopy (SEM) and X-ray diffraction (XRD), microstructure of the coating was investigated and microhardness was measured. The effect of TiN on microstructure is diThe re-melting coating of NiCrBSi+TiN metal-ceramic powders sprayed on the surface of Ti6Al4V alloy was performed by CO2 laser. By means of scan electron microscopy (SEM) and X-ray diffraction (XRD), microstructure of the coating was investigated and microhardness was measured. The effect of TiN on microstructure is discussed. The experimental results show that the phase of coating are composed of (Cr-Ni-Fe), TiN, NiB, Cr2Ti, Ti2Ni et al.. The TiN particles are dissolved into [Ti] and [N] during laser heating, intermetallic compound Cr2Ti and Ti2Ni result from some of the [Ti] combining with Ni, Cr, and TiN, TiN0.3, TiN0.9 precipitated during cooling in differ position. Thickness of the diffusion layer is approximately 5～6 μm existing between the dilution zone (DZ) and the heat-affected zone (HAZ), concentration gradient of Ni is distinctness in the diffusion layer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 292 (2005)
Laser Physics
Switchable and Spacing-Tunable Dual-Wavelength Erbium-Doped Fiber Laser Using a PM Fiber Bragg Grating
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A switchable and spacing-tunable dual-wavelength linear cavity erbium-doped fiber (EDF) laser based on a polarization-maintaining fiber Bragg grating (PM-FBG) is demonstrated experimentally. Feedback from the FBG results in the laser operating on two longitudinal modes that are separated in both wavelength and polarizaA switchable and spacing-tunable dual-wavelength linear cavity erbium-doped fiber (EDF) laser based on a polarization-maintaining fiber Bragg grating (PM-FBG) is demonstrated experimentally. Feedback from the FBG results in the laser operating on two longitudinal modes that are separated in both wavelength and polarization. The birefringence induced by the FBG is beneficial to diversify the polarization states of different wavelength in the EDF and enhance the polarization hole burning (PHB) effect. This PHB greatly increased the inhomogeneous gain broadening of EDF and accordingly reduced the wavelength competition. Then, it was possible to achieve stable dual-wavelength oscillations at room temperature. On the other hand, through adjusting the state of the polarization controller (PC), the transmission characteristic of the FBG is changed. When the eigenaxe of one mode is more populated than the other, it will oscillate stably in that mode. Especially, when the eigenaxes of both modes are equally populated, the two modes can co-exist with equal amplitudes. Thus mode selection is achieved in laser oscillation and the laser can be designed to operate in wavelength switching modes, only by simple adjustment of the PC. Applying strain in line with the fast axis reduces the birefringence of the fiber grating and causes the wavelength separation of the two modes to be decreased. On the other hand, strain applied in line with the slow axis increases the birefringence and a concomitant increase in wavelength spacing is produced. Then, transverse strain loading on the FBG allows the wavelength spacing to be controlled and a tunable wavelength separation from 0.2 to 1.1 nm was demonstrated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 145 (2005)
Laser Diode Pumped High-Slope-Efficiency Monolithic Unidirectional Single Frequency Ring Laser
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The crystal size and the reflectivity of S and P polarization components of the output coupling (RS and RP) are crucial for the operation of the monolithic single frequency ring laser. The working principle of single frequency operation of the monolithic ring laser was discussed by means of Jones matrix. In order to acThe crystal size and the reflectivity of S and P polarization components of the output coupling (RS and RP) are crucial for the operation of the monolithic single frequency ring laser. The working principle of single frequency operation of the monolithic ring laser was discussed by means of Jones matrix. In order to achieve high single frequency output power and high slope efficiency, RS and RP were determined by calculating the square eigenvalues and the differences of square eigenvalues of Jones matrix of the resonator as well as considering the optimum output coupling for given crystal size, magnetic field and pumping power. A fiber coupled diode laser was used as pumping source in experiment. Single frequency output power of 1.20 W with the slope efficiency of 47.4% was obtained when input pumping power was 2.83 W..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 149 (2005)
Improved Model Analysis of Fiber Bragg Grating External Cavity Semiconductor Lasers
