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1.
Surface evolution and laser damage resistance of CO2 laser irradiated area of fused silica 总被引:1,自引:0,他引:1
W. Dai X. Xiang Y. Jiang H.J. WangX.B. Li X.D. YuanW.G. Zheng H.B. LvX.T. Zu 《Optics and Lasers in Engineering》2011,49(2):273-280
A 10.6 μm CO2 laser has been reported to effectively mitigate the laser damage growth of fused silica. Two zones of the laser irradiated area are defined in this work: the distorted zone and the laser affected zone. The parameters of the two zones are studied at different CO2 laser beam sizes, irradiation times, and powers by microscopy, profilometry, and photoelastic method. The results show that the diameter of laser affected zone is almost completely determined by the laser beam size and the distorted zone is associated with the mitigation range of CO2 laser beam. The diameter and depth of the distorted zone increase as the laser power and irradiation time increase. The depth grows exponentially depending on the irradiation time. The maximum residual stress discrepancy is located near the boundary of the laser affected zone. The laser damage resistance test results show that the distorted zone and the laser affected zone have a better damage resistance than the original substrate. 相似文献
2.
Various criteria for designing high power convective cooled CO2 lasers have been discussed. Considering the saturation intensity, optical damage threshold of the optical resonator components
and the small-signal gain, the scaling laws for designing high power CW CO2 lasers have been established. In transverse flow CO2 lasers having discharge of square cross-section, the discharge lengthL and its widthW for a specific laser powerP (Watt) and gas flow velocityV (cm/s) can be given byL = 1.4 x 104
p
1/2
V
-1 cms andW = 0.04P
1/2 cms.
The optimum transmitivity of the output coupler is found to be almost constant (about 60%), independent of the small signal
gain and laser power. In fast axial flow CO2 lasers the gas flow should be divided into several discharge tubes to maintain the flow velocity within sonic limit. The
discharge length in this type of laser does not depend explicitly on the laser power, instead it depends on the input power
density in the discharge and the gas flow velocity. Various considerations for ensuring better laser beam quality are also
discussed. 相似文献
3.
Laser ablation can be achieved by delivering short power pulse with durations much smaller than the heat diffusion time. In this investigation, we are collimating and magnifying a beam from a CO2 laser with a Keplerian telescopic system. Then we study the quality of the cut performed by scanning the beam at a fast speed over an optical fiber just after focusing a well collimated CO2 beam at λ=10.6 μm. It is found that the best results for cutting optical fibers depend upon both the time required in raising matter temperature to the vaporization point and the scanning speed of the CO2 laser beam. Some aspects of the laser beam collimation before focusing is reviewed briefly and results for optical fibers being cleaved at low and fast speed under various conditions are also shown and discussed. 相似文献
4.
We present the measurements made on a medium power, 35 cm long, radio-frequency discharge CO2 slab laser operated in a pulsed regime obtained by switching the RF discharge. In this way, pulses with peak power up to 480 W at pulse repetition frequencies in the range 1 to 10 kHz have been obtained. Pulse energy and average extracted power have been experimentally characterized with respect to the pulse repetition frequency and to the pulse duration, and the pulse shape and characteristic times have been measured. We also investigated the propagation properties of the beam emerging from our laser. 相似文献
5.
The properties of a high density plasma focus produced inside a ring target with an Nd laser have been investigated. Studies of the axial propagation of a CO2 laser beam through the plasma focus have shown that the device can be used either as a fast pulse clipper or as an optical isolator for high power infra-red lasers. Self-focussing, strong refraction and defocussing and non-classical absorption of the CO2 laser beam have all been observed. 相似文献
6.
