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Contents
2005
Volume: 32 Issue 1
32 Article(s)
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Research Article
Study of Intra-Cavity Frequency-Doubling of a Nd∶YVO4 Laser Passively Q-Switched with GaAs
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By using GaAs saturable absorber, the running of a diode-pumped Q-switched intra-cavity frequency-doubled Nd∶YVO4/KTP laser is realized. The dependences of pulse width, pulse repetition rate, pulse energy and peak power on pump power are measured with different thickness of GaAs. At 3.22 W of pump power, the laser Q-swBy using GaAs saturable absorber, the running of a diode-pumped Q-switched intra-cavity frequency-doubled Nd∶YVO4/KTP laser is realized. The dependences of pulse width, pulse repetition rate, pulse energy and peak power on pump power are measured with different thickness of GaAs. At 3.22 W of pump power, the laser Q-switched by 300 μm GaAs produces 53.2 ns pulses at a pulse repetition rate of 381 kHz. The pulse energy is 0.18 μJ. The rate equations of intra-cavity frequency-doubling laser Q-switched by GaAs are introduced to analyze the experimental results. The numerical calculations of the rate equations are consistent with the experimental results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 35 (2005)
Technical Study of ZnGeP2 Optical Parametric Oscillator Pumped by a 2 μm Tm,Ho∶YLF Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
ZnGeP2 crystal with high nonlinear coefficient (d36=75 pm/V), broad infrared transmission region (0.7～12 μm) and very high thermal conductivity (0.18 W/(m?K)) is very suitable for high power mid-infrared radiation generation. Phase matching characteristics of ZnGeP2 optical parametric oscillator (OPO) are analyzed theoZnGeP2 crystal with high nonlinear coefficient (d36=75 pm/V), broad infrared transmission region (0.7～12 μm) and very high thermal conductivity (0.18 W/(m?K)) is very suitable for high power mid-infrared radiation generation. Phase matching characteristics of ZnGeP2 optical parametric oscillator (OPO) are analyzed theoretically, the requirement of type Ⅰ phase matching angle of 52.5～55.2° must be met to achieve continuously tuning of 3～5 μm. Experimentally, the acousto-optic Q-switched Tm, Ho∶YLF laser end pumped by fiber-coupled diode is employed as the pumping source of OPO with the maximum average power of 4 W, pulse duration of less than 40 ns, and pulse repetition rate of 100～10000 Hz. For higher extraction efficiency and low threshold operation to the quasi-three level laser system, the Tm,Ho∶YLF crystal is cooled by liquid nitrogen reserved in a small detector type dewar, and works at the temperature of 77 K. The 15-mm-long, 55.7° cut ZnGeP2 as a frequency converting crystal was placed in a plano-plano cavity with resonator length of 20 mm. Under a pumping power of 3.6 W and pulse repetition rate of 10 kHz, the mid-infrared coherent radiation of OPO near 4.1 μm was achieved with output power of 0.7 W, pulse width of 20 ns, optical-optical conversion efficiency of 20% and threshold pump power of 0.65 W..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 39 (2005)
Study on Low Pressure Discharge Character of Capillary Discharge
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The breakdown characteristics of capillary discharge are measured in Ar and He gases within the pressure range from 120 Pa to 10 Pa, which is the range for lasing by capillary discharge. The experimental results indicate that at least ～10 kV of discharge voltage is required for the breakdown of gas filled in a capillarThe breakdown characteristics of capillary discharge are measured in Ar and He gases within the pressure range from 120 Pa to 10 Pa, which is the range for lasing by capillary discharge. The experimental results indicate that at least ～10 kV of discharge voltage is required for the breakdown of gas filled in a capillary of 3 mm in diameter and 90 mm in length, which is much higher than that needed in parallel electrode system. The breakdown voltage is also greatly affected by the surface shape of electrode in low pressure. Studies show that the impedances of capillary for different lengths of gas column under the different discharge voltages represent the same character. The impedances reach the same minimum of ～5 Ω when the discharge currents reach the peak value, which makes it possible to obtain the same current peak value at the same discharge voltage for different lengths of capillary..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 43 (2005)
Model Target Existed in Q-Switched Laser and Instability of Output Pulse Power
[in Chinese]