[in Chinese], and [in Chinese]
A complete and precise static modal of fiber grating external cavity semiconductor laser is improved based on the coupled-cavity laser model. By taking consideration of the coupling efficiency between the laser diode and the fiber grating, the coupling coefficient η1 from the laser to the fiber grating and the couplingA complete and precise static modal of fiber grating external cavity semiconductor laser is improved based on the coupled-cavity laser model. By taking consideration of the coupling efficiency between the laser diode and the fiber grating, the coupling coefficient η1 from the laser to the fiber grating and the coupling coefficient η2 from the fiber grating to the laser diode are both involved in the elements of scattering matrix describing the coupled-cavity model, and the analytical expression of the coupled-cavity model is modified. It is found that the product of the coupling coefficient η1 and η2 affects the gain curve. Additionally, analysis indicates that shorter external cavity and shorter fiber grating length determine the single lasing mode oscillating in the lower region of the gain curve. Diode core and fiber facets reflectivity also play important roles in the threshold current and side mode suppression ratio (SMSR), especially in the case of relatively high reflectivity. This can be solved by carefully designing the length of air gap, resulting in the match of the external cavity modes and Fabry-Perot (F-P) modes of diode. Accordingly the optimized design principle is put forward by general considering of the parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 156 (2005)
High-Saturation Current 14xx nm Strained Quantum Well Lasers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The research of the 14xx nm strained quantum well (SQW) lasers is reported. The 14xx nm AlGaInAs/AlInAs/InP SQW lasers with tapered gain regions emitting at 1430 nm are fabricated. The SQW epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) and ridge-type waveguide structure with tapered gaiThe research of the 14xx nm strained quantum well (SQW) lasers is reported. The 14xx nm AlGaInAs/AlInAs/InP SQW lasers with tapered gain regions emitting at 1430 nm are fabricated. The SQW epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) and ridge-type waveguide structure with tapered gain regions is used as laser core. The process of preparing double-channel ridge-type waveguide laser epitaxial structure includes lithographic, etching, metallization (P-side.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 161 (2005)
Experimental Study of Overcoming Laser Rod′s Thermal Effect with Stimulated Brillouin Scattering Phase Conjugation Mirror
[in Chinese], and [in Chinese]
The beam quality of a single-rod Nd∶YAG laser can be improved almost up to the diffraction limit by using a phase-conjugating mirror (PCM) based on stimulated Brillouin scattering (SBS). As a single Nd∶YAG rod, whose thermal lens, stress birefringence and depolarization are surveyed experimentally, the stable output enThe beam quality of a single-rod Nd∶YAG laser can be improved almost up to the diffraction limit by using a phase-conjugating mirror (PCM) based on stimulated Brillouin scattering (SBS). As a single Nd∶YAG rod, whose thermal lens, stress birefringence and depolarization are surveyed experimentally, the stable output energy of 20 mJ with pulse duration of 11.8 ns, which has perfect beam quality, is obtained at repetition rate 5 Hz with pump energy of 10 J when the start cavity is the concave-convex cavity operating near a limit of stability in the g diagram and the SBS phase conjugation cavity is optimized..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 184 (2005)
Investigation on Nonlinear Optical Properties of AgOx-Type Super-Resolution Near-Field Structure
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The nonlinear optical properties of the AgOx-type super-resolution near-field structure (SuperRENS) films were studied using confocal Z-scan technique with 0.7 ns, 532 nm laser pulses. Nonlinear refractive indexes at different laser power were obtained through close-aperture Z-scan and compared with the measured resultThe nonlinear optical properties of the AgOx-type super-resolution near-field structure (SuperRENS) films were studied using confocal Z-scan technique with 0.7 ns, 532 nm laser pulses. Nonlinear refractive indexes at different laser power were obtained through close-aperture Z-scan and compared with the measured results of Au film and Ag film, The mechanisms of this change due to the photochemical reaction, thermal effects and optical response were discussed. The experimental results show that heat by laser illumination causes a phase transition, so results in the enhancement of the localized surface plasmon of dissociated Ag nanoparticles..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 188 (2005)