A. K. Nath T. Reghu C. P. Paul M. O. Ittoop P. Bhargava 《Optics & Laser Technology》2005,37(4):469-335
A transverse flow transversely excited (TFTE) CW CO2 with a maximum output power about 15 kW has been developed. This is excited by pulser sustained DC discharge applied between a pair of multi-pins anodes and a common tubular cathode. Though the laser power in convective cooled CO2 laser scales proportionally with the volumetric gas flow, it did not increase in this laser when the volumetric gas flow was increased by increasing the electrode separation keeping the flow velocity constant. The discharge voltage too remained almost unchanged with increase of the electrode separation. These observations are explained considering the electrical discharge being controlled by ionization instability. Laser materials processing applications often demand programming facilities for laser power modulation. A four-stage cascaded multilevel DC–DC converter-based high-frequency switch mode power supply has been developed to modulate the output power of the laser. Laser was operated up to 15 kW output power in four different modes viz. continuous wave mode, pulse periodic mode, single shot mode and processing velocity-dependent power mode with 1.2 kHz modulation bandwidth. We describe briefly the laser system, the SMPS, and the temporal behavior of laser beam. 相似文献
7.
Jijiang Xie Qikun Pan Ruhai GuoLaiming Zhang Peng Ruan Dianjun LiGuilong Yang Chuansheng ZhangJin Guo 《Optics and Lasers in Engineering》2012,50(2):159-164
A compacted size high power CO2 laser has been developed using an acousto-optically (AO) Q-switch. Performance characteristics have been investigated as a function of output mirror transmittance. The theory of six-temperature model for CO2 lasers has firstly been utilized to analyze the dynamical process in the AO Q-switched CO2 laser. This theory perfectly explains the behavior of energy transfer between different molecules in laser gain medium, and describes the shape of pulse laser. The calculated pulse waveforms are in good agreement with the experimental result. Both the experimental and theoretical results present that the optimal value of output mirror transmittance is 39%. Under this condition, the measured peak power is 4750 W and pulsed width is 160 ns, which is consistent with the calculations. Six-temperature model is a perfect theory for CO2 laser kinetics, which will lay a theoretical foundation for the laser optimum design. 相似文献
8.
T. Okada S. Inoue T. Ohga K. Muraoka M. Akazaki 《International Journal of Infrared and Millimeter Waves》1985,6(9):883-892
A D2O laser has been developed for collective Thomson scattering measurements of ion temperature in high temperature plasmas. A pulse duration and a spectral width of a high power D2O laser has been successfully controlled for this purpose, by using a TEA CO2 laser injection-locked by an etalon-tuned TEA CO2 laser as a pump source. 相似文献
9.
A transverse flow, transverse discharge cw CO2 laser in which de discharge is sustained by employing high repetition rate high voltage pulses has been developed. Pulser
sustained discharge through electrodes of innovative design provided uniform excitation at electrical input power densities
more than 10 W/cc. Laser output power more than 2.5 kW was obtained in a laser gas mixture consisting of 0.5 mbar of CO2, 16 mbar of N2 and 38.5 mbar of He. Design details and operational characteristics of this laser are presented. 相似文献
10.
Spectroscopic comparison of aluminium welding plasmas produced by high power CO and CO2 lasers 总被引:1,自引:0,他引:1
Welding tests on the aluminium alloy AlMgSi1 (6082) by the use of a high power CO laser with good beam quality show higher penetration depths and better weld seam quality compared with the results obtained with a commercial industrial CO2 laser. Spectroscopy of the laser-induced welding plasma shows a strong decrease of the intensities of Al(II) lines and no appearance of Al(III) lines in CO laser aluminium welding compared with CO2 laser welding at the same process parameters. This is a consequence of the shorter 5 to 5.6 μm wavelength of the CO laser leading to reduced beam-plasma interaction. 相似文献
11.
Three pressures of gases (CO2, N2 and He) added into CO2 laser tube are optimized for obtaining maximal laser output power by applying a genetic algorithm and solving the CO2 laser kinetics equations. After the optimization, the laser power is increased by 96% as compared with a non-optimal case. 相似文献
12.
