Journals >Chinese Journal of Lasers
Contents
2007
Volume: 34 Issue 9
30 Article(s)
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Research Article
Laser Diode-Pumped Domestic Yb:YAG Ceramic Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The output performance of a domestic Yb:YAG ceramic laser is studied. The laser diode-end-pumped Yb:YAG ceramic is doped with atomic fraction of 1%, with one end face of high transmission at 940 nm and 1030 nm and the other of high transmission at 1030 nm. The near infrared laser output at 1031 nm is obtained. The outpThe output performance of a domestic Yb:YAG ceramic laser is studied. The laser diode-end-pumped Yb:YAG ceramic is doped with atomic fraction of 1%, with one end face of high transmission at 940 nm and 1030 nm and the other of high transmission at 1030 nm. The near infrared laser output at 1031 nm is obtained. The output performance of Yb:YAG ceramic laser under different transmissivities (4%, 8%, 10%) is experimentally tested. The maximum output power of 1.63 W is obtained with output transmissivity of 10%, absorbed pump energy of 9 W, and slope efficiency of 23.2%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1171 (2007)
78 fs Passively Mode-Locked Er3+-Doped Fiber Ring Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A passively mode-locked fiber ring laser with a small segment of Er3+-doped fiber as gain medium, pumped by stable 976 nm laser diode (LD) and mode-locked by the nonlinear polarization rotation (NPR) technique, was successfully achieved. When the laser was pumped at 57 mW, stable mode-locked pulses centered at 1544.0 nA passively mode-locked fiber ring laser with a small segment of Er3+-doped fiber as gain medium, pumped by stable 976 nm laser diode (LD) and mode-locked by the nonlinear polarization rotation (NPR) technique, was successfully achieved. When the laser was pumped at 57 mW, stable mode-locked pulses centered at 1544.0 nm with 40.8 nm spectral bandwidth and 78 fs pulse width were obtained at the repetition rate of 11.18 MHz by modulating the wavelength-independent all-fiber on-line polarization controller. The output power of the laser was 5.4 mW, the pulse energy was about 0.5 nJ and the peak power was 6200 W..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1174 (2007)
All-Solid-State Red Laser with 83 W Output Power at 659.5 nm
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The experimental results of high-power red laser constituted of a symmetrical linear resonator with two pumping modules, and intracavity frequency-doubling with a KTP crystal are reported. The average output power of 83 W at 659.5 nm was obtained in the condition of 1250 W pump power and the acoustic-optical Q-switchinThe experimental results of high-power red laser constituted of a symmetrical linear resonator with two pumping modules, and intracavity frequency-doubling with a KTP crystal are reported. The average output power of 83 W at 659.5 nm was obtained in the condition of 1250 W pump power and the acoustic-optical Q-switching repetition rate of 10 kHz. The optical-optical efficiency was 6.5% and the optical slope efficiency was 17%. The laser adopted a plane-plane cavity structure. Every pumping head was equipped with a high power continuous wave (CW) side-pump module comprising of a Nd:YAG rod side-pumped by thirty-five 20 W laser diode arrays (LSAs) with pentagon geometry. To realize the oscillation of single wavelength of 1319 nm in Nd:YAG, the reflectivities of the resonator mirror are designed, which also leads to the single wavelength output of second-order harmonic (659.5 nm). The laser output characteristics of fundamental and frequency-doubled wavelengths have been studied..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1178 (2007)
High Power 650 nm Red Semiconductor Laser with Transparent Window
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Zn-diffused high power 650 nm AlGaInP/GaInP material with compressively strained multi-quantum-well (MQW) active layer was fabricated. The zinc diffusion was used on the material facet in a sealed quartz tube. Photoluminescence (PL) spectra shows 175 meV blue-shift in the Zn diffusion area, which is transparent for 650Zn-diffused high power 650 nm AlGaInP/GaInP material with compressively strained multi-quantum-well (MQW) active layer was fabricated. The zinc diffusion was used on the material facet in a sealed quartz tube. Photoluminescence (PL) spectra shows 175 meV blue-shift in the Zn diffusion area, which is transparent for 650 nm laser emission. It can greatly reduce the light absorption at the laser facet and increase the threshold of catastrophic optical damage (COD). At last, a gain-induced semiconductor laser with 100 μm tripe width and 1mm cavity length 650 nm was fabricated, and the high power output for red semiconductor laser was realized. The maximum output power reaches up to 1.55 W at 2.28 A operation current. Threshold current and slope efficiency are 382 mA and 0.82 W/A, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1182 (2007)
Tunable Long Pulse TE CO2 Laser with Pulser/Sustainer Excitation
