Journals >Chinese Journal of Lasers
Contents
2005
Volume: 32 Issue 6
30 Article(s)
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Research Article
Studies on the Optical Properties of Planar Intersect Microlens Arrays
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In the paper, ion-exchange technique fabrication method of planar intersect microlens arrays is given. Using ray equations in integral form, paraxial optical properties of microlens arrays are studies. The ray trajectory equation and imaging of microlens arrays are presented. Mathematics expressions of images distance,In the paper, ion-exchange technique fabrication method of planar intersect microlens arrays is given. Using ray equations in integral form, paraxial optical properties of microlens arrays are studies. The ray trajectory equation and imaging of microlens arrays are presented. Mathematics expressions of images distance, focal length, image height lateral magnification and plane by ABCD law are obtain. Theoretical calculated results of focusing length are in good agreement with the experimental date..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 743 (2005)
Study on Adjusting Accuracy in the Femtosecond Chirp-Pulse Amplification System
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Using the model of grating pair compressor with negative dispersion, the formulae of dispersion errors for the femtosecond chirped-pulse amplification system are presented. The relationship of the adjusting accuracy in the stretcher/compressor versus the distance, incidence angle, and density of the grating pair is disUsing the model of grating pair compressor with negative dispersion, the formulae of dispersion errors for the femtosecond chirped-pulse amplification system are presented. The relationship of the adjusting accuracy in the stretcher/compressor versus the distance, incidence angle, and density of the grating pair is discussed theoretically. The demand of adjusting accuracy for different width of input pulse is also studied. The grating incidence angle and the grating density must be selected properly to satisfy the requirement of the system and at the same time decrease the adjusting accuracy. The highest precision is offered to the grating incident angle in the system. The higher alignment sensitivity is needed for the shorter pulse duration. The mutual compensating among varied order dispersion should be considered to optimize whole system, allowing the decrease of the adjusting accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 749 (2005)
Passively Q-Switched Laser Operation of Composite Cr4+∶YAG-Nd3+∶YAG Crystal Fiber
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Monolithic composite Cr4+∶YAG-Nd3+∶YAG crystal fiber was grown by means of laser heated pedestal growth (LHPG) method. Preliminary results showed that the crystal fiber is well suited to a compact passively Q-switched laser operation. The output beam characteristics were observed with two kinds of cavity configuration Monolithic composite Cr4+∶YAG-Nd3+∶YAG crystal fiber was grown by means of laser heated pedestal growth (LHPG) method. Preliminary results showed that the crystal fiber is well suited to a compact passively Q-switched laser operation. The output beam characteristics were observed with two kinds of cavity configuration with different output couplers. A Q-switched laser output with 9 ns pulse duration, 19 mW maximum average power and 10 kHz repetition rate was achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 754 (2005)
Experimental Research on Watts Double Clad Fiber Superfluorescent Source
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The experimental results using two different configuration on high-power Yb-doped double-cladding fiber superfluorescent source (SFS) pumped by 975 nm laser diode are reported. In single-pass forward (SPF) and single-pass backward (SPB) design, the maximum superfluorescent output power is 1.46W and 1.82W, while the sloThe experimental results using two different configuration on high-power Yb-doped double-cladding fiber superfluorescent source (SFS) pumped by 975 nm laser diode are reported. In single-pass forward (SPF) and single-pass backward (SPB) design, the maximum superfluorescent output power is 1.46W and 1.82W, while the slope efficiency is 23.4% and 29.2% respectively. In double-pass forward (DPF) configuration using the dichroic mirror as the front cavity mirror, the maximum superfluorescent output power is 2.12 W with the slope efficiency of 43.2%. And central wavelength of superfluorescent spectrum is 1070 nm, the flatness of output SFS spectrum is greatly improved with the 3 dB bandwidth from 11 nm to 42 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 757 (2005)
Investigation on Properties of Reflection Phase Retarder
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
