Journals >Chinese Journal of Lasers
Contents
2005
Volume: 32 Issue 5
31 Article(s)
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Research Article
Study of Twisted Beam Symmetrization from Laser Diode Bar
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A principal drawback of high-power laser diode, which limits their applications such as pumping solid-state laser and fiber laser, is astigmatic brightness of output beam. The astigmatic beam emitted from laser diode bar is transformed into a beam with twisted symmetry by using a bifocal telescope and rotated cylindricA principal drawback of high-power laser diode, which limits their applications such as pumping solid-state laser and fiber laser, is astigmatic brightness of output beam. The astigmatic beam emitted from laser diode bar is transformed into a beam with twisted symmetry by using a bifocal telescope and rotated cylindrical lenses. The beam widths, divergences and the beam parameter products of the symmetrized beam are nearly the same in x and y directions. The beam transformation was theoretically analyzed and experimentally studied. As an example, the symmetrized beam was used to pump solid state laser. The efficiency of the fundamental mode operation was improved compared with the result of untransformed beam pumping..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 604 (2005)
A Novel C+L Band Erbium-Doped Fiber Broadband Light Source with High Power
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A high-power broadband light source covering C-band and L-band (1520～1610 nm) by using two kinds of different concentration erbium-doped fiber was reported in this paper. In the dual-stage double-pass structure, the double-pass forward pumping was used in the first stage, the fiber of lower doped concentration was 7.5 A high-power broadband light source covering C-band and L-band (1520～1610 nm) by using two kinds of different concentration erbium-doped fiber was reported in this paper. In the dual-stage double-pass structure, the double-pass forward pumping was used in the first stage, the fiber of lower doped concentration was 7.5 m, and the output of first stage was used as seed signal; in the second stage, backward pumping was used, and the fiber of much higher doped concentration was 31.2 m. The fiber loop reflector was used to enhance the conversion efficiency of pumping LD, and high output power and good flatness were also achieved. After matching the pumping power of the two stages, the amplified spontaneous emission (ASE) source with the high output power of 19.20 mW (12.83 dBm) and with the mean wavelength of 1552.82 nm was developed and obtained. Meanwhile, the relation between the output and the change of pumping in the configuration was discussed implicitly, it was important to the design of the source..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 609 (2005)
Frequency Conversion in a Birefringent Microstructure Fiber by Femtosecond Pulses
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Microstructure fibers (MFs) with a specially designed form birefringence are shown to be ideally suited for the creation of highly efficient frequency-tunable sources of short pulses in the visible range as a result of nonlinear-optical spectral transformation of unamplified femtosecond Ti∶sapphire laser pulses. The moMicrostructure fibers (MFs) with a specially designed form birefringence are shown to be ideally suited for the creation of highly efficient frequency-tunable sources of short pulses in the visible range as a result of nonlinear-optical spectral transformation of unamplified femtosecond Ti∶sapphire laser pulses. The modes of doublet polarized along the fast and small axes of the elliptical core of the fiber have different propagation constants. Controlled by a half waveplate, femtosecond pulses of 820 nm pump radiation polarized along the fast and slow axes of the elliptical core of the microstructure fiber can generate intense blue-shifted lines centered at 490 and 510 nm respectively, observed as bright blue and green emission at the output end of the microstructure fiber. The dependence factors, such as length, power, are also compared and analyzed experimentally..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 613 (2005)
AComparisons of Turbulence and Thermal Blooming Effects of High-Energy Laser with its Sampled One Propagating in the Atmosphere
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The ringed-energy-radius and expansion of the long-exposed far-field central patterns of the high-energy (HEL) laser and its sampled one propagating in the turbulent atmosphere are compared by numerical calculation, the results show that: both of them are the same in the merely turbulent situation, and the thermal blooThe ringed-energy-radius and expansion of the long-exposed far-field central patterns of the high-energy (HEL) laser and its sampled one propagating in the turbulent atmosphere are compared by numerical calculation, the results show that: both of them are the same in the merely turbulent situation, and the thermal blooming leads to attached expansion of the pattern; the smaller the transmission of the sampler is, the less the effect of thermal blooming on the attached expansion of the pattern is; the attached expansion of the central pattern of the high-energy laser with respect to its sampled one is due to the thermal blooming. The atmospheric thermal blooming effects thus can be diagnosed by the methods of utilizing the beam wavefront sampler and comparing the characteristics of the far-field central patterns of the high-energy laser with its sampled one propagating in the turbulent atmosphere..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 617 (2005)
