Journals >Chinese Journal of Lasers
Contents
2004
Volume: 31 Issue 7
29 Article(s)
Export citation format
Research Article
A Novel Homogenizer to Improve the Excimer Laser Beam Uniformity
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The excimer laser as the main light source of photolithographic device, whose energy distribution is required as homogeneous as possible. In order to improve the uniformity of its output energy density, this paper describes a novel trapezoid prism homogenizer. The working principle and the design requirement of the novThe excimer laser as the main light source of photolithographic device, whose energy distribution is required as homogeneous as possible. In order to improve the uniformity of its output energy density, this paper describes a novel trapezoid prism homogenizer. The working principle and the design requirement of the novel trapezoid prism are analyzed in theory. The optimal position of uniform section is calculated, and compared with the normal prism homogenizer. According to the theory that the beam energy refracted by the trapezoid prism is divided into 3 parts then overlapped in the base of the middle high energy, it realizes the use of association with the normal prism in two-dimensional. By means of adjusting the distance from homogenizer to receive screen, the optimal position of uniform section is determined which agreed with the theoretical calculation. Using this novel homogenizer ,the fluctuation of beam uniformity of XeCl excimer laser is less than 4%, it is better than that obtained by using a normal prism homogenizer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 785 (2004)
Research on the Nonlinear Refractive Index of Nd-Doped Fiber Amplifier
[in Chinese], [in Chinese], and [in Chinese]
This paper gives a numerical research on the Nd-doped fiber amplifier nonlinear refractive index and phase changing with the input signal power, pump power, signal wavelength, gain effect and Kerr effect. The results show that when the signal or pump power increases, the nonlinear refractive index is positive for the sThis paper gives a numerical research on the Nd-doped fiber amplifier nonlinear refractive index and phase changing with the input signal power, pump power, signal wavelength, gain effect and Kerr effect. The results show that when the signal or pump power increases, the nonlinear refractive index is positive for the signal wavelength being smaller than 1064 nm, and negative for the signal wavelength being bigger than 1064 nm. When the signal wavelength hold a certain value, the nonlinear refractive index increases with the pump power. When the pump is low, the gain effect have more influence on the change of nonlinear refractive index, and when the pump is high, the Kerr effect have more influence on the change of nonlinear refractive index, which caused mainly by gain saturation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 789 (2004)
Analysis of Coincidence Tolerance between F′ and C for the Transmission Spheres with Small F-Number
[in Chinese]
The lens assembly producing reference transmission spherical wavefront is important device for test of convex or concave spherical surfaces in an interferometer and it can offer a high-quality spherical wave and a reference spherical surface with peak-to-valley less than λ/20 (λ=0.6328 μm). According to their utility, The lens assembly producing reference transmission spherical wavefront is important device for test of convex or concave spherical surfaces in an interferometer and it can offer a high-quality spherical wave and a reference spherical surface with peak-to-valley less than λ/20 (λ=0.6328 μm). According to their utility, the curvature center (C) of its last spherical surface, as a reference, should coincide with its focus. The mathematical form is deduced for showing the relation between the deviation of F′ and C and the F-number for a reference transmission sphere. The simulation of calculating the coincidence tolerance between F′ and C is shown with ZEMAX software (Focus Software Inc.). The setup to test the coincidence tolerance is designed with the reference flat in Zygo GPI interferometer. The interferograms have been given to show the coincidence value for three self-developed transmission spheres. All the wavefront errors related to the coincidence tolerance between F′ and C are less than five wavelength. The coincidence tolerance between F′ and C is less than 0.03 mm for F/1.5 transmission sphere, and 5 μm for F/0.75 transmission sphere..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 793 (2004)
Study on a Novel Optical Fiber Temperature Sensor Based on Surface Plasmon Resonance
[in Chinese], [in Chinese], and [in Chinese]