In this paper, the instability of Q-switched laser pulse power output which was resulted from the phenomena of model target existed in Q-switched Nd-glass and YAG laser is reported. In order to dispel the phenomena of Q-switched laser waveform random modulation fundamentally, the pre-Q-switching and the Fabry-Perot (F-In this paper, the instability of Q-switched laser pulse power output which was resulted from the phenomena of model target existed in Q-switched Nd-glass and YAG laser is reported. In order to dispel the phenomena of Q-switched laser waveform random modulation fundamentally, the pre-Q-switching and the Fabry-Perot (F-P) standard panel assemble were used, a steady Q-switched laser output in pulse width of 40 ns and pulse energy of 85 mJ was obtained. The stabilities of pulse energy and pulse power were ±2% and ±3%, respectively, line width was 6.9×10-4 nm, the probability of single longitudinal mode output was 89%. With above-mentioned method, the modulating phenomena of mode target was eliminated, the stable pulse power output of Q-switched Nd-glass laser was realized..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 49 (2005)
Study on High Resolution Fiber Bragg Grating Temperature Sensor
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel fiber Bragg grating (FBG) temperature sensor system with high resolution and low cost demodulation mechanism was proposed. The metal groove encapsulating technique for FBG sensor was developed to improve the temperature sensitivity of FBG temperature sensor. Coefficient of thermal-expansion of the encapsulated A novel fiber Bragg grating (FBG) temperature sensor system with high resolution and low cost demodulation mechanism was proposed. The metal groove encapsulating technique for FBG sensor was developed to improve the temperature sensitivity of FBG temperature sensor. Coefficient of thermal-expansion of the encapsulated FBG sensor was studied. The comparison of results between encapsulated FBG sensor and bare FBG sensor indicted that the temperature sensitivity of encapsulated FBG sensor is improved and the sensitivity coefficient is 3.6 times as much as that of bare FBG sensor. A long period grating (LPG) was used as linear response filter to convert wavelength into intensity for interrogation. In experiment, a broadband source was modulated by the LPG and then it illuminated the sensor grating, which could interrogate the wavelength shifts of sensor system. The experimental results agreed well with the theoretical analysis. The FBG temperature sensor realized a high resolution of 0.02 ℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 83 (2005)
Beam Transmission
Strehl Ratios and Sharpness of Collimated Laser Beam in a Turbulent Atmosphere
[in Chinese]
Some parameters for describing optical qualities of a short-term beam pattern of a collimated laser beam propagating through a turbulent atmosphere are evaluated for a series of numerically-generated patterns. These parameters include the on-axis, peak, and energy Strehl ratios and the sharpness. Their statistical charSome parameters for describing optical qualities of a short-term beam pattern of a collimated laser beam propagating through a turbulent atmosphere are evaluated for a series of numerically-generated patterns. These parameters include the on-axis, peak, and energy Strehl ratios and the sharpness. Their statistical characteristics are analyzed and the validity of these parameters for describing optical qualities of the beam pattern is discussed. Main results could be summarized as follows. The energy Strehl ratio could reflect the energy concentration of the whole beam; the sharpness well reflects the energy concentration in a local area, and could be used for describing the optical quality of laser beam in the turbulence. Generally the turbulence is benefit for promoting the pattern sharpness..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 53 (2005)
Novel Supercell Lattice Method for the Photonic Crystal Fibers
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel supercell lattice method (SLM), induced from both the plane wave expansion method (PWM) and the semi vector method, is presented to analyze the photonic crystal fibers (PCF). The electric field is still expanded with the Hermite-Gaussian function, the dielectric constant of the PCF missing the center air hole cA novel supercell lattice method (SLM), induced from both the plane wave expansion method (PWM) and the semi vector method, is presented to analyze the photonic crystal fibers (PCF). The electric field is still expanded with the Hermite-Gaussian function, the dielectric constant of the PCF missing the center air hole can be considered as the sum of two perfect PCFs, which have different dielectric constant and different structure parameters (the hole pitch, the hole diameter). The periodical dielectric structures of the two perfect PCFs are expanded in cosine function with different periods. From the wave equation and the properties of Hermite-Gaussian function, the propagation characteristics of the PCF, such as the mode field distribution, birefringence, the dispersion property, can be obtained. The accuracy of the SLM can be scaled by the birefringence because the ideal triangular lattice PCF has no birefringence based on the group theory..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 59 (2005)