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A grating tuned long pulse ultraviolet (UV)-preionized TE CO2 laser excited by pulser/sustainer discharge is demonstrated. With gas mixture volume fraction of V(CO2):V(N2):V(He)=1:5:19 and total gas pressure of 30 kPa, the laser output pulse energies and laser pulse widths (full-width at half-maximum, FWHM) of altogethA grating tuned long pulse ultraviolet (UV)-preionized TE CO2 laser excited by pulser/sustainer discharge is demonstrated. With gas mixture volume fraction of V(CO2):V(N2):V(He)=1:5:19 and total gas pressure of 30 kPa, the laser output pulse energies and laser pulse widths (full-width at half-maximum, FWHM) of altogether 75 spectral lines are obtained. The measured results show that with the same pumping parameters the laser pulse width of each spectral line differs considerably as the grating is tuned from one line to another. Detailed measurement is carefully made on the laser output pulse widths of the four spectral lines 9R(20), 9P(20), 10R(20) and 10P(20) under different discharge voltage, discharge pulse width or gas mixture volume fraction, which strongly illustrate that the laser pulse width in a tunable long pulse TE CO2 laser with pulser/sustainer discharge varies with the output laser wavelength. By simultaneously measuring the discharge current waveform and the output laser pulse profile, it is found that the variation of the laser pulse width at each spectral line is perhaps mainly due to the gain difference of each spectral line..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1185 (2007)
1 kHz Electro-Optic Q-Switched Nd:YAG Laser with Complete Compensation of Thermally Induced Depolarization Loss
[in Chinese], [in Chinese], and [in Chinese]
A double Q-switcher-structured resonator that can completely compensate the thermally induced depolarization loss is designed to compensate thermally induced birefringence and thermal lens effect of solid gain medium to get higher output power from a 1 kHz laser diode (LD) side-pumped electro-optic Q-switched Nd:YAG laA double Q-switcher-structured resonator that can completely compensate the thermally induced depolarization loss is designed to compensate thermally induced birefringence and thermal lens effect of solid gain medium to get higher output power from a 1 kHz laser diode (LD) side-pumped electro-optic Q-switched Nd:YAG laser. We add a resonator branch along the way of the depolarization direction of the polarizer on the base of a conventional Q-switch uncompensated structure laser and the output is from the Nd:YAG crystal side. The experimental results show that, in the same situation, the pulse energy of the improved laser is 74.7% higher than that of original one. At a highest input energy of 307 mJ, the pulse energy of 26.2 mJ is obtained. The optic-optic efficiency is 8.5% and the angle of divergence is about 1 mrad..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1190 (2007)
Laser Diode End-Pumped, High-Power Continuous-Wave Single-Frequency Nd:YVO4 Ring Laser at 1064 nm
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The continuous-wave (CW) single-frequency single end-pumped 1064 nm laser with maximum output power of 9 W was experimentally demonstrated. An a-cut Nd:YVO4 crystal was end-pumped by a fiber-coupled laser diode (FCLD) at 808 nm. The four-mirror bow-tie ring cavity with a Faraday rotator and a half wave plate was applieThe continuous-wave (CW) single-frequency single end-pumped 1064 nm laser with maximum output power of 9 W was experimentally demonstrated. An a-cut Nd:YVO4 crystal was end-pumped by a fiber-coupled laser diode (FCLD) at 808 nm. The four-mirror bow-tie ring cavity with a Faraday rotator and a half wave plate was applied to eliminate the spatial hole-burning effect. A solid etalon was inserted into the cavity to obtain the single-frequency output with M2≈1.14. The maximum output power was 9 W and the optical-optical efficiency was 36.6% with 24.6 W of the incident power. The fluctuation of frequency was about 200 MHz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1194 (2007)
Laser Frequency Stabilization Based on Control of Intermode Beat Note
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new frequency-stabilized two-mode laser was introduced. Based on the relationship between optical frequency and intermode beat note, the intermode beat note was locked to the radio frequency standard by precise phase-locking technique to keep the cavity stable, so laser frequency stabilization was realized. TheoreticA new frequency-stabilized two-mode laser was introduced. Based on the relationship between optical frequency and intermode beat note, the intermode beat note was locked to the radio frequency standard by precise phase-locking technique to keep the cavity stable, so laser frequency stabilization was realized. Theoretical analysis shows that the stability of the laser frequency is identical with that of the intermode beat note. Experimentally, the intermode beat note of He-Ne laser was precisely locked to the radio frequency standard, and the laser frequency was also locked. The frequencies of two frequency-stabilized He-Ne lasers were compared. The result showed that the laser had a frequency stability of 5×10-10 at 1 s of averaging time and 5×10-11 in 100 s of averaging time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1198 (2007)
Steady-State Temperature Distribution Changes of Stripe Quantum-Well Laser Caused by Solder Void
