Journals >Chinese Journal of Lasers
Contents
2011
Volume: 38 Issue 3
44 Article(s)
Export citation format
Research Article
Far-Field Propagation of Focused Gaussian Beam through Atmospheric Turbulence and Effects of Adaptive Phase Compensation
He Yuanxing, Jiang Wenhan, and Li Xinyang
From the generalized Huygens-Fresnel principle, residual phase structure function method is used to calculate the modulation transfer function and far-field irradiance profile of a focused Gaussian beam blocked by a circular aperture through atmospheric turbulence, the Strehl ratio is a useful measure which is used herFrom the generalized Huygens-Fresnel principle, residual phase structure function method is used to calculate the modulation transfer function and far-field irradiance profile of a focused Gaussian beam blocked by a circular aperture through atmospheric turbulence, the Strehl ratio is a useful measure which is used here to evaluate the effects of several lower-order aberration modes corrections on the spot quality in the received plane, and the results derived here agree well with the results of correlation reference, moreover, the complexity of the new method used here is superior to the method used by correlation reference. The calculated results are analysed and discussed..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 312001 (2011)
Far Field Irradiance Profile Control in Inertial Confinement Fusion Drive Facility with Adaptive Optics
Wang De′en, Hu Dongxia, Dai Wanjun, Li Ping, Zhao Junpu, Jing Feng, and Li Xiaoqun
A novel method based on diffraction theory with adaptive optics to control far field irradiance profile in inertial confinement fusion device is proposed. Taking piezoelectricity film deformable mirror for example, the probability of this method used in profile control is studied. The results show that adaptive optics A novel method based on diffraction theory with adaptive optics to control far field irradiance profile in inertial confinement fusion device is proposed. Taking piezoelectricity film deformable mirror for example, the probability of this method used in profile control is studied. The results show that adaptive optics technique can be used to control the far-field intensity profile and uniformity easily by deformable mirror with high spatial resolution. In addition, more simulations show that this method is better than traditional method in the tolerance of wavefront distortion..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 312002 (2011)
Design of Staring Laser Threat Detection System Based on Michelson Interferometer
Wang Long, Wang Yongzhong, Shen Xueju, and He Yongqiang
A staring laser threat detection system based on Michelson interferometer is designed, and rules of orientation direction precision and filter’s transmission efficiency are analysed in theory. Results show that, round interference stripes are formed when input laser is transmitting through the laser threat detection syA staring laser threat detection system based on Michelson interferometer is designed, and rules of orientation direction precision and filter’s transmission efficiency are analysed in theory. Results show that, round interference stripes are formed when input laser is transmitting through the laser threat detection system, the direction and wavelength of input laser can be calculated based on the central coordinate and space of stripes.The direction precision is decided by the ratio of focal lengths of varying lens and spherical reflector when the pixel size of detector is fixed , and the precision rises when the ratio decreases. Filter’s transmission efficiency is decided by focal length of varying lens. If the varying lens’s focal length is ten times of fish eyes lens’s focal length, filter’s transmission will be 90.0%～87.5% for inputing laser with angle from 0°～90°, and this can make the detecting system have high sensitivity for every input laser from 0°～90°..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 312003 (2011)
Biomedical Photonics and Laser Medicine
Evaluation of Bonding Interface on Different Types of Dentin after Er:YAG Laser Irradiation
Lin Shi, Wu Weiliang, Zhan Zhenlin, Liu Qinghua, Li Xin, Lin Qi, and Huang Xiaolin
Bonding interface changes on different types of dentin after Er:YAG laser irradiation is evaluated. Normal dentin (ND) group and caries affected dentin (CAD) group samples are respectively irradiated with Er:YAG laser, and then etching with 38% phosphoric acid(phosphoric acid group), low-dose Er:YAG laser radiation (laBonding interface changes on different types of dentin after Er:YAG laser irradiation is evaluated. Normal dentin (ND) group and caries affected dentin (CAD) group samples are respectively irradiated with Er:YAG laser, and then etching with 38% phosphoric acid(phosphoric acid group), low-dose Er:YAG laser radiation (laser group) and no treatment (control group). The bonding interface changes are assessed via confocal laser scanning microscope (CLSM). There is no significant difference in thickness (p>0.05) within the same group with different etching methods or among different groups with the same etching, however, significant differences are existed in the length of resin tags (p<0.05). Maximum resin-tags are achieved in the phosphoric acid group, while control group minimum. Resin-tags in the bonding interface of ND are longer than that of CAD. The adhesive can infiltrate well into dentin bonding interface to achieve a quite ideal resin tags in the ND groups etching with 38% phosphoric acid..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 304001 (2011)
Laser Manufacturing
Formation and Suppression of Amplitude Modulation in Frequency Conversion
Wang Fang, Feng Bin, Li Fuquan, Han Wei, Jia Huaiting, Li Keyu, and Xiang Yong
The physical model of amplitude modulation formation in frequency conversion process is established by theoretical derivation, amplitude modulation of tripling beam can be caused by both amplitude modulation and phase aberration of fundamental beam. The evolution process of amplitude modulation during the third harmoniThe physical model of amplitude modulation formation in frequency conversion process is established by theoretical derivation, amplitude modulation of tripling beam can be caused by both amplitude modulation and phase aberration of fundamental beam. The evolution process of amplitude modulation during the third harmonic generation(THG) is researched by numerical simulation, the results show that tripling amplitude modulation caused by fundamental amplitude modulation can be reduced by optimize doubling crystal detuned angle, while the influence of fundamental phase aberration can be depressed by increasing accepting bandwidth of frequency converter. Moreover, because there is a little difference in the optimized tripling detuned angle between optimal THG efficiency and minimal temporal modulation, both factors in an optimal design should be synthesised..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302014 (2011)
Laser Cladding Fabrication of Micro-Fluidic Channel Mold of Stainless Steel
Wang Xuyue, Guo Huiru, Wu Yongbo, Xu Wenji, and Guo Dongming
Laser cladding on JK1002 NdYAG laser and the synchronous powder feeder are performed to fabricate micro-fluidic channels mold. Substrate material is HPM75 steel and clad powder is 316L stainless steel. Influences of the powder feed rate on clad layer geometrical dimensions and the combination of laser power and powder Laser cladding on JK1002 NdYAG laser and the synchronous powder feeder are performed to fabricate micro-fluidic channels mold. Substrate material is HPM75 steel and clad powder is 316L stainless steel. Influences of the powder feed rate on clad layer geometrical dimensions and the combination of laser power and powder feed rate with stable state of powder feeding on clad quality are investigated. Results show that the range of 1.5～2.5 g/min of powder feed rate obtains micro clad layers which meet geometrical dimensions′ requirement of micro-fluidic channel mold and combination parameters of laser power of 400 W and powder feed rate of 2.0 g/min make micro clad layer with good clad quality. Scanning paths of micro-fluidic channel mold with specific shape are planned by CAD-Mastercam software. Using optimum parameters combination, multilayer laser cladding experiment is carried out and a sample of micro-fluidic channels mold is fabricated with dense structure and hardness of 580 HV. A little milling and polishing makes the sample meet the requirement of mold. Sizes of the final sample are 0.1 mm in height and 0.3 mm in width. The mold fabricating time is 60～75 min totally..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 303001 (2011)
