JP5601305B2 - Carbon dioxide laser oscillator - Google Patents

Description

  The present invention relates to a carbon dioxide laser oscillator.

  There are mainly three types of carbon dioxide laser oscillators: an orthogonal type, an axial flow type, and a slab type.

  FIG. 11 shows an example of a schematic configuration of a conventional orthogonal carbon dioxide laser oscillator. FIG. 11 (a) is a transverse sectional view and FIG. 11 (b) is a longitudinal sectional view. Each component is attached to the vacuum vessel 1, and a laser medium 2 is contained therein at a pressure of about 30 to 300 Torr. The laser medium 2 circulates from the rectifying duct 4 to the electrode 5 as indicated by an arrow by the blower 3. A high voltage is supplied to the electrode 5 from the power supply unit 6, thereby generating a discharge 7. When the energy from the discharge 7 is applied to the laser medium 2, the carbon dioxide gas that is the laser medium 2 is excited, and the photoreflectors emitted at the time of transition are partially reflected mirrors 8 arranged facing each other across the laser medium 2. Are amplified by an optical resonator mirror including the total reflection mirror 9, and a part thereof is extracted as laser light 10 from the partial reflection mirror 8. The laser medium 2 given energy by the discharge 7 is cooled by the heat exchanger 11 because the temperature is rising. An aperture 12 is arranged between the electrode 5 and the partial reflection mirror 8 and between the electrode 5 and the total reflection mirror 9 and plays a role of determining the transverse mode order, cutting diffracted light, and scattered light. Impurities are gradually mixed in the laser medium 2 due to leakage of the vacuum vessel 1, that is, outgassing due to external air mixing or deterioration of components, and therefore the laser medium 2 is periodically removed by the vacuum pump 13. Evacuate and replace with a new laser medium 2. Cooling water is supplied from the cooling device 14 to the heat exchanger 11 and components that require cooling (not shown). A series of operations is controlled by the control device 15. The configuration of such an orthogonal carbon dioxide laser oscillator is described in Patent Document 1, for example.

  FIG. 12 shows an example of a schematic configuration of a conventional axial flow type carbon dioxide laser oscillator. The same parts as those in FIG. 11 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the orthogonal type, the direction in which the laser medium 2 circulates and the direction in which the laser beam 10 is emitted are orthogonal, but in the axial flow type, the direction is parallel. The configuration of such an axial flow type carbon dioxide laser oscillator is described in Patent Document 2, for example.

  A slab type carbon dioxide laser oscillator is not particularly shown, but is described in, for example, Patent Document 3.

Japanese Patent Laid-Open No. 7-94810 Japanese Patent Laid-Open No. 5-167133 Japanese Patent Application Laid-Open No. 2000-269569

In the carbon dioxide laser oscillator, vaporized organic matter and fine floating dust are present inside the vacuum vessel 1 for the following reasons, for example.
・ Oil mist in which the oil in the vacuum pump 13 is vaporized ・ Grease filled in the bearing of the blower 3 is vaporized ・ Vanity that solidifies the stator coil of the blower 3 and insulation paper is deteriorated ・ Heat exchanger 11 -Residual component of flux used when brazing pipes-Residual component of mold release agent adhering to blower 4 fan and casing-Residual component of cutting oil adhering to aperture 12 cutting-Rectification duct 4 Residual components of the processing oil adhering during the press processing of the product ・ Residual components of the cleaning fluid adhering to the cleaning of each component

  When these vaporized organic matter and fine floating dust adhere to the partial reflection mirror 8, the ratio of the partial reflection mirror 8 to absorb the energy of the laser beam 10 (hereinafter referred to as heat absorption rate) increases due to the dirt. To do. As a result, the refractive index changes due to the temperature rise inside the partial reflection mirror 8, and the characteristics of the laser beam 10 change.

  FIG. 9 shows the relationship between the oscillation time and the heat absorption rate of the partial reflecting mirror 8 when the orthogonal carbon dioxide laser oscillator continuously oscillates with laser light outputs of 2 kW and 4 kW. Even in the unused partial reflecting mirror 8, there is 0.1% heat absorption due to the base material and the dielectric coating on the surface, but this rises to 0.2% due to the laser oscillation of 1000 hr at an output of 4 kW. . Also, with the same oscillator, the higher the laser light output, the greater the heat absorption rate, and there is concern that it will become a major issue in the future development of high-power carbon dioxide laser oscillators, which are market needs. Is done.