When incoming light beams enter dielectric reflective mirror with certain incident angle, there is phase shift between the p-polarization and s-polarization. Based on optimizing design, when light is incident at 45 degree, the phase shift of 270°±0.15° is got in the range of 1285～1345nm, at the same timeWhen incoming light beams enter dielectric reflective mirror with certain incident angle, there is phase shift between the p-polarization and s-polarization. Based on optimizing design, when light is incident at 45 degree, the phase shift of 270°±0.15° is got in the range of 1285～1345nm, at the same time, the reflectivity of dielectric mirror maintains over 99.5%. The phase retarder was prepared with dual ion beam sputter system and then annealed at different temperatures in atmosphere, the spectrum and the phase of the sample were gained by spectrometer and the Fourier transform infrared spectroscopic ellipsomter, respectively. The results revealed that the as-deposited samples gained phase shift of 267.5°±0.5° and the reflectivity reached over 99.6%. It was found from the fitting analysis that the error of the outermost layer and deviation between refractive index and designed values play principal roles in decrease of phase shift, in addition, with the annealing temperature increasing, the refractive index of film decreases and physical thickness increases so that phase shift drops off..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 761 (2005)
Multi-Level Power Laser Writing Control Method for Multi-Level Mastering System
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A multi-level power laser writing control method based on industry standard architecture (ISA) bus interface and complex programmable logic device (CPLD) technique for multi-level mastering system is described in this paper. And the control circuit has been designed. It communicates with computer with ISA interface, usA multi-level power laser writing control method based on industry standard architecture (ISA) bus interface and complex programmable logic device (CPLD) technique for multi-level mastering system is described in this paper. And the control circuit has been designed. It communicates with computer with ISA interface, uses CPLD as processor, and controls the laser power by power feed back with photoelectric detector. It can control the writing power and writing time simultaneously, then the photo-sensitive material doped on the master disc can be exposed with several kinds of level power, at the same time, the writing time of the laser can be adjusted by pulse modulation, thus multi-level mastering is achieved. It has been applied in multi-level mastering system, which has a good compatibility to the different types of laser diodes. The experiment result shows that the control circuit can realize eight-level laser writing at least with the writing time adjusted (minimal 125 ns), and 8-level signal with higher stability (instability <1%) is achieved in photochromism material disc..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 765 (2005)
Comparison of the Back Laser Rader Cross-Section Calculation of Complex Object with the Measurement of Scale-model
[in Chinese], [in Chinese], and [in Chinese]
In this paper the difference of radar cross-section between laser′s band and electromagnetic band is described. A flow chart of calculating laser radar cross-section (LRCS) of complex object with visualizing calculation method is presented, the LRCS of a full-size plane object is calculated, and the LRCS of 1∶8 scale-mIn this paper the difference of radar cross-section between laser′s band and electromagnetic band is described. A flow chart of calculating laser radar cross-section (LRCS) of complex object with visualizing calculation method is presented, the LRCS of a full-size plane object is calculated, and the LRCS of 1∶8 scale-model is obtained by scale relation. Actual measurements were made for obtaining the LRCS of the scale-model by utilizing standard scatter board in the outfield. The results show that the calculation data are agreement with measurements on main scatter direction of object and the scattering characteristic of full size object can be achieved by scale-model measurement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 770 (2005)
Demodulation System for Fiber Bragg Grating Sensors Based on a Real-Time Calibration Technique
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
This paper reports a digital demodulation scheme for interrogating fiber Bragg grating (FBG) sensors based on a real-time calibration technique. The system controls a tunable fiber Fabry-Perot filter (TFFP) with sawtooth wave voltage and synchronous signal of its digital phase to interrogate FBG sensors in a single fibThis paper reports a digital demodulation scheme for interrogating fiber Bragg grating (FBG) sensors based on a real-time calibration technique. The system controls a tunable fiber Fabry-Perot filter (TFFP) with sawtooth wave voltage and synchronous signal of its digital phase to interrogate FBG sensors in a single fiber. Meantime, a reference FBG and a digital thermometer provide an accurate reference wavelength, which is used to calibrate the wavelength readout of the TFFP in real-time by a digital signal processor (DSP). This method eliminates the measurement error induced by temperature drift, nonlinearity and creepage of TFFP. The result demonstrates that this experimental system has scanning range of 1520～1570 nm, scanning frequency of 100 Hz, measured wavelength resolution of 5 pm, and measured strain resolution of 4.13 με..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 825 (2005)
