Journals >Chinese Journal of Lasers
Contents
2007
Volume: 34 Issue 1
26 Article(s)
Export citation format
Research Article
Investigation of Spectral Bandwidth of BBO Ⅰ Phase Matching Noncollinear Broadband Optical Parametric Amplification from Visible to Near-Infrared
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laser sources that are high power, short time duration and broadly tunable are needed for the application of ultra-fast laser. Femtosecond optical parametric amplification is one of the important techniques to produce broadly tunable and several femtoseconds pulse. To produce extremely short laser pulse, the femtoseconLaser sources that are high power, short time duration and broadly tunable are needed for the application of ultra-fast laser. Femtosecond optical parametric amplification is one of the important techniques to produce broadly tunable and several femtoseconds pulse. To produce extremely short laser pulse, the femtosecond optical parametric amplification should support large spectral bandwidth enough. The ultra-broadband optical parametric amplification of BBO type-Ⅰ phase matching is theoretically investigated. The achromatic phase matching technology is introduced in femtosecond optical parametric amplification, and broadband phase matching condition with angular dispersion of signal beam is given. The effects of noncollinear angle and angular dispersion of signal pulse on the phase mismatching and parametric bandwidth are also discussed. The results indicate that a suitable noncollinear angle of signal pulse and introducing suitable angular dispersion in near-infrared signal pulse can increase the parametric bandwidth dramatically. As an example, phase-matched noncollinear optical parametric amplifiers (NOPAs) pumped by the blue light of 400 nm are discussed. The method and the analysis results provide a theoretical guidance for obtaining broadband parametric amplifiers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 21 (2007)
High Efficiency and High Power All-Solid-State Ultraviolet Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A high power end-pumped Nd:YVO4 all-solid-state ultraviolet (UV) laser was demonstrated under acousto-optic Q-switched operation, using type Ⅰ phase-matched LiB3O5 (LBO) as second harmonic generation (SHG) crystal and type Ⅱ phase-matched LBO as third harmonic generation (THG) crystal. To improve the optical to opticalA high power end-pumped Nd:YVO4 all-solid-state ultraviolet (UV) laser was demonstrated under acousto-optic Q-switched operation, using type Ⅰ phase-matched LiB3O5 (LBO) as second harmonic generation (SHG) crystal and type Ⅱ phase-matched LBO as third harmonic generation (THG) crystal. To improve the optical to optical (O-O) efficiency of fundamental wave to THG UV laser, a concave reflection mirror is used to focus the laser into THG LBO crystal, which avoids the chromatic aberration of traditional focusing lens effectively. Finally, the output power of 355 nm UV laser reaches to 1.86 W at the incident pump power of 23.3 W, and the output power of fundamental wave is about 7.28 W at 20 kHz repetition rate, and O-O conversion efficiency is about 25.5% accordingly. The test results of UV laser beam quality indicate that the laser can still work at a good beam quality even at the maximum output, which means that the UV laser can have a very good beam quality even at the high power output..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 29 (2007)
Construction of the Tunable Diode Laser Based on Littrow Configuration
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Because of the large linewidth, dither and drift , the commercial diode laser cannot meet the requirement of the experiments of laser cooling and elaborating measurement of a single calcium ion trapped in an ion trap. In this paper, a tunable Littrow-configuration external cavity diode laser (ECDL) is constructed. The Because of the large linewidth, dither and drift , the commercial diode laser cannot meet the requirement of the experiments of laser cooling and elaborating measurement of a single calcium ion trapped in an ion trap. In this paper, a tunable Littrow-configuration external cavity diode laser (ECDL) is constructed. The free spectral range of the laser cavity is 1.5 GHz. By adjusting the angle of the grating, wavelength of the laser can be adjusted from 775 nm to 785 nm. Linewidth of the laser is less than 2.5 MHz, dithering of the laser is about 3～4 MHz, and drift of the laser is about 50 MHz within 30 minutes. These indexes are better than those commercial DL100 lasers. The laser is the base that will construct the next 397 nm and 866 nm lasers for laser cooling and elaborating measurement of a single calcium..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 33 (2007)