Experimental Study on Ion Extraction Process of Cesium Plasma of Static Electric Field between Two Parallel Plates
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Experiments of ion extractions of cesium plasmas produced between two parallel plates by the fourth harmonics of a YAG laser (266 nm) have been carried out. The influences of applied voltage and initial ion density on the ion extraction process have been discussed and a scaling relation has been formulated. But the ionExperiments of ion extractions of cesium plasmas produced between two parallel plates by the fourth harmonics of a YAG laser (266 nm) have been carried out. The influences of applied voltage and initial ion density on the ion extraction process have been discussed and a scaling relation has been formulated. But the ion extraction time does not always decrease with the applied voltage. In the experiment, the ion extraction time increases when the applied voltage is above 1200 V. The existence of ion sputtering peak has been observed above a certain applied voltage, which is coincident with the theoretical analysis. A best applied voltage is obtained from the experiments concerning not only the ion extraction time but the collection of target isotope ions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 622 (2005)
Biomedical Photonics and Laser Medicine
Influence of Permeation Characteristics of Hyperosmotic Agents on Optical Clearing of Gastric Tissue Studied with Near-Infrared Spectroscopy
[in Chinese], and [in Chinese]
With an effort to understand the influence of permeation characteristics of hyperosmotic agents on tissue clearing progress and to look for effective concentrations that minimise the side effect for clinical applications, porcine stomach tissues (mucosa) applied with a mixed solution of glycerol and dimethyl sulfoxide With an effort to understand the influence of permeation characteristics of hyperosmotic agents on tissue clearing progress and to look for effective concentrations that minimise the side effect for clinical applications, porcine stomach tissues (mucosa) applied with a mixed solution of glycerol and dimethyl sulfoxide (DMSO) are investigated with near-infrared reflectance spectroscopy and optical coherence tomography. Four solutions of 80% glycerol, 50% DMSO, 50% glycerol with 20% DMSO (GD1) and 30% DMSO (GD2) are studied, respectively. The significant improvement in light transmittance and thus enhancement of light penetration through tissue are demonstrated for all solutions. The development and effect of optical clearing accomplished by the four solutions in an increasing order for 50% DMSO, 80% glycerol, GD1, and GD2 are corresponding well to the rate and degree of water loss induced by the four solutions, which are in the same increasing order..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 717 (2005)
Laser Devices and Laser Physics
Photobiomodulation Action of the Marginal Irradiation of High Intensity KTP Laser Irradiations on Monolayer Skin Fibroblasts
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this study, cultured monolayer normal human skin fibroblasts (HSFs) were irradiated with the fundamental (1064 nm) and the second harmonics (532 nm) waves of Q-switched Nd∶YAG laser beams, to study the photobiomodulation of marginal irradiation of high intensity laser beam. For each laser beam, the power output rangIn this study, cultured monolayer normal human skin fibroblasts (HSFs) were irradiated with the fundamental (1064 nm) and the second harmonics (532 nm) waves of Q-switched Nd∶YAG laser beams, to study the photobiomodulation of marginal irradiation of high intensity laser beam. For each laser beam, the power output ranged from 0.2～1 W in pulsed mode, and the irradiation time was fixed at 20 s. Cell proliferation was performed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay immediately after laser treatment 24 hours and 48 hours, respectively. It was found that high pulse energy irradiation results in small survival rate and large damage radius, and HSFs proliferation was significantly promoted after 24 hours/48 hours 1064 nm laser treatment with 100 mJ and 150 mJ pulse energy, but significantly inhibited after 24 hours/48 hours 532 nm laser treatment with 100 mJ pulse energy. These results indicate that there is the photobiomodulation for marginal irradiation of high intensity laser beam, which might play an important role in the long term effects of laser surgery..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 723 (2005)
Laser Manufacturing
Focusing in Radiometric Temperature Measurement for Small Laser-Processed Region