Beam Transmission
Intracavity Continuous-Wave Optical Parametric Oscillator: Gaussian Beam Theory
[in Chinese], [in Chinese], and [in Chinese]
The Gaussian beam theory has been developed to describe the power characteristics of intracavity continuous-wave singly resonant optical parametric oscillator (ICCWSRO). The second-order nonlinear interaction in the resonant cavity of laser is treated as the output loss of laser. The nonlinear reflectivity of the laserThe Gaussian beam theory has been developed to describe the power characteristics of intracavity continuous-wave singly resonant optical parametric oscillator (ICCWSRO). The second-order nonlinear interaction in the resonant cavity of laser is treated as the output loss of laser. The nonlinear reflectivity of the laser and the power characteristics of the signal and idler waves are obtained, based on the solution for the equations describing the power characteristics of laser. The stand-wave cavity structure, the properties of the four-level, end-pumped laser gain medium, the mean-field approximation of second-order nonlinear interaction, the diffractive effect of the interacting waves are all considered in the derivations. If the diffractive effect in the laser gain medium is neglected and only the first-order approximation is retained, the nonlinear reflectivity of laser is obtained, based on the solution for the transcendental equation. In the numerical calculation, the Nd∶YVO4 is taken as the laser gain medium, and the periodically poled LiNbO3 (PPLN) is taken as the second-order nonlinear crystal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 791 (2005)
Relationship between Beam Quality Factor β and Wavefront Error
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The relationship between beam quality factor β and wavefront error was analyzed in this paper. Approximate formulas to calculate β from room-mean-square (RMS) of wavefront error were deduced. The relationship between β and several Zernike polynomials was obtained by numerical calculation through fast Forier transform (The relationship between beam quality factor β and wavefront error was analyzed in this paper. Approximate formulas to calculate β from room-mean-square (RMS) of wavefront error were deduced. The relationship between β and several Zernike polynomials was obtained by numerical calculation through fast Forier transform (FFT) method. The approximate formula to estimate β from atmosphere disturbed wavefront error was given too. These approximate formulas were compared and verified well with the results of numerical calculation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 798 (2005)
Misalignment Characteristic Analysis Beam-Converting Annular Resonant Cavity
[in Chinese], [in Chinese], and [in Chinese]
Beam-converting annular resonator (BCAR) possesses outstanding characteristics of high extraction efficiency and near-diffractive beam quality. It is applied specially to annular HF/DF gain medium. In this paper, numerical model of rear cone misalignment and compact leg tilt is presented, and this numerical model has bBeam-converting annular resonator (BCAR) possesses outstanding characteristics of high extraction efficiency and near-diffractive beam quality. It is applied specially to annular HF/DF gain medium. In this paper, numerical model of rear cone misalignment and compact leg tilt is presented, and this numerical model has been used in physical optics code. The numerical result shows that the output power is insensitive to rear cone decentration and compact leg tilt, but beam quality is very sensitive to the decentration and tilt. The rear cone decentration and compact leg tilt can both result in a phase shear and twist on the optical field, and lead to phase jump and tilt along the misalignment direction. When the misalignments increase, the phase distribution of BCAR output field is twisted more severely. The directions of misalignments have little effects on the output field. Among these misalignments, rear cone decentration has more severe effect on the output field, and it must be controlled carefully in engineer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 803 (2005)
Biomedical Photonics and Laser Medicine
Modeling and Simulation of the Acting Factors on Vascular Selectivity of Photodynamic Therapy
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Photodynamic therapy (PDT) based on topical application of photosensitizers has been under development over last years. Typical application of photodynamic therapy is treatment of port wine stain (PWS). The dosimetry for topically administered photosensitizers must take an inhomogeneous drug distribution into account tPhotodynamic therapy (PDT) based on topical application of photosensitizers has been under development over last years. Typical application of photodynamic therapy is treatment of port wine stain (PWS). The dosimetry for topically administered photosensitizers must take an inhomogeneous drug distribution into account together with the conventional parameters such as optical scattering, absorption, and photobleaching. To study the acting factors on vascular selectivity of photodynamic therapy, the mathematic modeling of vascular selectivity of photodynamic therapy was achieved. The singlet oxygen distributions in tissue were simulated with Monte Carlo simulated light distribution. Effect of different photobleaching velocity was discussed. The simulated results indicated that faster photobleaching velocity was helpful to protect the epidermis and dermis. These results were useful for the application of photodynamic therapy in treatment of port wine stain..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 864 (2005)
