JPH05110163A - Laser tube - Google Patents

Abstract

PURPOSE:To prevent a thermal damage at a capillary or near it and achieve a high output of a laser tube by forming the entire capillary with diamond or a diamond-shaped carbon film or coating what is made of a heat-resistance material with diamond or the diamond-shaped carbon film. CONSTITUTION:Diamond is allowed to grow around a capillary 2 by the heat filament CVD method and a base material is dissolved after growth. Then, it is mounted to a disc-shaped member 3 which consists of aluminum nitride. Then, a plurality of these disc-shaped members 3 are connected in series by a metal connection member 5, metal tube members 6 and 7 are provided at both edges, and then electrodes 8 and 10 are installed, thus enabling heat resistance, thermal conductivity, and sputter resistance of the capillary part to be improved and oscillation on a high-output ion user owing to improved resistance against an extremely high temperature.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in ion laser tubes. The ion laser is a laser that ionizes gas and generates light by electronic transition between ion levels. It has an emission region in the visible and ultraviolet regions due to the transition between excited states of rare gases such as neon, argon, krypton, and xenon, and monovalent or polyvalent ionized ions such as oxygen and chlorine. Especially, argon laser and krypton laser have high practical value among ion lasers. Widely used. The ion laser is useful because it can emit a short wavelength light having a large wavelength output. However, since the oscillation efficiency is extremely low, a large current must be passed to maintain oscillation while forced cooling.
This is because almost all of the power that is input becomes heat. The ion laser is a kind of gas laser. Some gases, such as carbon dioxide gas laser and helium neon laser, do not utilize the interlevel transition of ions. Argon laser is sometimes called gas laser, so it is not a mistake. Here, the ion laser is one kind of gas laser and does not mean all of the gas lasers.

[0002]

2. Description of the Related Art In an ion laser, a gas is caused to flow through a long laser tube, and a voltage is applied between an anode and a cathode to excite the gas into ions. Brewster windows are provided at both ends of the laser tube to form a resonator. The middle of the discharge path is a thin tube, which is surrounded by a water cooling jacket. A coil for generating an axial magnetic field is provided around the laser tube to confine the plasma in the center. Since the ion laser emits light by energy transition of ions in plasma, it is necessary to increase the density of ions in order to obtain high output. Therefore, a large current of several tens of amperes is discharged in a thin tube portion having an inner diameter of several mm. A small part of this electric power becomes light. Generally, the oscillation efficiency of the ion laser is extremely poor, and most of the supplied electric power becomes heat.
The temperature of the portion in contact with the discharge path and its vicinity becomes extremely high. If left unattended, this heat raises the temperature of the entire laser tube, causing thermal deformation and heat damage, damaging the device and degrading the laser light quality. Therefore, the laser tube is actively cooled during laser oscillation.

The material used near the discharge path withstands high temperatures,
Moreover, it must have high thermal conductivity in order to increase the cooling efficiency. Further, the plasma of the laser gas collides and sputters this, so a material that is strong against spattering must be used. Otherwise, the material will be worn and the laser light output will be unstable because the gas component contains impurities. In this way, the material of the discharge path has heat resistance,
High thermal conductivity and spatter resistance are required. Therefore, a ceramic such as AlN is used for the discharge path thin tube portion. Further, it has been proposed to provide silicon carbide (SiC) or tungsten (W), which has good spatter resistance, in a portion directly exposed to the laser gas plasma (Japanese Patent Laid-Open No. 63-18437).
8). But still not enough.

FIG. 1 shows the structure of a typical external mirror type laser tube having Brewster windows at both ends. In this ion laser tube, a plurality of disk-shaped members 3 each having a thin tube 2 having a through hole 1 for discharge arranged in the center are arranged on the same straight line and are connected to each other. A gas circulating hole 4 is bored in the disc-shaped member 3 in the axial direction. The plurality of disc-shaped members 3 are axially connected by a short annular metal connecting member 5 so that the discharge through holes 1 are aligned in a straight line. Annular metal pipe members 6 and 7 are connected to the disk-shaped members 3 at both ends. An anode 8 is provided inside one of the metal tube members 6. A gas introduction pipe 9 is connected to this space.
A cathode 10 is provided inside the metal tube member 7 on the opposite side. Brewster windows 11 and 11 are provided at both ends of the end plate 1.
It is provided before 2 and 13. Although not shown, a cooling water jacket is provided on the outer circumference of the laser tube for water cooling.

A gas to be ionized is introduced from a gas introduction pipe 9, and a voltage is applied between the anode 8 and the cathode 10. Electric discharge occurs between both electrodes and the gas becomes plasma.
Although gas atoms are ions, they are excited to a high level by discharge. Those in this state cause stimulated emission and laser oscillation. A large amount of heat and plasma are generated in the discharge through hole 1 by the discharge. Therefore, the thin tube 2 is made of silicon carbide (S
iC), tungsten (W), or the like, which is a material having a good sputtering resistance property against plasma. The disk-shaped member 3 is made of a material having heat resistance and high thermal conductivity, such as aluminum nitride (AlN).

