JP2017028211A - Gas laser oscillation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas laser oscillation device that enables prevention of discharge transition of an insulation joint portion and reduction of the loss in the insulation joint portion, and can efficiently achieve a laser beam having a large output.SOLUTION: A gas laser oscillation device comprises a discharge unit for exciting a laser medium, a blower for blowing laser gas as the laser medium, a laser gas flow path for connecting the discharge unit and the blower, at least two or more mirrors arranged on the axis of the discharge unit, and a connection unit for insulating and coupling the mirrors and the space of the discharge unit. The connection unit is provided with a transmission plate that transmits a laser beam therethrough and segments the space on the mirror side and the space on the side of the discharge unit and the laser gas flow path.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas laser oscillating device that generates a laser using a gas as a medium, and more particularly to improving the stability of excitation discharge of a gas medium.

  A conventional gas laser oscillation apparatus will be described with reference to FIG.

  In the gas laser oscillation device, a mixed gas such as carbon dioxide (hereinafter referred to as laser gas) serving as a laser medium is introduced into a discharge tube 901 such as glass. A laser beam is generated by applying an electric field into the tube and discharging it. In the high-power laser of the kilowatt class, the mixed gas is not enclosed in the discharge tube 901, but a system in which new gas is always introduced into the discharge space 905 and circulated is used.

  Such a circulation type gas laser oscillator includes a coaxial flow type and a three-axis orthogonal type. In the coaxial flow type gas laser oscillation device, the laser gas flow direction 909, the discharge direction, and the direction in which the laser beam 908 resonated between the mirrors 906 and 907 arranged opposite to each other are the same. For example, processing such as cutting the workpiece by irradiating the workpiece is performed.

  An insulating junction 914 is provided between the discharge space 905 and the mirrors 906 and 907 in order to maintain insulation. Further, in order to prevent a very small amount of impurities contained in the gas flow from adhering to the mirror and causing a decrease in laser oscillation efficiency, the mirrors 906 and 907 are separated from the gas flow by the insulating joint 914, and the gas flow is mirrored. A structure that does not flow in the vicinity is taken.

  Since the insulation depends on the temperature, the insulation bonding portion 914 is cooled by an air blower 924 from the outside to suppress the temperature rise of the insulation bonding portion 914 (see, for example, Patent Document 1).

JP 2013-247122 A

  However, the conventional gas laser oscillation device has two problems, namely, the discharge transfer to the insulating junction and the increase of the loss in the insulating junction.

  Since the laser gas does not circulate in the insulating junction, heat tends to be trapped due to heat transfer and radiation of heat generated in the discharge space, irradiation of scattered light on the mirror surface, etc., and the temperature tends to rise. When the temperature of the insulating junction increases in this way, the discharge start voltage decreases in the internal space of the insulating junction.

  Therefore, originally, an appropriate resonance state can be obtained by discharging in the discharge space. However, for the reasons described above, when the temperature inside the insulating junction becomes high and the discharge start voltage decreases, the discharge starts here. Had a problem of migrating.

  When the discharge shifts, the temperature inside the insulating junction rapidly rises, exceeds the heat resistance temperature of peripheral members such as mirrors, and causes damage.

  In addition, the length of the insulating junction becomes longer than necessary to prevent the discharge transition, and the loss when the laser beam passes through the inside of the insulating junction increases, which hinders the realization of a highly efficient gas laser oscillation device. It was.

  Certainly, cooling the insulating joint portion by blowing air from the outside to suppress the temperature rise of the insulating joint portion can provide a certain effect for preventing discharge transition. However, since the discharge start voltage in the insulating junction cannot be increased to the same level or more as that of the discharge space, the length of the insulating junction is required to be longer than the length of the discharge space.

  Therefore, in order to realize a highly efficient and high-power gas laser oscillation device in recent gas laser oscillation devices that require a large output from customers in order to expand applications such as sheet metal cutting and welding, the above means from the viewpoint of loss reduction Is insufficient, and a configuration capable of obtaining a greater effect has been demanded.

  In order to solve the above problems, a gas laser oscillation apparatus according to an embodiment of the present disclosure includes a discharge unit that excites a laser medium, a blower that blows a laser gas that is the laser medium, the discharge unit, and the blower. A laser gas flow path for connecting the discharge section, at least two or more mirrors disposed on the axis of the discharge section, and a connection section for insulating and coupling the space between the mirror and the discharge section. Is provided with a transmission plate that transmits laser light and divides the space on the mirror side and the space on the discharge portion and the laser gas flow path side.