1.5 kW Laser Diode-Pumped Nd:YAG Disk Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A laser diode (LD)-pumped Nd:YAG double-disk laser with an average output power of more than 1.5 kW is reported in this paper. A nearly flat top pump profile is achieved with a good design for the four-pass optical coupling system. The disk is coated with Ti, Pt and Au at the back side of the disk which is high-reflectA laser diode (LD)-pumped Nd:YAG double-disk laser with an average output power of more than 1.5 kW is reported in this paper. A nearly flat top pump profile is achieved with a good design for the four-pass optical coupling system. The disk is coated with Ti, Pt and Au at the back side of the disk which is high-reflectively (HR) coated for the wavelength of the pump and laser radiation, then is welded to the Cu-micro-channel cooler by indium-welding technology. An average output power of 1.52 kW is obtained from two disks with a diameter of 40 mm and a thickness of 1.3 mm. The pumping peak power on each disk is 17.7 kW with duty cycle of 10%. The optical efficiency of the laser system is about 43% and the electrical to optical efficiency is more than 20%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 37 (2007)
Laser Diode-Pumped Nd:YVO4/YVO4Composite Crystal Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The optical properties of Nd:YVO4/YVO4 composite crystal and Nd:YVO4 single crystal were studied contrastedly in the high power laser diode-pumped solid-state lasers. It was demonstrated that the composite crystal can effectively reduce the temperature gradient of crystal, relieve the thermal lens effect and get higherThe optical properties of Nd:YVO4/YVO4 composite crystal and Nd:YVO4 single crystal were studied contrastedly in the high power laser diode-pumped solid-state lasers. It was demonstrated that the composite crystal can effectively reduce the temperature gradient of crystal, relieve the thermal lens effect and get higher output power. The frequency-doubling property of Nd:YVO4/YVO4 composite crystal with KTP was studied in a “Z-shaped” folded cavity. With the incident pump power of 17 W, 6.23 W green light was achieved with an optical conversion efficiency of 37%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 41 (2007)
Thermal Distortion Influence on Single-Slab Heat Capacity Laser Output
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Experimental and theoretical studies of a laser diode (LD) array pumped solid-state heat capacity laser (SSHCL) were reported. The thermal lens effect of heat capacity slab Nd:YAG laser under side pumped condition was calculated, and the influence of the thermal lens effect on the output energy fluctuation of the SSHCLExperimental and theoretical studies of a laser diode (LD) array pumped solid-state heat capacity laser (SSHCL) were reported. The thermal lens effect of heat capacity slab Nd:YAG laser under side pumped condition was calculated, and the influence of the thermal lens effect on the output energy fluctuation of the SSHCL was studied. In experiment, slab crystal size is 57 mm×40 mm×4 mm, peak pumped power of the LD array is 12 kW with 1 kHz repetitive frequency and 20% duty ratio. In order to obtain high laser gain, the pump beams were focused as small as 15 mm×57 mm spot in profile. In the experimental examination, the output of single pulse energy was 1 J at the beginning, after 1 s operation it fell down to 50%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 45 (2007)
Laser Manufacturing
Investigation and Applications of Fiber Laser Precision Cutting System
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A fiber laser precision cutting system was designed with allodial optics system and control software. The cutting system has many advantages such as high precision, high cutting speed, good stabilization and so on. With this system, the cutting experiments of stainless steel mobile telephone panel and leaking stannum bA fiber laser precision cutting system was designed with allodial optics system and control software. The cutting system has many advantages such as high precision, high cutting speed, good stabilization and so on. With this system, the cutting experiments of stainless steel mobile telephone panel and leaking stannum board have been carried. The results indicate that there are many good characteristics, such as smoothness, uniformity, without residue and so on, through optimizing output power, frequency, pulse width, and assistant air pressure..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 135 (2007)
Determination of the Laser Supported Detonation Wave Ignition Threshold from Impulse Coupling between Laser and Target
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The ignition threshold of laser supported detonation wave (LSDW) can be determined based on the component variation of plasma in the laser absorption zone with laser power density. A kinetic pendulum equation is presented for being adopted in the experiment of impulse coupling between laser supported detonation wave anThe ignition threshold of laser supported detonation wave (LSDW) can be determined based on the component variation of plasma in the laser absorption zone with laser power density. A kinetic pendulum equation is presented for being adopted in the experiment of impulse coupling between laser supported detonation wave and aluminum target. Then considering the Jouguet relation between impulse and specific heat ratio of medium in the laser absorption zone (plasma and gas), the relation between specific heat ratio and laser power density can be obtained for analyzing the result of two-dimensional hydrodynamic simulation. The specific heat ratio decreases while laser power density increasing. Finally, considering the difference between plasma and gas, the component of plasma and gas can be determined. The laser supported detonation ignition threshold is calculated in the space interval from (1.62±0.01)×108 W/cm2 to (2.10±0.07)×108 W/cm2. By comparing to the ignition threshold determined by the impulse-coupling coefficient, there is an ideal concordance in these two ways..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 139 (2007)