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effects of focusing on the measurement precision of radiometric pyrometer have been analyzed. The results show that the larger of the high temperature region, the larger of the permissible focusing range. In experiment such as laser-induced diffusion, the diameter of the exposed region is only tens of microns. TherThe effects of focusing on the measurement precision of radiometric pyrometer have been analyzed. The results show that the larger of the high temperature region, the larger of the permissible focusing range. In experiment such as laser-induced diffusion, the diameter of the exposed region is only tens of microns. Therefore, the requirement of focusing is stringent. Then a focusing method was proposed to solve this problem. In the system used in the experiment, the image distance is fixed, and the focal length of the object lens is 30 mm at wavelength of 0.546 μm. The calculated results suggested that the change of focal lengths at different wavelengths causes the change of objective distances obviously. Based on these calculated results and the measured temperature distributions of the same object at different objective distances, the objective distance can be adjusted in the range of ± 0.05 mm around the ideal value, to meet the need of the radiometric temperature measurement for a small region..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 702 (2005)
Numerical Simulation of Pulsed Laser Surface Hardening and the Influence of Material Thermophysical Parameters on Hardened Zone
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A three dimensional (3D) finite element model for simulating pulsed laser surface hardening is established, in which laser spatial and time-dependent intensity distribution, temperature-dependent thermophysical properties of material, microstructural evolution and multi-phase transformations are considered. For the twoA three dimensional (3D) finite element model for simulating pulsed laser surface hardening is established, in which laser spatial and time-dependent intensity distribution, temperature-dependent thermophysical properties of material, microstructural evolution and multi-phase transformations are considered. For the two cases that thermophysical parameters are assumed to be constant, and are variable with temperature as well as latent heat is taken into account, temperature field and its evolution are validated with analytical method and general finite element software package MSC/NASTRAN, respectively. The hardening depth and width are verified with experimental ones. The influence of material thermophysical properties on hardened zone is investigated, and the regularity of relationship between hardening depth and thermophysical parameters in certain zone is obtained, i.e., hardening depth increases under invariable heat conductivity and decreases under invariable specific heat capacity with the increase of thermal diffusivity, and decreases with the increase of heat conductivity and specific heat capacity for given thermal diffusivity. Taking example for ductile iron, eutectoid steel and medium carbon steel, two methods to determine material thermophysical constants, i.e. mean value method and adopting parameters nearby austenitizing temperature method are explored, and results indicate that the mean value method can gain better predication..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 707 (2005)
Study of Conductor Fabrication by Laser Micro-Cladding Electronic Pastes on Glass Substrate
[in Chinese], [in Chinese], and [in Chinese]
Compared with traditional methods, conductor fabricaton technology by laser micro cladding electronic pastes (LMCEP) can improve the efficiency and lower the production cost. In this paper, processes of silver conductor fabrication were studied. The effect of laser power density and scanning speed on conductor thicknesCompared with traditional methods, conductor fabricaton technology by laser micro cladding electronic pastes (LMCEP) can improve the efficiency and lower the production cost. In this paper, processes of silver conductor fabrication were studied. The effect of laser power density and scanning speed on conductor thickness and linewidth was researched systematically, at the same time, the effect of firing time on resistivity and adhesion strength was also analyzed. The result showed that, they which had critical values had very little effect on thickness of conductor and played a very important role on its linewidth, and with increasing the power density and decreasing the scanning speed, the linewidth increased. Besides, with the delaying of sintering time, the resistivity decreased and adhesion strength enhanced, on base of which the conductive and adhesive mechanisms were explored too..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 713 (2005)
Laser Physics
1000 W Continuous Laser Diode Planar Array and the Silicon Micro-Channel Cooling Module
[in Chinese], [in Chinese], and [in Chinese]
The 1000 W continuous laser diode planar array is made up of 30 diode bars at the wavelength of 808 nm with each power of 40 W and forms a rectangle luminescence aperture of 12 mm×70 mm. These bars was mounted on modular microchannel cooled headsinks (MCC) and can continuously emit the laser by the coolant passingThe 1000 W continuous laser diode planar array is made up of 30 diode bars at the wavelength of 808 nm with each power of 40 W and forms a rectangle luminescence aperture of 12 mm×70 mm. These bars was mounted on modular microchannel cooled headsinks (MCC) and can continuously emit the laser by the coolant passing through MCC under 0.5 MPa pressure. The total continuous power is 1060 W and the average power density is 126 W/cm2 at wavelength of 808 nm when the current is fixed 50 A. Five uniformity K-type thermoelectric couples are placed on the different five silicon headsinks of the planar array and used to measure the temperature increase with the loss thermal power. The measuring result of thermal impedance of the planar array is about 0.009 ℃/W..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 585 (2005)