Effect of Applied Electrical and Magnetic Field on THz Radiation
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, the effects of the applied electrical and magnetic field on the generation of optically induced terahertz (THz) electromagnetic radiation are reported by measuring the signal from the semiconductor emitter. The biased electrical field and magnetic field can enhance optically induced THz electromagnetic rIn this paper, the effects of the applied electrical and magnetic field on the generation of optically induced terahertz (THz) electromagnetic radiation are reported by measuring the signal from the semiconductor emitter. The biased electrical field and magnetic field can enhance optically induced THz electromagnetic radiation. The emission spectra of time domain of semiconductors biased by applied electrical and magnetic field are obtained by the use of the reflection-type emitter irradiated by the femtosecond laser and the electro-optic sampling. The corresponding frequency domain spectra are obtained by fast Fourier transform (FFT). The results show that THz emission spectra are enhanced by the applied electrical and magnetic field, while their frequency components and bandwidths are not changed. By the classical electromagnetic theory, the effect of applied electrical and magnetic field on THz emission can be attributed to the acceleration motion of carriers in semiconductors..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 192 (2005)
Shape Modification of Stokes Pulses with Steep Leading Edge by Brillouin Amplification
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Brillouin amplification of Stokes seed pulses with steep leading edge is investigated. Various parts of Stokes seed pulse can be selectively amplified by changing the delay time between pump and Stokes seed pulse entering the cell, and Stokes pulse shape can be modified. Dependences of output Stokes pulse duration, theBrillouin amplification of Stokes seed pulses with steep leading edge is investigated. Various parts of Stokes seed pulse can be selectively amplified by changing the delay time between pump and Stokes seed pulse entering the cell, and Stokes pulse shape can be modified. Dependences of output Stokes pulse duration, the temporal ratio of leading edge to trailing edge β, and the energy extraction efficiency η on the encounter time are theoretically and experimentally researched. Output Stokes pulse with β=1 and η>80% is theoretically achieved at encounter time of 2.5 ns. Theoretical simulations fit with the experimental results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 196 (2005)
Autocorrelation Coefficient and Performance Parameter of Diffractive Optical Element for Beam Smoothing
[in Chinese], [in Chinese], and [in Chinese]
In this paper, based on the autocorrelation coefficient of the transmittance function of the diffractive optical element (DOE) for beam smoothing, two performance parameters, light efficiency and top non-uniformity, are re-defined. This definition is a kind of approximation of that defined by the spatial frequency specIn this paper, based on the autocorrelation coefficient of the transmittance function of the diffractive optical element (DOE) for beam smoothing, two performance parameters, light efficiency and top non-uniformity, are re-defined. This definition is a kind of approximation of that defined by the spatial frequency spectra of the far filed intensity distribution of the DOE for beam smoothing. The simulated results calculated with two definitions are almost same for the precise designed DOE, but different for the traditional designed DOE. When smoothing by spectral dispersion (SSD) is used with the DOE to realize beam smoothing, the simulated results show that the definition in this paper can reflect the practical performance of the DOE for beam smoothing, no matter whether the DOE for beam smoothing is designed with the precise design method or the traditional design method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 200 (2005)
Competition between Stimulated Thermal and Brillouin Scattering and Its Phase Conjugation Characteristic
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