Influence of Laser Shock Processing Times on TC4 Argon Arc Welding Joint Microstructure and Properties
Xu Haiying, Zou Shikun, Che Zhigang, and Cao Ziwen
Q-switched Nd∶glass laser with 30 ns pulse-width and 40 J energy is introduced to shock TC4 titanium alloy tungsten inert gas (TIG) welding joints once, twice and three times, separately. In order to study the influence of laser shock processing (LSP) disposal times on TC4 TIG welding joints microstructure and propertiQ-switched Nd∶glass laser with 30 ns pulse-width and 40 J energy is introduced to shock TC4 titanium alloy tungsten inert gas (TIG) welding joints once, twice and three times, separately. In order to study the influence of laser shock processing (LSP) disposal times on TC4 TIG welding joints microstructure and properties, surface HV hardness, microstructure, tensile property and scanning electron microscope (SEM) fracture photos of these joints are analyzed. Comparing with those joints without LSP treatment, surface HV hardness of weld beads treated by LSP is decreased. HV hardness on weld bead surface and that on the heat affected zone (HAZ) surface are hardly different. The amount of α′ phase near LSP treatment weld bead surface is reduced, and fine grains are increased in the HAZ. With the increase of LSP treatment times, HV hardness is improved on weld joints surface. Although LSP treatment joints tensile strength and yield strength are not distinctly change, specific elongation is shown fall trend along with LSP treatment times increased..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 303002 (2011)
CO2 Laser Hybrid Welding Processes and Microstructures of 10Ni3CrMoV Steel in T Joint Form
Hu Lianhai, Huang Jian, Ni Huifeng, and Wu Yixiong
Laser hybrid welding has become one of the most promising welding methods used to weld ship thickness steel plates with high efficiency due to combining the advantage of laser welding and arc welding. CO2 laser hybrid welding processes of ship steel plates are studied. The influences of the shielding gas composition onLaser hybrid welding has become one of the most promising welding methods used to weld ship thickness steel plates with high efficiency due to combining the advantage of laser welding and arc welding. CO2 laser hybrid welding processes of ship steel plates are studied. The influences of the shielding gas composition on the chemical composition of weld and the distance between the laser beam and arc on the stability of the welding process are mainly analyzed. Based on the optimizing process parameters, 10Ni3CrMoV steel plates with a thickness of 14 mm are welded on both sides in T joint form using high-power laser hybrid welding. The welds produced are assessed by X ray. No crack is found and there is only a small amount of pores. The microstructures of welded joints are examined by optical microscope. The results show that the microstructure of welded joints has good comprehensive mechanical properties. Especially after the weld overlap region experiences a re-melting and heat treatment, the microstructure is refined. The microhardness of welded joints is tested in different regions. The maximum hardness of welded joints is less than 360 HV. The welds obtained can meet the technical requirements for shipbuilding industry..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 303003 (2011)
Microstructure and High Temperature Tensile Properties of Laser Direct Deposited Ti60 Alloy and TiCP/Ti60 Composites
Sun Jingchao, Zhang Yongzhong, Huang Can, Li Yan, and Li Guowei
Wall-like Ti60 alloy and TiCP(mass fraction 5%)/Ti60 titanium matrix composites are fabricated by laser direct deposition process. Their microstructure and tensile properties under 600 ℃ are investigated. The results indicate that the deposited Ti60 alloy presents a widmanstatten structure with some spherical rare eartWall-like Ti60 alloy and TiCP(mass fraction 5%)/Ti60 titanium matrix composites are fabricated by laser direct deposition process. Their microstructure and tensile properties under 600 ℃ are investigated. The results indicate that the deposited Ti60 alloy presents a widmanstatten structure with some spherical rare earth phases distributing along the sub-grain boundaries and the α/β interface. For the deposited TiCP/Ti60 composites, there are some un-melted TiC particles and re-solidified TiC particles appear as discontinuous chain-like. The TiC particles distribute uniformly within the matrix with good interface bonding. Under 600 ℃, the ultimate tensile strength (UTS) of TiCP/Ti60 composites is 65 MPa higher than that of Ti60 alloy, following with decreased elongation. Ti60 alloy exhibit ductile fracture characteristics, while TiCP/Ti60 composite exhibit some complicated fracture characteristics including intergranular fracture, quasi-cleavage crack and local ductile rupture..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 303004 (2011)
Functionally Graded Interface Effects of Chromium Electrodeposits with a Laser-Discretely Treated Steel Substrate
Li Huaixue, Chen Guangnan, and Gong Shuili
The functionally graded interface (FGI) effects of a laser-discretely treated steel substrate and Cr electroplate are investigated in order to reveal the mechanism that the service life of the chromium-coated gun tubes is increased by laser-discretely pre-treating. The results show that a periodically graded structure The functionally graded interface (FGI) effects of a laser-discretely treated steel substrate and Cr electroplate are investigated in order to reveal the mechanism that the service life of the chromium-coated gun tubes is increased by laser-discretely pre-treating. The results show that a periodically graded structure is created on the surface layer of steel substrates due to laser-discretely pre-treating, and the periodically graded microstructural characteristics are inherited by the initially deposited chromium layer. Thus, there is an FGI layer between steel substrates and Cr coatings. The FGI layer can decrease the hardness gradient, and largely improve the corrosive-spallation resistance of Cr electrodeposits..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 303005 (2011)
Numerical Analysis of Temperature Field in Laser Cladding on Tooth Surface of Helical Gear Shaft
Chen Lie, Gu Chengzhong, and Xie Peilin
The laser cladding process on tooth surface of a helical gear shaft which is the rotor in lubricant pump of steam turbine is investigated. Temperature field is numerically simulated with finite element analysis software-ANSYS. Calculation results show that the heat caused by laser energy is concentrated inside the tootThe laser cladding process on tooth surface of a helical gear shaft which is the rotor in lubricant pump of steam turbine is investigated. Temperature field is numerically simulated with finite element analysis software-ANSYS. Calculation results show that the heat caused by laser energy is concentrated inside the tooth mostly, and the distribution of isothermal lines is very dense at the binding site of clad coating and tooth root. Large temperature gradient would be generated inside the tooth. In addition, an effect of preheating in the adjacent tooth would also be brought up by laser energy. It is also indicated that the isothermal lines are penetrated into the tooth tip, and the problems of excessive melted down and collapsing of tooth tip would be easily brought about if the tooth side and tooth tip are cladded at the same time. So the tooth side and tooth tip should be cladded step by step. Continuous and complete clad coating on tooth surface is produced in experiment by this technology..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 303006 (2011)