Comparison of Experimental Study of Atmospheric Coherence Length
[in Chinese], [in Chinese], and [in Chinese]
The atmospheric coherence length is a very important parameter of atmospheric propagation and adaptive optics. The principle of atmospheric coherence length measurement via differential image motion measure (DIMM) angle-of-arrival fluctuation of optical wave and the measurement method dealing with the irradiance scintiThe atmospheric coherence length is a very important parameter of atmospheric propagation and adaptive optics. The principle of atmospheric coherence length measurement via differential image motion measure (DIMM) angle-of-arrival fluctuation of optical wave and the measurement method dealing with the irradiance scintillation of laser propagation are introduced. The atmospheric coherence length along level propagation path is measured via differential image motion measure angle-of-arrival fluctuation of optical wave. In addition, the measurement systems dealing with the irradiance scintillation of laser propagation are used to check the results of the atmospheric coherence length measurement, and its time variation is similar, but they can be much different from each other under other conditions. Last, various errors caused by instrument are analyzed and discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 64 (2005)
Second Order Moment Propagation of TE Vector Gaussian Beam
[in Chinese], and [in Chinese]
Based on the nonparaxial vectorial moment theory of light beam propagation, the propagation of TE (transverse electric) vector Gaussian beam has been investigated, and the integral expressions of beam waist, transversal divergence angle and beam propagation factor have been presented. The results reveal that both the tBased on the nonparaxial vectorial moment theory of light beam propagation, the propagation of TE (transverse electric) vector Gaussian beam has been investigated, and the integral expressions of beam waist, transversal divergence angle and beam propagation factor have been presented. The results reveal that both the transversal beam widths defined as second order moment of energy flux follow a very simple hyperbolic law upon propagation. The numerical calculations show that TE polarization results in different propagating characteristic in the two transversal directions for highly nonparaxial case, and the maximum transverse divergences exceed the divergence angle limit of nonparaxial scalar Gaussian beam 63.43° and are close to 90°, which is in accordant with the theory of wave optics. Moreover, the divergence in the x direction is slightly larger than that in the y direction. Under paraxial condition of nonparaxial scalar Gaussian beam, the propagation of TE vector Gaussian beam is reduced to that of transversal fundamental mode paraxial scalar Gaussian beam for paraxial case. However, the beam propagation factor will always be greater than unity and cannot accurately equal to unity forever..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 67 (2005)
Biomedical Photonics and Laser Medicine
Numerical Simulation and Experimental Study on Thermal Damage Process in Tissue during High-Intensity Laser Irradiation
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Various phase-changing thermal effects, i.e. evaporization, carbonization and melting, occur sequentially in the biological tissue irradiated by high-intensity laser. According to this practical thermal effect, a new heat transfer model for laser-tissue thermal interaction is proposed. In the model two heterogeneous tiVarious phase-changing thermal effects, i.e. evaporization, carbonization and melting, occur sequentially in the biological tissue irradiated by high-intensity laser. According to this practical thermal effect, a new heat transfer model for laser-tissue thermal interaction is proposed. In the model two heterogeneous tissues, i.e. carbonization layer and bio-tissue layer, are considered and two different phase-changing interfaces are introduced. Some parameters such as the temperature and moving velocity on the interfaces as well as the carbonization depth are obtained by numerical solution. The relationship between these parameters and the laser power density is studied. Numerical simulation shows that the laser-tissue thermal interaction model has two stages.
