CN211661329U - Micro axicon manufacturing device based on femtosecond laser refractive index modification technology - Google Patents
Micro axicon manufacturing device based on femtosecond laser refractive index modification technology Download PDFInfo
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- CN211661329U CN211661329U CN201921784317.3U CN201921784317U CN211661329U CN 211661329 U CN211661329 U CN 211661329U CN 201921784317 U CN201921784317 U CN 201921784317U CN 211661329 U CN211661329 U CN 211661329U
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Abstract
The utility model belongs to the technical field of laser beam machining, a miniature axicon manufacturing installation based on femto second laser refracting index modification technique is disclosed, femto second laser that femto second laser instrument sent inserts the light path through the group of beam expanding mirror, high power electro-optic shutter, and high power electro-optic shutter right side has set gradually 1/2 wave plates, polarization scene prism and 1% transmission sampling mirror, and 1% transmission sampling mirror downside is provided with micro objective, and micro objective lower extreme is provided with the three-dimensional numerical control moving platform who has placed the sample. The utility model discloses utilize femto second laser and transparent material interact to change the mechanism of transparent material refracting index, the focus position of reasonable control femto second laser beam in transparent material obtains high accuracy, small-size, minimum angle axicon structure, and the axicon of this kind of special construction can be arranged in small structures such as optic fibre terminal surface, optical waveguide terminal surface for produce long diffraction distance, dark burnt bessel laser beam, and then be applied to fields such as laser micro-processing, atomic optics, nonlinear optics.
Description
Technical Field
The utility model belongs to the technical field of laser beam machining, especially, relate to a miniature axicon manufacturing installation based on femto second laser refracting index modification technique.
Background
Currently, the closest prior art in the industry: from the bessel beam propagation theory, it is known that the base angle γ of the axicon is an important parameter, which determines the maximum diffraction-free distance of the bessel beam, and the refractive index n of the axicon is another important parameter affecting the maximum diffraction-free distance. The bottom angle gamma of the axicon has a great influence on the maximum non-diffraction distance, and after the bottom angle of the axicon is larger than 0.8 degrees, the maximum non-diffraction distance value is obviously reduced, but the minimum bottom angle gamma of the current axicon which can be realized by a mechanical mode is 0.5 degrees, the manufacturing cost is very expensive, and the precision is low. An ideal bessel beam can be described by the following equation:
E(r,θ,z)＝A0exp(ikzz)Jn(krr)exp(±inθ)；
in the formula JnIs a Bessel function of order n, kzAnd krAre the longitudinal and transverse wave vectors, respectively, and
r, z are radial, angular and longitudinal coordinates, respectively. When the order n is zero, the zero order Bessel beam is corresponding. When the order n is more than zero, a high-order Bessel beam is corresponding to the order n. Higher order bessel beams have a point on the beam propagation axis that is singular in phase and therefore the center is dark, i.e. a hollow beam. This beam is called a bessel beam because its distribution of the optical field is described by a bessel function. The intensity distribution of the bessel beam is independent of the propagation axis, and therefore the bessel beam is diffraction-free. Mathematically, the bessel beam extends laterally to infinity, contains an infinite number of concentric rings, carries an infinite amount of energy, and is therefore impractical and experimentalCan only produce a truncated bessel beam. The zero order bessel beams can be viewed as a superposition of plane waves propagating along the cone, and truncated bessel beams can be generated by axicons. Both zero and higher order bessel beams have many applications in material processing.
In summary, the problems of the prior art are as follows:
the minimum base angle gamma of the axicon manufactured by the existing mechanical method is 0.5 degrees, the extremely small base angle has extremely high requirements on the straightness and angle errors of the surface of the axicon, and the straightness errors can cause the surface of the axicon to be an irregular curved surface. The angle error generally needs to be controlled to be one percent of a design value, and for a small base angle, the precision is extremely difficult to control, and usually, the distance from the design is large and exceeds the error tolerance range.
The difficulty of solving the technical problems is as follows: axicons are a simple, efficient method of generating diffraction-free bessel beams, commonly used for laser machining, microscopic imaging and long-focus depth focusing. The area after convergent interference by the axicon is a bessel beam, so the length of the bessel beam is determined by the size of the base angle. As can be seen from the following figures, the length of the interference region in the light beam transmission direction is proportional to the radius of the light beam and inversely proportional to the tangent of the base angle, and the smaller the base angle tg, the longer the interference region, and the more beneficial the deep hole and groove processing.
