CN110018565A - A kind of method and apparatus improving ultrafast laser light beam focusing capability - Google Patents
A kind of method and apparatus improving ultrafast laser light beam focusing capability Download PDFInfo
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- CN110018565A CN110018565A CN201910206674.XA CN201910206674A CN110018565A CN 110018565 A CN110018565 A CN 110018565A CN 201910206674 A CN201910206674 A CN 201910206674A CN 110018565 A CN110018565 A CN 110018565A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0012—Optical design, e.g. procedures, algorithms, optimisation routines
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
- G02B27/0927—Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
- G02B27/0938—Using specific optical elements
- G02B27/095—Refractive optical elements
- G02B27/0955—Lenses
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- Optics & Photonics (AREA)
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Abstract
The invention discloses a kind of method and apparatus for improving ultrafast laser light beam focusing capability, solve the problems, such as to cause focal beam spot to be greater than Focusing Theory value because beam divergence angle is easily caused to increase for common self-focusing effect in ultrafast laser focusing.The present invention is by way of the extension of ultrafast laser light beam collimation and limitation Laser edge energy, it eliminates laser-beam divergence angle and increases phenomenon, and diameter dimension is obtained by aplanatism Design of Aspherical Lenses can be to 5 μm of focal beam spots below, for ultrafast laser retrofit, especially micro-meter scale retrofit, provides effective guarantee.
Description
Technical field
The present invention relates to laser beam focusing field more particularly to a kind of methods for improving ultrafast laser light beam focusing capability
And device.
Background technique
Laser processing has the advantages such as high-energy, noncontact procession, is widely applied in manufacture field, but be
High efficiency, the high-precision index for realizing laser processing, diminution laser spot size becomes guarantees laser power under conditions of
The prerequisite of laser processing.
According to laser beam lens focus formula θ=Dm/ f is it is found that work as mono- timing of focal length f, laser beam radius DmWith angle of divergence θ
It is directly proportional, therefore the reduction of laser focal dimension is realized it is necessary to reduce the angle of divergence.But item is focused in high-peak power ultrafast laser
Under part, the refractive index that self-focusing effect will increase medium converges light beam in advance, so that increasing beam divergence angle causes to focus light
Spot is greater than theoretical hot spot.Chinese invention patent 201210534021.2 by being acquired respectively using two light intensity detector devices
The near field light intensity and far-field intensity distribution information of laser beam improve in conjunction with light distribution information, evaluation function closed-loop control and swash
Light light beam focusing capability, this method need repeatedly to extract light distribution information in focusing and carry out compensation operation, do not relate to
And laser focal dimension.Chinese invention patent 201010017159.6 is using the reflection of reflecting mirror and the focusing of focus lamp, sharp
The hot spot of light beam radially carries out the modulation of interior external position and focusing, this method change the spatial distribution of light beam, annular
Light is applicable in laser processing application to be limited in scope, and does not have universality, especially ultrafast laser often in micro-meter scale
Height finishing scope.Chinese invention patent 200910154784.2 provides a kind of laser focusing device, is existed using light laser
Self-focusing effect in high-order nonlinear medium realizes the focusing of laser, and the necessary condition of the realized focusing of the patent is laser
Power density is more than or equal to 100KW/cm2, and be only applicable to that the high-order nonlinear medium for generating self-focusing effect, light can be excited
The power density at spot center is uncontrollable.The invention discloses it is a kind of improve ultrafast laser light beam focusing capability method and apparatus,
Solve in ultrafast laser focusing causes focal beam spot big because beam divergence angle is easily caused to increase for common self-focusing effect
In the Focusing Theory value the problem of.The present invention passes through the extension collimation of ultrafast laser light beam and the side of limitation Laser edge energy
Formula eliminates laser-beam divergence angle and increases phenomenon, and obtaining diameter dimension by aplanatism Design of Aspherical Lenses can be to 5 μm or less
Focal beam spot, be ultrafast laser retrofit, especially micro-meter scale retrofit provides effective guarantee.
Summary of the invention
Aiming at the shortcomings existing in the above problems, the present invention, which provides, a kind of improves ultrafast laser light beam focusing capability
Method characterized by comprising
Step 1 carries out geometric optics optimization to original laser beam, obtains diameter expansion, while the angle of divergence reduces light beam,
Laser power density is reduced, avoids light beam from generating the angle of divergence caused by self-focusing effect and increases phenomenon；
Step 2, according to extension light beam Energy distribution, to extension beam edge energy shield, eliminate edge lasers
It induces the angle of divergence caused by self-focusing effect to increase phenomenon, while reducing the spherical aberration in direction of laser propagation；
Step 3 focuses laser beam under the conditions of aplanatism non-spherical lens, and the astigmatism reduced on focussing plane is gathered
Burnt hot spot.