Laser Physics
Mode-Locking and Multiwavelength Operation from All-Fiber Ytterbium Doped Laser
Zhang Panzheng, Fan Wei, Wang Xiaochao, and Lin Zunqi
Using a semiconductor saturable absorber mirror (SESAM) and a fiber loop mirror (FLM) as end mirror respectively, an all-fiber line-cavity Yb3+-doped laser is demonstrated. Q-switched pulse, Q-switched mode-locking, coherent mode-locking, harmonic pulses, and multiwavelength operation are obtained by adjusting the pumpUsing a semiconductor saturable absorber mirror (SESAM) and a fiber loop mirror (FLM) as end mirror respectively, an all-fiber line-cavity Yb3+-doped laser is demonstrated. Q-switched pulse, Q-switched mode-locking, coherent mode-locking, harmonic pulses, and multiwavelength operation are obtained by adjusting the pump power and the polarization controller (PC). Mode-locking can be self-started and the width of mode-locking pulses is 31 ps. The pulse repetition rate is 19.3 MHz, corresponding to 40 pJ pulse energy. The spectral bandwidth of the mode-locked operation is 2.3 nm, at the center wavelength of 1030.8 nm. While multiwavelength operation centered at about 1033 nm is achieved, the wavelength space and the number of wavelength can be changed by adjusting the pump power and the PC. At the maximum pump power of 420 mW, the average wavelength space can be as small as about 0.11 nm. Up to 35 wavelengths within the spectral range of 10 dB are obtained, with 34 wavelengths in the 3 dB scale..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302001 (2011)
Investigation on Infrared Continuous-Wave Laser Damage Mechanism of Polyurethane-Based Black Paint
Wu Lixiong, Ye Xisheng, and Liu Zejin
Polyurethane-based black paint is a kind of gloss and flat paint used for stray light shielding in optical imaging systems. Experiments of infrared laser irradiation effect on polyurethane-based black paint are carried out in a vacuum cryostat. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPPolyurethane-based black paint is a kind of gloss and flat paint used for stray light shielding in optical imaging systems. Experiments of infrared laser irradiation effect on polyurethane-based black paint are carried out in a vacuum cryostat. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) are used to investigate the changes of the surface morphology, chemical composition and structure. The mechanism of interaction between laser and polyurethane-based black paint is studied. Based on macro phenomenon and micro-appearance analysis, the degree of damage is proposed. The experimental data and results of simultaneously differential scanning calorimetry-thermogravimetry (SDT) analysis indicate that damage is mainly caused by laser heating; the deposition of heat generated by laser changes color of the coating and leads to pyrogenation, carbonization and thermal ablation. The morphologies obtained from SEM show that surface of the coating is covered by many nondirectional fine cracks and the pigment particles agglomerate together after laser irradiation. XPS analysis for the surface of coating with and without laser irradiation reveals that laser irradiation changes the chemical composition and structure of the coating, and the C-N bonds and O-C＝O double bonds of binder are more easily cut off and destroyed..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302002 (2011)
Acoustooptic Q-Switch Based on Raman-Nath Diffraction
Shao Zhongxing, Jiang Shoujun, Jiang Kunjun, Wu Peng, Gu Huadong, Zheng Chenqi, Wei Bing, and Wu Xiaodong
A series of experiments on the interaction length between the sound and the light with Raman-Nath diffraction is reported. Then the optimum interaction length at certain sound frequency is defined. Based on those results, the devices of acoustooptic Q-switch, made of H2O or TeO2 as the medium, in terms of Raman-Nath diA series of experiments on the interaction length between the sound and the light with Raman-Nath diffraction is reported. Then the optimum interaction length at certain sound frequency is defined. Based on those results, the devices of acoustooptic Q-switch, made of H2O or TeO2 as the medium, in terms of Raman-Nath diffraction are respectively designed. The diffraction and the loss of the devices are tested. Finally the device made of TeO2 is employed to modulate a long pulsed Nd:YAG/KTP laser. The modulated pulse width is measured as about 200 ns at the repetition frequency of 10 kHz..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302003 (2011)
Graphene Mode-Locked Er3+Doped Fiber Pulse Laser
Tian Zhen, Liu Shanliang, Zhang Bingyuan, Zheng Hongjun, Sun Yanxing, and Yan Xunling
A graphene-PVA film is fabricated by using polyvinyl alcohol(PVA), which provides excellent mechanical property and easy operation. Raman spectra of the graphene-PVA film and graphene sheets are measured, which show that the spectra have the same characteristics. The passively mode-lock Er-doped fiber laser with grapheA graphene-PVA film is fabricated by using polyvinyl alcohol(PVA), which provides excellent mechanical property and easy operation. Raman spectra of the graphene-PVA film and graphene sheets are measured, which show that the spectra have the same characteristics. The passively mode-lock Er-doped fiber laser with graphene-PVA film as saturable absorber is made, which produces the mode-locked pulses with duration of 10.29 ps, peak wavelength of 1532.75 nm, and repetition rate of 8.7 MHz..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302004 (2011)
Experimental Property Research of Far-Field Focusing of Laser Beam
Zhang Heyong, Guo Jin, Zhao Shuai, Wang Tingfeng, and Shao Junfeng
In order to lead the laser beam transmit in the atmosphere convergently, an experiment of laser focus at a distance of 450 m and 300 m has been operated in outdoor place. The actual manipulations are as follows: Firstly, the laser is collimated by a beam expander, then the near-parallel laser beam transmits through a GIn order to lead the laser beam transmit in the atmosphere convergently, an experiment of laser focus at a distance of 450 m and 300 m has been operated in outdoor place. The actual manipulations are as follows: Firstly, the laser is collimated by a beam expander, then the near-parallel laser beam transmits through a Galileo telescope system, and the distance between the concave lens and the convex lens can be tuned through a precise displacement platform, so the focus of the system can change due to the tiny displacement of the concave lens. Secondly, the average power of the laser spot can be measured using power meter, and the power is 47.67 mW and the standard deviation is 0.67 mW while the focal length is 450 m. Thirdly, the energy distribution is found through a laser beam analyzer. The spot images are saved by using the beam analyzer, then the saved image can be processed with Matlab software afterwards. The functions named EDGE and Sobel operator are used in the pre-processing of saving image, then method of median filter is used in the course of image de-noising and 53H filter is adopted in the signal analysis. The diameter of laser spot is obtained by the methods above, and the diameter is 5.56 mm and the standard deviation is 0.24 mm. The spot center excursion is 0.56 mm, and it is 10.43% of the total diameter of the laser spot. At last, the key factors of the energy dissipation in the focusing system can be summarized as follows: restriction of the diffraction limit, attenuation in the atmosphere, and geometrical aberration of optical system. The diffraction limit and the geometrical aberration are significant in the three factors above, so we can reduce the impact of the both factors during the design of optical system. The reliable referenced data of the design of the system can be acquired through the primary experimental research..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302005 (2011)