Liquid refractive index changes when temperature changes. According to this theory, a novel optical fiber optical temperature sensor based on surface plasmon resonance (SPR) is presented in this paper. And the theory of the SPR probe testing the change of environmental temperature is analyzed. The structure of SPR probLiquid refractive index changes when temperature changes. According to this theory, a novel optical fiber optical temperature sensor based on surface plasmon resonance (SPR) is presented in this paper. And the theory of the SPR probe testing the change of environmental temperature is analyzed. The structure of SPR probe is optimized in order to measure the temperature of liquid with high refractive index and enlarge the measurement range, The characteristic curve of SPR spectrum changing with temperature is obtained by using a optical fiber SPR temperature testing system. A real-time double-parameter measure method, based on resonance wavelength λspr and the lowest light intensity reflectivity Rmin, is also presented. The experimental results show that this sensing system features simple structure, all light transmitted by fiber, and easiness to realize long distance measurement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 838 (2004)
Research on Interferometric Polarization Maintaining Fiber Optic Micro-Vibration Vector Sensor
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The theoretic and experimental result of interferometric polarization-maintaining fiber micro-vibration vector sensor are represented. Because of polarization-maintaining fiber structure, the sensor avoided instability of polarization. With phase generated carrier (PGC) technology, the influence of initial phase of intThe theoretic and experimental result of interferometric polarization-maintaining fiber micro-vibration vector sensor are represented. Because of polarization-maintaining fiber structure, the sensor avoided instability of polarization. With phase generated carrier (PGC) technology, the influence of initial phase of interferometer was sliminated. Based on these methods, the stable signal detect was realized by the fiber optic micro-vibration vector sensor. The measured natural frequency of the system was 370 Hz, which agrees with the theoretic result 375 Hz. The acceleration sensitivity in experimental results reached 340 rad/g in frequency band of 5～200 Hz, and it matched 356 rad/g predicted by theory. Vector character of the sensor was obtained too. The acceleration sensitivity in 45° was 0.7 times of that in 0° and the orthogonal crosstalk coupling was -26 dB below. In the system, minimum measurable phase was 10-5 rad and minimum measurable acceleration reached 3×10-8 g..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 843 (2004)
Influence of Phase Modulator Non-Linearities on Measurement of Work Point and Signal Demodulation in Open-Loop Fiber Optic Gyroscope
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Piezoelectric transducer (PZT) are often used for providing reciprocal sine phase modulation in all-fiber optic gyroscope (FOG) and its non-linearities can affect the accuracy of FOG. In this article, expressions of the first, second and fourth harmonic components of the FOG signal are derived theoretically providing tPiezoelectric transducer (PZT) are often used for providing reciprocal sine phase modulation in all-fiber optic gyroscope (FOG) and its non-linearities can affect the accuracy of FOG. In this article, expressions of the first, second and fourth harmonic components of the FOG signal are derived theoretically providing that the second harmonic phase modulation exists in open loop FOG. Influences of phase modulator non-linearities on measurement of work point and signal demodulation are analyzed theoretically and tested by experiments. Both experimental results and theoretic analyses indicate that steps must be taken to decrease the amplitude of non-linearities in phase modulation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 848 (2004)
Biomedical Photonics and Laser Medicine
The in Vitro Effects of Low Power Laser Irradiation on Animal Erythrocyte Rheology
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Using the blood samples of animal, the in vitro effects of low power laser irradiation on erythrocyte rheology were investigated. After the deposited pig′s erythrocytes (the deformation of erythrocytes have already turned to worse) were irradiated with laser, the effects of laser irradiation on erythrocyte′s deformatioUsing the blood samples of animal, the in vitro effects of low power laser irradiation on erythrocyte rheology were investigated. After the deposited pig′s erythrocytes (the deformation of erythrocytes have already turned to worse) were irradiated with laser, the effects of laser irradiation on erythrocyte′s deformation were measured. When 650 nm laser was used for irradiation, the deformability of erythrocytes was improved obviously. The changing tendency is that, the erythrocyte′s deformation was enhanced with the increasing of irradiation power and then saturated around 4～5 mW. When the blood samples were irradiated by 650 nm and 632.8 nm lasers respectively with the same power (10 mW), the erythrocyte deformability in two cases were all obviously increased to the similar level. These phenomena can be explained by that, the hemoglobin in erythrocytes has the similar absorption to both lasers. Taking the mouse blood as the samples, the effects of laser irradiation on erthrocyte′s electrophoretic mobility was studied further. When irradiated by 632.8 nm laser, the electrophoretic mobility of erythrocytes was speeded also, reflecting the electric charges on the surface of erythrocytes were increased which will help to decrease the aggregation of erythrocytes. Under such low power irradiation (less than 20 mW), no morphological change was detected by the microscopy and no hemolysis was found also..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 888 (2004)