Laser Physics
Single Longitudinal Mode Fiber Laser with Multiple Ring Cavities and Its Frequency Stabilization
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A single longitudinal mode(SLM) erbium-doped fiber laser (EDFL) with multiple ring cavities (MRCs) is proposed and experimentally demonstrated. The EDFL is structured by insertion of three different short passive subring cavities, which serve as mode filters, into the main cavity, and it is combined with a fiber Bragg A single longitudinal mode(SLM) erbium-doped fiber laser (EDFL) with multiple ring cavities (MRCs) is proposed and experimentally demonstrated. The EDFL is structured by insertion of three different short passive subring cavities, which serve as mode filters, into the main cavity, and it is combined with a fiber Bragg grating (FBG), the MRCs resonator can make SLM lasing. The resonant theory of MRCs for SLM operation is discussed. At the same time, in order to stabilize, the frequency of output laser, external light injection techniques are employed to effectively suppress the mode jump and beat noise. Output power of 3.6 dBm and signal-noise-ratio (SNR) larger than 35 dB at 1550.225 nm, and linewidth less than 500 Hz are achieved for this laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 50 (2007)
Chaos Synchronization in Polarization Selective Mutually Coupled Semiconductor Lasers
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Systems of mutually coupled semiconductor lasers are widely used in optical chaos communication, spread spectrum communications and high power emissions. The chaos pass filtering effect and synchronization behaviors of mutually coupled semiconductor lasers are studied numerically in this paper. Single-mode rate equatioSystems of mutually coupled semiconductor lasers are widely used in optical chaos communication, spread spectrum communications and high power emissions. The chaos pass filtering effect and synchronization behaviors of mutually coupled semiconductor lasers are studied numerically in this paper. Single-mode rate equations are extended to two polarization modes. By selecting X-polarized mode for mutually coupling, not only chaotic dynamics and synchronization are obtained, but also Y-polarized modes are totally restrained, so pure polarization mode synchronization is realized. A frequency detuning is introduced to keep the first laser as a leader. Simulation results show that outputs of the leader and laggard lasers exhibit high frequency fluctuations in company with symmetry breaking and they are synchronous with a lag equal to the external delay. The system shows similar chaos pass filtering effect to unidirectionally coupled semiconductor lasers when the leader is modulated, while chaos pass filtering is bad when the laggard is modulated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 55 (2007)
Radiation of the Motion of an Electron in the Multilayer Film Wiggler
[in Chinese], and [in Chinese]
A novel free electron laser with multilayer film wiggler is reported, and the spontaneous radiation of the motion of an electron in the multilayer film wiggler has been discussed by using virtual photon and Compton scattering method. Antiferromagnetic coupling in ferromagnetic-nonmagnetic (such as (Fe/Cr)N) multilayersA novel free electron laser with multilayer film wiggler is reported, and the spontaneous radiation of the motion of an electron in the multilayer film wiggler has been discussed by using virtual photon and Compton scattering method. Antiferromagnetic coupling in ferromagnetic-nonmagnetic (such as (Fe/Cr)N) multilayers has been observed in experiments. Therefore the wiggler can be made of magnetic multilayers (MLs). Considering the space cycle of magnetostatic field is only 7.8 nm, the precise wavelength calculation and the precise radiating power calculation should consider the reaction propulsion of electron. The precise computing formulas of wavelength and radiating power are investigated, the results show that the formulas of both wavelength and radiating power include Compton wavelength..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 61 (2007)
Materials and Thin Films
Structure and Optical Property Changes of Heat Induced NiOxThin Films
[in Chinese], [in Chinese], and [in Chinese]
The NiOx thin films were deposited by reactive direct current (DC) magnetron sputtering from a nickel metallic target in Ar + O2 mixed gases with the relative O2 content 5%. The effects of heat treatment on the microstructure and optical properties of NiOx thin films were studied by X-ray diffraction (XRD), scanning elThe NiOx thin films were deposited by reactive direct current (DC) magnetron sputtering from a nickel metallic target in Ar + O2 mixed gases with the relative O2 content 5%. The effects of heat treatment on the microstructure and optical properties of NiOx thin films were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), atom force microscopy (AFM) and spectrometer respectively. In addition, the powders of the as-deposited NiOx thin films were investigated by thermal analysis. The results showed that the decomposition temperature of the as-deposited NiOx thin films was at about 262 ℃. After annealed at 400 ℃ for 30 min in air, the reflectivity decreased and transmittance increased obviously. XRD and differential scanning calorimetry (DSC) analysis show that no phase transformation occured during the heating process, the changes of optical properties were related to the decomposition of NiOx thin films. The activation energy of decomposition of NiOx thin films was 230.46 kJ/mol calculated by Kissinger formula, and the NiOx thin films have an excellent thermal stability. Its thermal stability and high optical contrast at 405 nm before and after annealing made it a good potential optical storage medium in write-once blue-ray disc..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 125 (2007)