A kind of device improving ultrafast laser light beam focusing capability, the device are successively coaxial along the transmission direction of incident beam
Geometric optics module, diaphragm module, focus module are set, which is characterized in that geometric optics module is by a coaxial concavees lens
With convex lens group at；Diaphragm module is made of an aperture diaphragm according to Laser beam energy distribution design；Focus module is by one side
Non-spherical lens is constituted.
A kind of device improving ultrafast laser light beam focusing capability as mentioned, which is characterized in that for geometric optics mould
Block, focal length of convex lens length are greater than Concave Mirrors Focus length, and the focal length that convex lens and concavees lens spacing distance are equal to concavees lens is long
Degree.
A kind of device improving ultrafast laser light beam focusing capability as mentioned, which is characterized in that for diaphragm module, light
Late Entry pupil diameters, which are equal to, expands laser gross energy 1/e2Spot diameter again, wherein e is natural constant.
A kind of device improving ultrafast laser light beam focusing capability as mentioned, which is characterized in that for focus module, benefit
With aplanatism condition, closed-loop optimization is carried out to non-spherical lens using damped least square method, spot size is obtained and is smaller than 5 μm
High focusing effect.
Compared with prior art, the invention has the benefit that
It solves to cause in existing ultrafast laser focusing because beam divergence angle is easily caused to increase for common self-focusing effect
Focal beam spot is greater than the problem of Focusing Theory value.While the present invention reduces the angle of divergence by the method for laser spacing shaping, subtract
The small spherical aberration and astigmatism of laser beam, improves the focusing capability of ultrafast laser beam, hot spot can be focused on 5 μm of diameter with
Under.In the case where low power loss, effectively extend geometric optics module and focus module under high-peak power ultrafast laser
Working time.
Detailed description of the invention
Fig. 1 is ultrafast laser focusing device figure；
Specific embodiment
In order to make the object, technical scheme and advantages of the embodiment of the invention clearer, below in conjunction with the embodiment of the present invention
In attached drawing, technical scheme in the embodiment of the invention is clearly and completely described, it is clear that described embodiment is
A part of the embodiments of the present invention, instead of all the embodiments.Based on the embodiments of the present invention, ordinary skill people
Member's every other embodiment obtained without making creative work, shall fall within the protection scope of the present invention.
To solve to lead in existing ultrafast laser focusing because beam divergence angle is easily caused to increase for common self-focusing effect
The problem of causing focal beam spot to be greater than Focusing Theory value.The invention discloses a kind of methods for improving ultrafast laser light beam focusing capability
And device, the angle of divergence of ultrafast laser beam is reduced by the method for laser spacing shaping, improves the poly- of ultrafast laser light beam
Burnt ability.
It is specifically included:
The present invention is described in further detail with reference to the accompanying drawing:
Laser beam A (the peak power density of step 1, the peak power 500KW launched from laser source, diameter 2mm
159.15KW/mm2) first pass around and obtain light beam B with rail concavees lens L1 and convex lens L2 the geometric optics module formed by one.
According to laser beam lens focus formula θ=Dm/ f is it is found that work as mono- timing of focal length f, laser beam radius DmWith angle of divergence θ
Directly proportional, the angle of divergence is bigger, then laser beam radius can focus on smaller.Focal length of convex lens length is set as Concave Mirrors Focus length
2 times, convex lens and concavees lens spacing distance are equal to the focal length of concavees lens.By expanding multiplying power M=F2/F1=θ/θ " (F2For
Focal length of convex lens, F1For Concave Mirrors Focus, θ is that incident beam divergence, θ " are the outgoing beam angle of divergence) it is found that expanding after
Beam diameter is exaggerated 2 times, and the angle of divergence reduces 2 times.In the case where peak power is constant, corresponding peak power density
4 times are reduced, light beam is avoided and generates the increase phenomenon of the angle of divergence caused by self-focusing effect.
Step 2, foundation Laser beam energy distribution formula I (r)=I0exp(-2r2/w2), wherein I0For laser gross energy, w is
Laser beam spot radius, r are the laser radius at corresponding laser energy I.Diaphragm Entry pupil diameters are equal to expanded laser light gross energy 1/
e2Spot diameter again, shields laser beam edge energy, can effectively eliminate edge lasers induction self-focusing effect and draws
The angle of divergence risen increases phenomenon, while reducing the spherical aberration in direction of laser propagation；It calculates power and drops to light beam A power 1e2
Diameter r again0=1.08mm.Circular aperture diaphragm M is designed, diaphragm Entry pupil diameters are r0.Make light beam B by diaphragm, obtains energy
Light beam C after adjusting.