Investigation of Visible Laser-Induced Hemoglobin Fluorescence Spectral Characteristics
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on argon laser of different wavelengths in visible light excited hemoglobin fluorescence spectra, it shows that there is one prominent fluorescence peak near 628 nm and the intensity increases with excitation light red shifting. The theoretical analysis indicates the hemoglobin fluorescence is mainly due to porphBased on argon laser of different wavelengths in visible light excited hemoglobin fluorescence spectra, it shows that there is one prominent fluorescence peak near 628 nm and the intensity increases with excitation light red shifting. The theoretical analysis indicates the hemoglobin fluorescence is mainly due to porphyrin fluorophores in it. In addition, it is found that the peak locations of 476.5 nm laser induced the fluorescence spectra hardly change with the sample concentration from 1% to 7%. The research indicated that the effects of laser are markedly different from that of normal light in the characteristics of low lever light-biotissue interaction..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 893 (2004)
Holography and Information Processing
Target Extraction of Underwater Laser Image Based on Statistic Counteraction
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The recognition of underwater laser target is a new disquisitive field, in which many problems are open, and extraction is the key problem. To recognize underwater target, extraction must be performed well because there is a lot of speckle noise in underwater laser images. Target segmentation of underwater laser image The recognition of underwater laser target is a new disquisitive field, in which many problems are open, and extraction is the key problem. To recognize underwater target, extraction must be performed well because there is a lot of speckle noise in underwater laser images. Target segmentation of underwater laser image based on statistic counteraction (SC) principle i.e. noise with identically statistic characteristics can counteract noise in images is proposed to remove speckle noise and extract the target in images with wavelet transform and statistics. Experiments demonstrate that this method is efficient and feasible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 815 (2004)
Optical and Thermal Properties of Nickel-Azo Complexes for Optical Storage
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The ultraviolet-visible (UV-Vis) absorption spectra, optical constants (complex refractive index N=n+ik) of the thin films and thermal characterizations of three kinds of novel nickel-azo dyes based on 4-methylthiazole, benzothiazole and 6-methylbenzothiazole were investigated. Particularly, a dye based on 4-methylthiaThe ultraviolet-visible (UV-Vis) absorption spectra, optical constants (complex refractive index N=n+ik) of the thin films and thermal characterizations of three kinds of novel nickel-azo dyes based on 4-methylthiazole, benzothiazole and 6-methylbenzothiazole were investigated. Particularly, a dye based on 4-methylthiazole, with higher refractive index n=2.46 and lower extinction coefficient k=0.18 at the wavelength 650 nm and a sharp threshold of thermal decomposition at 330℃ was obtained. The results of the static optical recording test indicated that higher reflectivity contrast can be obtained at a low laser power and narrow pulse width for a single layer of the dye film based on 4-methylthiazole. These results demonstrate that the nickel-azo dye is a promising candidate as a recording medium of digital versatile disc-recordable (DVD-R)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 820 (2004)
Laser Manufacturing
Temperature Rise on a Semiconductor Substrate Locally Heated by 10.6 μm Laser Beam
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In laser assisted microprocesing, such as laser induced diffusion, the substrate is irradiated by a focused laser beam. And a high temperature region is formed on the substrate surface. To acquire the desired temperature distribution, the temperature rise in a semiconductor substrate induced by 10.6 μm focused continuoIn laser assisted microprocesing, such as laser induced diffusion, the substrate is irradiated by a focused laser beam. And a high temperature region is formed on the substrate surface. To acquire the desired temperature distribution, the temperature rise in a semiconductor substrate induced by 10.6 μm focused continuous wave (CW) CO2 laser beam has been investigated numerically. The temperature-dependent absorption coefficients of the substrate material are incorporated in the