The significance of solving the technical problems is as follows:
the minimum base angle of the conventional axicon machined by mechanical grinding is 1 degree, and although it is possible to continuously reduce the base angle, the linear error of the conical surface is increased, particularly the sine and cosine conical surface, and the failure of the conical mirror is directly caused. The femtosecond laser causes the refractive index modification to be small, generally in a few thousandths, and can reach a few percent at most, and is in the optical material, the base angle of the manufactured conical mirror can reach 0.01 degree, and is 100 times smaller than that of the traditional mechanical grinding processing, the corresponding interference area, namely the Bessel beam area, is 100 times longer, and in the aspect of micro processing, the depth-diameter ratio is effectively improved; in slice imaging, data acquisition time can be greatly compressed.
SUMMERY OF THE UTILITY MODEL
To the problem that prior art exists, the utility model provides a miniature axicon manufacturing installation based on femto second laser refractive index modification technique.
The utility model discloses a realize like this, a miniature axicon manufacturing installation based on femto second laser refractive index modification technique is provided with:
a femtosecond laser;
the femtosecond laser emitted by the femtosecond laser is inserted into a light path through a beam expander set and a high-power electro-optic shutter, the right side of the high-power electro-optic shutter is sequentially provided with an 1/2 wave plate, a polarized wind-solar prism and a 1% transmission sampling mirror, the lower side of the 1% transmission sampling mirror is provided with a microscope objective, and the lower end of the microscope objective is provided with a three-dimensional numerical control moving platform for placing a sample;
and a CCD camera is arranged on the upper side of the 1% transmission sampling mirror and is connected with a computer.
The utility model discloses utilize femto second laser and transparent material interact to change the mechanism of transparent material refracting index, the focus position of reasonable control femto second laser beam in transparent material obtains high accuracy, small-size, minimum angle axicon structure, and the axicon of this kind of special construction can be arranged in small structures such as optic fibre terminal surface, optical waveguide terminal surface for produce long diffraction distance, dark burnt bessel laser beam, and then be applied to fields such as laser micro-processing, atomic optics, nonlinear optics.
Further, the 1/2 wave plate is connected with a computer.
The utility model discloses a computer control 1/2 wave plate rotation angle can cooperate PBS to be used for attenuating laser so that suitable laser inscription transparent material forms the axicon.
Further, a power meter is arranged on the right side of the 1% transmission sampling mirror and connected with a computer.
The utility model discloses a power meter can carry out real-time measurement to the power of decay laser.
Furthermore, a point light source is arranged on the lower side of the three-dimensional numerical control mobile platform, light beams generated by the point light source are reflected into the sample through a point light source high-reflection mirror and used for observing the position of the sample and determining the position of the axicon engraved by the femtosecond laser.
Drawings
Fig. 1 is a schematic structural diagram of a micro axicon manufacturing device based on a femtosecond laser refractive index modification technology according to an embodiment of the present invention;
in the figure: 1. a femtosecond laser; 2. a beam expander set; 3. a high power electro-optic shutter; 4. 1/2 a wave plate; 5. a polarized wind-solar prism; 6. a 1% transmission sampling mirror; 7. a CCD camera; 8. a power meter; 9. a microscope objective; 10. a point light source; 11. a point light source high-reflection mirror; 12. a three-dimensional numerical control mobile platform; 13. a sample; 14. and (4) a computer.
Fig. 2 is a schematic view of the femtosecond laser writing axicon provided by the embodiment of the present invention.
Detailed Description
In order to further understand the contents, features and effects of the present invention, the following embodiments are illustrated and described in detail with reference to the accompanying drawings.
The structure of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, the embodiment of the present invention provides a manufacturing apparatus of a micro axicon based on a femtosecond laser refractive index modification technology, including: the device comprises a femtosecond laser 1, a beam expander group 2, a high-power electro-optic shutter 3, an 1/2 wave plate 4, a polarized wind-solar prism 5, a 1% transmission sampling mirror 6, a CCD camera 7, a power meter 8, a microscope objective 9, a point light source 10, a point light source high-reflection mirror 11, a three-dimensional numerical control mobile platform 12, a sample 13 and a computer 14.