[0006]

Power of ion laser
If the temperature is further increased, the temperature of the portion of the thin tube 2 which becomes the discharge path becomes too high. This is a serious obstacle to pushing higher power. The outer peripheral portion of the laser tube is cooled by the cooling water jacket, but the inner thin tube 2 is heated to the greatest extent by the discharge and is far from the cooling water jacket, so that the temperature becomes considerably high. Not only that, non-uniform temperature rise may occur in the thin tube 2. For this reason, heat damage may occur to the thin tube 2. It is an object of the present invention to prevent thermal damage in the thin tube 2 forming the discharge path and its vicinity and to increase the output of the laser tube.

[0007]

In the laser tube of the present invention, a thin tube which is a discharge path is made of a diamond or diamond-like carbon film, or a heat-resistant material is coated with a diamond or diamond-like carbon film. Make with what you did. This is a feature. The diamond used for the thin tube can be produced by a vapor phase synthesis method. Diamond vapor phase synthesis methods include hot filament CVD method and microwave plasma CV.
A known method such as method D can be used.

[0008]

Function: Diamond has the highest thermal conductivity. It is also used in the heat sink of semiconductor lasers.
Diamond is also the hardest substance. Since it was hard, it was difficult to process and its applications were limited, but various shapes can be made by the vapor phase synthesis method. Further, diamond is also excellent in spatter resistance. The diamond-like carbon film also has the next best characteristics. The present invention uses a diamond or diamond-like carbon film for the capillary section. That is, the entire thin tube is made of diamond or a diamond-like carbon film, or a diamond or diamond-like carbon film is coated on a material made of a heat-resistant material. diamond,
The diamond-like carbon film is excellent in heat resistance, thermal conductivity, and spatter resistance. Therefore, if it is used in a thin tube that is a discharge path, it can withstand higher temperatures, and the laser output can be further increased. .. Further, since SiC and W used in the conventional thin tube portion have a lower thermal conductivity than AlN of the disk-shaped member, the thin tube portion has been thin, but when a diamond or diamond-like carbon film is used, the thermal conductivity is low. Since it is expensive, it can be made thicker. As the thickness increases, the mechanical strength also increases, so the spatter resistance increases and the cooling efficiency also increases.

[0009]

EXAMPLE The ion laser tube shown in FIG. 1 was produced by using a diamond thin tube by a vapor phase synthesis method. This thin tube 2
200 μm thick around a cylindrical Si substrate with a diameter of 2 mm
Is grown by the hot filament CVD method, and the substrate is melted after the growth. Therefore, the thin tube is a cylinder having an inner diameter of 2 mm and an outer diameter of 2.4 mm.
This diamond has 18 W / cm. It was confirmed that K had a good thermal conductivity. Aluminum nitride (A
1N) and attached to the disk-shaped member 3. A plurality of such disk-shaped members 3 were connected in series by a metal connecting member 5, metal tube members 6 and 7 were provided at both ends, and electrodes 8 and 10 were installed to produce an ion laser tube. This laser tube continued stable laser oscillation until the discharge current reached 50A.

For comparison, the thin tube 2 is made of silicon carbide (Si).
The same ion laser tube was made after making it in C) and attaching it to the disk-shaped member 3. The material of the thin tube is diamond and S
Others are the same except for iC. In the comparative example, when the discharge current was 35 A, the capillary caused thermal damage and
The oscillation has stopped. From this, the effect of the present invention by making the thin tube portion made of diamond becomes clear.

[0011]

INDUSTRIAL APPLICABILITY In the ion laser tube in which the heat generation of the discharge path is remarkable, the thin tube portion forming the discharge path is made entirely of diamond or is coated with diamond. The heat resistance, thermal conductivity, and spatter resistance of the thin tube portion are improved, and the thin tube portion can withstand extremely high temperatures well, so that a high-power ion laser can be provided. It is most suitable for ion laser tubes such as argon laser and krypton laser.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an ion laser tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Through hole for discharge 2 Capillary tube 3 Disc-shaped member 4 Gas circulation hole 5 Metal connection member 6 Metal tube member 7 Metal tube member 8 Anode 9 Gas introduction hole 10 Cathode 11 Brewster window

Claims (1)

[Claims] 1. A plurality of thin tubes 2 having a through hole 1 for discharge.
And the same number of disk-shaped members 3 in which the thin tubes 2 are attached,
Metal connecting member 5 for connecting a plurality of disc-shaped members 3 in the axial direction
And metal pipe members 6 and 7 provided at both ends of the disk-shaped member 3.
And electrodes 8 and 10 for discharge provided on the metal tube members 6 and 7 at both ends, a Brewster window 11 provided at the ends of the metal tube members 6 and 7, a metal connecting member 5, and a disk-shaped member. 3,
It is characterized in that it includes a cooling water jacket for cooling the thin tube 2, and that the thin tube portion which is the discharge path is entirely made of diamond or a diamond-like carbon film or is made of a heat-resistant material and is covered with the diamond or diamond-like carbon film. Laser tube.