Application of Laser Speckle Imaging: Monitoring Changes of Vessels in Photodynamic Therapy
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laser speckle contrast imaging (LSCI) technique is a new modality to monitoring blood flow dynamics with high spatio-temporal resolution. It records the full-field spatio-temporal characteristics of microcirculation without the need of scanning in real time. In this study, an in vivo model of chick chorioallantoic membLaser speckle contrast imaging (LSCI) technique is a new modality to monitoring blood flow dynamics with high spatio-temporal resolution. It records the full-field spatio-temporal characteristics of microcirculation without the need of scanning in real time. In this study, an in vivo model of chick chorioallantoic membrane (CAM) at embryo age (EA) of 10 days, was observed following photodynamic therapy (PDT) irradiated by semiconductor laser (λ=656.5 nm) whose light intensity incident on the treatment site was maintained 40 mW/cm2 using the photosensitizer of pyropheophorbide acid (Pyro-acid). The changes of vessel structure and blood flow velocity were recorded respectively. This study shows that LSCI can assess the efficacy of peripheral vessel damage of tumor in PDT by monitoring changes of vessels structure and blood flow velocity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 869 (2005)
Holography and Information Processing
Determination of the Poisson′s Ratio of Material by Digital Holographic Interferometry
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Base on the principle of digital holographic interferometry, two lensless Fourier transform holograms representing two different deformation states of object field are captured by CCD. Then the numerical reconstruction of digital holograms is implemented respectively to acquire the complex amplitude of object waves, anBase on the principle of digital holographic interferometry, two lensless Fourier transform holograms representing two different deformation states of object field are captured by CCD. Then the numerical reconstruction of digital holograms is implemented respectively to acquire the complex amplitude of object waves, and the interference phase difference is determined by subtracting the phases of the different states. According to the pure bending theory in elastic mechanics, the Poisson′s ratio is derived numerically from the angle between the asymptotic lines of the fringes of equal phase, which are caused from homogeneous deformation and reconstructed by digital holographic interferometry. This method for determination of Poisson′s ratio of material in the full-access performance by experiment is simple and easy to operate, especially suitable for material with rough surface, low value Poisson′s ratio and small size..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 787 (2005)
Laser Manufacturing
Plastic Hybrid Diffractive-Refractive Eyepiece for Head-Mounted Display
[in Chinese]
The diffractive optical element, with the negative dispersive characteristic and the random phase distributing to realize random phase modulation for wave-front, is helpful to simplify the optical system, and the optical plastic elements further reduce the weight of the system. A plastic hybrid diffractive-refractive eThe diffractive optical element, with the negative dispersive characteristic and the random phase distributing to realize random phase modulation for wave-front, is helpful to simplify the optical system, and the optical plastic elements further reduce the weight of the system. A plastic hybrid diffractive-refractive eyepiece for head-mounted display is designed, the features of the eyepiece are 30 mm effective focal length, 40° field-of-view (FOV), 20 mm exit pupil and 8 mm exit pupil size, and which consists of three lens and one diffractive element. The maximal diameter of lens and the overall weight of this eyepiece are 26 mm and 7 g, respectively. For the image quality, the astigmatic and lateral color of the key aberrations of eyepiece are 0.58 mm and 18 μm, and the distortion is only 3.3%. The angular resolution of this eyepiece is 0.44 mrad and less than that of human eyes..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 856 (2005)
Influence of Metal Powder on High Power CO2 Laser Welding of Aluminum Alloy