  FIG. 10 shows a change in the characteristics of the laser beam 10 when the heat absorption rate of the partial reflection mirror 8 is increased from 0.1% to 0.2%, and the solid line is 0.1%. And the broken line is 0.2%. It is clear that the beam diameter at the place where the laser beam is propagated 5 m in the nitrogen atmosphere is reduced by 20% from Φ40 to Φ32 due to the increase of the heat absorption rate, and the beam intensity density is increased accordingly. . Therefore, there is a high possibility that defects will occur in laser processing, and it becomes difficult to perform stable processing.

  The present invention is for solving such a problem, and vaporized organic matter or fine dust particles floating inside the vacuum vessel 1 adhere to the surface of the partial reflector 8 and the heat absorption rate is increased accordingly. An object of the present invention is to obtain a carbon dioxide laser oscillator that prevents the characteristics of the laser beam 10 from changing.

  In the carbon dioxide laser oscillator according to the present invention, the electrode-side surface of the partial reflection mirror is in contact with the laser medium, but the laser beam is covered so that the laser medium covers the inflow path approaching the surface of the partial reflection mirror. A part having an opening for passing is arranged in the vicinity of the electrode side surface of the partial reflector, and the inner surface of the opening is made of porous anodized so that the temperature is lower than that of the flowing laser medium. Is cooled.

  The present invention suppresses an increase in the heat absorption rate of the partial reflector by arranging parts made of porous anodized so as to cover the inflow path approaching the surface of the partial reflector. it can. For this reason, the characteristics of the laser beam are stabilized, and high-quality laser processing can be performed.

1 is a structural diagram showing a first embodiment of the present invention. FIG. 3 is a detailed structural diagram in the vicinity of a partial reflection mirror, illustrating Embodiment 1 of the present invention. It is a graph which shows the relationship between the oscillation time in Embodiment 1 of this invention and a prior art, and the heat absorption rate of a partial reflective mirror. It is a graph which shows the dispersion | variation in the relationship between the oscillation time in Embodiment 1 of this invention, and the heat absorption rate of a partial reflective mirror. It is a graph which shows the TOF-SIMS analysis result in Embodiment 1 of this invention, and a prior art. It is a schematic diagram which shows the mode of the anion in the membrane | film | coat of the porous type alumite in Embodiment 1 of this invention. It is a schematic diagram which shows the mode of the anion in the membrane | film | coat of the porous type alumite in Embodiment 2 of this invention. It is a graph which shows the relationship between the oscillation time in Embodiment 2 of this invention, and the heat absorption rate of a partial reflective mirror. It is a graph which shows the relationship between the oscillation time in the conventional orthogonal type | mold carbon dioxide laser oscillator, and the heat absorption rate of a partial reflective mirror. It is explanatory drawing which shows the influence which the heat absorption rate of the partial reflective mirror in the conventional orthogonal type | mold carbon dioxide laser oscillator has on the characteristic of a laser beam. It is a structural diagram showing a conventional orthogonal carbon dioxide laser oscillator. It is a structural diagram showing a conventional axial flow type carbon dioxide laser oscillator.

Embodiment 1 FIG.
FIG. 1 shows Embodiment 1 of the present invention, FIG. 1 (a) is a transverse sectional view, and FIG. 1 (b) is a longitudinal sectional view. Since the characteristic part of the present embodiment is the configuration in the vicinity of the partial reflection mirror 8, the same components as those in FIG. As shown in FIG. 1, the partial reflection mirror 8 is held by a mirror presser 16 and a mirror holder 17, and airtightness is secured by an O-ring 18. The mirror holder 16 holds the inside of the vacuum container 1 of the partial reflection mirror 8, and has a cylindrical opening 21 through which the laser light 10 passes to the partial reflection mirror 8, and the inner surface of the opening 21 is porous. Made of quality anodized. In addition, a flow path 20 through which a cooling medium flows to cool the mirror retainer 16 is provided in the mirror retainer 16, and a port 19 for supplying and discharging the cooling medium is provided in the flow path 20. With such a structure, the laser medium 2 can reach the partial reflection mirror 8 only through the opening 21 in which the inner surface of the mirror holder 16 is made of porous anodized.