Laser Induced Thermoelectric Voltage of Atomic Layer Thermopile Materials
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laser induced thermoelectric voltage (LITV) signals from thin films of La1-xSrxMnO3 (LSMO), La1-xPbxMnO3 (LPMO) and La1-xSrxCoO3 (LSCO) were measured at different wavelengths. The three thin films grown on vicinal cut LaAlO3 single crystal substrate were prepared by pulsed laser deposition (PLD). Computer controlled syLaser induced thermoelectric voltage (LITV) signals from thin films of La1-xSrxMnO3 (LSMO), La1-xPbxMnO3 (LPMO) and La1-xSrxCoO3 (LSCO) were measured at different wavelengths. The three thin films grown on vicinal cut LaAlO3 single crystal substrate were prepared by pulsed laser deposition (PLD). Computer controlled system with lock-in amplifier was used to measured LITV signal. It was found that sensitivity and time response were different at different wavelengths. At wavelengths of 532 nm and 632.8 nm, the sensitivity of LSMO was the largest and that of LSCO was the smallest, but the time response of LSMO and LSCO was opposite. However, the LPMO has the largest sensitivity at wavelength of 808 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 130 (2007)
Measurement and Metrology
Defect Measurement Based on Rotating Aperture-Stroboscopic Speckle Interferometry
[in Chinese]
A new method of the defect measurement is proposed by use of rotating aperture-stroboscopic speckle interferometry. The advantage of this method is that it is a non-contact measurement, not affected by form or place of the defect, and can accurately measure the size and form of the defect. Principle of rotating aperturA new method of the defect measurement is proposed by use of rotating aperture-stroboscopic speckle interferometry. The advantage of this method is that it is a non-contact measurement, not affected by form or place of the defect, and can accurately measure the size and form of the defect. Principle of rotating aperture-stroboscopic speckle interferometry and its application in defect detect and measurement are proposed. By using the method, defect and its size can be easily detected and measured in spite of the shape and position. The analytic formulas of average intensity of light and experimental result are given．Both theoretical analysis and experimental result show that a single specklegram can accommodate adequate information to replay the whole dynamic process of an object. During the process of replaying dynamic object, the position of defect doesnot change with the strip of speckle photograph by use of rotating filter aperture..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 78 (2007)
Measurement of Concentration Change Distribution Based on Theory of Interference and Image Processing Methods
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Digital holographic interferometry was used to measure concentration change distribution of the solution at the interface of electrode/solution during electrochemical reactions. In experiment, the first 1.6 s of the activation processes of potentiostatic current oscillation on iron in 0.5 mol/dm3 H2SO4 solution was stuDigital holographic interferometry was used to measure concentration change distribution of the solution at the interface of electrode/solution during electrochemical reactions. In experiment, the first 1.6 s of the activation processes of potentiostatic current oscillation on iron in 0.5 mol/dm3 H2SO4 solution was studied. With the introduction of carrier fringes in digital holographic interferometry, Fourier analysis method was used to analyze interference patterns and calculate their dynamic changes conveniently. The phase difference of object wave front, which was caused by the change of the solution′s concentration during the electrochemical reaction, was calculated from interference patterns to reflect the concentration change distribution. The obtained results have shown that the maximum phase difference caused by the concentration change of the solution was 41.2 rad and the corresponding change of solution′s refractive index was 0.0021 while the electrochemical reaction was at 1.6 s. The reconstructed images, which were distribution of the phase difference of object wave front, reflected the changes such as concentration distribution, diffusion layer, etc.. It provided a new method to detect and analyze dynamic concentration changes..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 82 (2007)
Data Processing Method for the Division-of-Amplitude Photopolarimeter Based on an Artificial Neural Network
[in Chinese], and [in Chinese]
