JPH03112180A - Metal steam laser device - Google Patents

Abstract

PURPOSE:To retain temperature distribution at a laser oscillation part within a reactor core tube, to increase output, and to reduce thermal loss for improving oscillation efficiency by using a specified optic filter at a brewster window. CONSTITUTION:An optic filter 30 which reflects infrared rays 25 and transmits a laser light 26 is used for a brewster window 27. With this configuration, a ZnSb film 33 at both surfaces of a crystal glass 32 which becomes a substrate of the center part of the optic filter 30 is applied and the outer surface is coated with an SiO2 film 34 where this multiple-layer film is a dielectric, has a mirror effect for light, and can reflect light of a specific wavelength. Also, since a metal steam laser is a laser within a visible range, the filter 30 transmits the laser light 26 within the visible range and suppresses heat radiation from the window 27 by reflecting the infrared rays 25 and returning it into the furnace core tube, thus maintaining the temperature distribution within the reactor core tube to be uniform. Therefore, thermal loss can be reduced and efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention particularly relates to a metal vapor laser device in which the Brewster window is improved to reduce heat loss in the furnace core tube.

(Conventional technology) In recent years, laser equipment has been used for cutting materials and optical communications.

Used in medical technology and nuclear industrial applications.

Hereinafter, a copper vapor laser device will be explained as an example of a metal vapor laser device.

This laser device uses electric discharge to energize metal copper housed in a furnace core tube, heats it to a high temperature, and generates copper vapor. At the same time, this vapor is excited by electric discharge to form a laser medium. This device oscillates a laser beam having the following characteristics.

FIG. 5 is a cross-sectional view showing the configuration of a conventional copper vapor laser device;
Figure 6 is an enlarged view of the main part of Figure 5, Figure 7 is A-A of Figure 6.
It is a sectional view taken along a cutting line. That is, as shown in FIG. 5, the oscillation tube body 1 is provided with a furnace core tube 2 constituting it along the central axis thereof. At both ends of the furnace core tube 2, a positive electrode 3 and a negative electrode 4 are supported by electrode support flanges 5 and 6 and are disposed facing each other, and a pulse discharge is performed using the inside of the furnace core tube 2 as a discharge space 7. A copper piece 8 for generating copper vapor is housed at the bottom of the furnace core tube 2.

A discharge heat retaining heat insulating layer 9 made of a material such as alumina fiber is formed on the outer periphery of the furnace core 2, and in order to fix and support the heat insulating layer 9 in a predetermined position, the outer periphery of the heat insulating layer 9 is made of quartz or the like. A protection tube 10 is provided. A vacuum insulation chamber 12 is formed by the protection tube 10 and the vacuum container 11 arranged around its outer periphery.
The discharge space 7 within the furnace core tube 2 is connected to an exhaust device 13.

A break tube 14 made of an insulating material such as ceramics or glass is interposed between the external vacuum vessel 11 and the electrode support flange 6 in order to insulate the positive electrode 3 and the negative electrode 4 and obtain a good discharge. There is. In addition, each electrode support flange 5,
Blue metal windows 19 and 20 are provided on the outer end side in the axial direction of 6.

To explain the laser beam oscillation process, first, the vacuum insulation chamber 12 and the discharge space 7 are evacuated by the exhaust device 13. Subsequently, a buffer gas such as Ne is introduced into the discharge space 7 from the buffer gas supply source 15 to maintain the inside of the furnace core tube 2 at a constant pressure. In this state, high voltage power supply 16. Pulse circuit 17.
When the pulse drive power supply 18 is excited, a high pulse voltage is applied between the positive electrode 3 and the negative electrode 4, and discharge plasma is generated in the discharge space 7. Floating copper vapor collides with the free electrons in this discharge plasma, and they are excited. Laser light of a predetermined wavelength is generated when the excited copper vapor transitions to a lower energy level. The laser light generated in the discharge space passes through the blue meta windows 19 and 20, and as it is repeatedly reflected between the output mirror 22 and the total reflection mirror 23 that constitute the laser light oscillator 21, its light intensity increases, and the final Specifically, the light intensity increases while the laser beam is repeatedly reflected between the output mirror 22 and the total reflection mirror 23, and finally the laser beam passes through the output mirror 22.

(Problem to be Solved by the Invention) In a conventional metal vapor laser device, for example, in order to generate and retain copper vapor, the temperature of the furnace core tube 2 must be set to 1300 degrees Celsius.
It is necessary to maintain the temperature between 1400 degrees and 1400 degrees. In order to obtain the maximum laser output, an optimum amount of copper vapor (evaporation amount) is required. The temperature conditions at this time are said to be around 1500 degrees. If the temperature inside the furnace core tube 2 is uniform, the entire interior of the furnace core tube 2, which is the oscillation part of the laser, will be under optimal copper vapor conditions, and the laser output will be maximized.

However, since the temperature is actually so high that the copper is melting, the heat escapes in various directions. FIG. 8 is a diagram showing the flow of heat. Here, the heat generated by the discharge 24 is transferred to the heat insulating layer 9. It propagates in the vacuum layer 12 and in the form of infrared rays 25 as radiation. Figure 9 shows the furnace core tube 2.
FIG. 2 is an enlarged cross-sectional view of a blue metal window for laser light extraction provided on the outside of both ends of the laser beam. Here, Blue Meta Window 19.20 is
The laser beam 26 is made of a glass medium in order to be led out from the furnace core tube 2. Therefore, Blue Meta Window 19.
20 allows infrared rays 25 to pass through, so that heat escapes to the outside as infrared rays 25.