Experimental Study of Diode Side-Pumped Nd∶YLF Multi-Pass Amplification
[in Chinese], and [in Chinese]
The experiment of diode side-pumped Nd∶YLF multi-pass amplification was studied. The high gain amplifying cavity of diode side-pumped Nd∶YLF was designed optimally, to avoid the self-emission of amplifier. In the amplifier laser wavelength was 1053 nm, laser material was c-axis Nd∶YLF, repetition rate was 1 Hz, four-paThe experiment of diode side-pumped Nd∶YLF multi-pass amplification was studied. The high gain amplifying cavity of diode side-pumped Nd∶YLF was designed optimally, to avoid the self-emission of amplifier. In the amplifier laser wavelength was 1053 nm, laser material was c-axis Nd∶YLF, repetition rate was 1 Hz, four-pass structure was used, the total pumped power of amplifier was 1.8 kW, the central wavelength of diode was 797 nm, in the amplified cavity the diode was arranged compactly, and the high pumped efficiency was obtained. In the amplifier the seeder was 0.1 μJ, 6.5 ns, M2≤1.1 and stability was ±8%, the output was 2.9 mJ, 5.2 ns, mean of M2 was 1.65, stability was ±6.9%, total gain was 2.9×104..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 590 (2005)
LD Pumped High-Efficiency High-Repetition-Rate Nd∶YAG Ceramic Laser
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the analysis of the optical characteristic of Nd∶YAG ceramic, a laser diode (LD) pumped high-efficiency high-repetition-rate acousto-optic (A-O) Q-switched miniature Nd∶YAG ceramic laser was developed. Near infrared laser at 1064 nm was obtained with LD end-pumping Nd∶YAG ceramic. Fused silica was adopted as ABased on the analysis of the optical characteristic of Nd∶YAG ceramic, a laser diode (LD) pumped high-efficiency high-repetition-rate acousto-optic (A-O) Q-switched miniature Nd∶YAG ceramic laser was developed. Near infrared laser at 1064 nm was obtained with LD end-pumping Nd∶YAG ceramic. Fused silica was adopted as A-O Q-switch crystal and the Q-switch repetition rate is adjustable from 1 Hz to 115 kHz. With a 2W LD pumping, stable operation with pulse width of 16.4 ns peak power of 2.46 kW and energy per pulse of 40.5 μJ, was achieved. At 110 kHz repetition rate, 495 mW average output power of 1064 nm was obtained, corresponding to total optical-to-optical conversion efficiency being as high as 24.75%. The experimental study about the influence of repetition rate and pumping power on the performance of A-O Q-switched pulse laser was emphasized, and the experiment results were analyzed and discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 593 (2005)
Diode-Pumped Passively Q-Switched Nd∶YAG 1.319 μm Lasers with a V3+∶YAG Crystal
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
V3+∶YAG is a new type of saturable absorber. LD-pumped Nd∶YAG lasers passively Q-switched at 1.319 μm with a V3+∶YAG were reported. When the pump power was 1.6 W, the results of average output power of 93 mW and 192 mW, minimum pulse width (FWHM) of 7.9 ns and 9.2 ns, pulse repetition rate of 8.4 and 27.8 kHz, peak powV3+∶YAG is a new type of saturable absorber. LD-pumped Nd∶YAG lasers passively Q-switched at 1.319 μm with a V3+∶YAG were reported. When the pump power was 1.6 W, the results of average output power of 93 mW and 192 mW, minimum pulse width (FWHM) of 7.9 ns and 9.2 ns, pulse repetition rate of 8.4 and 27.8 kHz, peak power of greater than 1.4 kW and 750 W, pulse energy of 11 μJ and 6.9 μJ were obtained for the small signal transmission of 89% and 96%, respectively. The stability of pulse energy and repetition rate was measured by the statistic function of the oscillograph. The results showed that the stability was better than 5% for 4 h..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 597 (2005)
High-Repetition-Rate LD-Pumped Solid State Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The experimental results of an active mode-locked Nd∶YVO4 laser end-pumped by a laser diode (LD) are reported. Laser pulses at repetation rate of 320 MHz are gained. The curvature radii of two cavity mirrors are both infinite, the cavity length is 452 mm, and coupling-out mirror transmittance is 3.6%. A high frequency The experimental results of an active mode-locked Nd∶YVO4 laser end-pumped by a laser diode (LD) are reported. Laser pulses at repetation rate of 320 MHz are gained. The curvature radii of two cavity mirrors are both infinite, the cavity length is 452 mm, and coupling-out mirror transmittance is 3.6%. A high frequency melted quartz acousto-optic modulator (AOM) is used as inner modulator. With the LiNbO4 crystal as energy transducer and driving power of 4.5 W, the diffractive efficiency at 1064 nm wavelength and modulating depth are 5% and 0.31, respectively. The laser average output is 15 mW at optimal mode-locking status (the pumping power is 3.5 W), and pulse width is 680 ps. The measured beam quality factor M2 is less than 1.5. Moreover, this laser pulse train is stable when cavity length deviates no more than ±100 μm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 601 (2005)