calculation model. The relations between the temperature rise and parameters such as the preheating temperature, the power of the laser beam and the beam width have been obtained. It is shown that when the substrate is in room temperature before the irradiation and the diameter of the focused laser beam is smaller than 100 μm, the highest stable temperature on the substrate can not exceed 600 K. It is also shown that increasing the preheating temperature can reduce the size of high temperature region, when the induced temperature rise is kept to meet the requirement. Under the condition that the temperature distribution meets the experimental requirement, the laser spot size and the power of the incident laser beam should be adopted as large as possible in order to make the control of the temperature distribution easier..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 870 (2004)
Temperature Rise Model of Laser Cladding Material Powder by Side-Injection with Experiment Investigation
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A temperature rise model of laser cladding material powder by side-injection is established. In this model, the distribution of laser power is considered. The relation formula between the temperature rise of the powders and the time that the particles moves under the laser beam shine is deduced by considering two kindsA temperature rise model of laser cladding material powder by side-injection is established. In this model, the distribution of laser power is considered. The relation formula between the temperature rise of the powders and the time that the particles moves under the laser beam shine is deduced by considering two kinds of circumstances when the diameter of laser beam is larger or smaller than the diameter of powder spot. The paper presents the relationship between the temperature rise and moving time of the powders for different laser power. The paper also presents the relation between the temperature rise and the interaction time for different powder diameters. The micro-distance photograph technique and the image segmentation technique are used to investigate the state and temperature of the cladding material particles after its passing through the laser beam. The experiment analysis validates the model prediction..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 875 (2004)
Study on Microstructures and Mechanical Properties of in-situ Formed Multiphase Coatings Produced by Laser Cladding of Titanium Alloy with Silicon and Graphite Mixed Powders
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A wear resistance multiphase coatings is fabricated by laser cladding of silicon and graphite mixed powders on the substrate of titanium alloy (Ti-6Al-4V). The microstructures and phases in the coatings are investigated by means of electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that aA wear resistance multiphase coatings is fabricated by laser cladding of silicon and graphite mixed powders on the substrate of titanium alloy (Ti-6Al-4V). The microstructures and phases in the coatings are investigated by means of electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that a lot of compounds are formed in-situ in the coatings, which are metallurgically bonded to the substrate. The compounds in the coatings are chiefly composed of pre-eutectic SiC, TiC and eutectic Ti5Si3. The test results show that the hardness of the coatings is up to 2000 Hv0.1, much higher than that of the Ti-6Al-4V substrate (about 320 Hv0.1) and the friction coefficient of the coatings is about 0.3, lower than that of the substrate (about 0.55). Changing the parameters of laser cladding has an effect on the properties and microstructures of the claddings. Thus an ideal claddings freeing from the pores and cracks can be obtained by optimizing the cladding parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 879 (2004)
A New Technology of Conductive Line Preparation by Laser Micro-Cladding Metal-Organic Pastes on PCB Board
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laser direct writing technique has attracted much attention in the past years, as it can fabricate the conductive lines on insulator board directly without mask and with high precisions. However, the direct writing speeds are very low for the current techniques, which restrict its industrial applications greatly. In thLaser direct writing technique has attracted much attention in the past years, as it can fabricate the conductive lines on insulator board directly without mask and with high precisions. However, the direct writing speeds are very low for the current techniques, which restrict its industrial applications greatly. In this paper, a new technology named laser micro-cladding technique is introduced, in which the metal-organic conductive pastes are used as the cladding materials, and the organic insulator resin boards are used as the substrate. The CO2 laser with the power of 0～20 W and the beam spot of 100 micron are used. The microstructure and the conductive properties as well as the bonding strength of the conductive lines with the substrate are studied. The results demonstrate that the conductive lines have excellent conductive properties and strong bonding strength with the substrate, which can satisfy the demands for industrial applications. Finally the mechanisms of the conductive line formation and conductivity are also analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 883 (2004)