  With the above configuration, in the gas laser oscillation device according to the present invention, the discharge start voltage of the insulating junction is increased by cutting off the discharge space and the insulating connection portion and providing a gas pressure difference, thereby preventing the discharge transition of the insulating junction and the insulating junction. It is possible to reduce the loss within the unit, and to obtain a high-power laser beam efficiently.

1 is a configuration diagram of a gas laser oscillation apparatus according to Embodiment 1. FIG. It is a graph which shows the relationship between the product of the gas pressure and discharge distance by Paschen's law, and a discharge start voltage. It is a figure which shows the modified example from which the insulation junction part of the gas laser oscillation apparatus which concerns on Embodiment 1 differs. It is a block diagram of the gas laser oscillation apparatus which concerns on a prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same components are denoted by the same reference numerals, and the description thereof may be omitted.

(Embodiment 1)
FIG. 1 shows a configuration of a gas laser oscillation apparatus according to an example of an embodiment of the present invention. The gas laser oscillation apparatus 100 includes a discharge tube 101, electrodes 102 and 103, a power source 104, a total reflection mirror 106, a partial reflection mirror 107, a laser gas flow path 110, a blower 111, and heat exchangers 112 and 113. And an insulating joint 114, an insulation holder 115, and a transmission plate 116. Further, for internal intake and exhaust, the laser gas cylinder 128, the exhaust part 117, the first exhaust valve 118 and the second exhaust valve 119, the first exhaust path 120 and the second exhaust path 121, and the first 1 laser gas inlet 122 and second laser gas inlet 123, a first laser gas supply path 124 and a second laser gas supply path 125, a first supply valve 126 and a second supply valve 127 are provided. .

  The discharge tube 101 is made of a dielectric such as heat-resistant borosilicate glass, the electrodes 102 and 103 are provided around the discharge tube 101, and the power source 104 is connected to the electrodes 102 and 103. A discharge space 105 is formed in the discharge tube 101 sandwiched between the electrodes 102 and 103. The discharge part is configured as described above.

  In this embodiment, an example in which two mirrors are provided is shown. Two total reflection mirrors 106 and partial reflection mirrors 107 are fixedly disposed at both ends of the discharge space 105 to form an optical resonator. The laser beam 108 is output from the partial reflection mirror 107.

  The laser gas flow 109 circulates in the laser gas flow path 110 connected to the discharge tube 101 by the blower 111, and the flow velocity is about 100 m / sec in the discharge space 105. The heat exchangers 112 and 113 have a role of lowering the temperature of the laser gas that has risen due to the operation of the discharge space 105 and the blower 111.

  Since a high voltage is applied to the electrodes 102 and 103 provided in the discharge tube 101 for discharge, the discharge tube 101 and the total reflection mirror 106 and the partial reflection mirror 107 are connected by an insulating junction 114. Further, the discharge tube 101 itself is also held by the insulating holder 115.

  The transmission plate 116 divides the space in the insulating junction 114 into the mirror side, that is, the space on the total reflection mirror 106 and the partial reflection mirror 107 side, and the space on the discharge part and laser gas flow path side.

  The exhaust unit 117 is used to depressurize the space on the mirror side and the space on the discharge unit and laser gas flow path side separated by the transmission plate 116. It is common to use a vacuum pump such as a rotary pump. Exhaust is performed by opening / closing the first exhaust valve 118 via the first exhaust path 120 in the mirror side space. In the space on the discharge part and laser gas flow path side, the second exhaust valve 119 is opened and closed via the second exhaust path 121.

  Each of the two types of spaces described above has a laser gas inlet. In the mirror-side space, new gas is supplied from the laser gas cylinder 128 through the first laser gas supply path 124 and the first laser gas inlet 122 by opening and closing the first supply valve 126. In the space on the discharge part and the laser gas flow path side, new gas is supplied from the laser gas cylinder 128 via the second laser gas supply path 125 and the second laser gas inlet 123 by opening and closing the second supply valve 127.

  The above is the configuration of the gas laser oscillation apparatus according to the embodiment of the present invention. Next, the operation will be described.

  The laser gas sent out from the blower 111 is introduced into the discharge tube 101 through the laser gas flow path 110. In this state, a high voltage is applied to the discharge space 105 from the electrodes 102 and 103 connected to the power source 104 to generate a discharge.

  The laser gas in the discharge space 105 is excited by obtaining this discharge energy, and the excited laser gas is brought into a resonance state by an optical resonator formed by the total reflection mirror 106 and the partial reflection mirror 107, and the laser is emitted from the partial reflection mirror 107. A beam 108 is output. This laser beam 108 is used for applications such as laser processing.