Mixing Performance of HYLTE Nozzle in CW DF/HF Chemical Lasers
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The hypersonic low temperature (HYLTE) nozzle is widely used in continuous wave (CW) DF/HF chemical laser. To realize the mixing performance of this kind of nozzle, the laser induced iodine fluorescence (LIIF) was used to visualize the mixing flowfield of the single HYLTE nozzle. The measured result is concordant with The hypersonic low temperature (HYLTE) nozzle is widely used in continuous wave (CW) DF/HF chemical laser. To realize the mixing performance of this kind of nozzle, the laser induced iodine fluorescence (LIIF) was used to visualize the mixing flowfield of the single HYLTE nozzle. The measured result is concordant with the theory and the mixing performance of the HYLTE nozzle is better than the trip and rampnozzles..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 627 (2005)
Theoretical Analysis on Dynamics and Bifurcations Characteristics of VCSELs with Phase Conjugate Optical Feedback
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The micro-cavity characteristics of vertical-cavity surface-emitting lasers (VCSELs) and the time inversion characteristics of phase conjugate feedback (PCF) are considered, the compound cavity model with PCF is set up based on the typical dynamical equation of semiconductor lasers. When the feedback index is below 0.0The micro-cavity characteristics of vertical-cavity surface-emitting lasers (VCSELs) and the time inversion characteristics of phase conjugate feedback (PCF) are considered, the compound cavity model with PCF is set up based on the typical dynamical equation of semiconductor lasers. When the feedback index is below 0.05, the dynamics of VCSELs and side emitters are different due to their cavity size. The number of chaotic bands and their range for the two types are discussed in this paper. The phase change cumulated for PCF is zero, so the nonlinearity for VCSELs under this feedback mechanism is more complex. Three chaotic bands can be seen for common optical feedback (COF) mechanism; while only two chaotic bands can be seen for PCF and the steady state regions are larger than those of COF. A phenomenal is found that in the creation process of the chaos attractor, the phase diagram for optical field with COF is symmetric, but it is a symmetry-founding process in the case of PCF..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 632 (2005)
Studies on Method of Phase-Shift Controlling Chaos for Dual-Ring Erbium-Doped Fiber Lasers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Method of chaos controlled by phase-shift and its physical model are presented for dual-ring single erbium-doped fiber lasers. The maximum Lyapunov exponent is numerically calculated to analyze the effect of the coupler′s coupling coefficient on kinetic behavior from bifurcation into chaos in the laser. The phase-shiftMethod of chaos controlled by phase-shift and its physical model are presented for dual-ring single erbium-doped fiber lasers. The maximum Lyapunov exponent is numerically calculated to analyze the effect of the coupler′s coupling coefficient on kinetic behavior from bifurcation into chaos in the laser. The phase-shift controller is explained by controlling external-modulation-voltage of electro-optical phase-modulator. The method can adjust the optical field phase to control the polarization-coupling effect to control laser chaos kinetic behavior. Single-phase-shift can control real-time dynamically effectively laser chaos into stable states and periodic states. Dual-phase-shift can also control real-time dynamically effectively laser chaos into stable states and periodic states by adjusting flexibly phase shifts of two phase-shift controllers. And it can produce a lot of laser kinetic phenomena..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 642 (2005)
Relationship of Third Harmonic Conversion Efficiency and Phase Ripples for High-Intensity Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A theoretical analysis is presented for third harmonic conversion in KDP (KH2PO4) for type Ⅰ/ type Ⅱ angle-detuning scheme of high-intensity laser. Taking into account the third-order nonlinear, transverse walk-off and diffraction, the conversion efficiency of the third harmonic has been calculated. The results show thA theoretical analysis is presented for third harmonic conversion in KDP (KH2PO4) for type Ⅰ/ type Ⅱ angle-detuning scheme of high-intensity laser. Taking into account the third-order nonlinear, transverse walk-off and diffraction, the conversion efficiency of the third harmonic has been calculated. The results show that the efficiency decreases with the phase ripples of the fundamental wave, and the higher of the THG conversion efficiency is, the smaller of the modulate depth of the output intensity of 3ω radiation is, which indicates that by increasing the conversion efficiency the beam quality of the third harmonic can be improved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 647 (2005)
Space-Selective Color Centers Formation by the Irradiation of Near Infrared Ultra-Fast Intense Laser in LiF Crystal