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 139 (2005)
Holography and Information Processing
Digital Holograms with Large Viewing Angle
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new technique of digital holography is proposed, which can make the holograms with large viewing angle. According to the theory of two-step rainbow holography, rainbow holograms H1 are generated by computer and the new algorithm of mirror image is proposed which can fold the holograms with large dimension into littleA new technique of digital holography is proposed, which can make the holograms with large viewing angle. According to the theory of two-step rainbow holography, rainbow holograms H1 are generated by computer and the new algorithm of mirror image is proposed which can fold the holograms with large dimension into little ones. After the downsizing by taking pictures, a hologram with high density is made. When H2 is made on optical setup, two right mirrors must be matched in order to returning the reconstructed wave to the original condition. The advantages of both computer generated holograms and optical holograms are adopted in this technique. The technique of mirror image can successfully make the holograms with large viewing angle. The principle of the proposed method and the experimental result prove that the technique not only resolves the problem on the output of holograms with large dimension and reduces the data volume greatly, but also breaks a new path for hologram three-dimensional display..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 87 (2005)
Experimental Study on Photochromic Three-Dimensional Optical Storage under Two-Photon Absorption
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The storage mechanism of photochromic three-dimensional optical storage under two-photon absorption is presented. The experiments on the effect of writing power, exposure time and recording depth on the contrast of the readout signal intensity and bit size were carried out by use of three-dimensional optical memory setThe storage mechanism of photochromic three-dimensional optical storage under two-photon absorption is presented. The experiments on the effect of writing power, exposure time and recording depth on the contrast of the readout signal intensity and bit size were carried out by use of three-dimensional optical memory setup with single-beam two-photon and a reflection confocal scanning readout setup. The results show that the signal intensity and the bit size of the recorded bits depend strongly on the writing power and exposure time. The signal intensity initially shows an I2 dependence on power, followed by saturation. The saturation effect is also evident as exposure time is longer. Bit size is increased with writing power or exposure time increased. Furthermore, signal intensity is decreased with an increase in recording depth. Storage rate is higher by use of higher power and shorter exposure time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 92 (2005)
Signal Process of Photoacoustic Tomography
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A method of photoacoustic (PA) tomography with the filtered back projection is proposed. For the PA signals of the source, real PA pressures are obtained by deconvoluting the impulse response of the transducer used for detecting the PA signals of samples. The optical absorption distributions of the samples are reconstrA method of photoacoustic (PA) tomography with the filtered back projection is proposed. For the PA signals of the source, real PA pressures are obtained by deconvoluting the impulse response of the transducer used for detecting the PA signals of samples. The optical absorption distributions of the samples are reconstructed using the filtered back projection with sufficient PA pressures in different directions. The data are filtered with SL (Slion-Line) filter before back projecting. Simulations and experiments were performed to compare the filtered back projection and the direct back projection. The results prove the filtered back projection method is valid for PA imaging. Combining this image method, the two-dimension PA images of four absorbers buried in 12 mm were reconstructed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 97 (2005)
Laser Devices and Laser Physics
LBO Frequency Doubled CW Red Laser at 671 nm up to 1.8 W
[in Chinese], [in Chinese], and [in Chinese]
The Nd3+ ion doped in Nd∶YVO4 crystal has a weak laser transition at 1.342 μm in addition to 1.064 μm stimulated transition. The laser at 1.342 μm can be frequencydoubled to obtain red light at 671 nm. In this paper, the analysis and the experiment of a Nd∶YVO4 crystal pumped by 400μm fibercoupled diode array, typeThe Nd3+ ion doped in Nd∶YVO4 crystal has a weak laser transition at 1.342 μm in addition to 1.064 μm stimulated transition. The laser at 1.342 μm can be frequencydoubled to obtain red light at 671 nm. In this paper, the analysis and the experiment of a Nd∶YVO4 crystal pumped by 400μm fibercoupled diode array, typeⅠ critical phase matching and intracavity frequencydoubled LBO (LiB3O5) crystal, and red laser at output wavelength of 671 nm were performed. By using a short foldedcavity resonator, the thermal focal length of Nd∶YVO4 crystal was calculated, and the parameters of laser cavity were selected by computer optimum design. At last, with incident pump power of 8 W, TEM00 mode (transverse electromagnetic mode) red laser at 671 nm of 1.8 W was obtained, with the optical conversion efficiency up to 22.5%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 9 (2005)
Laser Manufacturing
Research on Weld Penetration Monitoring by Laser Plasma Optical Signal in Laser Welding
[in Chinese], [in Chinese], and [in Chinese]