FIG. 2 is an enlarged view of a portion B in the vicinity of the partial reflection mirror 8 and the mirror presser 16 surrounded by a one-dot chain line in FIG. The porous type alumite actually has a very fine structure on the order of nano to micron, but is intentionally enlarged for the sake of explanation.
From the electrode 5 side, vaporized organic matter and floating fine dust come together with the laser medium 2. Among these, a relatively large fine dust can not enter the opening 21 of the mirror retainer 16 because the porous alumite serves as a pressure barrier, and changes its direction in front. Although very fine dust may enter into the opening 21, there is no forced flow in the direction of the arrow C toward the partial reflector 8 due to the pressure barrier inside the opening 21, and natural convection. Therefore, while drifting in the opening 21, it is eventually trapped in a porous hole.

Although the vaporized organic matter may also enter the opening 21, as described above, natural convection occurs inside the opening 21. Since the mirror holder 16 is cooled so as to have a temperature lower than that of the entering laser medium 2, it is cold trapped in the porous portion.
The porous type alumite has a ratio of the pore diameter to the pore depth of about 1: 1000, and there are an infinite number of very thin and deep pores. In addition, since it is difficult to draw a shape at 1: 1000, the ratio was intentionally changed in the drawing. For this reason, the surface made of porous anodized has a surface area that is orders of magnitude greater than that of other types. Since it has such a large surface area, it functions sufficiently as a cold trap even if the cooling temperature is not so low.

  An example of the shape and manufacturing conditions that were actually manufactured and confirmed the effect is shown. The material of the mirror retainer 16 is A5052, and the surface is coated with 10 μm of normal alumite sulfate, the dimension D in the length direction of the opening 21 is 25 mm, and cooled with water at 20 ° C. (hereinafter referred to as [Example 1] Call).

  FIG. 3 corresponds to FIG. 9 and shows the relationship between the laser light oscillation time and the heat absorption rate of the partial reflecting mirror 8. In the orthogonal carbon dioxide laser oscillator, the solid line is the data of the oscillator to which the conventional technique to which the first embodiment is not applied is applied, the broken line is the data of the oscillator to which the first embodiment is applied, and the laser light output is 4 kW. It oscillates continuously. In the conventional technique, the heat absorption rate of the partial reflection mirror 8 is increased by 0.1% due to the laser light oscillation of 1000 hr. However, by applying the first embodiment of the present invention, the increase in absorption rate is 0.05. %, And the effect of decreasing the heat absorption rate is 50%.

  Actually, when the technology of the present invention is commercialized, the effect obtained in FIG. 3 is not unique to the shape and manufacturing conditions of [Example 1] described above, and is due to variations caused in manufacturing and use. However, it is necessary to confirm that the effect is not greatly impaired. Therefore, the shape and manufacturing conditions were changed to some extent, and how much the obtained effect changed was confirmed. As an experiment, an effect was confirmed by changing the material that does not vary in actual manufacturing, for example, the material, and making the amount of change larger than the amount of variation assumed in manufacturing and use.

FIG. 4 is a graph showing the results of an experiment measuring the relationship between the laser light oscillation time and the heat absorption rate of the partial reflection mirror when the shape and production conditions are changed, both of which are orthogonal carbon dioxide laser oscillators. Used and continuously oscillated at a laser light output of 4 kW.
In FIG. 4A, the material of the mirror presser 16 is changed to A1100, A5052, and A6063. Other shapes and manufacturing conditions are the same as those in [Example 1].
FIG. 4B shows a type of anodizing bath that is changed to a sulfuric acid bath, an oxalic acid bath, or a chromic acid bath. Other shapes and manufacturing conditions are the same as those in [Example 1].
FIG.4 (c) changes the film hardness into normal alumite and hard alumite. Other shapes and manufacturing conditions are the same as those in [Example 1].
In FIG. 4D, the film thickness is changed to 5 μm, 10 μm, and 20 μm. Other shapes and manufacturing conditions are the same as those in [Example 1].
FIG.4 (e) changes the temperature of a cooling water with 10 degreeC, 20 degreeC, and 30 degreeC. Other shapes and manufacturing conditions are the same as those in [Example 1].
FIG. 4F shows the dimension D changed to 20 mm, 25 mm, and 30 mm. Other shapes and manufacturing conditions are the same as those in [Example 1].
From FIG. 4, it can be said that the effect obtained by the shape and production conditions is not exactly the same, but within the range of the shape and production conditions tested in FIGS. 4A to 4F, the heat absorption rate increases. The reduction effect is within the range of 50 ± 10%, and it has been confirmed that the technology is sufficiently applicable to commercialization, that is, mass production.