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A model of internal heat source distribution is presented for quantum-well laser. Three-dimensional temperature distribution of the stripe quantum-well laser is simulated by using the finite element method, and the influence of solder voids between chip and heat sink on the steady-state temperature distribution is discA model of internal heat source distribution is presented for quantum-well laser. Three-dimensional temperature distribution of the stripe quantum-well laser is simulated by using the finite element method, and the influence of solder voids between chip and heat sink on the steady-state temperature distribution is discussed. It is found that the chip′s internal temperature distribution is influenced by the position and size of solder voids. The localized hot spot may result from the nether solder voids, and the strong localized temperature rises and the hot spot expands with the expanding of the void′s dimension. Simulated result shows further that the strongest temperature rise is caused by solder voids under the center of the electrode stripe, and moreover, the highest temperature lies at the front facet. So catastrophic optical damage (COD)will be found at the front facet most possibly, which is in agreement with the test..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1203 (2007)
Experimental Study on Polarization-Maintaining Fiber Laser
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By means of numerical analysis, based on the coupling wave function, the distribution of pump and output laser power along the fiber has been researched, and the optimal fiber length is calculated. The experimental research of the Nd3+-doped polarization-maintaining fiber laser is reported, which is pumped by 808 nm seBy means of numerical analysis, based on the coupling wave function, the distribution of pump and output laser power along the fiber has been researched, and the optimal fiber length is calculated. The experimental research of the Nd3+-doped polarization-maintaining fiber laser is reported, which is pumped by 808 nm semiconductor laser. The dichroic mirror of high transission (HT) at 808 nm and high reflection (HR) at 1060 nm is employed to construct the Fabry-Perot (F-P) cavity with the vertically-cut fiber cross section (Fresnel reflectivily of 4%). The influences of pump current on output power and polarization characteristic of the laser are studied. The fluorescence spectrum of Nd3+-doped fiber is measured. The maximum output power of the laser is 7.5 W at 1060 nm, and the slope efficiency is 56%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1208 (2007)
New Combined Phase Conjugator Consisting of Fused Silicon Rod and Optical Fiber
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new type of combined phase conjugator consisting of a fused silicon rod and an optical fiber is realized in experiment. This conjugator combines a large diameter fused silicon rod with high laser damage threshold and a fiber with a low stimulated Brillouin scattering (SBS) threshold. The composed SBS oscillator-ampliA new type of combined phase conjugator consisting of a fused silicon rod and an optical fiber is realized in experiment. This conjugator combines a large diameter fused silicon rod with high laser damage threshold and a fiber with a low stimulated Brillouin scattering (SBS) threshold. The composed SBS oscillator-amplifier construction of the two cells type makes a forced SBS process, in which the Stokes beam reflected from fiber injects in the fused silicon rod. According to this mechanism the combined phase conjugating mirror possesses lower SBS threshold and higher reflectivity than the conjugator with bulk fused silicon, single optical fiber or combined fiber. It can also be used in a high power laser system. In a laser diode (LD) pumped high power high repetition rate master oscillator power amplifier (MOPA) laser system with the proposed conjugator, 42.05% reflectivity under 100 Hz was obtained with high beam quality. The beam quality parameter M2 was reduced from 3 to 1.6 and the beam spot was stable. Under 400 Hz repetition the beam quality parameter M2 reached 1.7..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1212 (2007)
A Novel Method for Stability Analysis and Design of Laser Folded Cavity
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In order to optimize the design of laser resonant cavity, analytical solutions concerning Gaussian beam were derived in a three-mirror V-folded cavity by using the theory of optical propagation matrix. The cavity stability of the folded cavity laser was investigated with an equivalent simplified model. The influence ofIn order to optimize the design of laser resonant cavity, analytical solutions concerning Gaussian beam were derived in a three-mirror V-folded cavity by using the theory of optical propagation matrix. The cavity stability of the folded cavity laser was investigated with an equivalent simplified model. The influence of resonator parameters, such as folded mirror focus, cavity length and curvature radius, on the stability of Q-switched lasers were studied. The stable region′s boundary curve expression is obtained with the off-focus amount as a design parameter. According to theoretical analysis, a mechanically chopper-typed Q-switched CO2 pulse laser was taken as an application example. It was found that for one resonator with preset parameters, as long as the other resonator chose appropriate off-focus amount, the whole laser folded cavity was stable. Either of the resonator cavities can work with two stable regions, instead of previously supposed one. Appropriate stable position can be selected according to preset conditions. By adopting off-focus amount instead of factor g as the parameter, the stable region boundary and maladjusted error are derived directly, which is simple, straightforward and convenience for application..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1217 (2007)