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The influences of the filler metal powder on the intensity threshold, weld formation and process stability have been studied during high power CO2 laser welding of aluminum alloy through the comparison between welding with and without metal powder. The experiment results demonstrate that the addition of the metal powdeThe influences of the filler metal powder on the intensity threshold, weld formation and process stability have been studied during high power CO2 laser welding of aluminum alloy through the comparison between welding with and without metal powder. The experiment results demonstrate that the addition of the metal powder enhances the energy coupling efficiency during laser welding and reduces the power density threshold which has been validated by the testing data of Laserscope UFF 100.The power density threshold of A2219 can be reduce to about 50%. Meanwhile, the pictures collected by the high speed camera indicate that the addition of the metal powder weakens the fluctuation of the laser-induced plasma and keeps the plasma stabilizing above the workpiece. So a stable welding process and well-formed weld can be obtained in a relatively easy way..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 860 (2005)
Laser Physics
All-Solid-State CW Doubly Resonant All-Intracavity Sum-Frequency Mixing 593 nm Laser
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new resonator which designed for doubly resonant continuous-wave intracavity sum-frequency mixing (SFM) laser is reported. Two Nd∶YVO4 were pumped by two laser diode array (LDA) which coupled by optical fiber respectively, 4F3/2→4I11/2 transition is chosen in one Nd∶YVO4 and 4F3/2→4I13/2 transition is chosen in anothA new resonator which designed for doubly resonant continuous-wave intracavity sum-frequency mixing (SFM) laser is reported. Two Nd∶YVO4 were pumped by two laser diode array (LDA) which coupled by optical fiber respectively, 4F3/2→4I11/2 transition is chosen in one Nd∶YVO4 and 4F3/2→4I13/2 transition is chosen in another one, 1064 nm wavelength is gotten from 4F3/2→4I11/2 transition and 1342 nm wavelength is gotten from 4F3/2→4I13/2 transition,two laser beam oscillated in two sub-cavity. Considering thermal effect of laser crystal, a thermal insensitive cavity is designed, and type Ⅱ critical phase match (CPM) KTiOPO4 (KTP) is used to generate 593 nm SFM. 520 mW continuous-wave TEM00 yellow laser was obtained. The output beam is low noise, its M2 factor is less than 1.2, and the power instability is less than ±2％ in 24 hours..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 729 (2005)
Continuous-Wave Passively Mode-Locked Diode End-Pumped Nd∶YVO4 Laser with a Semiconductor Saturable Absorber Mirror
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A diode end-pumped passively mode-locked Nd∶YVO4 picosecond laser with home made semiconductor saturable absorber mirror (SESAM) is presented. By choosing a low-transmission output coupler and extending the cavity length, the Q-switching mode-locked pulses are suppressed and the proportion of direct current is decreaseA diode end-pumped passively mode-locked Nd∶YVO4 picosecond laser with home made semiconductor saturable absorber mirror (SESAM) is presented. By choosing a low-transmission output coupler and extending the cavity length, the Q-switching mode-locked pulses are suppressed and the proportion of direct current is decreased in V shaped resonator. When the cavity length is increased from 0.66 m to 1.27 m and 1.86 m, the proportion of direct current is decreased from 52% to 13.6% and 0.3%. At last, a stable continuous mode-locked pulses are attained and the pulse repetition rate is 80 MHz. The spectral width is measured to be 0.15 nm. Considering the thermal effect of the crystal, a four-mirror Z-cavity is designed using the matrix method. Average output power of 1 W at a pulse repetition rate of 150 MHz is obtained. The benefit and disadvantage of the V-shaped cavity and the four-mirror Z-cavity are compared and analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 734 (2005)
Investigation on Tunable High Repetition Rate TEA CO2 Laser
[in Chinese], [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]
Tunable high repetition rate transversely excited atmospheric-pressure (TEA) CO2 laser has potential applications in laser chemistry, laser radar and optically pumped far-infrared laser investigation. In this paper, with the aim of development of kilowatt-level high repetition rate tunable TEA CO2 laser, inject-lockingTunable high repetition rate transversely excited atmospheric-pressure (TEA) CO2 laser has potential applications in laser chemistry, laser radar and optically pumped far-infrared laser investigation. In this paper, with the aim of development of kilowatt-level high repetition rate tunable TEA CO2 laser, inject-locking method, low fitness Fabry-Perot (F-P) coupler method and grating line selection method were investigated. With the method of grating line selection, kilowatt-level high repetition rate tunable TEA CO2 laser output was realized by grating resonator. The pulse energies of 10P(20), 10R(20), 9P(20) and 9R(20) are 5.8 J, 5.8 J, 5.5 J and 5.6 J respectively, at the repetition rate of 200 Hz. The far-field divergence angles are 1.66 mrad (horizontal) and 1.43 mrad (vertical), namely, about 2 times of diffraction limitation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 739 (2005)
