High-power low-mode dynamic laser resonant
The invention belongs to laser technology.It is the lateral flow high power CO
2Laser provides a kind of high-output power, low-order mode (TEM
Mn, m+n≤2 wherein), the optical resonator of good beam quality.
In laser processing industry, except laser beam being required certain power, also having an important indicator is optical quality, i.e. beam directionality's (or angle of divergence) of indication usually.Have only the beam directionality good more, the power density of focusing is high more, just can be widely used in the processing such as cutting, welding of material.Realize this requirement, need carry out modeling laser.At present industrial multikilowatt crossing current CO
2Laser, because its gain length is shorter, and it is bigger to activate (discharge) volume, as adopts common steady chamber to add light hurdle modeling, certainly will greatly sacrifice power output and does not have Practical significance.Therefore adopt the refrative cavity technology mostly,, make full use of activation volume, obtain the output of high power single transverse mode laser by increasing the gain by one path that light path improves medium.The SPECTRA820 type CO of Spectra-Physics for example
2Laser adopts many folding cavity configurations, and Huazhong Institute of Technology also is many foldings chambeies.This refrative cavity structure, optical element is many, complex structure, it is big to adjust difficulty, accomplish difficulty of high chamber stability, and particularly owing to the intercrossing of folded optical path, discharging structure also need be complementary with it, and this changes too big to laser that China produces at present.
The purpose of this invention is to provide a kind of laserresonator simple in structure, the industrial multimode CO of multikilowatt that can produce at present in China
2Use on the laser product, obtain the output of multikilowatt low-mode laser, beam divergence angle is less than 3.5 milliradians, and the photoelectric conversion efficiency height, can running steady in a long-term.
Technical solution of the present invention is, design a kind of concavo-convex chamber of dynamic stability, its static structure is made up of completely reflecting mirror, modeling light hurdle and output eyeglass, said completely reflecting mirror is the sphere completely reflecting mirror of concave surface in the chamber of water-cooled, be characterized in that modeling light field is in the resonant cavity of output eyeglass one end, said output eyeglass is flat, a recessed double-sided lenses, and the plane is in the chamber, when the laser high power turned round, this output eyeglass absorbing light caused the protruding change in plane and forms the concavo-convex resonant cavity of dynamic stability with the completely reflecting mirror sphere.
Described output eyeglass is that material of infrared window is made, and preferably its plane is plated and increased anti-film, concave surface plating anti-reflection film, the optimum transmission of output eyeglass when the transmitance of eyeglass is the laser multimode cavity, the radius of curvature R of concave surface=(2~3L
o), L wherein
oBeam waist is to the distance of output eyeglass when being multimode flat-concave cavity Maximum Power Output.
Described modeling light hurdle is a sheet metal, and the two sides is diffuse surface, and the pass of the unthreaded hole on light hurdle and the power output of selected zlasing mode is:
(Pmn)/(P0) = (Sn)/(S0)
S in the formula
nBe the area of light hurdle circular hole, S
oLong-pending when being multimode output in output minute surface glazing area of beam, P
oBe multi-mode laser power, P
MnPower output for institute's lectotype.
Described spherical reflector is the copper gold-plated spherical reflector of back side water-cooled, and radius of curvature R is greater than 2L, and L is the distance that spherical reflector arrives the output eyeglass here.
The present invention and refrative cavity relatively have following advantage:
1. cavity configuration is simple, and folded module feature is good, the beam quality height, and installation cost is low.
2. be concavo-convex cavity configuration when the present invention works, its mode volume utilance is big, and is low to the uniformity requirement of medium, so the electrical efficiency height, the utilization air pressure range is big.
3. easy for installation, it is low to adjust required precision, does not need additional other to suppress the measure of parasitic oscillation in the chamber, and the long-term operation good stability in chamber.
4. be used for common multimode CO
2Laser only need change the output eyeglass, can become the laser output of multimode into low-order mode on same laser.Therefore, except carrying out LASER HEAT TREATMENT, also can carry out processing such as laser cutting and welding, improve the utilization benefit and the economic benefit of laser machine.
The invention will be further described below in conjunction with accompanying drawing.
Fig. 1 is a prior art refrative cavity schematic diagram.
Fig. 2 is a low-order mode resonant cavity schematic diagram of the present invention.
Fig. 3 is the various low step modes of embodiment of the invention power output 1 kilowatt hour.
Fig. 4 is the relation curve of embodiment TEM10 mould beam directionality and power output.
In Fig. 1 and Fig. 2,1-sphere completely reflecting mirror, 2-modeling light hurdle, 3-exports eyeglass, 4-folding mirror.
The present invention is at industrial kilowatt of crossing current CO
2Experimentize on the laser, laser is at working gas (CO
2: N
2: when He=1: 8: 11) being 80 holders, multimode power output 1.8KW, under the same conditions, adopting resonant cavity of the present invention is embodiment, and its parameter is as follows: Guang Lan aperture φ 18mm, output window GaAs, the reflectivity on plane is 83%, concave surface plating anti-reflection film, and radius of curvature is 2.2L
o, obtained multikilowatt low order film (TEM
10) output.When recording power output 1030W with the focal spot method, beam divergence angle is less than 1.95 milliradians, and wherein contained power accounts for 93%, and running was greater than 12 hours continuously, and power stability is less than ± 1.16%.
Fig. 3 changes the various low-order modes distributions of multikilowatt that the Guang Lan aperture obtains, and (a) is the TEM00 mould among the figure, (b) is the TEM01 mould, (c) is the TEM10 mould, (d) is the TEM11 mould.
Fig. 4 represents that embodiment exports the variation relation of beam divergence angle 2 θ of TEM10 mould under the different capacity, abscissa is the power of outgoing laser beam among the figure, unit is * 100 watts, the beam divergence full-shape that ordinate records for the focal spot method, visible TEM10 mould in 1200 watts the angle of divergence about 2 milliradians.
In sum, the present invention is simple and practical, and the modeling characteristic is good, the beam quality height, and stable performance reaches the technical indicator that like product is in the world rolled over the chamber more.And its cost of manufacture is low, can use on multimode laser, has reached goal of the invention.Be CO
2Application prospects has been opened up in laser processing.