An Approach to Improve Switch Performance of λ/4 Phase-Shifted Grating
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the coupled mode theory, by using the reversely recursive transmission matrix method, the switching characteristics of the λ/4 phase-shifted fiber grating and the influence of introducing chirp on the switching characteristics have been numerically studied when the reflection on the transmission facet is takenBased on the coupled mode theory, by using the reversely recursive transmission matrix method, the switching characteristics of the λ/4 phase-shifted fiber grating and the influence of introducing chirp on the switching characteristics have been numerically studied when the reflection on the transmission facet is taken into account. For coherent superposition reflection strengthening, it can reduce the threshold switching energy of the λ/4 phase-shifted grating, but the switching contrast will decline. With the introduction of negative chirp in λ/4 phase-shifted grating, the switching contrast is greatly improved, but the bistable threshold switching energy will increase. With the introduction of positive chirp in λ/4 phase-shifted grating, the switching threshold can be further reduced, but the switching contrast will decline. The bistable loop width will be influenced greatly by the chirp..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1250 (2007)
Laser Manufacturing
Microscopic Morphology and Microstructure of Phases between Dilution Zoneand Clad Zone in Laser Remelting NiCrBSi/TiN Layer
[in Chinese], and [in Chinese]
The microscopic morphology and microstructure of the phase between the dilution zone and the clad zone in laser remelting NiCrBSi/TiN layer on Ti-6Al-4V alloy surface were characterized by use of scanning electron microscope (SEM) and transmission electron microscope (TEM). The experimental results show that the microsThe microscopic morphology and microstructure of the phase between the dilution zone and the clad zone in laser remelting NiCrBSi/TiN layer on Ti-6Al-4V alloy surface were characterized by use of scanning electron microscope (SEM) and transmission electron microscope (TEM). The experimental results show that the microstructures between the dilution zone and the clad zone are Ti-Ni, Ti-Cr intermetallic and Ti-N compounds. The Ti and Ni atoms of Ti-Ni and Ti-Cr intermetallic compounds are replaced partly by Cr, Al etc., forming Ti2Ni, TiNi and Cr2Ti type intermetallic compound during laser remelting. Honeycomb structure exists in the Ti2.6Ni1.33 between Ti-N with maximum size around 40 nm and minimum size around 10 nm.The origin is that “gas mass” can not escape and keeps in the microstructure under rapid solidification..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1292 (2007)
Ablation of Metallic Glasses by Femtosecond Laser Pulses
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Femtosecond laser ablation of Zr-based metallic glasses in air, including micro-drilling, trenching and cutting, has been investigated. The surface profile of the ablated glass and the associated effect in the ablation area were examined by means of scanning electron microscope (SEM), energy dispersive X-ray (EDX) analFemtosecond laser ablation of Zr-based metallic glasses in air, including micro-drilling, trenching and cutting, has been investigated. The surface profile of the ablated glass and the associated effect in the ablation area were examined by means of scanning electron microscope (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscope (TEM) and electron diffraction. These studies indicate that slight oxidation occurs at the machined region. Molten trace, spatter and crystallization are not found in the vicinity of machined area. The result shows that femtosecond laser ablation with selected parameters is a promising method for micromachining metal glasses without crystallization..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1297 (2007)
Numerical Simulation of Bending Properties for Sheet Metal with Different Laser Source Modes
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The three-dimensional elastoplastic thermo-mechanical coupled finite element model of laser forming for pure aluminum plates is established with nonlinear finite element analysis software Msc.Marc. Circular, square, rectangular 1/4 ( the size ratio of laser spot along the laser scanning direction and its vertical direcThe three-dimensional elastoplastic thermo-mechanical coupled finite element model of laser forming for pure aluminum plates is established with nonlinear finite element analysis software Msc.Marc. Circular, square, rectangular 1/4 ( the size ratio of laser spot along the laser scanning direction and its vertical direction is 1:4, same as below) and rectangular 4/1 laser spots with the same area are chosed as the heat sources. The bending properties of sheet metal with four different laser source modes are simulated, and the temperature field, displacement field, stress and strain field are analyzed. The results show that the circular laser spot acquires the highest temperature peak value and temperature differences between upper and lower surfaces, while the rectangular1/4 laser spot acquires the largest width of high temperature zone. The rectangular 1/4 laser spot which owns the widest plastic strain zone and highest total plastic strain differences between upper and lower surfaces obtains the highest bending angle,and also the lowest residual stress..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1303 (2007)