A Wavelength-Intensity Splitter and a New Derivative Spectrum Technique
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The derivative spectrum technique has been widely applied to spectral analysis due to its high resolution and sensitivity. A new kind of derivative spectrum technique is presented in this paper. In order to realize derivative spectrum, a wavelength-intensity splitter has been designed to obtain two light beams with sliThe derivative spectrum technique has been widely applied to spectral analysis due to its high resolution and sensitivity. A new kind of derivative spectrum technique is presented in this paper. In order to realize derivative spectrum, a wavelength-intensity splitter has been designed to obtain two light beams with slim difference in wavelength. The two light beams were complementarily modulated with an optical complementary chopper. The modulated light beams were focalized to a photoelectric detector and realized intensity difference. By scanning the wavelength, the derivative spectrum was obtained. The derivative spectrum signal from the detector was acquired and recorded by a computer. Through a lot of experiments, the rationality of the system was approved. The emission spectrum and its first derivative spectrum of the xenon lamp were measured on this system. Finally, the result shows that the first derivative spectrum sensitivity and resolution are both higher than that of the emission spectrum..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 775 (2005)
Differential Cross Sections for Electrons Scattered by Ar Atom in the Laser Field
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The absolute differential cross sections of e-Ar scattering in the laser are calculated employing the second Born approximation with optical potential model in special scattering geometry that the incident electron beam is parallel to the polarization direction of laser field. In order to test these results, the differThe absolute differential cross sections of e-Ar scattering in the laser are calculated employing the second Born approximation with optical potential model in special scattering geometry that the incident electron beam is parallel to the polarization direction of laser field. In order to test these results, the differential cross sections of e-Ar scattering are calculated with the static screen potential by the second Born approximation and low-frequency formula, respectively. The second Born approximation obtains better results compared with the experimental data. The absolute differential cross sections of e-Ar scattering are calculated employing the second Born approximation with optical potential model and the best results are obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 779 (2005)
Two-Dimensional Wavefront Reconstruction of Shearing Interferograms with Big Shears
[in Chinese], [in Chinese], and [in Chinese]
A novel technique is proposed based on Fourier modal expansion and least-square fitting to reconstruct a two-dimensional wavefront from phase difference resulting from large shear. By using Fourier expansion, the Fourier coefficients of two-dimensional wavefront are computed from two one-dimensional difference wavefronA novel technique is proposed based on Fourier modal expansion and least-square fitting to reconstruct a two-dimensional wavefront from phase difference resulting from large shear. By using Fourier expansion, the Fourier coefficients of two-dimensional wavefront are computed from two one-dimensional difference wavefronts which are acquired by shearing interferometer. A recipe for data pre-processing is presented to solve information leakage resulting from large shear. This technique is applicable to situation where the shear amount is larger than one sampling interval, and can alleviate the limitation on the shear amount imposed by conventional algorithm. Investigation into the influences of shear amount and noise level on reconstruction accuracy is made..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 782 (2005)
Materials and Thin Films
Analysis of Optical Characteristics of Gradient Refractive Index Coatings Prepared by Linear Co-Evaporation
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In this paper, based on the Drude theory and Lorentz-Lorenz theory and started with the dielectric constant,the refractive index of mixed coatings is discussed. Under some special conditions such as, two materials′ molecule sizes is similar, the total deposition rate is constant and their deposition rate change is lineIn this paper, based on the Drude theory and Lorentz-Lorenz theory and started with the dielectric constant,the refractive index of mixed coatings is discussed. Under some special conditions such as, two materials′ molecule sizes is similar, the total deposition rate is constant and their deposition rate change is linear, the refractive index expression is obtained. Then the optical characteristics of gradient refractive index coatings are discussed from different aspects such as negative change or positive change, single layer or multi-periods, different periods or different single layer′s thickness. At last, the preparation, applications and some problems of gradient refractive index coatings are discussed separately..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 829 (2005)