It was experimentally investigated that competition between stimulated thermal scattering (STS) and stimulated Brillouin scattering (SBS) in absorbing liquids and that its phase conjugation characteristic in a master oscillator power amplifier (MOPA) system with a cell containing acetone dyed with small amounts of Cu(NIt was experimentally investigated that competition between stimulated thermal scattering (STS) and stimulated Brillouin scattering (SBS) in absorbing liquids and that its phase conjugation characteristic in a master oscillator power amplifier (MOPA) system with a cell containing acetone dyed with small amounts of Cu(NO3)2 served as phase-conjugation mirror. It was showed that the stimulated thermal Rayleigh scattering (STRS) would predominate over the stimulated Brillouin scattering or stimulated thermal Brillouin scattering (STBS) by increasing the absorption coefficient of acetone, the gain of the stimulated thermal Rayleigh scattering increased and relative fluctuation of the output energy decreased with the absorption coefficient increased;under weaker pumping conditions stimulated thermal Rayleigh scattering would loss weaker phase information in original wavefront as same as stimulated Brillouin scattering did due to threshold effect; it is really possible to obtain high-quality phase conjugation by stimulated thermal Rayleigh scattering in absorbing liquid with appreciable absorption coefficient under appreciable pumping conditions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 204 (2005)
Materials and Thin Films
Red and Blue Light Generations in a Periodically Poled LiTaO3 by 1342 nm Laser
[in Chinese], and [in Chinese]
When incident fundamental wave and frequency-doubling wave were fitted to quasi-phase matching, with diode-pumped Q-switched 1342-nm Nd∶YVO4 laser, generations of red light at 671 nm and blue light at 447 nm in a periodically poled LiTaO3 (PPLT) were demonstrated. Principles of frequency-doubling and sum-frequency wereWhen incident fundamental wave and frequency-doubling wave were fitted to quasi-phase matching, with diode-pumped Q-switched 1342-nm Nd∶YVO4 laser, generations of red light at 671 nm and blue light at 447 nm in a periodically poled LiTaO3 (PPLT) were demonstrated. Principles of frequency-doubling and sum-frequency were applied in the course. Temperature of PPLT was modulated in order to accomplish quasi phase matching. When average power of 1342-nm fundamental wavelength was 1.58 W, the maximum average power of red light (671 nm) was 750 mW with corresponding matching temperature of 92.3℃ and temperature of full wave half width of 3.2℃, and the maximum average power of blue light (447 nm) was 128 mW with matching temperature of 83.2℃, temperature of full wave half width of 4.5℃. The optical-optical conversion efficiency of red light was 47.4% and that of the blue light was 8.1%. Output powers of red light and blue light were stable by double-frequency and sum-frequency in a PPLT for a longer time. These results indicated that PPLT may be used to construct an all-solid-state red and blue dual-wavelength laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 262 (2005)
Studies on Photochromism and Holographic Recording of Chiral Azobenzene Derivative
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Characterization of the photochromism, photoinduced birefringence, and holographic recording in the chiral azo molecule, N-[4-(4-dodecyloxyphenylazo)benzoyl]-L-glutamic acid (C12-Azo-L-Glu), doped polymer films were studied. C12-Azo-L-Glu underwent a reversible trans-cis-trans isomerization in the polymer matrix. PhotoCharacterization of the photochromism, photoinduced birefringence, and holographic recording in the chiral azo molecule, N-[4-(4-dodecyloxyphenylazo)benzoyl]-L-glutamic acid (C12-Azo-L-Glu), doped polymer films were studied. C12-Azo-L-Glu underwent a reversible trans-cis-trans isomerization in the polymer matrix. Photoinduced birefringence and holographic recording were performed by using Ar+ laser (488 nm) as writing beam and He-Ne laser (632.8 nm) as reading beam. The dependence of photoinduced birefringence and holographic recording on the intensities of writing beam was presented. The results indicated that C12-Azo-L-Glu was a kind of ideal material for holographic recording and it allowed multiple uses without apparent fatigue..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 265 (2005)
Characterization of Photoinduced Refractive Index Change in the Azobenzene Doped Polymer
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The characterization of photoinduced refractive index change (Δn) and the relation between Δn and the intensity of pumping beam in the azobenzene doped polymer are investigated using surface-reflection configuration in which a circularly polarized pumping beam at 514 nm and a probing beam (s-ray) at 632.8 nm are used. The characterization of photoinduced refractive index change (Δn) and the relation between Δn and the intensity of pumping beam in the azobenzene doped polymer are investigated using surface-reflection configuration in which a circularly polarized pumping beam at 514 nm and a probing beam (s-ray) at 632.8 nm are used. For a given pumping intensity (0.570 W/cm2), the surface reflectivity of the sample is measured at a series of incident angles of the probing beam, and the Δn is about -0.0035. Furthermore, the investigation shows that Δn increases with increasing the intensity of pumping beam, and Δn reaches a value of 10-2 when the intensity of pumping beam is 0.800 W/cm2..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 269 (2005)