Laser induced plasma is an important physical phenomena companied with laser keyhole welding. In this paper, the relation between weld penetration and optical signal was studied. Through many experiments, variety of optical signals were obtain when weld penetration was different. The results showed that the optical sigLaser induced plasma is an important physical phenomena companied with laser keyhole welding. In this paper, the relation between weld penetration and optical signal was studied. Through many experiments, variety of optical signals were obtain when weld penetration was different. The results showed that the optical signals had better stability in full-penetration, and in partial- or non- penetration, optical signals had higher fluctuations. The aim of this study was to find a method to monitor and control weld penetration in laser welding..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 131 (2005)
Theoretical Analysis on Deformation of Sheet Metal under One Laser Shot Loading
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laser shock forming (LSF) is a novel technique realized by applying a compressive shock wave generated by laser shock on the surface of the metal. It is a mechanical, not a thermal process, and has a significant characterization of ultra-pressure and super plastic forming etc. In this paper, a physical model and the esLaser shock forming (LSF) is a novel technique realized by applying a compressive shock wave generated by laser shock on the surface of the metal. It is a mechanical, not a thermal process, and has a significant characterization of ultra-pressure and super plastic forming etc. In this paper, a physical model and the estimated formula of shockwave pressure of laser shock forming were found according to the detonation wave and explosive gas dynamical theory. On the base of experimental results and theory analysis, a mathematical model of the sheet deformation under one laser shot loading was established, the relationship between shockwave pressure and deformation of sheet metal was discussed, and the effects of factors such as laser parameters, boundary condition on the deformation of sheet metal were analyzed. These model and formula are very useful and can be used to predict the deformation of sheet metal loaded by laser shock, and provide a theory foundation to choose laser processing parameters reasonably and program the controlled software of laser shock forming..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 135 (2005)
Laser Physics
High Rep-Rate TEA CO2 Laser with Sequential Discharge
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A high rep-rate TEA CO2 laser with two sets of electrodes in the optical cavity is described. Each set of electrodes has an active gain volume of 2.5 cm×2.5 cm×55 cm. The device produces high intensity pulse pairs with varied time separations and varied rep-rates. When the two sets of electrodes discharge synA high rep-rate TEA CO2 laser with two sets of electrodes in the optical cavity is described. Each set of electrodes has an active gain volume of 2.5 cm×2.5 cm×55 cm. The device produces high intensity pulse pairs with varied time separations and varied rep-rates. When the two sets of electrodes discharge synchronously, the device generates an average output power of 1.1 kW with rep-rate 200 Hz. When the two sets of electrodes discharge sequentially, the device generates an average output power of 550 W with rep-rate 400 Hz and maximum pulse-pair interval of 2.5 ms. With the same rep-rate, the average output power from the device decreases with the increase of the pulse-pair time interval. In addition, the pulse-pair profiles with various time intervals are given..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 1 (2005)
Experimental Study of 30 W CW Fiber Laser by Two-End Pumping
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A two-end pumping high power continuous-wave (CW) Yb3+-doped double-clad fiber laser was reported. In experiments, two types of laser diodes with center wavelength around 975 nm were adopted as pumping sources, and the characteristics of output power and laser spectrum were measured under different pumping conditions. A two-end pumping high power continuous-wave (CW) Yb3+-doped double-clad fiber laser was reported. In experiments, two types of laser diodes with center wavelength around 975 nm were adopted as pumping sources, and the characteristics of output power and laser spectrum were measured under different pumping conditions. Under the pumping of the pigtailed laser diode, output power was 9.2 W, slope efficiency was 42% and laser peak spectrum was 1103.8 nm. Under the pumping of the collimated laser diode, output power was 20.0 W, slope efficiency was 57% and laser peak spectrum was 1104.4 nm. When both laser diodes were used to pump the fiber laser together, the maximum output power of 30.6 W, laser peak spectrum of 1108.4 nm and total optical-to-optical efficiency of 49% were achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 5 (2005)
Laser-Diode Pumped 500 W Continuous-Wave Nd∶YAG Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The output power of homemade all-solid-state laser-diode (LD) pumped Nd∶YAG laser above 500 W has been demonstrated in this paper. Experimental setup and the properties of its input-output power were introduced. From the point of gain distribution, the configuration of the LD-pumped laser was optimized. The maximum outThe output power of homemade all-solid-state laser-diode (LD) pumped Nd∶YAG laser above 500 W has been demonstrated in this paper. Experimental setup and the properties of its input-output power were introduced. From the point of gain distribution, the configuration of the LD-pumped laser was optimized. The maximum output power of the Nd∶YAG laser was about 575 W. The output power was increased linearly with the pump power at the slope efficiency of 47% above the threshold. The optical-to-optical efficiency of 26.1% was obtained. Through He-Ne laser probe method, the thermal lens effects of the LD-pumped laser were measured. The focal length of thermal lens was measured and compared with the theory. When the pump power was increased, the focal length was decreased, and a kind of means to effectively compensate the thermal lens effects was used in the experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 13 (2005)