Lasers for materials processing: specifications and trends 总被引:2,自引:0,他引:2
K. Du J. Biesenbach D. Ehrlichmann U. Habich U. Jarosch J. Klein P. Loosen J. Niehoff R. Wester 《Optical and Quantum Electronics》1995,27(12):1089-1102
An overview is given of the types of lasers dominating the field of laser materials processing. The most prominent lasers in this field are the CO2 and the Nd: YAG laser. The domain of CO2 lasers is applications which demand high laser powers (up to 30 kW are available at present), whereas the domain of Nd:YAG lasers is micro-machining applications. In the kilowatt range of laser output power, the two types of lasers are in competition. New diffusion-cooled CO2 laser systems are capable of output laser powers of several kilowatts, with good beam qualities, while still being quite compact. The output power and beam quality of Nd:YAG lasers has been improved in recent years, so that Nd:YAG lasers are now an alternative to CO2 lasers even in the kilowatt range. This is especially true for applications that demand optical fibre transmission of the laser beam, which is possible with Nd:YAG laser light but not with the longerwavelength light emitted by CO2 lasers. The main problem in solid-state lasers such as Nd:YAG is the thermal lensing effect and damage due to thermal stresses. In order to reduce thermal loading, cooling has to be enhanced. Several alternative geometries have been proposed to reduce thermal loading and, by this, thermal lensing effects. There are now slab and tube geometries which allow much higher output powers than the conventionally used laser rods. A very new scheme proposes a thin slab whose cooled side is also used as one of the laser mirrors, so that thermal gradients occur mainly in the direction of the beam propagation and not perpendicular to it, as is the case in the other geometries. As well as CO2 and Nd:YAG lasers, semiconductor laser diodes are very promising for direct use of the emitted light or as pump sources for Nd:YAG and other solid-state lasers. When packaging together thousands of single laser diodes, output powers of several kilowatts can be realized. Major problems are collimation of the highly divergent laser beams and cooling of the laser diode bars. 相似文献
13.
Sung-Joon Park 《Optics & Laser Technology》2010,42(2):269-273
A microprocessor-based algorithm was developed to control the power supply to a CO2 laser using an AC-chopper method. This system was connected directly to a CO2 laser tube without the need for a dc-dc converter or the storage capacitance of a multilevel circuit. The typical CO2 laser power supply system had a full-bridge series resonant inverter or voltage multiplier. AC-to-AC converter schemes using zero voltage switching (ZVS) can be used efficiently and economically for low and medium power applications.This paper reports the performance characteristics of a symmetrical AC-chopper technology that can maintain the quality of the ac output of a CO2 laser tube, regardless of the amount of switching loss. The laser was operated to an output power, maximum system efficiency total gas mixture of 37.2 W, 92%, and CO2:N2:He=1:9:15, respectively. The laser system, AC-chopper power supply and its operation were examined. 相似文献
14.
O. De Pascale C. Esposito M. Lepore P. Boffi M. Gaudio M. Vilnio 《Optics and Lasers in Engineering》1989,10(2)
Plane-polarized CO2 laser beams can be successfully employed in controlled surface temperature laser heat treating in order to improve the coupling between radiation and steel. The coupling efficiency has been quantitatively determined by means of a simple energy balance model, by using a medium-power CO2 laser. In this way, the angle at which the best coupling can be obtained has also been singled out. Moreover, some heat treatments performed with a high power laser beam obliquely impinging on medium carbon steel samples have confirmed that controlled surface temperature laser heat treating can be completely free of the problems concerning the use of coatings generally employed. 相似文献
15.
The formation mechanism of rapidly solidified microstructures in a magnesia partially stabilised zirconia (MgO-PSZ) following CO2 laser radiation has been investigated. The influence of laser processing parameters on the microstructures of this material was analysed based on a review of the basic concepts of solidification, the theories of constitutional suppercooling and morphological stability. The different microstructures that were brought about by various laser parameters and appeared across the same track were examined based on the CO2 laser beam profile of a transverse electromagnetic mode (TEM01). The contact angle measurement revealed a better wettability characteristic of CO2-laser-modified MgO-PSZ. The clear differences were observed in the change in contact angle for glycerol across the range of rapid solidification microstructures obtained with various power densities. It was therefore determined that the degree of rapid surface resolidification could be the most predominant element governing the wettability characteristics of the MgO-PSZ. The sharp reduction of contact angle for glycerol took place when the cellular microstructure appeared and might be accompanied by the onset of melting on the modified surface of the MgO-PSZ. Moreover, the CO2 laser treatment also brought about the change in the surface oxygen content and surface roughness. The analysis showed that surface oxygen content was also an influential factor in changing the wettability characteristics of the MgO-PSZ, whilst surface roughness was found to play an insignificant role. The work provides the clear evidence that laser radiation can be a workable and controllable technique to modify the wetting characteristic of the MgO-PSZ. 相似文献
16.