The division-of-amplitude photopolarimeter (DOAP) is a sensor that can rapidly determine the polarization state of the incident light. A data processing method for the DOAP based on an artificial neural network (ANN) was presented. A multilayer feedforward neural network model was set up whose inputs are the electricalThe division-of-amplitude photopolarimeter (DOAP) is a sensor that can rapidly determine the polarization state of the incident light. A data processing method for the DOAP based on an artificial neural network (ANN) was presented. A multilayer feedforward neural network model was set up whose inputs are the electrical signals produced by an electronics system of the DOAP, and outputs are the Stokes parameters of the incident light. The mapping relationships between the electrical signals and the Stokes parameters can be determined by training the neural network. After the electrical signals were measured, the Stokes parameters of the incident light can be calculated via the neural network which has been trained. The total root-mean-square deviation of Stokes parameters is 1.9%.The testing results show that the data processing method based on the neural network is slightly better than that based on the matrix operation on the aspects of measuring precision..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 89 (2007)
Optical Design of Double Grating Monochromator of a Pure Rotational Raman-Lidar
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The double grating monochromator for a pure rotational Raman-lidar can provide for better than 10-7 suppression of the spectral line due to unshifted Mie+Rayleigh scattering, obtain high-purity rotational Raman spectrum, and improve transmission and stability of the optical system. The complexly structure of the doubleThe double grating monochromator for a pure rotational Raman-lidar can provide for better than 10-7 suppression of the spectral line due to unshifted Mie+Rayleigh scattering, obtain high-purity rotational Raman spectrum, and improve transmission and stability of the optical system. The complexly structure of the double grating monochromator is always difficulty to Raman-lidar. Two optical paths of grating are compared and a conclusion can be drawn that the structure of beam path of grating of symmetrical arrange of optical fibre is better in grating efficiency than the structure of beam path of grating of linear arrange of optical fiber. Then a formula about relative of range of diffractive angle and order of grating is obtained through grating equation and rotational Raman equation. When grating constant is 600 line/mm, the fifth order of grating is optimal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 94 (2007)
Analysis on an Improved Fourier Transform Profilometry
[in Chinese], [in Chinese], and [in Chinese]
In order to obtain the correct height reconstruction of a measured object through the traditional Fourier transform profilometry (FTP), the connecting-line between the exit pupil of the projecting lens and the entrance pupil of the imaging lens must be horizontal and set to parallel to the reference plane. Here an imprIn order to obtain the correct height reconstruction of a measured object through the traditional Fourier transform profilometry (FTP), the connecting-line between the exit pupil of the projecting lens and the entrance pupil of the imaging lens must be horizontal and set to parallel to the reference plane. Here an improved optical geometry of FTP is discussed, and a strict theoretical analysis about an improved phase-height mapping formula based on a new description of a reference fringe and a deformed fringe in FTP is proposed in this paper when the location of the exit pupil of the projecting lens and that of the entrance pupil of the imaging lens do not meet the conditions. Employing the new theory, it is easier to obtain the full-field fringe through adjusting either the location of the projector or imaging device. Especially, in some cases, i.e., the connecting-line of the two pupils cannot be set parallel to the reference plane and the requived conditions that the projecting and imaging axes must be horizontal cannot be met, the new method offers a flexible way to obtain the reliable height distribution of a measured object. Computer simulations and experiments have proved its correctness..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 99 (2007)
A J0-J1Method for Measurement of Dynamic Phase Changes in an Interferometric Fiber Sensor
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A J0-J1 method for measurement of dynamic phase changes in an interferometric optical fiber sensor is described. This method has the advantages of no electric elements in the sensing head and the simplicity of signal processing. The detection principle of this method is introduced in details. The demodulation error is A J0-J1 method for measurement of dynamic phase changes in an interferometric optical fiber sensor is described. This method has the advantages of no electric elements in the sensing head and the simplicity of signal processing. The detection principle of this method is introduced in details. The demodulation error is analyzed and simulated theoretically. The measurable amplitude of the dynamic phase change and the permitted varying range of the work-point restrict each other. A system of data acquisition and processing is programmed, and an interferometric fiber-optic hydrophone is tested. The average acoustic pressure sensitivity is -162 dB (0 dB=1 rad/μPa) over the frequency range of 20 Hz to 1300 Hz, the fluctuation is smaller than ±1.0 dB, and the change at 500 Hz is smaller than ±0.5 dB, which accords well with the results obtained with the method of phase generated carrier (PGC) modulation and demodulation. The experimental results prove that this J0-J1 method is feasible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 105 (2007)
