JPH0423375A - Solid laser - Google Patents

Abstract

PURPOSE:To prevent electrodes from being sputtered and to prolong semipermanently the life of an exciting lamp by a method wherein the electrodes are respectively provided outside of both ends of the lamp and the lamp is discharged by applying a highfrequency voltage to the electrodes. CONSTITUTION:A DC power supply part 1 rectifies a commercial power supply and stabilizes to feed a DC voltage to a high-frequency inverter 2. The inverter 2 is constituted of 4 pieces of switching elements 3a to 3d and outputs a high-frequency voltage by making a group of the elements 3a and 3d and a group of the elements 3b and 3c turnON alternately. The output of the high-frequency voltage from the inverter 2 is fed to an exciting lamp 5 through a transformer 4. There are electrodes 11 and 12 at both ends of the lamp 5 and electrode supports 13 and 14 are respectively provided outside of the electrodes 11 and 12. Diluent gas, such as krypton gas, exnon gas or the like, is encapsulated in the lamp 5. High-frequency discharge is performed in the lamp 5 by applying the high-frequency voltage to the electrodes 11 and 12 via the supports 13 and 14 and light for laser excitation use is emitted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state laser device, and more particularly to the structure and discharge method of an excitation lamp used to excite a solid-state laser.

[Conventional technology]

Nd; YAG (yttrium aluminum garnet doped with neodymium, hereinafter referred to as YAG) laser device uses quartz, which is often used for optical communications because its oscillation wavelength is near-infrared light (1°06 μi). The laser beam can be guided freely through the manufactured fiber, and the optical absorption rate of the metal material that is the object to be laser processed is CO. In recent years, YAG laser devices have been increasingly used for laser processing because the wavelength is several times higher than the laser oscillation wavelength of 10.6 μi.

Generally, in a YAG laser device, an excitation voltage is applied to an excitation lamp, and a YAG rod is excited by light generated by a discharge between electrodes inside a tube wall of the excitation lamp, thereby outputting laser light.

[Problem to be solved by the invention]

However, in the combination configuration of an excitation lamp and an excitation power source as described above, whether the discharge method is DC discharge or AC discharge, the electrode inserted inside the tube wall of the excitation lamp will sputter due to the discharge, and the tube near the electrode will become sputtered. Stick to the wall. This attached sputtered material absorbs the radiation, causing a local temperature rise. As a result, distortion occurs only in the 8 minutes that spatter adheres, and in the worst case, it may lead to an accident in which the lamp is destroyed. Furthermore, since the sputtered material covers the inner wall of the excitation lamp, the luminous efficiency is also reduced.

Therefore, there is a problem in that the excitation lamp has a short lifespan of about 200 to 500 hours and must be replaced with a new one. That is, in the past, this excitation lamp was considered a consumable item.

Furthermore, it is necessary to use about 10 to 20 excitation lamps in one YAG laser device with a laser output of 1 to 2 KW, and the cost per lamp is high, which is a major problem with YAG laser devices.

The present invention has been made in view of these points, and it is an object of the present invention to provide a solid-state laser device in which the electrode of the excitation lamp is provided outside the tube and the emission discharge method of the excitation lamp is a high-frequency discharge method. .

Another object of the present invention is to provide a solid-state laser device that can obtain more efficient excited discharge by setting the electric field frequency of high-frequency discharge to a frequency at which an ion trap phenomenon or an electron trap phenomenon occurs. be.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a solid-state laser device configured to emit light by discharging an excitation lamp filled with a rare gas, and excite a solid-state laser active medium with the emitted light to perform laser oscillation. , characterized in that it has a DC power supply section that supplies a DC voltage, an inverter that converts the DC voltage into a high frequency voltage, and the excitation lamp in which an electrode section to which the high frequency voltage is applied is provided outside the tube. A solid state laser device is provided.