Temperature/Stress Field Numerical Simulation of Hollow Blade Produced by Laser Rapid Forming
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A transient temperature/stress field finite-element model for the laser rapid forming (LRF) process of a hollow blade of aeroengine is developed. The deposition process is simulated with the finite element birth and death technology, the thermo-plastics is analyzed by bilinear isotropic hardening and Von Mises yield crA transient temperature/stress field finite-element model for the laser rapid forming (LRF) process of a hollow blade of aeroengine is developed. The deposition process is simulated with the finite element birth and death technology, the thermo-plastics is analyzed by bilinear isotropic hardening and Von Mises yield criteria, and the indirectly coupled temperature/stress field evolution during the LRF process of a TC4 alloy hollow blade is simulated. The results show that during the LRF process of a TC4 alloy hollow blade, the temperature/stress field in the TC4 alloy hollow blade is dynamically developed with the movement of melting pool and increase of forming height. For the reason of cooling/constrain effect of the substrate and heating/stress-release effect of the melting pool, the temperature/stress field gradient distributes along the altitude direction. The temperature declines from the top to the bottom, and the heat dispersing direction was from the top to the bottom i.e., from the melting pool to the substrate. The stress field increases from the top to the bottom, and reaches a maximum at the bottom of the blade. When the blade was cooled to room temperature, the residual stress distribution is similar to that in the cladding process, expect for a larger stress at the top of the blade..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1308 (2007)
Laser Physics
Calculation for Electronic Structure and Optical Properties of LiNbO3 Crystals
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The electronic energy band structure and linear optical coefficient of LiNbO3 crystal were calculated by first-principle calculation pseudo-potential plane wave method in CASTEP package, and the nonlinear optical coefficient of LiNbO3 was calculated based on coupled Hatree-Fock (CPHF) model. The calculated refractive iThe electronic energy band structure and linear optical coefficient of LiNbO3 crystal were calculated by first-principle calculation pseudo-potential plane wave method in CASTEP package, and the nonlinear optical coefficient of LiNbO3 was calculated based on coupled Hatree-Fock (CPHF) model. The calculated refractive indices and second-harmonic-generation (SHG) coefficients matched well with experimental results. The results shows that the 4d orbital of Nb atom and 2p orbital of O atom in LiNbO3 crystal are hybridized, which is the origin of the nonlinear property which can be deduced from the characteristics of electronic density of states on upper part of valence bands and bottom part of conduction bands. The calculated results also indicate that the Li－O bond in the crystal shows typical covalent characteristic..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1227 (2007)
Efficiency Analysis of Transversly Pumped-Dye Laser Oscillator
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
According to various pumping styles, the laser output efficiency and optimal output coupling are different, and so do other parameters. Based on theory of rate equation, the optical-to-optical conversion efficiency of 511 nm copper vapor laser (CVL) transversely pumped Rh6G dye laser oscillator is studied. Result showsAccording to various pumping styles, the laser output efficiency and optimal output coupling are different, and so do other parameters. Based on theory of rate equation, the optical-to-optical conversion efficiency of 511 nm copper vapor laser (CVL) transversely pumped Rh6G dye laser oscillator is studied. Result shows that the major reason of the difference of optical-to-optical conversion efficiency and output coupling between transverse pumping and longitudinal pumping is dye self-absorption. Experiments of transverse pumping have been done for various Rh6G concentration and output coupling mirror′s reflectivity, and the highest optical-to-optical conversion efficiency 8.2% was obtained. The relation between the efficiency and dye concentration and the reflectivity of output mirror was given. Experimental results show that the lower Rh6G concentration could reduce the influence of dye self-absorption on laser output efficiency, and meanwhile the optimal output coupling mirror′s reflectivity in transverse pumping is bigger than that in longitudinal pumping..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1232 (2007)
Radiation and Collision Energy Transfer of Excitated Cs(6P) Atoms Mixed with He