Laser Physics
High Efficient Second Harmonic at 416 nm and Fourth Harmonic Generation at 208 nm in Compacted All-Solid-State Ti∶Sapphire Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Second harmonic and fourth harmonic are generated from Ti∶sapphire laser pumped by a diode-Q-switched, doubling-frequency YLiF4 (YLF) laser at 527 nm. The nonlinear crystal LiB3O5 (LBO) is used to generate the second harmonic wave in the Ti∶sapphire cavity at Ⅰ-phase match with birefringent filter, and β-BaB2O4 (BBO) cSecond harmonic and fourth harmonic are generated from Ti∶sapphire laser pumped by a diode-Q-switched, doubling-frequency YLiF4 (YLF) laser at 527 nm. The nonlinear crystal LiB3O5 (LBO) is used to generate the second harmonic wave in the Ti∶sapphire cavity at Ⅰ-phase match with birefringent filter, and β-BaB2O4 (BBO) crystal is used to generate ultraviolet at 208 nm. Maximum average power of 610 mW at 416 nm, and 64 mW at 208 nm are obtained at 1 kHz repetition rate when the pumping power is 3.8 W. The high conversion efficiency is attributed to the birefringent filter which narrows the linewidth of Ti.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 769 (2004)
Single-Lobed Nearly Diffraction-Limited Output from a Laser Diode with External Cavity
[in Chinese], [in Chinese], Andreas Hermerschmidt, and H. J. Eichler
A broad area laser diode (BALD) with external cavity feedback is experimentally investigated and analyzed by using ray transfer matrices. In the experiment, a grating or a plane mirror that is placed at the image plane of the output facet of the BALD is used as an external cavity mirror. By tilting the grating or planeA broad area laser diode (BALD) with external cavity feedback is experimentally investigated and analyzed by using ray transfer matrices. In the experiment, a grating or a plane mirror that is placed at the image plane of the output facet of the BALD is used as an external cavity mirror. By tilting the grating or plane mirror, the certain transverse mode is selected and other transverse modes oscillating in the cavity are limited. With this setup, a single-lobed nearly diffraction-limited laser beam with an output power of 230 mW and a spectral line width of 0.6 nm (300 GHz) is obtained with a grating, while a laser beam with an output power of 320 mW and a spectral line width of 1.5 nm is obtained with plane mirror..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 773 (2004)
59 mW Green Light Second Harmonic Generation of Quasi-CW Double-Cladding Fiber Laser in Periodically Poled Lithium Niobate
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The combination of the double-cladding fiber laser and the periodically poled material provides a compact and high efficiency approach for wavelength conversion with high beam quality. Green laser source is demonstrated using a combination of laser-diode-seeded Yb-doped double-cladding fiber laser and quasi-phase-matchThe combination of the double-cladding fiber laser and the periodically poled material provides a compact and high efficiency approach for wavelength conversion with high beam quality. Green laser source is demonstrated using a combination of laser-diode-seeded Yb-doped double-cladding fiber laser and quasi-phase-matched second harmonic generation in periodically poled lithium niobate (PPLN). The uncoated 20-mm-long, 5-mm-wide, 0.5-mm-thick PPLN has 6.5 μm poling period and is temperature stabilized at 193.1℃. The 6.7% conversion efficiency and the 59 mW green light power are achieved with the pump fundamental average power of 650 mW and 970 mW, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 777 (2004)
Effects of Buffer Gas on the Spectrum Characteristics of Optically Pumped Miniature Cavity Far-Infrared Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the theory of vibrational relaxation, the buffer gas mechanic model is developed. The mechanism of buffer gas and spectrum characteristics of optically pumped miniature cavity NH3 far-infrared laser are calculated by semi-classical density matrix theory and quantum mechanics theory. The effects of operating gaBased on the theory of vibrational relaxation, the buffer gas mechanic model is developed. The mechanism of buffer gas and spectrum characteristics of optically pumped miniature cavity NH3 far-infrared laser are calculated by semi-classical density matrix theory and quantum mechanics theory. The effects of operating gas pressure and pumping power on spectrum characteristics are studied quantitatively. And the theoretical results are verified by the experiments. The results shows that the spectrum of far-infrared laser can be widened when certain buffer gas is added into the laser medium, and the output power of far-infrared laser increase too..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 780 (2004)