Step 3 is based on Z=cr using aplanatism condition according to the spot size of light beam C2/(1+(1-(1+K)c2r2)1/2)
+A4r4+A6r6+A8r8It is excellent to carry out closed loop to non-spherical lens using damped least square method for aspherical focussing lens curvature equation
Change, wherein r is into the beam radius for injecting aspherical focus lamp, and c is curvature of the curved surface at center, value 0.037；K is non-
Asphere coefficient, value 0.32285； AiFor the multinomial coefficient that opposite shape is modified, A4=-5.423 × 10-6, A6=-
1.122×10-8, A8=-4.766 × 10-12.In the case where reducing astigmatism and low power loss, further focal beam spot ruler
It is very little.The focal length of aspherical mirror is 100 μm, and distance l of the gauss light beam waist apart from non-spherical lens is 18000 μm at this time, at this time
L > > f, then according to hot spot formula r1=Fr0/ l is it is found that obtained focal beam spot diameter is 3 μm.It is assumed that the focal length of focus lamp and
Gauss light beam waist is constant away from distance from the lens, and routinely focusing obtained spot diameter is 22 μm.
The invention discloses a kind of method and apparatus for improving ultrafast laser light beam focusing capability, and it is poly- to solve ultrafast laser
Focal beam spot is caused to be greater than asking for Focusing Theory value because beam divergence angle is easily caused to increase for common self-focusing effect during burnt
Topic.The present invention eliminates laser-beam divergence by way of the extension of ultrafast laser light beam collimation and limitation Laser edge energy
Angle increases phenomenon, and obtaining diameter dimension by aplanatism Design of Aspherical Lenses can be ultrafast to 5 μm of focal beam spots below
Laser focus, especially micro-meter scale retrofit, provides effective guarantee.In the case where low power loss, effectively prolong
The working time of long geometric optics module and focus module under high-peak power ultrafast laser.
These are only the preferred embodiment of the present invention, is not intended to restrict the invention, for those skilled in the art
For member, the invention may be variously modified and varied.All within the spirits and principles of the present invention, it is made it is any modification,
Equivalent replacement, improvement etc., should all be included in the protection scope of the present invention.
Claims (5)
1. a kind of method for improving ultrafast laser light beam focusing capability, characterized in that it comprises the following steps:
Step 1 carries out geometric optics optimization to original laser beam, obtains diameter expansion, while the angle of divergence reduces light beam, reduces
Laser power density avoids light beam from generating the angle of divergence caused by self-focusing effect and increases phenomenon；
Step 2, according to extension light beam Energy distribution, to extension beam edge energy shield, eliminate edge lasers induction
The angle of divergence caused by self-focusing effect increases phenomenon, while reducing the spherical aberration in direction of laser propagation；
Step 3 focuses laser beam under the conditions of aplanatism non-spherical lens, reduces the astigmatism on focussing plane and obtains focusing light
Spot.
2. a kind of device for improving ultrafast laser light beam focusing capability, the device successively coaxial are set along the transmission direction of incident beam
Set geometric optics module, diaphragm module, focus module, which is characterized in that geometric optics module by a coaxial concavees lens and
Convex lens group at；Diaphragm module is made of an aperture diaphragm according to Laser beam energy distribution design；Focus module is non-by one side
Spherical lens is constituted.
3. a kind of device for improving ultrafast laser light beam focusing capability as claimed in claim 2, which is characterized in that for geometry
Optical module, focal length of convex lens length are greater than Concave Mirrors Focus length, and convex lens and concavees lens spacing distance are equal to concavees lens
Focal length.
4. a kind of device for improving ultrafast laser light beam focusing capability as claimed in claim 2, which is characterized in that for diaphragm
Module, diaphragm Entry pupil diameters, which are equal to, expands laser gross energy 1/e2Spot diameter again, wherein e is natural constant.
5. a kind of device for improving ultrafast laser light beam focusing capability as claimed in claim 2, which is characterized in that for focusing
Module carries out closed-loop optimization to non-spherical lens using damped least square method, it is small to obtain spot size using aplanatism condition
In 5 μm of high focusing effect.
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| CN201910206674.XA CN110018565B (en) | 2019-03-19 | 2019-03-19 | Method and device for improving focusing capacity of ultrafast laser beam |
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| CN201910206674.XA CN110018565B (en) | 2019-03-19 | 2019-03-19 | Method and device for improving focusing capacity of ultrafast laser beam |
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| CN110018565B CN110018565B (en) | 2021-10-01 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112748581A (en) * | 2020-12-30 | 2021-05-04 | 中国人民解放军国防科技大学 | Semiconductor laser's circular flat top beam shaping system that can integrate |
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| CN110018565B (en) | 2021-10-01 |
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