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By applying the laser absorption and fluorescence method, the cross sections for the fine structure mixing and quenching of the Cs(6P) state, induced by collision with He atoms, have been measured. Cesium atoms were optically excited to the 6P3/2 state. The excited atom density and spatial distribution were mapped by mBy applying the laser absorption and fluorescence method, the cross sections for the fine structure mixing and quenching of the Cs(6P) state, induced by collision with He atoms, have been measured. Cesium atoms were optically excited to the 6P3/2 state. The excited atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single mode laser beam, which was tuned to the 6PJ→8S1/2 transitions. The effective radiative rates were calculated for the 6PJ→6S transitions. The fluorescence intensity I895 of the sensitized 6P1/2→6S1/2 emission was measured as a function of He density in the range 0.5×1018～4×1018cm-3 at constant temperature T=337 K. It was found that the quantity N/I895 exhibited a parabolic dependence on N, confirming that the quenching of the 6PJ states was due to collision with He atoms, not ground state Cs atoms. The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections σ3/2→1/2=(1.46±0.51)×10-19 cm2 and σD=(2.28±0.80)×10-18 cm2 for the 6PJ fine structure mixing and quenching, respectively, due to collision with He atoms..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1237 (2007)
Materials and Thin Films
Anti-Reflection Coating Designed by Genetic Algorithm
[in Chinese], and [in Chinese]
An approach for designing multilayer optical coatings is presented by use of genetic algorithm. With a predetermined maximum layer number, the algorithm automatically specifies the appropriate layer number and material and thickness of each layer. Evaluation function used here is different from the others before. The 1An approach for designing multilayer optical coatings is presented by use of genetic algorithm. With a predetermined maximum layer number, the algorithm automatically specifies the appropriate layer number and material and thickness of each layer. Evaluation function used here is different from the others before. The 1064 nm, 532 nm frequency-doubled anti-reflection coating is designed on LBO (LiB3O5) substrate with two evaluations functions. Two coating structures are found with high transmissivities, one with transmissivity 99.98% at 1064 nm and 99.99% at 532 nm, the other with transmissivity of 100.00% at both wavelengths. The broad-band anti-reflection coating on K9 glass substrate is designed. The transmissivities of two broad-band antireflection coatings optimized over a range of wavelength (450～650 nm) and (390～780 nm) are above 99.91% and 99.30% respectively. If the evaluation function is sensitive to the deviation of coating structure, the approach by genetic algorithm is effective..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1271 (2007)
Spectra and Nonlinear Optical Properties of Two Azobenzene Compounds in Langmuir-Blodgett Films
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The N=N bridge in azobenzenes molecules with push-pull structures at the two ends provides excellent channels for electrons. This is an advantage for generation of nonlinear optics effect. And the nonlinear optical properties of the azobenzene compounds are greatly affected by the push-pull electronic groups. The spectThe N=N bridge in azobenzenes molecules with push-pull structures at the two ends provides excellent channels for electrons. This is an advantage for generation of nonlinear optics effect. And the nonlinear optical properties of the azobenzene compounds are greatly affected by the push-pull electronic groups. The spectra and nonlinear optical properties of Langmuir-Blodgett (LB) films of two kinds of push-pull azobenzene compounds were investigated by using ultraviolet (UV)-visible absorption spectra and second harmonic generation (SHG) technique. The steady mono-molecular film could be formed at the interface of air/water and transferred well onto solid substrates, forming high-quality LB multilayer films for the 4-(nitro)-4′-(amido)-azobenzene (NAA) and 4-(carboxylic)-4′-(amidogen)-azobenzene(CAA) molecules. Because the －NO2 has a stronger ability on pulling electron than －COOH, the transfer of the intra-molecular electron is easier and could form bigger molecular dipole for NAA than that for CAA. So it could have a more significant second-order nonlinear hyperpolarizability. The second-order nonlinear optical coefficient d33 of experimental measurement for NAA and CAA in LB films were 40.8 pm/V and 24.2 pm/V, and the hyperpolarizabilities β were 1.97×10-29 esu and 1.17×10-29 esu respectively. The hyperpolarizabilities β of NAA molecule was about 1.7 times bigger than CAA molecule′s. The experimental results agreed well with the theoretical calculation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1276 (2007)
Effect of Temperature on Structure and Properties of Femtosecond Laser Deposited Silicon Based Zinc Oxide Thin Films