Mechanisms Research on Continous Wave Laser Induced Damage to Solar Cells
Qiu Dongdong, Wang Rui, Cheng Xiang′ai, Zhang Zhen, and Jiang Tian
Aiming at the damage effects of solar cells under the irradiation of continous wave laser, the output parameter decrease of damaged solar cells and impact induced by laser irradiation are analyzed, the damage mechanisms of solar cells are researched through the observation of morphology of damaged area combined with thAiming at the damage effects of solar cells under the irradiation of continous wave laser, the output parameter decrease of damaged solar cells and impact induced by laser irradiation are analyzed, the damage mechanisms of solar cells are researched through the observation of morphology of damaged area combined with the equivalent circuit diagram and I-V curves. The results show that laser ablated solar cell resulted in the ablation area is disabled, causes the increase of series resistance and the decrease of parallel resistance at the same time, and finally induces the output performance of solar cell to decrease largely..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302006 (2011)
Compact and Highly Efficient 3.8 W Intracavity Frequency-Doubled Nd:YVO4/PPMgLN Green Laser
Yan Boxia, Bi Yong, Wang Dongdong, Bao Guang, Qi Yan, Fang Tao, and Zhang Ying
A compact and highly efficient green-light source is demonstrated based on periodically poled Mg:LiNbO3 (PPMgLN) crystal. The MgO:LiNbO3 samples of 1 mm thick, 6.95 μm domain period, uniform periodicity, near 50% duty cycle are fabricated by use of a high-voltage multi-pulse poling method. A maximum power of 3.8 W at 5A compact and highly efficient green-light source is demonstrated based on periodically poled Mg:LiNbO3 (PPMgLN) crystal. The MgO:LiNbO3 samples of 1 mm thick, 6.95 μm domain period, uniform periodicity, near 50% duty cycle are fabricated by use of a high-voltage multi-pulse poling method. A maximum power of 3.8 W at 532 nm is obtained by a 6.8 W laser diode (LD) pumped, the PPMgLN length in Nd:YVO4 intracvity is only 1 mm, and the corresponding optical to optical conversion efficiency is 56%..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302007 (2011)
9.3 μm Branch Selection Research of High Power Pulse CO2 Laser
Shao Chunlei, Yang Guilong, Li Dianjun, and Guo Jin
For obtaining high power 9.3 μm laser, high power pulse CO2 laser is used to select band. Band selection is done by resonator mirror filming. By controlling the transmittance or reflectivity of different wavelengths, 9.3 μm laser is got both in stable resonators and unstable resonators. With the same operation parameteFor obtaining high power 9.3 μm laser, high power pulse CO2 laser is used to select band. Band selection is done by resonator mirror filming. By controlling the transmittance or reflectivity of different wavelengths, 9.3 μm laser is got both in stable resonators and unstable resonators. With the same operation parameters, the energy of 9.3 μm laser is 95% of 10.6 μm in stable resonators, while 93% in unstable resonators. Both in two different resonators, the thermo-sensitive paper colors by 9.3 μm laser are evidently different from those by 10.6 μm laser. Experimental results show that the resonator mirror filming method can lead 9.3 μm laser output both in stable and unstable resonators, and the energy is changing slightly. The thermosensitive paper displays the 9.3 μm laser has stronger impact erosion than the 10.6 μm laser..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302008 (2011)
Small Signal Gain Coefficients in Nd3+ Doped Phosphate Glass
Wen Lei, Yang Jingxin, Liu Renhong, Feng Suya, Luan Fei, Chen Wei, and Hu Lili
Small signal gain coefficients(SSGC) of 93 pieces N31 Nd3+ doped glasses for Shenguang Ⅱ high power laser system are tested. Results show that the average SSGC of Nd glasses with 2.2% mass fraction of Nd2O3 and 3.0% mass fraction of Nd2O3 are 0.0387 cm-1 and 0.0416 cm-1 respectively. Gain fluctuation range of these twoSmall signal gain coefficients(SSGC) of 93 pieces N31 Nd3+ doped glasses for Shenguang Ⅱ high power laser system are tested. Results show that the average SSGC of Nd glasses with 2.2% mass fraction of Nd2O3 and 3.0% mass fraction of Nd2O3 are 0.0387 cm-1 and 0.0416 cm-1 respectively. Gain fluctuation range of these two kinds of Nd glasses are 0.86% and 0.76% respectively. This result demonstrates that the gain fluctuation range of N31 Nd glasses meets the requests of Shenguang Ⅱ projects and definitely provides the gain equilibrium for every beam laser in this system. This experiment is a valuable experience for controlling the gain properties of even larger Nd glass in the future..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302009 (2011)
Characteristics of Fused Silica Rod Brillouin Amplifier Simulated Brillouin Scattering Seeded by Large Aperture Tapered Fiber
Cui Lingling, Zhao Zhigang, Pan Sunqiang, Liu Chong, Chen Jun, Xie Gang, Tong Lixin, Gao Qingsong, and Tang Chun
Detailed experimental investigations on the amplification characteristics of back-injected simulated Brillouin scattering (SBS) seed laser in solid fused silica rod Brillouin amplifier under different pump power levels have been done, in which a master oscillator power amplifier (MOPA) single longitudinal mode Nd∶YAG lDetailed experimental investigations on the amplification characteristics of back-injected simulated Brillouin scattering (SBS) seed laser in solid fused silica rod Brillouin amplifier under different pump power levels have been done, in which a master oscillator power amplifier (MOPA) single longitudinal mode Nd∶YAG laser with repetition rate of 400 Hz is used as pumping source, and a large aperture tapered fiber as SBS generator and solid fused silica rod as SBS amplifier. These characteristics include amplified SBS output power, amplification ratio of injected SBS seed laser, total SBS reflectivity, extraction efficiency of fused silica rod Brillouin amplifier, pulse width and beam quality versus SBS seed laser power. A maximum amplified SBS output power of 15.5 W, amplification ratio of 70, total SBS reflectivity of more than 50%, and extraction efficiency of 52% are obtained. Pulse width broadening and gain guiding have been observed. The experimental results indicate that the fused silica rod Brillouin amplifier has different amplification characteristics with small signal SBS seed laser and large signal SBS seed laser. Additionally, the degree of spatial superposition of SBS seed laser and pump laser and the pump power density in fused silica rod are found to be two important aspects which influence the amplified SBS output power..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302010 (2011)
Design and Fabrication of InP-Based Low Threshold Microring Laser with Unique Unidirectional Bistability Operation
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Semiconductor microring lasers (SMLs) have received increasing attention in the areas of all-optical logic and random storage owing to their unique characteristics for wavelength conversion, tunability and optical bistability. Based on the analysis of relationship between backscattering coupling and SML operation regimSemiconductor microring lasers (SMLs) have received increasing attention in the areas of all-optical logic and random storage owing to their unique characteristics for wavelength conversion, tunability and optical bistability. Based on the analysis of relationship between backscattering coupling and SML operation regimes (bidirectional continuous-wave, bidirectional alternate oscillations, unidirectional bistability), the structure parameters and process of microring resonator are optimized, and an InP-based low threshold SML with unique unidirectional bistability is fabricated. The experimental results indicate that the laser with a threshold current of 56 mA has a lasing wavelength of 1569.65 nm. Once the driving current exceeded the threshold, the SML entered into the unidirectional bistability without any bidirectional regimes. Thus the driving current and power consumption of bistability operation are reduced greatly, and the device reported here is very suitable to the optical random storage memory unites..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302011 (2011)