Analyses of Thermal Depolarization in Ring Laser Diode Array Side-Pumped Rod Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The thermal depolarization in ring laser diode array side-pumped rod laser is studied. Based on the intensity distribution of laser diode (LD), a inhomogeneous heat distribution in the laser rod has been obtained by using the ray tracing method. And then, the transient temperature rise and thermal stress distribution aThe thermal depolarization in ring laser diode array side-pumped rod laser is studied. Based on the intensity distribution of laser diode (LD), a inhomogeneous heat distribution in the laser rod has been obtained by using the ray tracing method. And then, the transient temperature rise and thermal stress distribution are obtained by using the finite element method. In this paper, the relative thermal optic pass difference (OPD) and output beam patterns with depolarization are simulated at both thermal steady state and transient state. Simulation results show that the thermal induced depolarization grows with the input power, and the transient depolarization grows with the temperature rise and reaches to a steady state as well..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 797 (2004)
Stimulated Brillouin Scattering Suppression and Optical Parametric Amplification in Highly Nonlinear Optical Fiber
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Suppression of the stimulated Brillouin scattering (SBS) is an important technology for realization of fiber parametric amplification. Phase modulation is employed in the early literatures to meet this purpose. A new method is proposed that a secondly phase modulation is applied on a modulated optical source. Based on Suppression of the stimulated Brillouin scattering (SBS) is an important technology for realization of fiber parametric amplification. Phase modulation is employed in the early literatures to meet this purpose. A new method is proposed that a secondly phase modulation is applied on a modulated optical source. Based on this technique, by adding a 365 MHz phase modulation to the 2 GHz phase modulated laser source, the stimulated Brillouin scattering threshold is improved from 10 dBm to 23.5 dBm. Continuous wave (CW) pump optical parametric amplification is demonstrated experimentally in a 1450 m-long highly nonlinear fiber (HNLF), with the nonlinear coefficient γ=11.9 W-1km-1, dispersion slope S=0.0155 ps/(nm2?km). Using an external cavity laser (ECL) as the signal, 26 nm bandwidth (gain>10 dB) and 24 dB maximum gain for small signal are obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 802 (2004)
Studies on Relaxation Oscillation Characteristics of Fiber Lasers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Transient characteristics of Fabry-Perot cavity fiber lasers are analyzed by using the transient rate equations in this paper. Simulation for relaxation oscillation of the laser shows that its frequency decreases with increasing of the fiber length, and changes little with pump power; the amplitude of relaxation oscillTransient characteristics of Fabry-Perot cavity fiber lasers are analyzed by using the transient rate equations in this paper. Simulation for relaxation oscillation of the laser shows that its frequency decreases with increasing of the fiber length, and changes little with pump power; the amplitude of relaxation oscillation increases with pump power; the time constant of oscillation decay ascends with increasing of reflectivity of the cavity mirror, but changes little with pump power or fiber length. The experimental results on Er/Yb co-doped double-cladding fiber laser pumped by 975nm source showed good agreement with the theoretical calculations, indicating the simulation is reasonable..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 807 (2004)
Investigation of Transient Properties of Electromagnetically Induced Transparency with Different Pump Laser Energy
[in Chinese]
The transient properties of electromagnetically induced transparency (EIT) with different pump laser energies in a Λ-type three-level system are studied by solving the time-dependent matrix equation. The time evolution of the probe laser absorption, the population of the three levels and the coherent term ρ23 are analyThe transient properties of electromagnetically induced transparency (EIT) with different pump laser energies in a Λ-type three-level system are studied by solving the time-dependent matrix equation. The time evolution of the probe laser absorption, the population of the three levels and the coherent term ρ23 are analyzed. It is shown that transient amplification without inversion can be realized with high pump laser energy and that transient EIT would reduce and transient amplification without inversion would disappear with the decrease of the pump laser energy. Since the probe absorption depends on the product of Rabi frequency of the pump laser and the coherent term ρ23, the nonzero damping coherent term ρ23 results in the transient absorption and amplification without inversion at high pump laser energy, and the decrease of the coherence with the decrease of the pump laser energy leads to the disappearance of the amplification and enhancement of absorption..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 811 (2004)