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In an attempt to form space-selective color centers in LiF crystal, photon induced color centers were continuously created by focusing an ultra-fast intense laser through a microscope objective and translating the LiF crystal sample perpendicular to the axis of the laser beam. The resulting stable color centers region In an attempt to form space-selective color centers in LiF crystal, photon induced color centers were continuously created by focusing an ultra-fast intense laser through a microscope objective and translating the LiF crystal sample perpendicular to the axis of the laser beam. The resulting stable color centers region was induced inside the LiF crystal along the path traversed with the focal point of the laser. The absorption spectra of color centers regions were measured, which express that it is possible space-selective to form color centers with lasing effect by the irradiation of near infrared ultra-fast intense laser in LiF crystal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 651 (2005)
Modulation Transfer Spectroscopy of I2 Enhanced by an External Optical Cavity
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel high sensitive laser spectroscopy technique, double-frequency phase modulation ring-cavity enhanced modulation transfer spectroscopy, is presented. Using ring-cavity absorption enhancement and double-frequency phase modulation with one crystal, this technique combines the advantages of high sensitivity, high reA novel high sensitive laser spectroscopy technique, double-frequency phase modulation ring-cavity enhanced modulation transfer spectroscopy, is presented. Using ring-cavity absorption enhancement and double-frequency phase modulation with one crystal, this technique combines the advantages of high sensitivity, high resolution, Doppler-free with modulation transfer spectroscopy and high signal to noise ratio with ring-cavity enhancement technique. The hyperfine spectrum of molecular 127I2 with high signal to noise ratio was observed at 532 nm. The experimental results show that this new spectroscopy technique enhances detection sensitivity greatly compared with traditional modulation transfer spectroscopy. It is promising for improvements of ultrasensitive spectroscopy and laser frequency stabilization..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 655 (2005)
Materials and Thin Films
A High-Reflectivity Al2O3/MgF2 Mirrors for 193 nm
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The single-layer films of Al2O3 and MgF2 were deposited upon super polished fused-silica by electron-beam evaporation and were characterized. The subsequent optical constants n and k were reported for the spectral range of 180～230 nm. High-reflectivity (HR) Al2O3/MgF2 mirrors were designed and produced for the wavelengThe single-layer films of Al2O3 and MgF2 were deposited upon super polished fused-silica by electron-beam evaporation and were characterized. The subsequent optical constants n and k were reported for the spectral range of 180～230 nm. High-reflectivity (HR) Al2O3/MgF2 mirrors were designed and produced for the wavelength of 193 nm. The annealed mirrors with a reflectance of more than 96% at 193nm were obtained. It was found that the single layers of Al2O3 and MgF2 deposited according to optimized process could get suitable optical properties at 193 nm. And it was easier for HR mirrors to form the oxygen-deficient Al2O3 films than the single layers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 685 (2005)
A Modification of Scattering Theory on Powered Nematic Droplets and Parameter Fitting
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Parameter fitting between anomalous diffraction approach (ADA) theory and experimental data is applied to analyze scattering properties, which related with droplet size, refractive index of polymer in polymer dispersed liquid crystal (PDLC). Besides scattering from liquid crystal droplets, there are additional scatteriParameter fitting between anomalous diffraction approach (ADA) theory and experimental data is applied to analyze scattering properties, which related with droplet size, refractive index of polymer in polymer dispersed liquid crystal (PDLC). Besides scattering from liquid crystal droplets, there are additional scattering factors, such as interface scattering, impurity scattering, and the scattering caused by non-uniform refractive index of the polymer matrix, so ADA model is modified. Parameter fitting approach is proposed to measure refractive index of polymer, radii of droplet, as well as volume percentage of liquid crystal, to measure the parameters of four types of PDLC, in which the diameter of the droplet is about 2 μm. The result indicates that the error of the test for refractive index of polymer is less than 5％, while for volume percent of liquid crystal, the maximum error reaches about 10％..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 689 (2005)
Electro-Optic Modulator Fabricated Using Langasite Crystal