The femtosecond laser emitted by the femtosecond laser 1 is inserted into a light path through the beam expander group 2 and the high-power electro-optic shutter 3, the 1/2 wave plate 4, the polarized wind-solar prism 5 and the 1% transmission sampling mirror 6 are sequentially arranged on the right side of the high-power electro-optic shutter 3, the microscope objective 9 is arranged on the lower side of the 1% transmission sampling mirror 6, and the three-dimensional numerical control moving platform 12 with the sample 13 is arranged at the lower end of the microscope objective 9; the CCD camera 7 is arranged on the upper side of the 1% transmission sampling mirror 6, and the CCD camera 7 is connected with the computer 14.
Preferably, 1/2 wave plate 4 is connected to computer 14.
Preferably, a power meter 8 is arranged on the right side of the 1% transmission sampling mirror 6, and the power meter 8 is connected with a computer 14.
Preferably, a point light source 10 is arranged on the lower side of the three-dimensional numerical control moving platform 12, and light beams generated by the point light source 10 are emitted into the sample through a point light source high-reflection mirror 11.
The utility model discloses a theory of operation is:
the utility model discloses when using, femto second laser instrument 1 sends femto second laser, through the group 2 of beam expanding mirror, high power shutter 3 inserts in the light path for the switch of control light in the later stage axicon manufacturing process, response speed is the nanosecond magnitude, 1/2 wave plate 4 is used for changing laser power by computer 14 control rotation angle cooperation polarization beam splitter prism 5, so that suitable laser inscription is located the transparent material 13 formation axicon on three-dimensional electric control moving platform 12. The appropriate laser power after passing through the polarization beam splitter prism is transmitted through the 1% transmission sampling mirror 6 into the power meter 8 for real-time measurement. The laser writing adopts a microscope objective 9, and visible light emitted by a point light source 10 enters a 7CCD through a point light source reflector 11 for observing the writing state in real time. And the computer 14 is connected with the 1/2 wave plate 4, the power meter 8, the imaging CCD camera 7 and the three-dimensional moving platform 12, and controls and detects the state of the axicon engraved by the femtosecond laser in real time. Writing to axicons is achieved by changing the refractive index of a transparent medium, such as quartz glass, gorilla glass, lithium niobate crystals, magnesium fluoride crystals. The laser focal area causes a refractive index different from that of the original substrate through a complicated physicochemical and chemical process. By finely controlling the laser scanning shape, a line is formed by points, a surface is formed by lines, and then the surface forms the shape of an axicon.
The precision of the numerical control three-dimensional moving platform needs to reach the nm magnitude, the axicon is composed of an un-engraved part and an engraved part together, and the axicon with the refractive index close to 1 is obtained (the refractive index of the axicon engraved by the method can reach 1.001 through experimental measurement).
The following describes in detail the process of fabricating the axicon by femtosecond laser writing, taking a glass material with a base angle of 0.3 °, a base length of 1mm, and a refractive index of 1.5 as an example.
After the femtosecond laser with the wavelength of lambda is accurately attenuated and enters a microscope objective with the damage threshold energy of glass for focusing, the size of a focus can be focused to lambda/2 which is far smaller than that of an axicon. The numerical control three-dimensional moving platform is controlled by a computer, so that the focus is controlled to be positioned at a target position in the glass material, the first layer is etched by the moving platform, the second layer is etched by the same method after the position of one focus is moved upwards, and the subsequent layer structure is etched according to the method. The femtosecond laser writing on the glass can cause the refractive index of the glass to change, and the increment is 10-3 orders of magnitude.
The length and the number of layers of each layer of writing determine the size of the base angle of the axicon, and the base angle can be obtained according to a geometric trigonometric relation, and the base angle is 0.3 degrees, and the length of the base edge is 1 mm. The height h of the axicon should be:
substituting the corresponding numerical value into the formula (1) to obtain the height h of the axicon, wherein the height h is as follows: 2.6 μm.