Diffraction Characteristics of Vortex Beams by a Fork-Shaped Grating
Liu Yongxin, Chen Ziyang, and Pu Jixiong
Based on the Huygens-Fresnel integral and the transmittance function of the fork-shaped grating, analytical expression of a vortex beam passing through a fork-shaped grating is derived. The diffraction characteristics of vortex beams by a fork-shaped grating embedded with topological charge l are studied in great detaiBased on the Huygens-Fresnel integral and the transmittance function of the fork-shaped grating, analytical expression of a vortex beam passing through a fork-shaped grating is derived. The diffraction characteristics of vortex beams by a fork-shaped grating embedded with topological charge l are studied in great detail. It is shown that the topological charge of the center spot of the diffracted beam is the same as that of the incident vortex beam, and that the topological charge of the nth diffracted beam is nl+m with different diffraction order n. The nth diffracted beam spot is plane wave when it satisfies nl+m=0. While on both sides of the plane wave spot, the doughnut radius of the diffracted beam spot increases as the diffraction order n changes. According to nl+m=0, the topological charge of the incident vortex beam can be detected through the order n of the plane wave spot and the topological charge l embedded in the fork-shaped grating. The results are compared with the experimental results and it is found that they are both in good agreement..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302012 (2011)
Analysis of Uplink Propagation in Relay Mirror System Based on Coherent Beams Combination
Wu Huiyun, Wu Wuming, Xiong Chengping, Xu Xiaojun, Chen Jinbao, and Zhao Yijun
Model of a relay mirror system with source composed of coherent beam array is established. Phase distribution of the source is optimized by using the stochastic parallel gradient descent algorithm. The influence factor induced by the intensity non-uniformity of receiving beam is defined and the evaluation function of uModel of a relay mirror system with source composed of coherent beam array is established. Phase distribution of the source is optimized by using the stochastic parallel gradient descent algorithm. The influence factor induced by the intensity non-uniformity of receiving beam is defined and the evaluation function of uplink propagation process is theoretically analyzed. Under H-V5/7 turbulent model, performances of uplink propagation in the relay mirror systems with coherent beam array source and flat beam source are calculated. Results show that power coupling efficiency of uplink propagation and intensity uniformity of received beam are both effectively improved by using the coherent multi-beams array controlled by the stochastic parallel gradient descent algorithm. The evaluation function of 10 km uplink propagation is improved from 0.6730 to 0.8838 and the evaluation function of 30 km uplink propagation is improved from 0.4266 to 0.8560..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302013 (2011)
Temporal Evolution of Laser Pulses with Small-Scale Self-Focusing in Different Spatial Positions
Hou Yanchao, Fu Xiquan, and Liu Hui
Based on the process of broadband chirped pulse with small-scale self-focusing, spatial-temporal nonlinear Schrdinger equation is used for calculation. The temporal evolutions in different spatial positions have been investigated, especially the modulation peak and the modulation bottom in space. The results show thatBased on the process of broadband chirped pulse with small-scale self-focusing, spatial-temporal nonlinear Schrdinger equation is used for calculation. The temporal evolutions in different spatial positions have been investigated, especially the modulation peak and the modulation bottom in space. The results show that temporal evolutions in different spatial positions are completely different. The pulse width at modulation peak in space is decreasing with the increasing of transmission distance, and it will reach minimum when the intensity of modulation peak reaches maximum. However, the pulse width at modulation bottom is always broadend. In the end, chirps on the impact of temporal revolution in different locations have been studied. Negative chirp accelerates the pulse compression of modulation peak, but it inhibites the pulse broadening of modulation bottom. However, the positive chirp is counterproductive..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302015 (2011)
Mode Competition and Laser Power Tuning Property of Orthogonal Polarized Laser with Y-Shaped Cavity
Xiao Guangzong, Long Xingwu, Zhang Bin, Lu Guangfeng, and Zhao Hongchang
Output power tuning experimental setup of Y-shaped cavity orthogonal polarized He-Ne laser is built. The mode split frequency difference is changed through changing voltage applied on the end mirror of S sub-cavity (or P sub-cavity), while the common cavity′s length is tuned with the voltage applied on the end mirror oOutput power tuning experimental setup of Y-shaped cavity orthogonal polarized He-Ne laser is built. The mode split frequency difference is changed through changing voltage applied on the end mirror of S sub-cavity (or P sub-cavity), while the common cavity′s length is tuned with the voltage applied on the end mirror of the common cavity varied. It is reported that the light power tuning curves and their beat frequencies variation tune in the cases of different mode split frequency difference with common cavity. Based on the Lamb semiclassic gas laser theory of three-order perturbation, influencing factors and their mechanism are investigated and generalized detailedly. Theoretical analysis shows that longitudinal modes loss, gain per pass and their frequency difference affect the pattern and result of mode competition, which obey the self-consistent equations of light intensity. In the end the light power tuning curves and beat frequencies variation of different frequency difference are theoretically analyzed and explained..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 302016 (2011)
Materials and Thin Films
Ag Doping Effects on La2/3Ca1/3MnO3 Thin Films and Laser-Induced Voltage Effect
Cao Minggang, Zhang Hui, Liu Xiang, Shang Jie, Duan Yunbiao, Lan Jun, Zhang Shaochun, and Zhang Pengxiang
Ag doped La2/3Ca1/3MnO3 (LCMO∶Agx) polycrystalline pellets, which are prepared by solid-state reaction, are employed to fabricate LCMO∶Agx epilayer on single crystalline LaAlO3(100) substrate by pulsed laser deposition technique. X-ray diffraction (XRD) and ω-θ rocking cure analysis show that all the films are c-orientAg doped La2/3Ca1/3MnO3 (LCMO∶Agx) polycrystalline pellets, which are prepared by solid-state reaction, are employed to fabricate LCMO∶Agx epilayer on single crystalline LaAlO3(100) substrate by pulsed laser deposition technique. X-ray diffraction (XRD) and ω-θ rocking cure analysis show that all the films are c-oriented and presented good crystalline quality. The morphology of the as-grown films are detected by atomic force microscope (AFM), and the results demonstrate that the surface roughness increases with increased Ag doping level, further, numerous laser droplets could be observed in all films. Laser induced voltage (LIV) effect is found in those films grown on the vicinal-cut LaAlO3(100) substrates, and with Ag content increasing, the peak value of LIV signal (Up) increases firstly and arrives to its maximum at x=0.05. Up decreases up to x=0.10 and gets its minimum at x=0.10, while Ag content dependence of response time τ of LIV signal just presents an opposite behavior..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 307001 (2011)