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new electro-optic modulator is fabricated using langasite (LGS, La3Ga5SiO14) crystal, and the electro-optic effect of langasite single crystal is studied. The half-wave voltage and the corresponding electro-optic coefficient γ11 are determined by the extreme method as well as the double frequency method. It is shown A new electro-optic modulator is fabricated using langasite (LGS, La3Ga5SiO14) crystal, and the electro-optic effect of langasite single crystal is studied. The half-wave voltage and the corresponding electro-optic coefficient γ11 are determined by the extreme method as well as the double frequency method. It is shown that it is relatively easy, convenient to measure γ11 by the double frequency method compared with the extreme method. The specific optical activity of 21.1°～2.6°/mm in the range of 0.3～0.6328 μm of langasite is determined by using a new method. The electro-optic modulating experiment of langasite crystal has been completed with home-made high-voltage modulating power. The results show that langasite crystal having optical activity is a kind of new electro-optic crystal and suitable for fabricating electro-optic modulator..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 694 (2005)
Nanocrystallization of Amorphous Fe73.5Cu1Nb3Si13.5B9 Irradiated by Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Ferromagnetic Fe73.5Cu1Nb3Si13.5B9 amorphous ribbon samples were exposed to CO2 laser irradiation with various powers (150 W,200 W,250 W,300 W) and the same scanning speed (20 mm/s) in order to produce nanocrystalline phase on the surface of amorphous Fe73.5Cu1Nb3Si13.5B9. The nanocrystallization of amorphous Fe73.5Cu1Ferromagnetic Fe73.5Cu1Nb3Si13.5B9 amorphous ribbon samples were exposed to CO2 laser irradiation with various powers (150 W,200 W,250 W,300 W) and the same scanning speed (20 mm/s) in order to produce nanocrystalline phase on the surface of amorphous Fe73.5Cu1Nb3Si13.5B9. The nanocrystallization of amorphous Fe73.5Cu1Nb3Si13.5B9 radiated by CO2 laser is studied by means of Mssbauer spectra (MS), transmitance electron microscope (TEM) and X-ray diffraction (XRD). The crystalline phase is α-Fe(Si),it has four hyperfine structure , and the size of which is about 10～20 nm; the nanocrystalline evenly distributes in the amorphous matrix to form the amorphous and crystalline composite structure. The amount of crystallization along with laser energy increases. The control of the nanocrystal phase quantity can be gotten with the control of the laser treatment process parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 697 (2005)
Measurement and Metrology
Calibration of the Axis of the Turntable in 4-Axis Laser Measuring System and Registration of Multi-View
[in Chinese], [in Chinese], and [in Chinese]
Since laser scanner only samples the surface of an object which is visible from a given viewpoint, in order to scan the entire object, it is necessary that the multiple views around the object are captured and aligned in a common coordinate system. Locating the center axis of a turntable precisely is essential for measSince laser scanner only samples the surface of an object which is visible from a given viewpoint, in order to scan the entire object, it is necessary that the multiple views around the object are captured and aligned in a common coordinate system. Locating the center axis of a turntable precisely is essential for measuring the object which turned on the axis and the registration of multi-view. A new method is proposed to calibrate the axis of the turntable. Firstly, a ball as the calibration normal is mounted on the turntable, then measuring the surface of the calibration ball and calculating its center at different rotational angles. These centers define a circle and a plane. The normal of the plane and the center of the circle counted by geometric transform decide the orientation of the axis of the turntable. The multiple views turn around the axis and can be integrated automatically. The error of registration is about 70 μm within 80 mm rotational radius on the measuring platform which accuracy is 50 μm. Compared with the previous methods, the new method is simple and efficient and can be used in other measuring system with a turntable..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 659 (2005)
Auto-Alignment of Polarizer and Analyzer and Error Analysis in Fourier Magneto-Optic Spectrometry
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In conventional Fourier-type magneto-optic spectrometer, the starting azimuth angle of polarizer and analyzer should be determined and aligned before the measurements. A novel method for the auto-alignment of polarizer and analyzer is proposed. The magneto-optical rotation angle can be measured and calculated without kIn conventional Fourier-type magneto-optic spectrometer, the starting azimuth angle of polarizer and analyzer should be determined and aligned before the measurements. A novel method for the auto-alignment of polarizer and analyzer is proposed. The magneto-optical rotation angle can be measured and calculated without knowing the starting positions of polarizer and analyzer. The starting positions of polarizer and analyzer are computed during the measurement and can be automatically aligned. A formula of magneto-optical rotation angle error resulting from the positioning deviation of analyzer is derived, which gives a inverse proportional relation between measuring error and the square root of step number of rotating analyzer through a revolution. Numerical simulation is presented to demonstrate the theoretical analysis. As an example, the magneto-optical Kerr angle of Co films as a function of strength of magnetic field is given..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 663 (2005)
Optical Communication