[Effect]

The high frequency voltage from the inverter is applied to electrodes provided on the outside of the tube of the excitation lamp. The discharge of the excitation lamp is caused by the high frequency voltage applied to this outer electrode, and light is emitted. Therefore, there is no adverse effect caused by sputtering or sputtered materials. As a result, the life of the excitation lamp becomes semi-permanent.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing a high frequency power supply circuit section for driving a laser excitation lamp and a laser excitation lamp section of a YAG laser device according to an embodiment of the present invention. The DC power supply B1 rectifies and stabilizes the commercial power supply and supplies the DC voltage to the high frequency inverter 2. The high frequency inverter 2 has four switching elements 3
a, 3b, 3C, and 3d, a pair of switching elements 3a and 3d, and a pair of switching elements 3b and 3d.
A high frequency voltage is output by alternately turning on the sets of 0's. FETs or the like are used as the switching elements 3a to 3d. The high frequency voltage output of the high frequency inverter 2 is supplied to an excitation lamp 5 through a transformer 4.

There are electrodes 11 and 12 at both ends of the excitation lamp 5, and electrode supports 13 and 14 are provided on the outside thereof. The excitation lamp 5 is filled with a rare gas such as krypton or xenon.

A high frequency voltage is applied to the electrode 1 via the electrode support 13.14.
1 and 12, a high-frequency discharge is caused within the excitation lamp, and light for laser excitation is emitted.

FIG. 2 is a diagram showing details of the structure of the excitation lamp. Note that, since the excitation lamp 5 has a symmetrical structure, only the details of one side thereof are shown. The tube 5a of the excitation lamp 5 is made of quartz or the like, and an electrode 11 is bonded to the end thereof by metallization.

On the outside thereof, there is a water-cooled electrode support 13 that cools the electrode 11, and an electric wire 18 that applies a high-frequency voltage is connected to the electrode support. Further, pipes 15 and 16 for cooling water are connected to the electrode support 13, and cooling water 17 is supplied to cool the electrode 11.

The excitation lamp has a thickness of 0.1 to 0.3 mm at the end to which the electrodes are bonded. Tube 5 of excitation lamp 5
The length of a, that is, the length of the discharge path is 30 mm, and the inner diameter is 6
760 Torr of Kr (krypton) inside
sealed under pressure.

Here, the mobility μi of krypton ion (Kr+) is 0
℃, 760 Torr, 17 (cm/se
c/v/cm).

Here, in order to increase luminous efficiency, an ion trap is generated. For this purpose, the output frequency f1 of the high frequency inverter needs to be equal to or higher than the following value. That is, μ
i is the ion velocity in the tube 5a, Em is the electric field strength, L
It is necessary to set the frequency f1 to satisfy the following equation expressing the ion trap condition: f1≧[(μe·E)/(π·L), where is the discharge distance of the tube 5a and π is the circumference.

Moreover, if the frequency is set to be higher than the frequency at which electron traps occur, the luminous efficiency will further increase. In other words, μ8 is connected to tube 5a
As the electron velocity within the equation, f2≧[(μe・Em)/(π
・L) By selecting a frequency f2 that satisfies the following, it is possible to generate an electron trap.

Generally, since μe>μi, f2>fl. Therefore, at a frequency f where f2>f>f1, only an ion trap is generated, and at a frequency f, where f>f2, both an ion trap and an electron trap can be generated. Which of these should be selected depends on the switching elements 3a to 3 of the high frequency inverter 2.
It is determined by the 3D frequency characteristics, etc.

Next, the operation will be explained. The DC output voltage of the DC power source 1 is chopped to 2 MHz by a high frequency inverter 2 to generate a high frequency voltage, which is boosted to about 300 V by a transformer 4 in accordance with the electrical characteristics of the excitation lamp 5. However, at the start of discharge, the voltage is increased to 2 to 3 KV.

Here, an increased voltage is applied to an electrode support 13.14 which is electrically coupled to electrodes 11.12 provided at both ends of the excitation lamp 5. The tube wall thickness of the excitation lamp 5 is 0.
When a sufficient discharge current flows between a pair of electrodes 1112, which are made of a capacitive electric dielectric with a thickness of 1 to 0.3 mm and provided at both ends of the tube 5a of the excitation lamp 5, the excitation lamp 5 emits light, and the YAG laser rod emits light. YA absorbs excitation light
G laser oscillates.

Further, by controlling the high frequency voltage applied to the excitation lamp 5, it can be operated as a flash lamp or an arc lamp.

Next, the outline of the YAG laser device will be explained.

FIG. 3 is a schematic configuration diagram of the YAG laser device.