Electromagnetically Induced Transparency in Λ-Type Zeeman Sublevels of Cesium Atoms
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Employing two lasers as the coupling and probe fields which have opposite circular polarization (σ+ and σ-), electromagnetically induced transparency (EIT) in Λ-type Zeeman sublevels of cesium 62S1/2F=3-62P3/2F′=2 degenerate two-level system has been demonstrated via probe absorption spectra. The effect of the intensitEmploying two lasers as the coupling and probe fields which have opposite circular polarization (σ+ and σ-), electromagnetically induced transparency (EIT) in Λ-type Zeeman sublevels of cesium 62S1/2F=3-62P3/2F′=2 degenerate two-level system has been demonstrated via probe absorption spectra. The effect of the intensity and detuning of different coupling. Laser on EII was also investigated in experiments. Within the Doppler background, optical pumping among Zeeman sub-levels and the population of different Zeeman sub-levels can dominate the intensity of EIT effect. And the physical reason of the rugged spectra are presented qualitatively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 16 (2005)
Re-Investigation on the Solution to Two-Dimensional Coupled Wave Equations for Volume Holographic Gratings
[in Chinese], [in Chinese], and [in Chinese]
The complete derivation of two-dimensional (2-D) coupled wave equations is given for total overlap gratings in the Bragg regime. The analytical solution in closed mathematical form is also given. General diffraction properties of total overlap gratings, can be solved with the solution. Diffraction properties, especiallThe complete derivation of two-dimensional (2-D) coupled wave equations is given for total overlap gratings in the Bragg regime. The analytical solution in closed mathematical form is also given. General diffraction properties of total overlap gratings, can be solved with the solution. Diffraction properties, especially effects of the grating dimension and absorption coefficient on the diffraction efficiency are researched based on the solution in this paper. The results show that diffraction efficiency of a lossless grating increases with the higher ratio of reference beam width to object beam width. However, for strongly-coupled gratings if the absorption of medium cannot be ignored, the diffraction efficiency decreases with widening of reference beam. It is suggested that for efficiency optimization of a lossy grating the geometrical dimension of the grating should be carefully designed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 21 (2005)
Theoretical Investigation of Free-Electron Driven X-Ray Lasers
[in Chinese], [in Chinese], and [in Chinese]
X-ray lasers are an important area in the fields of laser and plasma physics. At present, the studies of X-ray lasers focus mostly on Z-pinch carbon discharge and the short and multiple laser pulse from high power lasers, and most of which confine in Soft X-ray laser. Inspired by the device of free-electron lasers, a nX-ray lasers are an important area in the fields of laser and plasma physics. At present, the studies of X-ray lasers focus mostly on Z-pinch carbon discharge and the short and multiple laser pulse from high power lasers, and most of which confine in Soft X-ray laser. Inspired by the device of free-electron lasers, a newly designed device of X-ray laser is put forward. This device is converting free electron laser tool into free electron pumped laser tool through replacing wiggler by capillary hollow tungsten electrode which is full of specially metal steam such as copper steam. Its working principle and feasibility are analysed and proved by many theory such as electron impact ionization, equilibria system of high-energy particle beams and recombination properties of plasma produced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 26 (2005)
Study of Temporal and Spatial Coherence of Light Emitting Diode
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The temporal and spatial coherence of light emitting diode (LED) is studied by Michelson interferometer with subfemtosecond time resolution. LEDs′ spectral characteristics and coherence time are measured, and their emitting area is estimated by LEDs′ interference signal. Systematic errors in the experiments are discussThe temporal and spatial coherence of light emitting diode (LED) is studied by Michelson interferometer with subfemtosecond time resolution. LEDs′ spectral characteristics and coherence time are measured, and their emitting area is estimated by LEDs′ interference signal. Systematic errors in the experiments are discussed and the solutions to reduce the errors are suggested. Results show that LED can be applied as a light source for stable and time resolved spectroscopy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 31 (2005)
Materials and Thin Films
Effects of Composition on Spectroscopic Properties of Er3+-doped Na2O-Al2O3-SiO2 Glasses