Measurement and Metrology
Tiled-Grating Rotation Detecting Technology
Xia Lan, Yang Xuedong, Xu Guang, and Dai Yaping
Tiled-grating technology is a possible approach to improve the high power laser output energy. For the protection of high-power laser beam temporal and spatial beam quality, stitching error of grating angle must be less than 0.4 μrad, and the piston deviation is less than 20 nm. A detecting system is designed to measurTiled-grating technology is a possible approach to improve the high power laser output energy. For the protection of high-power laser beam temporal and spatial beam quality, stitching error of grating angle must be less than 0.4 μrad, and the piston deviation is less than 20 nm. A detecting system is designed to measure the error of rotation angle between tiled-gratings to meet the high accuracy and high stability of the tiled-grating assembly. A phase-shift interferometer is used to measure the detecting beam which is coaxial with the main laser beam, and some interference patterns are gotten and analyzed to reconstruct the wave front. The feasibility of the system has been verified by a series of experiments and the accuracy of the system is 0.45 μrad. Tiled-grating measurement program with only the requirements of wavefront tilt error, which simplifies the optical interferometry and image analysis process, will help grating tiling technology applied in engineering..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 308001 (2011)
Bonding Quality Detection of Composite Structure by Laser Shock Wave
Gu Zhuowei, Mathieu Perton, Silvio E., Martin Lord, Alain Blouin, and Jean-Pierre Monchalin
The carbon fiber reinforced polymer (CFRP) is more and more attractive because of its excellent mechanical performances, while the application of CFRP is limited because the non-destructive evaluation method is still not well done. A method based on shock waves produced by a pulsed laser is applied to the evaluation ofThe carbon fiber reinforced polymer (CFRP) is more and more attractive because of its excellent mechanical performances, while the application of CFRP is limited because the non-destructive evaluation method is still not well done. A method based on shock waves produced by a pulsed laser is applied to the evaluation of bond quality of CFRP plates joined by an adhesive layer. A laser shock wave can cause a tension when it propagates through the adhesive/plate interface. A good bond will be unaffected by a certain level of shock wave stress whereas a weaker one will be damaged. In the experiments, the sample surface velocities are optically measured with an interferometer. The signals give a signature of well-bond or bad ones, and are used to obtain an estimate of the bond strength. Results show that the proposed test is able to differentiate bond quality. Laser-ultrasonic measurements made on shocked samples also confirm that weak bonds are revealed by the laser shock wave. The development of this technique will probably make the on line evaluation of CFRP structure possible in the future..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 308002 (2011)
Particle Sizing and Size Distribution Measurement of Alcohol Spray by Interferometric Particle Imaging
Lü Qieni, Ge Baozhen, Chen Yiliang, and Zhang Yimo
A method for the measurement of particle size with interferometric particle imaging (IPI) technique is studied. The interferometric pattern of the scattering light of particle is formed in the defocused image plane and the center of the fringe pattern is extracted by the wavelet transform and template matching method. A method for the measurement of particle size with interferometric particle imaging (IPI) technique is studied. The interferometric pattern of the scattering light of particle is formed in the defocused image plane and the center of the fringe pattern is extracted by the wavelet transform and template matching method. The number of fringe/fringe spacing of the interferogram by Fourier transform and the modified Rife algorithm is obtained, and particle size with subpixel accuracy is calculated. The experiment is conducted for standard particles of diameter 51.1 μm. The particle diameter is measured of (49.79±0.41) μm with the absolute error of 1.31 μm. And this technique is applied to alcohol spray measuring. The particle size distribution, mean particle diameter and Sauter mean diameter (SMD) of the spray field with different measuring locations along x-axis and y-axis are also given..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 308003 (2011)
Using SHG-FROG to Measure Intensity and Phase of Infrared Long Wavelength Ultra-Fast Laser Pulse in Single Shot
Xu Canhua, Leng Yuxin, Zhang Chunmei, Huang Yansui, Lu Xiaoming, Ge Xiaochun, Li Chuang, Song Liwei, and Chen Xiaowei
A frequency-resolved optical gating (FROG) apparatus which can be used to measure the intensity and phase of infrared long wavelength ultra-fast laser pulse in single-shot is described. Because the high damage threshold coating in this waveband is difficult and expensive, we use two half-semicircle mirrors to substitutA frequency-resolved optical gating (FROG) apparatus which can be used to measure the intensity and phase of infrared long wavelength ultra-fast laser pulse in single-shot is described. Because the high damage threshold coating in this waveband is difficult and expensive, we use two half-semicircle mirrors to substitute traditional transmitted beam splitter. Meanwhile, error of measurement in the improved configuration will be diminished, and the whole device becomes more compact and easier to be adjusted. We utilized the apparatus to characterize optical parametric amplifier ultra-fast pulse pumped by Tisapphire laser. With the center-wavelength of 1.8 μm, the pulse has duration of 66.9 fs and spectral width of 54.5 nm. The group delay dispersion (GDD) in spectrum region is 202.9 fs2..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 308004 (2011)
Micro and Nano Optics
Design and Fabrication of Polymer Microlens Array with Self-Written Waveguide
Li Feng, Chen Sihai, Lai Jianjun, Zhou Yifan, and Gao Yiqing
Polymer microlens array with self-written waveguides is fabricated with SU-8 material which is a kind of epoxy based photoresist. Melting photoresist and image transferring are employed to fabricate the microlens array. Because of the melting and attendant expanding process of the photoresist, the actual fill factor ofPolymer microlens array with self-written waveguides is fabricated with SU-8 material which is a kind of epoxy based photoresist. Melting photoresist and image transferring are employed to fabricate the microlens array. Because of the melting and attendant expanding process of the photoresist, the actual fill factor of the array exceeds the design one, which is 0.749. SU-8 photoresist and glass substrate are separated by a layer of polydimethylsiloxane (PDMS) due to the strong bonding force between them. With the good separation effect of PDMS film, UV-cured SU-8 microlens array is obtained without mechanical damage. Profile, performance of the light spots at the end of the self-written waveguides and their uniformity are observed and tested. It is concluded that the SU-8 microlens array with self-written waveguides is fine, it images the filament of the metallographic microscope well and its light spots at the end of the waveguide are of high uniformity. By using this polymer microlens array, the assembling between the microlens array and detector array is expected to be achieved easily. This polymer microlens array has great potential applications in many optoelectronic devices..