  In the configuration described with reference to FIGS. 1 and 2, the mirror retainer 16 is provided with the opening 21 and the porous anodized is formed on the inner surface thereof, but the opening 21 through which the laser beam passes is provided separately from the mirror retainer 16. What has porous type alumite formed on the inner surface may be provided in the vicinity of the partial reflection mirror 8.

  Although the above experiment was performed with an orthogonal carbon dioxide laser oscillator, the same effect can be obtained by adopting a similar configuration in the vicinity of the partial reflection mirror in other types such as an axial flow type and a slab type. it can.

Embodiment 2. FIG.
As described above, by applying the first embodiment of the present invention, the increase in the heat absorption rate of the partial reflection mirror 8 could be reduced to about 50% of the conventional one. However, in other words, the remaining 50% means that the heat absorption rate increases. The remaining value of 50% is a level that cannot be ignored in consideration of the effect of changing the characteristics of the laser beam 10.

Therefore, by applying [Example 1] in the first embodiment of the present invention, the partial reflection mirror 8 continuously oscillated for 1000 hr with a laser light output of 4 kW, that is, the heat absorption rate is increased from 0.1% to 0.15%. Surface analysis was performed on the product. The result is shown in FIG.
The analysis technique used is TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry), and the greatest feature is the ability to detect trace elements on the order of ppm. There are various surface analysis methods such as SEM-EDS, XPS, AES, etc., and each has its own characteristics. However, in terms of detection sensitivity, these analysis methods do not have elements in% order. Cannot be detected.
In the case of a carbon dioxide laser, a material that is not transparent to light with a wavelength of 10.6 μm causes an increase in the heat absorption rate of the partial reflector 8 even if a small amount less than% order is deposited. Therefore, TOF-SIMS is suitable for the analysis to find the causative substance of the increase in absorption rate as in this case.

In FIG. 5A, the horizontal axis is the depth, which means that depth profile analysis was performed. In other words, the depth direction is analyzed by sputtering the surface with Ar ions and performing TOF-SIMS measurement at regular intervals. Therefore, although the original horizontal axis is the sputtering time, the sputtering rate is obtained and converted to the depth.
In FIG. 5A, Se and Zn are substances derived from ZnSe that is a constituent material of the partial reflection mirror 8. Further, C and Cl are attached to the surface, and S diffuses into ZnSe to a depth of about 30 nm from the surface.

FIG. 5 (b) corresponds to FIG. 5 (a), and is a conventional technique to which the first embodiment of the present invention is not applied, and a partial reflecting mirror 8 that continuously oscillates for 1000 hr at a laser light output of 4 kW, That is, TOF-SIMS depth profile analysis is performed on the heat absorption rate increased from 0.1% to 0.2%. Comparing FIG. 5A and FIG. 5B, the following can be said.
The one to which the first embodiment of the present invention is applied (FIG. 5A) has lower detection intensity of C and Cl on the surface. That is, as described in the first embodiment, it can be said that the effect of the present invention for trapping vaporized organic matter and fine floating dust is supported by analysis.
Only in the case where the first embodiment of the present invention is applied (FIG. 5A), S diffuses into the ZnSe from the surface to a depth of about 30 nm. This is thought to be due to the generation of S as a new source of contamination from the mirror holder 16 whose surface is made of porous anodized.

If the generation of S, which is a new contamination source, can be prevented, it is expected that the increase in the heat absorption rate of the partial reflection mirror 8 can be further reduced. Therefore, the generation mechanism of S was examined. Regarding anodizing, the following is known. “The amount of anions mixed in the porous oxide film is several tens of percent. A report that the porous oxide film formed in the sulfuric acid bath contains 17% or more of sulfate radicals, or 13% as SO3. There is a report that it is contained .... The binding state of sulfate radicals present in the oxide film has also been studied.The oxide film having a SO3 content of 13% is washed with water for a long time. As a result of chemical analysis, the SO3 content was 8%, and from this experiment, 8% SO3 was incorporated into the film, and 5% SO3, which is the difference between 13% and 8%, was oxidized. This is thought to be the sulfate radical that is weakly adsorbed on the surface of the film or remains in the pores of the porous layer.The former is called "bound anion" and the latter is called "free anion". (Toshihiko Sato, Kyoko Kaminaga, “New Anodized Theory” Scan publication, May 8, 1997, p.24-25)
Based on these findings, the inventor has concluded that this free anion adheres to the surface of the partial reflector 8 and diffuses to a depth of about 30 nm. FIG. 6 shows the state of anions based on this conclusion. FIG. 6 is an enlarged view of the portion E surrounded by the alternate long and short dash line in FIG. 2, and is a diagram schematically showing the state of anions in the porous alumite film.