Fluid Refractive-Index Sensor Base on Return Strength from Fiber End
[in Chinese], [in Chinese], and [in Chinese]
A new refractive index fiber sensor with simple operation, low cost and high sensitivity has been explored. The new refractive index fiber sensor is based on the principle of return strength modulation. A laser diode module and two optical power meters are used as the light source and photo-detectors, respectively. TheA new refractive index fiber sensor with simple operation, low cost and high sensitivity has been explored. The new refractive index fiber sensor is based on the principle of return strength modulation. A laser diode module and two optical power meters are used as the light source and photo-detectors, respectively. The relationship between relative return strength and refractive index is derived from the mechanism that the return loss from the end reflection interface of an optical fiber varies with the refractive index of the material contacted with the fiber. The relative return strength technology can improve measuring accuracy effectively and eliminate the measuring error resulted from the instability and internal loss of the instrument, as well as environmental effect. The sensitivity analysis of the sensor shows that the resolution of refractive index is 2×10-4 index-unit, with measurement precision of 0.01 dBm. It is found that the experimental data agree well with the theory values, and the relative error is smaller than 5% within the refractive index ranging from 1.30 to 1.45..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 109 (2007)
Dynamic Torque Measurement Technique Using Laser Doppler Effect and Two-Section Speed Fluctuation
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on laser Doppler effect and principle of rotational dynamics, a novel approach to dynamic torque measurement is proposed. Mathematical model of measurement method is deduced. Four highly coherent laser beams irradiate four points of two sections of rotating shaft by designed optical measurement system. BackscatteBased on laser Doppler effect and principle of rotational dynamics, a novel approach to dynamic torque measurement is proposed. Mathematical model of measurement method is deduced. Four highly coherent laser beams irradiate four points of two sections of rotating shaft by designed optical measurement system. Backscattered lights with Doppler frequency shift are mixed onto the surface of photo-detectors, heterodyning takes place, and the output current is modulated. The photocurrent frequency difference is proportional to rotational velocity. Speed fluctuation values of rotating shaft segment and relative speed fluctuation values of between sections are obtained directly by measuring instantaneous rotational velocity of double sections in two successive times, and then dynamic torque values are obtained. Experimental results indicate that the identification values of dynamic torque are improved 5%～10%, which reflects the dynamic characteristic of torque fluctuation. Compared to conventional measurement approaches, this approach can promote the dynamic measurement range, and is more real-time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 113 (2007)
Sub-Pixel Measurement Accuracy Experiment of Complementary Metal Oxide Semiconductor Imager
[in Chinese], [in Chinese], and [in Chinese]
The sub-pixel measurement technique based on image processing technique and software design technique, is a good choice for the improving of measurement precision. The measuring technique and results of sub-pixel measurement accuracy of complementary metal oxide semiconductor (CMOS) imager are researched in this paper The sub-pixel measurement technique based on image processing technique and software design technique, is a good choice for the improving of measurement precision. The measuring technique and results of sub-pixel measurement accuracy of complementary metal oxide semiconductor (CMOS) imager are researched in this paper in order to give references for correlative systems. A test system based on high precision piezoelectric translator (PZT) fast-steening mirror (FSM) and OV7620 CMOS imager based digital camera is constructed, several sub-pixel measurement accuracy experiments for the CMOS imager are taken. The results indicate that sub-pixel measurement accuracy is about 0.17 pixel, it is of great importance to consider the influence of the fill-factor on sub-pixel measurement accuracy. According to the results above, CMOS imager has the capability to achieve sub-pixel measurement accuracy, and can be widely used in many measuring systems which count on facula centroid sub-pixel interpolation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 118 (2007)
Optical Communication
Influence of Dispersion Compensation Schemes on Phase Noise of Phase Modulation Systems