At both ends of the YAG laser rod 23 on an extension of the central axis of the crystal, a rear mirror 27 and an output mirror 21 forming an optical resonator are placed on a plane perpendicular to the central axis (optical axis). The YAG laser rod 23 is irradiated with an excitation lamp 5 and energy is injected therein. At this time, in order to efficiently absorb the energy of the excitation lamp 5 into the YAG laser rod 23,
A condensing reflector (not shown) is provided inside the excitation cavity 31 surrounding the G laser rod 23 and the excitation lamp 5.

Furthermore, a Q switch module 24 that enables pulse oscillation, a unit 25 that integrates a linear polarization unit that converts random polarization into linear polarization and a mechanical shutter unit as a safety protection device, and a mode selector 26 that selects the transverse mode of the laser beam. is provided.

Although not shown in FIG. 3, in the case of a YAG laser, the efficiency with which the energy injected into the excitation lamp 5 is converted into laser light is about 3 to 4%, so the energy injected into the excitation lamp 5 is is a fairly large value, and it is necessary to efficiently cool the heat consumed there. In addition, the YAG laser rod 23 and the excitation cavity 31 are also water-cooled,
In order to maintain the stability of laser output, it is necessary to accurately manage the temperature of the cooling water.

In this way, a high-frequency discharge was generated through a pair of electrodes provided on the outside of the excitation lamp to excite the rare gas sealed within the excitation lamp and cause it to emit light. As a result,
The problems of wear of the electrodes of the excitation lamp and adhesion of sputtered materials to the tube wall are completely eliminated, and an excitation lamp with a semi-permanent life can be provided.

In addition, an electrode was fabricated using a metallization method on the outside of the quartz tube that makes up the excitation lamp, but the surface of the metal rod that made up the electrode was coated with a substance different from that of the quartz tube, and the electrode rod was bonded to the quartz tube. It is also possible to construct an electrode using the same method.

Further, in the above description, the YAG laser device was used as an example, but the present invention can also be applied to other solid-state laser devices that pump the laser with other excitation lamps.

〔Effect of the invention〕

As explained above, in the present invention, an electrode is provided on the outside of the excitation lamp, and a high frequency voltage is applied to cause discharge. Therefore, sputtering of the electrode can be prevented, and the life of the excitation lamp can be made semi-permanent. be able to. As a result, excitation lamps do not need to be replaced and costs are reduced.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a high frequency inverter and an excitation lamp for driving a laser excitation lamp of a YAG laser device according to an embodiment of the present invention, Fig. 2 is a diagram showing details of the structure of the excitation lamp, and Fig. 3 is a diagram showing a YAG laser device.
FIG. 1 is a schematic configuration diagram of an AG laser device. DC power supply section High frequency inverter Excitation lamp Electrode Electrode support Electrode support

Claims (6)

[Claims] (1) In a solid-state laser device configured to cause an excitation lamp filled with rare gas to emit light by discharging it, and to excite a solid-state laser active medium with the emitted light to perform laser oscillation, a DC power supply that supplies a DC voltage is used. A solid-state laser device comprising: an inverter that converts the DC voltage into a high-frequency voltage; and an excitation lamp having an electrode portion to which the high-frequency voltage is applied provided outside the tube. (2) The laser control device according to claim 1, wherein the electrode portion is fixed to the tube wall by a metallization method. (3) The solid-state laser device according to claim 2, further comprising a cooling electrode support provided outside the electrode. (4) The voltage output frequency of the inverter is determined by the following formula expressing the ion trap conditions, where μ_i is the ion velocity in the tube, E_m is the electric field strength, L is the discharge distance of the tube, and π is pi. The solid-state laser device according to claim 1, characterized in that the frequency satisfies the following: (μ_i·E_m)/(π·L)]. (5) The voltage output frequency f of the inverter is expressed by the following formula, where μ_e is the electron velocity in the tube, E_m is the electric field strength, L is the discharge distance of the tube, and π is pi, expressing the electron trap condition, f≧ The solid-state laser device according to claim 1, characterized in that the frequency satisfies the following: [(μ_e·E_m)/(π·L)]. (6) The solid-state laser device according to claim 1, wherein the excitation lamp is a flash lamp or an arc lamp.