Chinese Journal of Lasers
- Publication Date: Aug. 06, 2021
- Vol. 38, Issue 3, 310003 (2011)
Numerical Simulation of a Surface Plasmonic Waveguide with Double Parallel Columniform Metallic Nanorods Coated with Gain Medium
Qin Xiaojuan, Guo Yanan, and Xue Wenrui
A kind of surface plasmonic waveguide with double parallel columniform metallic nanorods coated with the gain medium is introduced. The dependence of distribution of longitudinal energy flux density, effective index, propagation length and mode area of the fundamental mode with longer propagation length supported by thA kind of surface plasmonic waveguide with double parallel columniform metallic nanorods coated with the gain medium is introduced. The dependence of distribution of longitudinal energy flux density, effective index, propagation length and mode area of the fundamental mode with longer propagation length supported by this waveguide on geometrical parameters and electromagnetic parameters are analyzed using the finite-difference frequency-domain (FDFD) method. Results show that the longitudinal energy flux density distributes mainly in the middle area which is formed by the two columniform metallic rods. The propagation properties can be adjusted by changing the geometrical parameters and electromagnetic parameters. The propagation length can be extended obviously with the help of the gain medium. This kind of surface plasmonic waveguide can be applied in the field of photonic device integration and sensors..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 310001 (2011)
Electromagnetic Enhancement by a Single Subwavelength Groove in Metallic Substrate
Zhang Siwen, Liu Haitao, and Mu Guoguang
The electromagnetic enhancement generated by a single subwavelength groove in metallic substrate is analyzed for the application of surface enhanced Raman scattering (SERS) on metallic micronano-structure. The electromagnetic field distribution out of the groove illuminated by a plane-wave is calculated using fully-vecThe electromagnetic enhancement generated by a single subwavelength groove in metallic substrate is analyzed for the application of surface enhanced Raman scattering (SERS) on metallic micronano-structure. The electromagnetic field distribution out of the groove illuminated by a plane-wave is calculated using fully-vectorial numerical method. The rigorous fully-vectorial data are well predicted by a simple semi-analytical Fabry-Perot (F-P) model. The computation amount for designing the optimal groove depth can be saved by using the model. Physical mechanism of electric-field enhancement out of the groove, based on the model is analysed, which shows that the enhancement is mainly attributed to the transmitted field of enhanced fundamental groove mode under resonance. The range of the enhanced electric-field out of the groove is studied. The results show that, for different groove widths and illumination wavelengths, the electric-field enhancement is considerable at vertical distances to the groove mouth less than 0.1 times of the wavelength and that out of this range, the electric-field enhancement factor attenuates rapidly to about unitary magnitude..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 310002 (2011)
Optical Communication
Effects of Phase Modulation on Threshold of Stimulated Brillouin Scattering in Optical Fibers
Chen Wei, and Meng Zhou
Phase modulation is an effective method to increase the threshold of the stimulated Brillouin scattering. Effects of modulation amplitude and frequency on the threshold are analyzed in theory. Experiments at different modulation amplitudes and frequencies are conducted to investigate the variance of the threshold. It iPhase modulation is an effective method to increase the threshold of the stimulated Brillouin scattering. Effects of modulation amplitude and frequency on the threshold are analyzed in theory. Experiments at different modulation amplitudes and frequencies are conducted to investigate the variance of the threshold. It is shown that the threshold increases with not only the modulation amplitude but also the modulation frequency. When the modulation amplitude is 7.7 and the modulation frequency is 25 MHz, the threshold is improved by about 7 dB. When the modulation amplitude is 1.5 and the modulation frequency is as small as 5 MHz, the effect of phase modulation on the threshold is not obvious..
Chinese Journal of Lasers
- Publication Date: Aug. 06, 2021
- Vol. 38, Issue 3, 305002 (2011)
Spectral Characteristics of Dual Amplitude Pulse Position Modulation in Optical Communications
Zhang Tieying, Wang Hongxing, Shi Jianguo, and Wang Qingguan
It is necessary to analyze the power spectral density of modulation mode in optical communications. A detailed derivation of power spectral density of the dual amplitude pulse positiion modulation(DAPPM) scheme is presented and the continuous spectrum and discrete spectrum of DAPPM spectrum are analyzed respectively. NIt is necessary to analyze the power spectral density of modulation mode in optical communications. A detailed derivation of power spectral density of the dual amplitude pulse positiion modulation(DAPPM) scheme is presented and the continuous spectrum and discrete spectrum of DAPPM spectrum are analyzed respectively. Numerical results show that the spectral profile resembles a general sinc envelope shape, which contains direct component. The amplitude coefficient α has nothing to do with shape of continuous spectrum, but the amplitude of continuous spectrum. The amplitude of both components and the location of the slot frequency component largely depend on the modulation level and the pulse duty cycle. The maximum power level of slot frequency components is achieved when pulse duty cycle is 0.5, and decreases linearly at a rate of about 5 dB with the increase of modulation level. It is also shown that the slot frequency is hard to pickup from random DAPPM sequence at large modulation level..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 305001 (2011)
Optimum Design for Optical Modulator in Coherent Optical Orthogonal Frequency-Division Multiplexing System
Hao Yaohong, Li Yuquan, and Wang Rong
Coherent optical orthogonal frequency-division multiplexing (COOFDM) is being considered as a promising technology for future optical transmission. In COOFDM systems, optical Mach–Zehnder modulators (MZM) are used to up-convert orthogonal frequency-division multiplexing (OFDM) signal from radio frequency (RF) domain toCoherent optical orthogonal frequency-division multiplexing (COOFDM) is being considered as a promising technology for future optical transmission. In COOFDM systems, optical Mach–Zehnder modulators (MZM) are used to up-convert orthogonal frequency-division multiplexing (OFDM) signal from radio frequency (RF) domain to optical domain. However, OFDM is very sensitive to nonlinearity, so subsequently study of nonlinearity impact from MZM is of great interest. The impact of COOFDM systems introduced by the nonlinearity of MZM is focused on and a numerical simulation to identify system Q-value under various MZM bias points and modulation index is performed. Results show that in contrast to intensity-modulation/direct-detected system (bias point is quadrature point), optimal modulator bias point is zero point and optimal modulation index is 0 dB for COOFDM system..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 305003 (2011)
Adaptive Cancellation of Background Noise of Fiber Optic Vector Sensor System
Wu Yanqun, Luo Hong, Hu Zhengliang, Xiong Shuidong, and Hu Yongming
Background noise is one of the most important properties for the interferometric fiber optic vector sensor systems, which limits the systems’ application of the detection of the long distance and low frequency targets. To reduce the background noise, a noise suppression scheme based on an adaptive noise canceller is prBackground noise is one of the most important properties for the interferometric fiber optic vector sensor systems, which limits the systems’ application of the detection of the long distance and low frequency targets. To reduce the background noise, a noise suppression scheme based on an adaptive noise canceller is proposed. A pressure insensitive reference fiber optic Michelson interferometer is added as a reference sensor, whose structural parameters are the same as those of the sensing fiber optic interferometers. Then the background noises of the pressure or acceleration signal, which are highly correlated with the reference signal, can be cancelled by the normalized least root mean square error algorithm. The results of a lake trial show that the scheme can effectively reduce both the background noise of the pressure and the accelerometer channels, which can suppress the 50 Hz multiples of the electromagnetic interference by 15～25 dB, and the flat phase noise above 500 Hz by about 3 dB..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 305004 (2011)
Novel Radio over Fiber Frequency Up-Conversion in Millimeter Wave Band
Wang Wenrui, Yu Jinlong, Wu Bo, Han Bingchen, Luo Jun, Guo Jingzhong, Li Bin, Gao Chao, Liu Jia, Yan Ziheng, and Yang Enze
A novel technique to achieve optical frequency up-conversion in millimeter wave (mm) band without any local microwave oscillator is proposed. It is hard to directly get mm band carrier frequency because the efficiency of mode-locking decreases as the carrier frequency increases. Thanks to dynamic charge carrier densityA novel technique to achieve optical frequency up-conversion in millimeter wave (mm) band without any local microwave oscillator is proposed. It is hard to directly get mm band carrier frequency because the efficiency of mode-locking decreases as the carrier frequency increases. Thanks to dynamic charge carrier density responses during the injection locking of Febry-Perot laser diode (FP-LD), the wavelength of the leading part of carrier is red-shifted while that of falling part is blue-shifted. With a suitable negative dispersion device, the carrier pulse is compressed and its 2nd harmonic is greatly enhanced. Thus it is feasible to make the radio over fiber(RoF) frequency up-conversion in mm band. Subcarriers of 13.9 GHz are obtained from 2 Gb/s nonreturn-to-zero(NRZ) signal injection while that of both 13.9 GHz and 15.4 GHz are obtained from 2.5 Gb/s NRZ signal injection into FP-LD. And the 2nd harmonic at 27.8 GHz and 30.8 GHz are enhanced by more than 20 dB, 25 dB and 23 dB, respectively. The simpleness and tunability of the proposed scheme make it a great candidate for low cost mm band RoF frequency upconversion up to 60 GHz..