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effects of Na2O contents on spectroscopic properties of Er3+-doped Na2O-Al2O3-SiO2 glasses were studied in this paper. The Ωt parameters, radiative transition probability, and radiative lifetime of the Er3+-doped sodium aluminosilicate glasses were calculated by the Judd-Ofelt (J-O) theory and absorption spectra. TThe effects of Na2O contents on spectroscopic properties of Er3+-doped Na2O-Al2O3-SiO2 glasses were studied in this paper. The Ωt parameters, radiative transition probability, and radiative lifetime of the Er3+-doped sodium aluminosilicate glasses were calculated by the Judd-Ofelt (J-O) theory and absorption spectra. Then the relationship between Ωt parameters and Na2O contents, and the effect of Na2O contents on absorrption cross section, and the spontaneous emission probability of the 4I13/2 level of Er3+, and the full width at half maximum(FWHM) of 1.53 μm were analysed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 110 (2005)
Nonlinear Optical Properties of Soluble Poly (phenylene vinylene) Derivatives
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The soluble π-conjugated polymer materials, poly(2-methoxy-5-butoxy)-p-phenylene vinylene (PMOBOPV), poly[2-methoxy-5-(3′-methyl)butoxy]-p-phenylene vinylene (PMOMBOPV) and poly(2-methoxy-5-octoxy)-p-phenylene vinylene (PMOCOPV), were prepared by dehydrochlorination reaction from p-methoxylphenol and alkyl bromide as rThe soluble π-conjugated polymer materials, poly(2-methoxy-5-butoxy)-p-phenylene vinylene (PMOBOPV), poly[2-methoxy-5-(3′-methyl)butoxy]-p-phenylene vinylene (PMOMBOPV) and poly(2-methoxy-5-octoxy)-p-phenylene vinylene (PMOCOPV), were prepared by dehydrochlorination reaction from p-methoxylphenol and alkyl bromide as raw materials. Their third-order nonlinear optical properties were studied with the backward degenerate four-wave mixing (DFWM) at 532 nm. The experimental result showed that the third-order nonlinear optical susceptibilities χ(3) values of PMOBOPV, PMOMBOPV and PMOCOPV were 3.14×10-10, 5.96×10-10 and 3.71×10-10 esu, respectively, and corresponding hyperpolarizability γ values were 4.22×10-28, 7.78×10-28 and 5.00×10-28 esu, respectively. The effects of molecular structures on nonlinear optical properties of poly(p-phenylene vinylene) (PPV) derivatives were also studied. Moreover, the optical bandgaps, Eg, of PPV derivatives were measured by spectrometer and the result of data fitting showed that Eg values of PMOBOPV, PMOMBOPV and PMOCOPV were 2.08 eV, 2.03 eV and 2.05 eV, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 115 (2005)
Femtosecond Laser Induced Darkening and Refractive Index Change in K9 Glass
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Femtosecond laser induced darkening and permanent refractive index changes in K9 glass under different radiation conditions were experimentally studied. The micro-process of darkening generation in K9 glass was analyzed depending on the results of microscope photograph, absorption spectra, electron spin resonance spectFemtosecond laser induced darkening and permanent refractive index changes in K9 glass under different radiation conditions were experimentally studied. The micro-process of darkening generation in K9 glass was analyzed depending on the results of microscope photograph, absorption spectra, electron spin resonance spectra (ESR) and laser diffraction. It was found that hole-trapped color centers give rise to the darkening generation. Darkening and refractive index change varied with laser intensity, scan speed and line interval. Nonlinear ionization enhanced color center formation. Permanent refractive index changes were explained simply. The mechanism was still under discussion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 119 (2005)
Optical Characterization and Stability Study of LiNbO3 Optical Waveguides Fabricated by Buffered Acid
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Proton exchange waveguides were fabricated by buffered acid (benzoic acid doped with a certain amount of lithium benzoate) in Z-cut LiNbO3. The effective diffusion coefficients and the index profile were calculated for the waveguides fabricated in buffered benzoic acid with different molar fractions of lithium benzoateProton exchange waveguides were fabricated by buffered acid (benzoic acid doped with a certain amount of lithium benzoate) in Z-cut LiNbO3. The effective diffusion coefficients and the index profile were calculated for the waveguides fabricated in buffered benzoic acid with different molar fractions of lithium benzoate with aspect to benzoic acid (0.5%, 1.0% and 1.5%). The effective diffusion coefficient decreases exponentially as the molar fraction of lithium benzoate increases. The surface index increment decreases linearly with the increase of the Li+ mole percent in the proton source. The stabilities of these fabricated waveguides are studied. The results are compared with those from the waveguides fabricated by pure benzoic acid. The stabilities of LiNbO3 proton exchange waveguides can be improved by the exchange with buffered benzoic acid..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 123 (2005)
Measurement and Metrology
Research on the Laser Beat-Wave Interferometry