  Next, features of the gas laser oscillation apparatus according to the embodiment of the present invention will be described.

  In the present invention, the mirror-side space, the discharge portion, and the laser gas flow path-side space are divided in the insulating bonding portion 114 by the transmission plate 116, and the mirror-side space is decompressed by the exhaust portion 117, so that the gas in the mirror-side space is reduced. The pressure is set to be equal to or lower than the gas pressure in the space on the discharge part and laser gas flow path side. The procedure will be described below.

  When starting the gas laser oscillation device, first, the first supply valve 126 and the second supply valve 127 are closed, and the first exhaust valve 118 and the second exhaust valve 119 are opened. The pressure is reduced. Next, when the gas pressure reaches about 0.005 kPa (the basis will be described later), the first exhaust valve 118 is closed, and the gas pressure in the mirror side space is maintained at about 0.005 kPa.

  On the other hand, the space on the discharge part and laser gas flow path side closes the second exhaust valve 119 and opens the second supply valve 127 and fills the laser gas until the optimum gas pressure for laser oscillation (for example, about several tens of kPa) is reached. To do. As described above, each of the two types of spaces can be set to an individual predetermined gas pressure.

  In the space on the discharge portion and the laser gas flow path side, gas divergence occurs due to discharge, and the laser gas gradually deteriorates with use. Therefore, the second exhaust valve 119 and the second supply valve 127 are opened and closed in a timely manner. Keep the laser gas fresh.

  Further, when the gas laser oscillation device is stopped, the first exhaust valve 118 and the second exhaust valve 119 are closed, and the first supply valve 126 and the second supply valve 127 are opened to fill the laser gas. Return the gas pressure in both spaces to uniform. In the configuration of the present invention, the gas in the mirror-side space does not contribute to discharge and optical resonance, and therefore, gas such as dry air may be filled instead of laser gas.

  Incidentally, the laser gas flow 109 contains a small amount of impurities such as abrasion powder of the electrodes 102 and 103 and circulates them. For this reason, when the laser gas flow 109 flows in the vicinity of the total reflection mirror 106 and the partial reflection mirror 107, impurities adhere to the surfaces of the total reflection mirror 106 and the partial reflection mirror 107 and cause a decrease in laser oscillation efficiency. Therefore, conventionally, an insulating junction 114 is provided between the total reflection mirror 106 and the partial reflection mirror 107 and the discharge tube 101 so that the laser gas flow 109 does not flow through the insulation junction.

  However, since there is no gas circulation, the temperature of the insulating junction 114 is likely to rise, the discharge start voltage is lowered, and the discharge transition from the electrode 102 is caused. Is necessary, leading to an increase in the absorption loss of the laser beam passing through the insulating junction 114.

  Therefore, in the embodiment of the present invention, the transmission plate 116 that transmits the laser beam is disposed in the vicinity of the discharge space 105 and the laser gas flow path 110, and the space on the total reflection mirror 106 and the partial reflection mirror 107 side is separated from the gas, The laser gas flow 109 is prevented from flowing into the vicinity of the total reflection mirror 106 and the partial reflection mirror 107, and the space on the side of the total reflection mirror 106 and the partial reflection mirror 107 is reduced by the exhaust unit 117, so that the transmission plate 116 and the total reflection are totally reflected. The discharge start voltage between the mirror 106 and the partial reflection mirror 107 is increased to prevent discharge transition.

  According to the generally known Paschen's law, the discharge start voltage depends on the product of the pressure of the gas serving as the medium and the discharge distance. FIG. 2 is a graph showing the relationship between the product of gas pressure and discharge distance according to Paschen's law and the discharge start voltage. As shown in this graph, the discharge start voltage in this space can be increased by reducing the pressure between the space between the transmission plate 116 and the total reflection mirror 106 and the space between the transmission plate 116 and the partial reflection mirror 107. it can.

  For example, when the length between the transmission plate 116 and the total reflection mirror 106 and the partial reflection mirror 107 is about 100 mm, the discharge start voltage can be sufficiently increased by reducing the pressure to about 0.005 kPa according to the graph of FIG. Recognize. As an additional effect, the number of molecules in the space between the transmission plate 116, the total reflection mirror 106, and the partial reflection mirror 107 is greatly reduced, so that the absorption loss when passing through the laser beam can be greatly reduced.

  As described above, since the discharge start voltage between the transmission plate 116, the total reflection mirror 106, and the partial reflection mirror 107 can be greatly increased, the insulating junction 114 can be shortened.