Influence of Polarization Mode Dispersion and Group Time Delay Ripple on Dispersion Compensation by Chirped Fiber Grating
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Influence of polarization mode dispersion (PMD) and group time delay ripple of the chirped fiber grating on dispersion compensation were investigated in this paper. It is shown experimentally that ripple of polarization-dependent differential group delay (DGD) has very similar variation behavior with the ripple of grouInfluence of polarization mode dispersion (PMD) and group time delay ripple of the chirped fiber grating on dispersion compensation were investigated in this paper. It is shown experimentally that ripple of polarization-dependent differential group delay (DGD) has very similar variation behavior with the ripple of group delay (GD) in their spectra, though the former amplitude is about 40 times higher than the later. The minimum period of the ripples was measured to be 0.024 nm. A simplified theory is proposed to explain the similarity qualitatively. Simulations show that PMD and DGD ripples bring harmful influence to the dispersion compensation using the chirped fiber grating in high-speed optical transmission system. The relation between the incident polarization direction to the principal states of polarization (PSP) and the power penalty was calculated both by an approximate formula and numerical simulation. Simulations on eye patterns show that PMD of the linear chirped fiber Bragg grating (FBG) lowers the effectiveness of its dispersion compensation and worsens the performances of the communication in longer transmission length..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 668 (2005)
Application of Edge Detection Technique to Distributed Fiber Sensor
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Measurement of Brillouin frequency shift distribution in fiber sensor based on double-edge technique is proposed. Utilizing the characteristic that the edge signal is sensitive to the change of frequency, edge detection technique is proposed, and the system is operated on the best sensitive point by setting the optimumMeasurement of Brillouin frequency shift distribution in fiber sensor based on double-edge technique is proposed. Utilizing the characteristic that the edge signal is sensitive to the change of frequency, edge detection technique is proposed, and the system is operated on the best sensitive point by setting the optimum point. From the theoretical analysis, in order to achieve Brillouin frequency shift accuracy of 0.5 MHz, the signal to noise ratio (SNR) required are 65.1127 dB, 37 dB and 31 dB for conventional detection by measuring the maximum signal, single-edge technique, and double-edge technique, respectively. So, for the same SNR, edge techniques can improve the measurement accuracy of Brillouin frequency shift greatly comparing with the conventional detection techniques..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 673 (2005)
New Simulation Method for Small-Signal Modulation Response of Laser with Parasitic Network
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In order to accurately analyze the high frequency modulation response of laser diode (LD) in high speed communication, it is necessary to take the effect of the parasitic network into account. In this paper, the relation between the scattering parameters of laser measurement system and the transfer function of intrinsiIn order to accurately analyze the high frequency modulation response of laser diode (LD) in high speed communication, it is necessary to take the effect of the parasitic network into account. In this paper, the relation between the scattering parameters of laser measurement system and the transfer function of intrinsic response is deduced. By combining the rate equation with its equivalent circuit model, a new method for extracting the intrinsic response of laser and simulating the modulation response of the overall laser diode is proposed. The advantage of this method lies in that there is no need to measure the parasitic network separately and estimate the circuit parameters of active region. The results of measuring Fabry-Perot (F-P) laser sample are in good agreement with the simulation, which indicates that the method is simple and accurate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 676 (2005)
Close-Loop Controlled Fiber Grating Dynamic Dispersion Compensator
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new chirped fiber Bragg grating dynamic dispersion compensator at 1550 nm band is presented by using stain-tuning characteristics of the grating, and using a narrow band fiber Bragg grating fixed on the same bent beam as a sensor for close-loop control of the dispersion compensation amount. Its typical measured data A new chirped fiber Bragg grating dynamic dispersion compensator at 1550 nm band is presented by using stain-tuning characteristics of the grating, and using a narrow band fiber Bragg grating fixed on the same bent beam as a sensor for close-loop control of the dispersion compensation amount. Its typical measured data are as follows. Dispersion compensation tunable range was measured to be -1000～-1680 ps/nm; its insertion loss and dynamic response time were measured less than 1.5 dB and 50 ms, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 5, 681 (2005)
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