Fabrication and Properties Study of Harmonic Beam Splitter at 1064 nm
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A harmonic beam splitter with a simply regular structure and good optical characteristics was designed by adding matching layers between the basic stack and its media and optimizing with a computed-aided film stack design procedure. Coatings were deposited on K9 glass substrates by electron beam evaporation and photoelA harmonic beam splitter with a simply regular structure and good optical characteristics was designed by adding matching layers between the basic stack and its media and optimizing with a computed-aided film stack design procedure. Coatings were deposited on K9 glass substrates by electron beam evaporation and photoelectric maximum control method, and then annealed in air at 260 ℃ temperature for three hours. The optical properties of coatings were characterized with a Lambda 900 spectrophotometer, the weak absorption of coatings was measured by surface thermal lensing technique (STL), and laser-induced damage threshold (LIDT) was assessed using 1064 nm Q-switch pulsed laser at a pulse length of 12 ns. It was found that a good agreement between the theoretical and the experimental transmittance was obtained, there was almost no shift for the center wavelength after annealing at 260 ℃, which showed the sample had a good temperature stability, the absorption of the coating decreased after annealing, and a remarkable increase of LIDT was found with the decrease of absorption. The experimental results as well as the theoretical ones indicated that it was a good method to add matching layers to the basic stack for a harmonic beam splitter at 1064 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 835 (2005)
Measurement and Metrology
Inverted Differential Grating Demodulation System of Laser Doppler
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
To resolve the contradiction between the measurement of micro-displace or high-accuracy detecting of micro-vibration of ultra-low frequency and the convenience of building and adjusting, a inverted differential 4f grating demodulation system of laser Doppler is put forward. Using two phase gratings to realize frequencyTo resolve the contradiction between the measurement of micro-displace or high-accuracy detecting of micro-vibration of ultra-low frequency and the convenience of building and adjusting, a inverted differential 4f grating demodulation system of laser Doppler is put forward. Using two phase gratings to realize frequency shift and mixing, the measurement accuracy is enhanced. Adopting 4f configuration to enhance the spatial coherence, building and adjusting of the system are more convenient. Further more, adding λ/4 wave plate and Wollaston lens cooperating with differential amplifier in order to get sin, cos signals judging displacement direction, and that the energy of both ±1 and ±3 diffraction lights is taken use to improve the intensity and signal to noise ratio (SNR) of Doppler signal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 844 (2005)
Real-Time Testing for Fine Defects beneath Precision Surface Using Magnetic-Optic Imaging Technique
[in Chinese], [in Chinese], and [in Chinese]
A new, laser supported, magneto-optic/eddy current imaging technique is introduced for fine defects testing beneath precision surface. In the experimental setup, the induction of eddy currents is conventionally performed by an alternating current excitation coil above the object surface. The magnetic field induced by tA new, laser supported, magneto-optic/eddy current imaging technique is introduced for fine defects testing beneath precision surface. In the experimental setup, the induction of eddy currents is conventionally performed by an alternating current excitation coil above the object surface. The magnetic field induced by the eddy currents is detected by using Faraday effect. For this target, a laser beam is passed through a special magneto-optic crystal integrated in the excitation coil. The polarization direction of laser beam is rotated in the crystal depending on the local magnetic field. The area distribution of rotation angle caused by the defects is transformed into “light” or “dark” picture using an optical setup, which comprises a conventional microscope, a lighting, a polarimeter, and a CCD sensor..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 848 (2005)
Error Analysis of Frequency Mixing for Heterodyne Interferometer
[in Chinese], [in Chinese], and [in Chinese]