Zirconium dioxide (ZrO2) thin films were deposited on BK7 glass substrates by the electron beam evaporation method. A continuous wave CO2 laser was used to anneal the ZrO2 thin films to investigate whether beneficial changes could be produced. After annealing at different laser scanning speeds by CO2 laser, weak absorption of the coatings was measured by the surface thermal lensing (STL) technique, and then laser-induced damage threshold (LIDT) was also determined. It was found that the weak absorption decreased first, while the laser scanning speed is below some value, then increased. The LIDT of the ZrO2 coatings decreased greatly when the laser scanning speeds were below some value. A Nomarski microscope was employed to map the damage morphology, and it was found that the damage behavior was defect-initiated both for annealed and as-deposited samples. The influences of post-deposition CO2 laser annealing on the structural and mechanical properties of the films have also been investigated by X-ray diffraction and ZYGO interferometer. It was found that the microstructure of the ZrO2 films did not change. The residual stress in ZrO2 films showed a tendency from tensile to compressive after CO2 laser annealing, and the variation quantity of the residual stress increased with decreasing laser scanning speed. The residual stress may be mitigated to some extent at proper treatment parameters. 相似文献
17.
The laser beam absorption lengths of CO2 and a high power diode laser (HPDL) radiation for concrete have been determined. By employing Beer–Lambert’s law the absorption lengths for concrete of CO2 and a HPDL radiation were 470±22 μm and 177±15 μm, respectively. Indeed, this was borne out somewhat from a cross-sectional analysis of the melt region produced by both lasers which showed melting occurred to a greater depth when the CO2 laser was used. 相似文献
18.
In this article, the construction of P-type germanium (Ge) photon drag detector which is used to characterize the gain and output powers of a 10 W CO2 laser and a CO2 laser amplifier is described. Gain and laser amplifier output power versus laser input power measurements collected at 4.7 mbar and 12.0 mbar amplifier tube pressures are discussed. Moreover, measurements relating the CO2 laser output power to the laser tube discharge current are provided at 6.9 mbar and 7.3 mbar tube pressures. 相似文献
19.
This paper presents a heat transfer model to calculate the temperature field in moving glass rods heated by a CO2 laser. Conduction and radiation heat transfer in radial and axial directions are taken into account in the current model. The Rosseland diffusion approximation is incorporated to analyze the radiation heat transfer in the glass rod. A two-band model is used to simulate the spectral property of the glass. Results of the simulation show that glass rods of sufficiently large optical thickness should be treated as a semitransparent medium for radiative transfer, and it is reasonably accurate to assume it to be opaque to CO2 laser irradiation. It has been shown that the resulting temperature profile is strongly dependent on the laser parameters, i.e., the size of laser beam and the power of the laser. The diameter and speed of the moving glass rod are also important in determining the temperature field although the convective heat transfer coefficient between the glass rod and the environment has little effect. 相似文献
20.
J. Kobayashi Y. Izumi M. Kumakura Y. Takahashi 《Applied physics. B, Lasers and optics》2006,83(1):21-25
By stabilizing the beam pointing of optical trapping beams, we have succeeded in stable formation of Bose–Einstein condensate
(BEC) of 87Rb with all-optical method. The thermal effect of acousto-optic modulator (AOM) is usually one of the most serious problems
to induce beam-pointing instability, especially for high power CO2 laser. By passing the beam through AOM twice, we have improved the beam pointing from about 4.8 mrad to less than 0.4 mrad,
which has been experimentally confirmed to be small enough to stably form BEC at the crossed region of CO2 lasers as well as to perform experiments using an optical lattice which might have been affected by beam-pointing instability.
PACS 32.80.Pj; 42.79.Jq; 03.75.Mn 相似文献