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Zinc oxide films were prepared on n type Si(100) substrate using femtosecond laser deposition with laser parameters as follows: pulse width 50 fs, wavelength 800 nm, repeat frequency 1 kHz, and pulse energy 2 mJ. The effects of substrate temperature change and annealing on the structure, surface morphology and optical Zinc oxide films were prepared on n type Si(100) substrate using femtosecond laser deposition with laser parameters as follows: pulse width 50 fs, wavelength 800 nm, repeat frequency 1 kHz, and pulse energy 2 mJ. The effects of substrate temperature change and annealing on the structure, surface morphology and optical properties of the ZnO films were discussed. The X-ray diffraction (XRD) results showed the ZnO films deposited under different temperature (20～350 ℃) were with wurtzite structure and highly c-axis oriented. When the substrate silicon was 80 ℃ the film was highly (002)-oriented, and (103)-oriented at 500 ℃. The nano-crystal structure of the films and hexagonal structure of ZnO were observed with a field-emission electron microscope (FEEM). The effects of substrate temperature and annealing on the optical transmissivity of ZnO films were discussed by transmitted spectra, and the transmissivity was increased after annealing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1282 (2007)
Optimal Design and Arithmetic on Stack of Angle-Tuned Filter
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
According to the characteristics of the thin film narrowband filter, the angle-tuned filter with stable transmission peak and bandwidth can be designed by amelioration of the structure of the stack and adjust of effective refractive index of the spacer. At the same time, the central wavelength of S-polarization and P-pAccording to the characteristics of the thin film narrowband filter, the angle-tuned filter with stable transmission peak and bandwidth can be designed by amelioration of the structure of the stack and adjust of effective refractive index of the spacer. At the same time, the central wavelength of S-polarization and P-polarization will separate when the filter is tilted, which causes the polarization dependent loss. The phenomena of polarization separation and its relationship to the effective refractive index of the filter are analyzed. A method about eliminating the polarization separation is presented. Theoretical analysis model is built up and an angle-tuned filter design method is provided based on the theory of thin film matrix. A 100 GHz dense wavelength division multiplexing (DWDM) four-cavity angle-tuned narrowband filter with low polarization dependent loss is optimized and fabricated based on the programme. The experimental results prove it meets the demand of design and its tunable range is about 20 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1287 (2007)
Measurement and Metrology
Dynamic Measurement of Small Angle with Two Prisms
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A method is presented based on tangent relationship and phase modulation technique for dynamic small angle measurement. Two parallel beams reflected by a measurement arm composed of two prisms are directed into a beam splitter to form an interference signal which is analysed to obtain the measurement result of small anA method is presented based on tangent relationship and phase modulation technique for dynamic small angle measurement. Two parallel beams reflected by a measurement arm composed of two prisms are directed into a beam splitter to form an interference signal which is analysed to obtain the measurement result of small angle. A position sensitive device (PSD) is used to measure the separations between the two parallel beams, the measurement equation is simplified and the symmetry requirement of the two prisms in the optical configuration is eliminated. The phase of interference signal is modulated in time domain by sinusoidally changing the injection current of a laser diode. This results in a quasi-heterodyne measurement mode, which increases the measurement accuracy of optical path difference. The method is experimentally demonstrated and the factors affecting measurement accuracy are discussed. The experimental results show the dynamic small angle can be measured with a repeatability of 10-8 rad order of magnitude..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1255 (2007)
Long-Focal-Depth Lens for Laser Plasma Diagnostic System
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Aiming at the requirement of long-focal-depth elements used for the plasma diagnosis in inertial confinement fusion (ICF), a spheric lens with 150 mm aperture, 450 mm focus length, and 5 mm depth of focus is designed by nonlinear phase fitting method. In order to verify the correctness and feasibility of this method, aAiming at the requirement of long-focal-depth elements used for the plasma diagnosis in inertial confinement fusion (ICF), a spheric lens with 150 mm aperture, 450 mm focus length, and 5 mm depth of focus is designed by nonlinear phase fitting method. In order to verify the correctness and feasibility of this method, a lens with a long-focal-length and the same F numbers (calibre 80 mm, focal length 240 mm) is fabricated. Moreover, the on-axis and transverse intensity distributions of parallel light after passing the lens are measured. The theoretical and experimental result indicates that the beam from the long-focal-depth lens has long focal depth, small focal spot and side lobe and it can meet the requirements of inertial confinement fusion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1260 (2007)
Sensing Characteristics to Ethanol Vapor of Sol-Gel Stripe Waveguides Incorporated in a Sagnac Loop