Investigation on the Preparation and Fluorescence Properties of Oxy-Fluoride Glass Co-Doped with Er3+ and Yb3+
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
To improve the luminescence efficiency of up-conversion glasses in the blue and green wavebands in hope of realizing short wavelenth laser, through the fusion method, the sample based on 45PbF2+45GeO2+10WO3 host glass co-doped with Yb3+/Er3+ rare-earth ions was prepared. During the preparation,glass annealing temperatuTo improve the luminescence efficiency of up-conversion glasses in the blue and green wavebands in hope of realizing short wavelenth laser, through the fusion method, the sample based on 45PbF2+45GeO2+10WO3 host glass co-doped with Yb3+/Er3+ rare-earth ions was prepared. During the preparation,glass annealing temperature is 380℃ and maintaining constant-temperature lasts over 4 hours. By using the V-prism, it is found that the refractive index of host glass and the sample are 1.517 and 1.65, respectively. The transmittance is measured by using the ultraviolet-visible-infrared spectrometer in the wavelength range from 0.35 μm to 2.5 μm. The transmittance of the host glass is beyond 73%. That of the sample co-doped with Yb3+/Er3+ rare-earth ions is beyond 50% and there are characteristic absorption peaks of rare-earth ions. The emission spectrum was measured by using Japanese Hitachi F-4500 fluorescent photometer whose pump light is 980 nm semiconductor laser. There are a strong emission peak at 545 nm and a weak peak at 650 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 274 (2005)
Investigation on Preparation and Performance of Phase Retarder in Chemical Oxygen-Iodine Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
When incoming light beam enters dielectric reflective mirror with certain incident angle, there is phase shift between the p-polarization and s-polarization. In terms of Fresnel formulas and boundary conditions of electromagnetic field, the phase shift between p- and s-polarization was deduced with methods of matrix. BWhen incoming light beam enters dielectric reflective mirror with certain incident angle, there is phase shift between the p-polarization and s-polarization. In terms of Fresnel formulas and boundary conditions of electromagnetic field, the phase shift between p- and s-polarization was deduced with methods of matrix. Based on optimizing design, when light beam enters with 54 degree incident angle, phase shift of 270°±1° in the range of 1285～1345 nm was reached, at the same time, the reflectivity of dielectric mirror maintained is over 99.5%. The phase retarder was prepared with dual ion beam sputter system and then annealed at different temperatures in atmosphere, the spectrum and the phase of the sample were gained by spectrometer and the Fourier transform infrared spectroscopic ellipsometer, respectively. The results revealed that the as-deposited samples gained phase shift of 262.4°±1.8° and the reflectivity reaches over 99.6%. The error mainly originates from non-homogeneous transition layer, posed by working properties of ion source, and surface transition layer, resulting from surface adsorption for moisture and dust. The physical thickness and variety of refractive index for transition layer were gained from error analysis, and it was found that the error of the outermost layer and deviation of refractive index and designed values play a principal roles in decrease of phase shift..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 277 (2005)
Optical Communication
Study of Spectrum Broadening Characters with LiTaO3 Phase Modulators