Nonlinear errors caused by mis-installation of common-path heterodyne interferometer affected the measurement precision of the system. Frequency mixing errors caused by the two factors existing at same time, which are elliptic polarization of laser source and installation azimuthal error of Wollaston prism, were analyzNonlinear errors caused by mis-installation of common-path heterodyne interferometer affected the measurement precision of the system. Frequency mixing errors caused by the two factors existing at same time, which are elliptic polarization of laser source and installation azimuthal error of Wollaston prism, were analyzed especially in common path heterodyne interferometer. It was found that the nonlinear error is up to 2.2 nm and the error caused by the two factors may be counteracted each other a certain extent on some condition. The magnitude of error and the way of changing were given, which are of great importance in improving the measurement accuracy in common-path heterodyne interferometry. To the above basis, procedures to improve the accuracy of the measured system were suggested..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 852 (2005)
Optical Communication
Performance Optimization of the Wavelength Converter Based on Cross-Polarization-Modulation in SOA
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In order to weaken the bit format effect of converted signal of wavelength converter based on cross-polarization-modulation in semiconductor optical amplifier (CPM-SOA), the principle of CPM-SOA wavelength converter is analyzed; and after discussing the characteristics of frequency chirping of converted signal pulses, In order to weaken the bit format effect of converted signal of wavelength converter based on cross-polarization-modulation in semiconductor optical amplifier (CPM-SOA), the principle of CPM-SOA wavelength converter is analyzed; and after discussing the characteristics of frequency chirping of converted signal pulses, a simple method is proposed to improve the bit format effect by using the positive or negative transmission slope of a filter to optimize the converted signal of in-phase or out-of-phase. 10 Gb/s wavelength conversion based on CPM-SOA experiment is demonstrated by using a JDS filter with 0.3 nm optical bandwidth, the bit format effect of long “1” bit and long “0” bit in converted signal is mostly eliminated, the converted signal of in-phase or out-of-phase is reshaped and their power penalties are reduced by more than 3 dB..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 810 (2005)
Study of Two Stage Modulation Formats in High-Speed Dense Wavelength Division Multiplexing Systems
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The fundamental of two stage modulation in intensity modulation direct detection (IM-DD) high-speed dense wavelength-division multiplexing (DWDM) systems is depicted. And based on the transfer characteristic of Mach-Zehnder modulator, the mathematical expressions of four modulation formats are derived including: full fThe fundamental of two stage modulation in intensity modulation direct detection (IM-DD) high-speed dense wavelength-division multiplexing (DWDM) systems is depicted. And based on the transfer characteristic of Mach-Zehnder modulator, the mathematical expressions of four modulation formats are derived including: full frequency modulated return-to-zero (FFMRZ), half frequency modulated return-to-zero (HFMRZ), single sideband modulated return-to-zero (SSBRZ) and carrier suppressed return-to-zero (CSRZ). The characteristics of both time domain and frequency domain are represented according to optical eye diagrams and normalized spectrum. Then the dispersion limit and nonlinearity limit are numerically investigated respectively by comparing the eye opening penalty (EOP), and CSRZ performs better than other formats. At last, the Q-factor, which is relative to the system bit error ratio (BER), is obtained via numerical simulation utilizing comprehensive DWDM system model. The performance of CSRZ still maintains the best and the superiority is more evident when polarization mode dispersion (PMD) is considered. In conclusion, CSRZ is a preferable choice in IM-DD systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 815 (2005)
Investigation on Application of Optical Code Division Multiple Access System with Bipolar Codes
[in Chinese], and [in Chinese]
The base-band bipolar optical code division multiple access (OCDMA) system is introduced, with transform of unipolar-bipolar and bipolar-unipolar, transmission of signal with bipolar codes is realized through unipolar medium. Gold sequence and m sequence in OCDMA system, and channel effect on the performance of OCDMA sThe base-band bipolar optical code division multiple access (OCDMA) system is introduced, with transform of unipolar-bipolar and bipolar-unipolar, transmission of signal with bipolar codes is realized through unipolar medium. Gold sequence and m sequence in OCDMA system, and channel effect on the performance of OCDMA system are studied here. The simulation results demonstrate that Gold sequence and m sequence are adapted to bipolar OCDMA system according to the performance of the auto/cross-correlation, but Gold sequence in bipolar OCDMA system is better than m sequence. When the number of users is 20, the bit error rate (BER) is 10-9 for Gold sequence, and about 10-7 for m sequence. Channel model significantly influences the performance of the OCDMA system (～20 dB)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 6, 820 (2005)
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