  The second embodiment is for solving the above-described problems. An anion contained in the porous alumite film adheres to the surface of the partial reflecting mirror 8, and the laser absorbs the heat absorption rate accordingly. The object is to further suppress the heat absorption of the partial reflection mirror 8 than the carbon dioxide laser oscillator of the first embodiment by preventing the characteristics of the light 10 from changing.

  FIG. 7 shows a characteristic part of the second embodiment of the present invention, in which a secondary electrolytic treatment is performed on the surface of the porous alumite in the opening 21 of the mirror retainer 16 of the first embodiment of the present invention. FIG. 5 is a diagram schematically showing that free anions are covered with a secondary electrolytic substance and cannot move freely. Thereby, it is possible to prevent anions in the porous type alumite film from adhering to the surface of the partial reflection mirror 8.

An example of the manufacturing conditions that were actually manufactured and confirmed the effect is shown. The element deposited by secondary electrolysis was treated with Ni.
FIG. 8 corresponds to FIG. 3 and shows the relationship between the laser light oscillation time and the heat absorption rate of the partial reflecting mirror 8. In the orthogonal carbon dioxide laser oscillator, the solid line is the data in the prior art to which the first embodiment is not applied, the broken line is the data to which the first embodiment is applied, and the alternate long and short dash line is the data to which the second embodiment is applied. Both are continuously oscillated at a laser light output of 4 kW. In the conventional technique, the heat absorption rate of the partial reflecting mirror 8 is increased by 0.1% due to the laser light oscillation of 1000 hr. However, by applying the second embodiment, the increase in the absorption rate is suppressed to 0.01%. As a result, the heat absorption rate increase reduction effect was improved to 90%.

  As in the first embodiment, the manufacturing conditions were changed to some extent, and how much the obtained effect changed was confirmed. Although illustration is omitted, as a result of conducting an experiment by depositing Ag and Cu in addition to Ni, it was confirmed that the heat absorption rate increase reducing effect was within the range of 90 ± 3%. The numerical value of ± 3 is similar to the measurement variation of the heat absorption rate, indicating that there is no significant difference.

  The experimental results described above were obtained with an orthogonal carbon dioxide laser oscillator, but vaporized organic matter and fine dust particles that float inside the vacuum vessel 1 adhere to the surface of the partial reflector 8 and accompany it. The problem that the characteristics of the laser beam 10 change due to an increase in the heat absorption rate is common to the orthogonal type, axial flow type, and slab type systems, and the technology of the present invention is based on the principle of each of the above systems. It can be applied to the effect.

DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Laser medium 3 Blower 4 Rectification duct 5 Electrode 6 Power supply unit 7 Discharge 8 Partial reflection mirror 9 Total reflection mirror 10 Laser beam 11 Heat exchanger 12 Aperture 13 Vacuum pump 14 Cooling device 15 Control device 16 Mirror holder 17 Mirror holder 18 O-ring 19 Port 20 Flow path 21 Opening

Claims (3)

The laser medium circulating inside the vacuum vessel is excited by the energy generated by the discharge, and the photons emitted at the time of transition are amplified by the optical resonator mirror arranged opposite to the laser medium, and a part of the photon is amplified. In the carbon dioxide laser oscillator that takes out from the partial reflector as laser light,
The laser medium has an opening through which laser light passes so as to cover the inflow path approaching the surface of the partial reflector, and the inner surface of the opening is made of porous anodized and is arranged in the vicinity of the partial reflector. Equipped with
A carbon dioxide laser oscillator characterized in that this component is cooled so that the temperature is lower than that of the flowing laser medium. 2. The carbon dioxide laser oscillator according to claim 1, wherein the surface of the porous alumite on the inner surface of the opening is subjected to secondary electrolytic treatment. 3. The carbon dioxide laser oscillator according to claim 1, wherein the component is a mirror holder that holds a surface of the partial reflection mirror on the inner side of the vacuum container. 4.

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