Measurement and Metrology
Rayleigh-Raman Scattering Lidar for Atmospheric Temperature Profiles Measurements
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A Rayleigh-Raman scattering lidar has been developed for measuring atmospheric temperature profiles at night. The triple frequency of Nd∶YAG laser at 355-nm is operated as the transmitting laser beam. Molecular Rayleigh and nitrogen vibration Raman scattering returns are detected by the photon counting technique. Then,A Rayleigh-Raman scattering lidar has been developed for measuring atmospheric temperature profiles at night. The triple frequency of Nd∶YAG laser at 355-nm is operated as the transmitting laser beam. Molecular Rayleigh and nitrogen vibration Raman scattering returns are detected by the photon counting technique. Then, vertical profiles of atmospheric temperature are derived in the stratosphere and mid-upper troposphere. Comparison experiments are conducted among L625 lidar, HALOE/UARS satellite and radiosonde measurements. Stratospheric temperature profiles obtained by L625 Rayleigh lidar agree well with HALOE results over 25 km to 65 km altitudes, their mean differences of 20 nights are basically less than 2 K. The profiles of tropospheric temperature measured by L625 Raman lidar show the good agreements with radiosonde results over the altitudes of 5 km to 18 km, their bias of mean temperature over 15 nights are usually less than 3 K from 6 km to 16.5 km altitude. The results above indicate that measurements of L625 Rayleigh-Raman are reliable, and can be employed for the routine observations and analysis of atmospheric temperature..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 851 (2004)
Measuring the High-Frequency Characteristics of Chip Photodiodes
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
An accurate measurement technique for the impedance and modulation frequency response of photodiodes is presented. In the measurement, the photodiode is mounted on a submount, and bond wires are used to connect the electrodes of chip. The test fixture consists of a microwave probe, a submount, and bond wires, and theirAn accurate measurement technique for the impedance and modulation frequency response of photodiodes is presented. In the measurement, the photodiode is mounted on a submount, and bond wires are used to connect the electrodes of chip. The test fixture consists of a microwave probe, a submount, and bond wires, and their scattering parameter can be attained by some accurate measurements. So the intrinsic characteristics of chips can be obtained by completely removing the effect of test fixture using microwave network theory and overcome the dependency on the electrode figures in conventional methods. Experimental results for a photodiode with coplanar electrodes demonstrate the validity of the proposed technique in the region 50 MHz～16 GHz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 857 (2004)
Effect of Phase Shifter′s Sub-Processional Motion on Interferometry
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In modern digital phase-shifting interferometry (PSI), the phase-shifting error of piezoelectric transducer (PZT) optical phase shifter, which is the basic device of phase-shifting interferometer, directly effects measurement accuracy during wavefront phase unwrapping with phase-shifting interferograms. A phenomenon naIn modern digital phase-shifting interferometry (PSI), the phase-shifting error of piezoelectric transducer (PZT) optical phase shifter, which is the basic device of phase-shifting interferometer, directly effects measurement accuracy during wavefront phase unwrapping with phase-shifting interferograms. A phenomenon named sub-processional motion that can result in fringes′ rotation in the processing of phase shift is described. This phenomenon is derived from the normal-line rotation of standard reference surface revolving around the elongate direction of PZT phase shifter. In terms of the classic phase-shifting algorithm-Hariharan 5-Bucket algorithm, the error formula of phase unwrapping is given due to sub-processional motion, and the error distribution on aperture is also derived. Based on error factor analysis, criterions to control the error are presented at such aspects.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 861 (2004)
A Novel Fiber Bragg Grating Wavelength Detection Technique
[in Chinese], [in Chinese], and [in Chinese]