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A stripe waveguide was fabricated by organic-inorganic hybrid sol-gel technology. The waveguide was connected into a Sagnac fiber loop to measure output power under environment of different ethanol vapor volume fraction. It was found that the output signal varied in a sinusoidal function of ethanol vapor volume fractioA stripe waveguide was fabricated by organic-inorganic hybrid sol-gel technology. The waveguide was connected into a Sagnac fiber loop to measure output power under environment of different ethanol vapor volume fraction. It was found that the output signal varied in a sinusoidal function of ethanol vapor volume fraction within the measured range. According to the property of Sagnac loop, the measured behavior indicates that there exists birefringence caused by ethanol vapor absorption into the sol-gel material. The birefringence phase shift was observed to vary with ethanol vapor volume fraction in a sub-linear way. The coefficients of the linear term and second order term were calculated from the experimental data fitting, and the birefringence sensitivity to ethanol volume fraction was evaluated to be Δn≈4.4×10-2. The temporal signal change was also measured, and the typical rising and falling time constants were obtained to be 3 min and 12 min respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1263 (2007)
All Fiber-Optic Sinusoidal Phase-Modulating Interferometer Insensitive to Intensity Modulation of Light Source
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In a laser-diode (LD) sinusoidal phase-modulating (SPM) interferometer, the wavelength of the LD is modulated by varying its injection current, but at the same time the intensity of the LD is modulated too, which causes a major measurement error. To decrease the effect of the intensity modulation of the LD on measuremeIn a laser-diode (LD) sinusoidal phase-modulating (SPM) interferometer, the wavelength of the LD is modulated by varying its injection current, but at the same time the intensity of the LD is modulated too, which causes a major measurement error. To decrease the effect of the intensity modulation of the LD on measurement accuracy, a novel LD-SPM fiber-optic interferometer is presented, and the theory of the interferometer is analyzed. The all fiber-optic structure decreases the influence of extermal perturbation on interference measurement effectively. Using this interferometer with simple pre-signal process circuit and real-time phase detector, the measurement error caused by LD intensity modulation is eliminated, and the displacements are measured with a higher accuracy (a few nanometers). And the measurement repeatability is less than 1 nm. The experimental results are consistent with those with other methods to eliminate influence of intensity modulation. The validity of the new interferometer is proved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1267 (2007)
Optical Communication
10 GHz Short Optical Pulses Source with Ultra-Low Jitter
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The highly stable 5.3 ps wide optical pulse source with a repetition rate of 10 GHz, and 184 fs timing jitter is reported. 10 GHz optical pulses generated by a deeply directly modulated laser (DML)enter a LiNbO3 electroopitc phase modulator to enhance the negative chirp and enlarge pulse width, and pass through dispersThe highly stable 5.3 ps wide optical pulse source with a repetition rate of 10 GHz, and 184 fs timing jitter is reported. 10 GHz optical pulses generated by a deeply directly modulated laser (DML)enter a LiNbO3 electroopitc phase modulator to enhance the negative chirp and enlarge pulse width, and pass through dispersion compensation fibers (DCF) to compress chirps. The optical pulses generated by DML have negative chirp, and phase modulation can generate both positive and negative chirp at different timing intervals. By appropriately tuning optical time delay before optical pulses enter the phase modulator, the output optical pulses can have more negative chirp. Then, the chirped optical pulses can be compressed into low timing-jitter short pulses without pedestal by positive dispersion fiber..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1241 (2007)
Analysis of Error Performance for Turbo Coded Digital Pulse Interval Modulation under Weak Turbulence
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The symbol length of digital pulse interval modulation (DPIM) is variable, so there are some difficulties to analyze error performances of Turbo coded DPIM. After the analytic model is set up and the error rate is derived, the system error performances of uncoded and Turbo coded DPIM are simulated and analyzed under weThe symbol length of digital pulse interval modulation (DPIM) is variable, so there are some difficulties to analyze error performances of Turbo coded DPIM. After the analytic model is set up and the error rate is derived, the system error performances of uncoded and Turbo coded DPIM are simulated and analyzed under weak turbulence channel, and the system error performances under Gaussian channel are simulated for comparison. The results show that error performances under weak turbulence channel are inferior to those under Gaussian channel, but for the two channels, introduction of Turbo code can get the code gain of 3～6 dB, which improves the error performance of system effectively and has applied value for military communications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 9, 1245 (2007)
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