Chinese Journal of Lasers
- Publication Date: Aug. 12, 2021
- Vol. 38, Issue 3, 305005 (2011)
Remote Sensing and Sensor
Impacts of Random Attitude Measurement Errors on Airborne Laser Scanning Image
Wang Jianjun, Xu Lijun, and Li Xiaolu
The impacts of random attitude measurement errors on the positioning accuracy of laser footprints and digital surface model (DSM) accuracy of airborne lidar are studied. The principle of airborne lidar is analyzed. The transformation formulas between the random attitude measurement errors and the positioning errors of The impacts of random attitude measurement errors on the positioning accuracy of laser footprints and digital surface model (DSM) accuracy of airborne lidar are studied. The principle of airborne lidar is analyzed. The transformation formulas between the random attitude measurement errors and the positioning errors of laser footprints are derived. Three terrains are simulated and the impacts of the random attitude measurement errors on laser point clouds and the corresponding DSM of the three terrains are analyzed. A semi-physical simulation experiment is carried out. The impacts of the random attitude measurement errors on the positioning accuracy of laser footprints and the DSM accuracy are quantitatively evaluated. The simulation and experimental results show that the random attitude measurement errors decrease the accuracy of laser point cloud and DSM. With the parameters used in this research, the horizontal coordinate errors caused by the random attitude measurement errors are about 4～5 times higher of the vertical coordinate error. In addition, when the random attitude measurement errors increase 10 times, the coordinate errors of laser point cloud increase about 10 times, while the error of the DSM increases by about 40 times statistically..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 314001 (2011)
Analysis of Doppler Wind Lidar Detecting Data Based on Fabry-Perot Etalon
Wang Guocheng, Sun Dongsong, Du Hongliang, Shu Zhifeng, Tang Lei, Hu Dongdong, Xu Wenjing, Dong Jihui, and Dou Xiankang
Doppler wind lidar (DWL) is the tool with high accuracy and high temporal and spatial resolution. Wind has been detected with DWL and its data are analyzed. The fundamental of transmission of laser in atmosphere based on aerosol and molecule scattered and principle of Rayleigh Doppler wind lidar discriminating frequencDoppler wind lidar (DWL) is the tool with high accuracy and high temporal and spatial resolution. Wind has been detected with DWL and its data are analyzed. The fundamental of transmission of laser in atmosphere based on aerosol and molecule scattered and principle of Rayleigh Doppler wind lidar discriminating frequency based on Fabry-Perot (FP) etalon, the framework and parameters of the DWL are presented. The results from DWL are compared with wind profile radar (Airdal 6000) and Balloon, in the lower atmosphere its maximum wind speed error is 1.2 m/s and direction error is 9°, its minimum wind speed error is 0.1 m/s, while in the higher atmosphere its maximum wind speed error is 2 m/s and direction error is 12°, its minimum wind speed error is also 0.1 m/s. Experimental results indicate good agreement. The precision of the DWL is analyzed, and the incidence angle, emanative angle, signal noise ratio and parameters of detector are the master factors affecting the precision. From the transmission curve of FP etalon, the actual error of DWL is calculated and it is 2.07% higher than the simulated value..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 314002 (2011)
Study of Fiber Laser Ranging System Using Pseudorandom Modulation and Single Photon Counting Techniques
Yang Fu, He Yan, and Chen Weibiao
A 1550 nm fiber laser ranging experiment system combining pseudorandom modulation technique and single photon counting method is developed. In order to overcome the low detection rate problems of ordinary InGaAs single photon detectors due to restraining after pulses, a discrete amplification photo detector is used as A 1550 nm fiber laser ranging experiment system combining pseudorandom modulation technique and single photon counting method is developed. In order to overcome the low detection rate problems of ordinary InGaAs single photon detectors due to restraining after pulses, a discrete amplification photo detector is used as the single photon detector with a counting rate of 100 MHz in this system. A sensitivity of -83.6 dBm is achieved under room temperature with the detector’s biasing voltage of 53 V and the pseudorandom serial length of 81.91 μs. The system performance is tested under different signal powers and pseudorandom serial lengths. A range accuracy of 12.7 cm is obtained with -78.6 dBm signal average power and 163.83 μs pseudorandom serial length. The system parameters of a spaceborne laser altimeter with this technique are proposed according to the experimental results..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 314003 (2011)
Spectroscopy
Quantative Elemental Analysis Using Laser Induced Breakdown Spectroscopy and Neuro-Genetic Approach
Shen Qinmei, Zhou Weidong, and Li Kexue
A quantitative analysis technique based on laser induced breakdown spectroscopy (LIBS) of neuro-genetic model is proposed. A three-layer back-propagation (BP) artificial neural networks (ANN) is constructed as a basic calibration model for LIBS analysis. The weight and threshold of the ANN are optimized by genetic algoA quantitative analysis technique based on laser induced breakdown spectroscopy (LIBS) of neuro-genetic model is proposed. A three-layer back-propagation (BP) artificial neural networks (ANN) is constructed as a basic calibration model for LIBS analysis. The weight and threshold of the ANN are optimized by genetic algorithm. By combining calibration model with LIBS technique, high precision detection is achieved. The concentrations of Ba and Ni in soil samples are detected by using the given quantitative analysis technique. The mean relative errors are 4.15% and 6.06% respectively, and the correlation coefficients are 0.983 and 0.990 respectively. The presented results demonstrate that the neuro-genetic approach performs better than BP-ANN and conventional calibration method in LIBS quantitative analysis. The analytical results based on neuro-genetic approach in this study are well predicted, which provide a new modeling of high accuracy quantitative elemental analysis for LIBS technique..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 315001 (2011)
Optical Emission Spectral Characteristics of Glass Plasma Induced by Nanosecond Laser Pulse
Gao Xun, Song Xiaowei, Guo Kaimin, Li Haijun, and Lin Jingquan
The time and space resolved optical emission spectroscopy (OES) of optical glass plasma produced by nanosecond laser pulse (wavelength of 355 nm and pulse width of 5 ns) in air are investigated in this paper. Results show that OES is mainly consisted of continuous spectrum at the early stage of plasma expansion (withinThe time and space resolved optical emission spectroscopy (OES) of optical glass plasma produced by nanosecond laser pulse (wavelength of 355 nm and pulse width of 5 ns) in air are investigated in this paper. Results show that OES is mainly consisted of continuous spectrum at the early stage of plasma expansion (within the first 200 ns) and the continuous spectrum weakens gradually while the line spectrum becomes dominating. The spectral intensity decreases when the ablated pulse energy increases more than 35 mJ for the existence of the plasma shielding. The wavelength red-shift of Si I 390.6 nm, which has a second order exponential decay with delay time, has been found based on the time-resolved emission spectroscopy..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 38, Issue 3, 315002 (2011)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20