  For example, when the length of the discharge space 105 is 250 mm, the length of the insulating joint 114 is conventionally required to be about 400 mm from experience, but can be shortened to about 200 mm by the effect of the present invention.

  This number takes into account that it is possible to lower the discharge start voltage inside the space, and it is necessary to ensure a creepage distance that does not cause dielectric breakdown outside the space exposed to the atmosphere. It is a number. Therefore, as shown in FIG. 3, by using the insulating bonding portion 301 having an uneven outer surface and increasing the creepage distance, the insulating bonding portion can be further shortened to about 100 mm.

  As a result, the resonator length is shortened, so that a reduction in diffraction loss can be expected, and the gas laser oscillation device can be downsized as compared with the prior art.

  Next, the transmission plate 116 will be described in detail.

  Since the transmission plate 116 is disposed in the optical resonance space formed between the total reflection mirror 106 and the partial reflection mirror 107, it is necessary to transmit the laser beam. When carbon dioxide gas is used as the laser medium, the wavelength of the generated laser beam is mainly 10.6 μm, so use a zinc selenide or CVD diamond transmission plate having a high transmittance for this wavelength band. Is effective.

  However, when a transmission plate coated with an amorphous dielectric multilayer film for preventing light absorption and scattering is used as in a general resonance reflector, it is used in the vicinity of the discharge space 105. There is a risk of the coating being damaged by the electric field. Therefore, it is effective to use a non-coating material.

  Further, the transmission plate 116 is used in the vicinity of the laser gas flow 109, and it is expected that the above-described impurities adhere and the transmittance is lowered. Therefore, as shown in FIG. 1, it is preferable to provide a second laser gas inlet 123 at a position near the transmission plate 116. Specifically, the second laser gas inlet 123 is provided between the transmission plate 116 and the laser gas flow path 110. By doing so, since a new laser gas is introduced from the transmission plate 116 side toward the laser gas flow path 110, it is effective to prevent adhesion of impurities.

  As described above, according to the gas laser oscillation apparatus of the present embodiment, the discharge start voltage of the insulating junction is increased by cutting off the discharge space and the insulating connecting portion and providing a gas pressure difference, thereby discharging the insulating junction. This makes it possible to prevent the transition and reduce the loss in the insulating junction, and to obtain a high-power laser beam efficiently.

  The gas laser oscillation apparatus according to the present invention is capable of preventing the discharge transition of the insulation junction and reducing the loss in the insulation junction, and can efficiently obtain a high-power laser beam. This is useful in a generated gas laser oscillation device or the like.

DESCRIPTION OF SYMBOLS 100 Gas laser oscillation apparatus 101 Discharge tube 102, 103 Electrode 104 Power supply 105 Discharge space 106 Total reflection mirror 107 Partial reflection mirror 108 Laser beam 109 Laser gas flow 110 Laser gas flow path 111 Blower part 112, 113 Heat exchanger 114 Insulation junction 115 Insulation holding Body 116 Transmission plate 117 Exhaust section 118 First exhaust valve 119 Second exhaust valve 120 First exhaust path 121 Second exhaust path 122 First laser gas inlet 123 Second laser gas inlet 124 First laser gas Supply path 125 Second laser gas supply path 126 First supply valve 127 Second supply valve 128 Laser gas cylinder 301 Insulation junction 901 Discharge tube 905 Discharge space 909 Laser gas flow direction 906, 907 Mirror 908 Laser beam 914 Insulation junction Part 924

Claims (4)

A discharge part for exciting the laser medium;
A blower for blowing laser gas as the laser medium;
A laser gas flow path connecting the discharge part and the blower part;
At least two or more mirrors disposed on the axis of the discharge part;
A connecting portion for insulating and coupling the space between the mirror and the discharge portion;
A gas laser oscillating device comprising a transmission plate that transmits laser light to the connecting portion and divides the space on the mirror side and the space on the discharge portion and the laser gas flow path side. A laser gas inlet and an exhaust path are provided in each of the space on the mirror side and the space on the discharge part and the laser gas flow path side,
The gas laser oscillation apparatus according to claim 1, wherein a gas pressure in the space on the mirror side is lower than a gas pressure in the space on the discharge part and the laser gas flow path side.   3. The gas laser oscillation apparatus according to claim 2, wherein a laser gas introduction port in a space on the discharge portion and the laser gas flow path side is provided between the transmission plate and the laser gas flow path.   The gas laser oscillation device according to claim 1, wherein unevenness is provided on an outer surface of the connection portion.

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