A method of fiber Bragg grating (FBG) wavelength detection based on an all fiber Mach-Zehnder edge filter is proposed. Each output port of the edge filter shows comb-like transmission characteristics, and its spectrum is opposite to the other port. Wavelength message of FBG sensors is transformed into power message by A method of fiber Bragg grating (FBG) wavelength detection based on an all fiber Mach-Zehnder edge filter is proposed. Each output port of the edge filter shows comb-like transmission characteristics, and its spectrum is opposite to the other port. Wavelength message of FBG sensors is transformed into power message by a pair of the filtering edges of the filter. The wavelength measurement range and resolution are tunable in fabrication by adjusting the length difference of the two interference arms of the filter. And the affection of power variation of the system can be eliminated through two types of comparing calculation. FBG temperature sensing with this wavelength detection method gives a wavelength accuracy of about ±10 pm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 865 (2004)
Optical Communication
Gain Enhancement of L-Band Erbium-Doped Fiber Amplifiers Based on Fiber Loop Mirror
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel reflection L-band erbium-doped fiber (EDF) amplifier is constructed based on fiber loop mirror (FLM), which reflects the backward ASE to the EDF as a secondary pumping source. And the signal can also be reflected into the EDF by the FLM so that it is amplified secondly. In the wavelength region from 1570 nm to A novel reflection L-band erbium-doped fiber (EDF) amplifier is constructed based on fiber loop mirror (FLM), which reflects the backward ASE to the EDF as a secondary pumping source. And the signal can also be reflected into the EDF by the FLM so that it is amplified secondly. In the wavelength region from 1570 nm to 1605 nm, the small signal gain is 29.14 dB increasing by 5.33 dB compared to the forward end-pumped erbium-doped fiber amplifier (EDFA) when the pump power is 115 mW. The saturated output power is 7.63 and 7.6 dBm for 1580 nm and 1600 nm signal increasing 2.98 and 3 dB compared to the forward end-pumped EDFA, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 825 (2004)
Design on Gain-Flattening Filters of L-Band EDFAs
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Gain flattening of EDFA (erbium-doped fiber amplifier) is a critical issue for WDM (wavelength-division-multiplex) system, and cost efficiency and insertion loss make in-fiber gratings very attractive candidates for this application. A chirp fiber grating to flatten the gain spectrum of L-EDFAs by using layer-peeling mGain flattening of EDFA (erbium-doped fiber amplifier) is a critical issue for WDM (wavelength-division-multiplex) system, and cost efficiency and insertion loss make in-fiber gratings very attractive candidates for this application. A chirp fiber grating to flatten the gain spectrum of L-EDFAs by using layer-peeling method is designed. This algorithm, based on the law of causality, considers fiber Bragg gratings as a discrete model, which divides the entire grating into a series of discrete, complex reflectors with a distance Δ between the adjacent reflectors, the coupling coefficient at the back of a reflector can be derived from one at the front of this reflector recursively, so coupling coefficient function can be extracted rapidly and accurately. The target reflection spectrum of chirp gratings is derived from the ideal transmission spectrum of gain-flattening filters. A constant, α, is utilized to control the length of chirp gratings, which is relative with group time delay of reflection spectrums. When α is equal to 0.0024 cm2, the grating has a short length of 3.5 cm. After extracting coupling coefficients of the chirp grating using layer-peeling algorithm, transmission spectrum of the synthesized grating by solving Riccati equation is simulated, numerical analysis indicates that peak-to-peak error function is below 0.1 dB between ideal and realistic transmission spectrums. The variation of group time delay in transmission spectrum is less than 0.6 ps over entire operation bandwidth; therefore, the grating has no impact of additional chromatic dispersion on system performance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 829 (2004)
Experimental Study of Fiber Distributed Raman Amplifiers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, the performance of distributed Raman fiber amplifiers (DRA) with 40-channel wavelength division multiplexing (WDM) signals has been investigated. And the Raman fiber amplifiers with different pumping schemes and different fiber lengths have been reported. The gain and noise figures of the Raman fiber ampIn this paper, the performance of distributed Raman fiber amplifiers (DRA) with 40-channel wavelength division multiplexing (WDM) signals has been investigated. And the Raman fiber amplifiers with different pumping schemes and different fiber lengths have been reported. The gain and noise figures of the Raman fiber amplifier with 50 km of G.652 fiber have been compared at different pumping schemes. When the pump power and the signal power are not high enough, the Raman gain increases with the fiber length and the noise figure (NF) decreases with the fiber length. The optical signal to noise ration (OSNR) has also been investigated. It is found that the OSNR increases with the pump power, until saturated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 7, 833 (2004)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20