For a given laser wavelength λ, the number of layers N to be inscribed can be calculated
And (3) taking the wavelength lambda of the common green light as 532nm, calculating to obtain the number of layers to be written as 9.7, and writing 9 layers by considering the small errors of the displacement platform and the laser focus. The length of each layer to be written can be calculated by a geometric trigonometric relation.
The first layer of the axicon has a writing length L1 of 1mm and a height h of 2.6 μm. The length of the second layer is:
……
and strictly controlling the position of the three-dimensional mobile platform according to the calculation result, and finally preparing the axicon of the target parameters. Compared with a machining mode, the method for producing the axicon has higher precision and smaller angle, and the refractive index of the axicon is close to 1.
The utility model discloses an utilize femto second laser to prepare miniature axicon's device in transparent material, transparent material's optional scope contains nonlinear crystal, laser crystal and glass, but wide application in fields such as processing, nonlinear optics, atomic optics are received a little to laser. Compared with the axicon made by a mechanical method, the maximum diffraction-free distance of the Bessel beam generated by the prepared axicon is more than thousand times of that of a mechanical means. Importantly, the femtosecond laser has high preparation speed and strong expandability, can prepare the axicons with various requirements, and has rapid preparation, which is a place far beyond the reach of the traditional preparation method.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all the modifications and equivalents of the technical spirit of the present invention to any simple modifications of the above embodiments are within the scope of the technical solution of the present invention.
Claims (5)
1. A micro axicon manufacturing device based on femtosecond laser refractive index modification technology is characterized in that the micro axicon manufacturing device based on femtosecond laser refractive index modification is provided with:
a femtosecond laser;
the femtosecond laser emitted by the femtosecond laser is inserted into a light path through a beam expander set and a high-power electro-optic shutter, the right side of the high-power electro-optic shutter is sequentially provided with an 1/2 wave plate, a polarized wind-solar prism and a 1% transmission sampling mirror, the lower side of the 1% transmission sampling mirror is provided with a microscope objective, and the lower end of the microscope objective is provided with a three-dimensional numerical control moving platform for placing a sample;
and a CCD camera is arranged on the upper side of the 1% transmission sampling mirror and is connected with a computer.
2. The femtosecond laser refractive index modification technology-based micro axicon manufacturing device according to claim 1, wherein the 1/2 wave plate is connected with a computer.
3. The femtosecond laser refractive index modification technology-based micro axicon manufacturing device according to claim 1, wherein a power meter is arranged on the right side of the 1% transmission sampling mirror and is connected with a computer.
4. The femtosecond laser refractive index modification technology-based micro axicon manufacturing device according to claim 1, wherein a point light source is arranged on the lower side of the three-dimensional numerical control moving platform, and a light beam generated by the point light source is reflected into a sample through a high reflection mirror of the point light source.
5. The femtosecond laser refractive index modification technology-based micro axicon manufacturing device according to claim 1, wherein the three-dimensional numerical control moving platform performs three-dimensional scanning according to a programmed axicon pattern to change the original refractive index of the material.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112539847A (en) * | 2020-11-04 | 2021-03-23 | 中国科学院上海光学精密机械研究所 | Large-caliber ultrashort pulse sampling device |
| CN115182045A (en) * | 2022-07-27 | 2022-10-14 | 山东铂锐激光科技有限公司 | Preparation method of sesquioxide single crystal optical fiber cladding |
| WO2022252300A1 (en) * | 2021-06-04 | 2022-12-08 | 西安交通大学 | Femtosecond-laser-based optical fiber probe preparation device and method combined with super-resolution lens |
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2019
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112539847A (en) * | 2020-11-04 | 2021-03-23 | 中国科学院上海光学精密机械研究所 | Large-caliber ultrashort pulse sampling device |
| CN112539847B (en) * | 2020-11-04 | 2022-06-28 | 中国科学院上海光学精密机械研究所 | Large-caliber ultrashort pulse sampling device |
| WO2022252300A1 (en) * | 2021-06-04 | 2022-12-08 | 西安交通大学 | Femtosecond-laser-based optical fiber probe preparation device and method combined with super-resolution lens |
| CN115182045A (en) * | 2022-07-27 | 2022-10-14 | 山东铂锐激光科技有限公司 | Preparation method of sesquioxide single crystal optical fiber cladding |
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