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel method of broadening spectrum with LiTaO3 crystal by switching microwave signal modulation is presented in this paper. The theory model of phase modulation is illustrated, with the according formulae in details. The output result of broading spectrum in a certain microwave power is computed and simulated by theA novel method of broadening spectrum with LiTaO3 crystal by switching microwave signal modulation is presented in this paper. The theory model of phase modulation is illustrated, with the according formulae in details. The output result of broading spectrum in a certain microwave power is computed and simulated by the formulae. Furthermore, from a practical microwave phase modulator system framed in this paper, the actual spectrum is measured corresponding to variant level of modulating microwave power. The spectrum calculated by theory agrees with the spectrum of real system in shape, except for the disaccord of the level due to the impedance mismatch in practical transmission. Using the integrated waveguide eletrooptic phase modulator made of LiTaO3, the input light at 1053 nm is modulated by a 4.3 GHz microwave frequency, whose switching signal is 1 kHz repetition frequency and square-wave of 4∶6 duty cycle. The 90 percent of input power is broadened to the fundamental frequency, first and second side frequency. The both side powers are nearly same..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 209 (2005)
Parametric Wavelength Conversion Based on a Holey Fiber
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The guidance properties of the holey fiber are determined by the solid-silica core region and the size and pattern of air holes. The fundamental principle of parametric wavelength conversion is presented by the coupled-wave equations. The relation between phase mismatch and pump wavelength with a fixed signal wavelengtThe guidance properties of the holey fiber are determined by the solid-silica core region and the size and pattern of air holes. The fundamental principle of parametric wavelength conversion is presented by the coupled-wave equations. The relation between phase mismatch and pump wavelength with a fixed signal wavelength is analyzed. Conversion efficiency of a holey fiber based parametric wavelength conversion is calculated by the numerical simulation and compared with the measured result, which indicates that numerical calculation is coincident with the experimental measurement. A maximum conversion efficiency of about -16 dB and a 3-dB tuning bandwidth of ～10 nm are achieved for a 15 m holey fiber, and the tuning range can be improved with lower dispersion slope. So a compact wavelength converter can be realized by utilizing a highly nonlinear holey fiber..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 212 (2005)
An Optical Pulse Splitting-Delaying Device Based on Optical Fiber and Its Optimization
[in Chinese], [in Chinese], and [in Chinese]
An optical pulse splitting-delaying device based on optical fiber was proposed for the replication of a high-speed analog pulse in the measurement system for high-speed optical pulses. Comparing with other optical pulse splitting-delaying devices, its virtues are low loss and small amplitude deviation between pulses. IAn optical pulse splitting-delaying device based on optical fiber was proposed for the replication of a high-speed analog pulse in the measurement system for high-speed optical pulses. Comparing with other optical pulse splitting-delaying devices, its virtues are low loss and small amplitude deviation between pulses. In the following, the power of output pulses from the device and its affect factors are analyzed theoretically. Simulation and optimal analyses indicate that the amplitude of the minimal output pulse can be increased and the amplitude deviation between pulses as a result of nonzero uniformity can be decreased by choosing appropriately uniformity of each 2×2 fiber coupler and arranging reasonably the connection order of those fiber couplers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 216 (2005)
Study of ATP Accuracy and the Optimum Optical Signal Transmitting Angle
[in Chinese], [in Chinese], and [in Chinese]
Acquisition, tracking, pointing (ATP) system is one of the key components for intersatellite laser communication. After acquiring, the accuracy of pointing and tracking is an important performance index of ATP system. Because many factors restrict, in fact, the ATP system can only attain limited precision. The optical Acquisition, tracking, pointing (ATP) system is one of the key components for intersatellite laser communication. After acquiring, the accuracy of pointing and tracking is an important performance index of ATP system. Because many factors restrict, in fact, the ATP system can only attain limited precision. The optical signal beam divergence angle seriously affects the performance of intersatellite laser communication, so the choice of it for the entire system is very important. Three influencing factor of beam divergence angle are put forward and an optimum beam divergence angle based on the analysis of ATP accuracy is given out. The optimum divergence angle consumes the minimum transmitting power to satisfy indexes of communication system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 2, 221 (2005)
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