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A precision measuring system for large size measurement is described. The frequency-stabilized He-Ne laser with thermoregulation is used as the light source, which operates on the double longitudinal modes, has high frequency stability and good anti-disturbance performance. The frequency stability is better than 10-7 (A precision measuring system for large size measurement is described. The frequency-stabilized He-Ne laser with thermoregulation is used as the light source, which operates on the double longitudinal modes, has high frequency stability and good anti-disturbance performance. The frequency stability is better than 10-7 (in open air). It has the beat frequency about 790 MHz and beat wavelength 376 μm. The node of the beat-wave is used as sampling flag and the distance between the node and the close measuring point is measured with double frequency interferometer, which is combined in the same optical system. In this system, an adaptive filter and a wavelet transform program are used to improve the measurement accuracy. The test indicates that the measuring accuracy is better than 30 μm/10 m and the measuring range is 0～20 m..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 101 (2005)
Parallel Confocal Measurement though Integrated Optical Fiber Bundle Plate
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In order to solve the problems of slow scanning speed and mechanical complexity in a single point scanning confocal microscope,a new way based on the principle of multiple-beam confocal was proposed. A parallel beam becomes a series of point sources by an integrated optical fiber bundle plate. The confocal system basedIn order to solve the problems of slow scanning speed and mechanical complexity in a single point scanning confocal microscope,a new way based on the principle of multiple-beam confocal was proposed. A parallel beam becomes a series of point sources by an integrated optical fiber bundle plate. The confocal system based that device is set up. A special prism is designed to separate the signal light from illumination light in the system. The principle of this new way is described in detail and some characteristics are given. A practical setup is shown and the confocal image is got to prove its feasibility..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 105 (2005)
Optical Communication
Second Harmonic Generation Based on Er-Yb Co-Doped Fiber Gratings
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel method of second harmonic generation (SHG) is reported. A permanent second order nonliearity which is zero in theory has been induced simultaneously by ultraviolet (UV)-excited poling in a high concentration Er-Yb co-doped fiber Bragg gratings, and the phase-match has been satisfied with periodic structure. WheA novel method of second harmonic generation (SHG) is reported. A permanent second order nonliearity which is zero in theory has been induced simultaneously by ultraviolet (UV)-excited poling in a high concentration Er-Yb co-doped fiber Bragg gratings, and the phase-match has been satisfied with periodic structure. When a 980-nm laser diode (LD) pumped the fiber gratings, SHGs in such a fiber gratings with low pump power (<4 mW) were abserved and the intensity increased with the increase of pump power. The SHG light radiating phenomenon was observed under microscope and some microscope photograph were taken. It was found that the radiation occurred only in the core of the fiber gratings. And then UV radiation from the structure was also recorded..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 72 (2005)
Nonlinear Coefficient and Dispersion Parameters Measurement Utilizing Optical Parametric Amplification
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The analytical relations of parametric peak gain versus fiber nonlinear coefficient and fiber dispersion versus the difference between gain peak and pump wavelengths were derived when the fiber loss was taken into account, based on which a new method to measure the nonlinear coefficient and dispersion parameters was prThe analytical relations of parametric peak gain versus fiber nonlinear coefficient and fiber dispersion versus the difference between gain peak and pump wavelengths were derived when the fiber loss was taken into account, based on which a new method to measure the nonlinear coefficient and dispersion parameters was proposed with only simple algebraic calculation required. In the experiment, a 1450-m-long highly nonlinear dispersion flattened fiber (HNLF) was measured by using two different pump wavelengths, the measured nonlinear coefficient was γ=11.8 W-1?km-1, and the dispersion slope was S=0.0157 ps/(nm2?km) with the error from the value given by the manufacturer below 5%. The measured asymmetry of gain spectrum ascribed to the Raman effect was discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 75 (2005)
Investigation of the PMD Compensation System with the DOP as a Feed Back Signal
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The monitoring performance of monitor window and degree of polarization (DOP) sensitivity to defferetial group delay (DGD) can be improved greatly by using the band-pass and band-reject filters are presented in the polarization mode dispersion (PMD) compensation system, where the DOP is used for the feed back signals. The monitoring performance of monitor window and degree of polarization (DOP) sensitivity to defferetial group delay (DGD) can be improved greatly by using the band-pass and band-reject filters are presented in the polarization mode dispersion (PMD) compensation system, where the DOP is used for the feed back signals. A comparison is made for the filters in improving the monitoring performance of the feed back signals between the 40 Gbit/s return-to-zero (RZ) and 10 Gbit/s nonretrun-to-zero (NRZ) transmission system, and numerical analysis is made for the selection of the bandwidth of the filters. The results showed that the local extremum can be avoid in the searching process of the searching algorithm, so a bypass searching is reduced greatly, which is significant for the compensation effects and the stabilization of the system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 1, 79 (2005)
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