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The formulas for calculating nonlinear phase noise are proposed for both dispersion pre-compensation and post-compensation schemes. Based on these formulas, the phase noise, power tolerance and optimal signal peak power of both dispersion compensation schemes are analyzed and discussed in detail, respectively. ComparedThe formulas for calculating nonlinear phase noise are proposed for both dispersion pre-compensation and post-compensation schemes. Based on these formulas, the phase noise, power tolerance and optimal signal peak power of both dispersion compensation schemes are analyzed and discussed in detail, respectively. Compared with the post-compensation scheme, pre-compensation scheme is more effective in reducing the nonlinear phase noise. Its suppression ability is improved with signal energy, amplified spontaneous emission (ASE) power spectral density and transmission distance increasing. The pre-compensation system possesses higher power tolerance than post-compensation system, and the optimal signal power is increased when dispersion is taken into account, which results in the optimal phase shift greater than 1 rad. And the optimal signal power for pre-compensation system is larger than post-compensation system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 64 (2007)
Size Selection of Dispersive Spot Imaging on CCD in a Satellite Optical Communication Terminal
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The propagating laser in free space was imaged by charge coupled device (CCD), so the incidence beam angles information can be obtained for the transmitting laser beam control. In satellite optical communications, improving the real-time measure precision for the angle errors of the incoming beam, higher tracking perfoThe propagating laser in free space was imaged by charge coupled device (CCD), so the incidence beam angles information can be obtained for the transmitting laser beam control. In satellite optical communications, improving the real-time measure precision for the angle errors of the incoming beam, higher tracking performance of a terminal can be reached and the laser link can be maintained steadily. The principium of the beam angle errors measurement was analyzed, and a model was founded for the angle errors measurement capability evaluation of the tracking assembly in satellite optical communications. The relationship of angle errors measurement precision with the size of dispersive spot imaging on CCD was analyzed using the model, and then some experiments were implemented to validate the results. It showed that considering the requirement for angle measurement precision and condition of the terminal power limitation, the relative size of the spot imaging on CCD should be between 2 and 3 in the design of a satellite optical communication system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 69 (2007)
Signal Shaping Based on Phase Pre-Modulation in Fiber Transmission Systems
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Phase pre-modulation is investigated to overcome the impacts of sensitivity reduction and chromatic dispersion in high-speed and long-distance fiber transmission systems. The bit-synchronous phase pre-modulation imposed on non-return-to-zero (NRZ) signals at the transmitter can reshape the NRZ pulse to return-to-zero (Phase pre-modulation is investigated to overcome the impacts of sensitivity reduction and chromatic dispersion in high-speed and long-distance fiber transmission systems. The bit-synchronous phase pre-modulation imposed on non-return-to-zero (NRZ) signals at the transmitter can reshape the NRZ pulse to return-to-zero (RZ) waveform and hence improve the eye opening. Experiments are performed to measure the spectra, eye diagrams and power penalties of conventional NRZ signals and phase-pre-modulated NRZ signals under different modulation depth and dispersion. Results of 10 Gb/s transmission show that the phase-pre-modulated NRZ signals have a power penalty lower than 1 dB with the absolute value of link dispersion less than 1000 ps/nm, exhibiting higher sensitivity and lower dispersion-induced penalty than conventional NRZ signals. This modulation scheme relaxes the requirements to optical signal-to-noise ratio and dispersion management, extends the transmission distance and is easy to implement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 74 (2007)
Reviews
Laser Communications in Space Ⅰ Optical Link and Terminal Technology
[in Chinese]
The free-space laser communications are of potential applications in the space, the satellite lasercom terminals have reached a level of high data rate, compact and light construction, and low-power consumption in the world. This paper reviews the international progresses on the satellite lasercom, discusses the relateThe free-space laser communications are of potential applications in the space, the satellite lasercom terminals have reached a level of high data rate, compact and light construction, and low-power consumption in the world. This paper reviews the international progresses on the satellite lasercom, discusses the related key techniques, and gives the suggestions for the design of overall scheme. In the next paper, the test and verification techniques on the ground for satellite lasercom terminals will be introduced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 1, 3 (2007)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20