From the above, the heat released from the blue metal windows 19 and 20 distorts the temperature distribution, especially at the ends, so that the distribution is no longer uniform, leading to a decrease in output. The temperature distribution at this time is shown by the broken line a in FIG.

Here, the temperature distribution has an overall convex shape as shown by the broken line a, and there is a problem that a sufficient range of --like temperature distribution cannot be obtained.

The present invention was made to solve these problems, and it maintains a uniform temperature distribution in the laser oscillation part in the furnace core tube, leading to an increase in output, and reducing heat loss to improve laser oscillation efficiency. The object of the present invention is to provide a metal vapor laser device that can improve the performance.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a furnace core tube that houses a metal vapor source, and a furnace core tube that is provided oppositely to both ends of the furnace core tube and generates a pulse discharge in the furnace core tube. a pair of discharge electrodes that apply discharge energy for excitation to the steam source and generate plasma to serve as a laser medium; a heat insulating layer formed on the outer periphery of the furnace core tube; and a heat insulating layer provided on the outside of both ends of the furnace core tube. In a metal vapor laser device equipped with a blue metal window for guiding laser light,
The blue meta window is characterized in that it consists of an optical filter that reflects infrared rays and transmits laser light.

(Function) By using an optical filter that reflects infrared rays and transmits laser light in the blue meta window, it is possible to maintain a uniform temperature distribution within the furnace core tube.

In other words, metal vapor lasers are generally lasers in the visible range, and the wavelength of the infrared rays is different. Therefore, by transmitting the laser light in the visible range and reflecting the infrared rays back into the furnace core tube, it is possible to generate blue metal. It suppresses heat release from the window and maintains a uniform temperature distribution within the furnace core tube. This also reduces heat loss and improves efficiency.

(Example) An example of a metal vapor laser device according to the present invention will be described with reference to FIGS. 1 to 4.

The present invention improves the blue metal windows 19 and 20 in the conventional metal vapor laser device, and other parts are the same as the device shown in FIG. 5, so a description of the overlapping parts will be omitted.

FIG. 1 is a sectional view showing a blue meta window 27 used in the present invention, and FIG. 2 is a longitudinal sectional view showing an optical filter 30 incorporated into the blue meta window 27.

That is, the blue metal window 27 shown in FIG. 1 consists of an optical filter 30 fixed to a pedestal 29 of a cylindrical mounting body 28 with a holding plate 31. The optical filter 30 is the second
As shown in the figure, a Zn5b film 33 is coated on both sides of a quartz glass 32 serving as a base at the center, and a 5f02 film 34 is coated on the outer surface of this Zn5b film 33.

The multilayer film of the Zn5b film 33 and the 5in2 film 34 is a dielectric material and has a mirror effect with respect to light. In particular, light of a specific wavelength can be reflected by a combination of the wavelength of the light, the optical refractive index of the film, the incident angle of the light, etc. This allows the laser beam 26 to pass through as shown in FIG. 1, but infrared rays are reflected.

That is, the wavelength of infrared rays is on the order of 1 μm (1000 nm), but the wavelength of metal vapor lasers is often visible light (green and yellow for copper vapor, red for all vapor, etc.). The wavelength of visible light is in the range of 400 to 700 nm.

Here, since the blue meta window 27 is made up of a built-in optical filter 30 as described above, this optical filter 30 is basically made of a transparent material [quartz, glass such as BK-7 (trade name)]. main body] and a high dielectric film that serves as a reflective material (
ZnSb, 5in2°TiO2MgO, etc.). The reflective material is coated on the surface of a transparent material such as glass, and the thickness of this coat-in determines the wavelength that is reflected.

Based on optical principles, the thickness of the coating is defined as 1/4 wavelength of the wavelength of interest. In reality, a single layer of film cannot reflect 100% of the light, so what passes through is reflected again with a film thickness of 1/4 wavelength. For this reason, the reflective ability can be improved by multilayering as shown in FIG. here,
As an optical system, each of the multilayer films is alternately composed of materials having different dielectric constants. According to this embodiment, the temperature distribution within the furnace core tube 2 is flattened along the axial length as shown by the solid line in FIG. 3, and the oscillation portion of the furnace core tube can be made wide.

FIG. 4 shows an example of transmittance measurement for typical wavelengths. This data is for the case where the light is incident perpendicularly to the surface, but in reality, infrared rays are not laser light and therefore include components in various directions. Since the reflectance also depends on the angle of incidence, the overall reflectance is a combination of each component and is apparently small.

[Effects of the Invention] According to the present invention, there is no heat loss from the Blue Meta window, the efficiency of the entire laser device is improved, and the temperature distribution approaches uniformity. The output can be increased by effectively utilizing the oscillating part of the furnace core tube.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing a Brewster window of an embodiment of a metal vapor laser device according to the present invention, FIG. 2 is a vertical sectional view showing an optical filter in FIG. 1, and FIG. 3 is an example of the present invention. and a conventional example are curve diagrams showing examples of laser tube axial lengths, FIG. 5 is a vertical cross-sectional view showing a conventional metal vapor laser device as a partial block, and FIG. 6 is a partial diagram showing the furnace core tube in FIG. 5. 7 is a cross-sectional view taken in the direction of arrow A-A in FIG. 6, FIG. 8 is a schematic diagram showing the flow of heat inside the laser device in FIG. 5, and FIG. 5 is an enlarged longitudinal sectional view of the Brewster window in FIG. 5. FIG. ■... Oscillator tube body 2... Furnace core tube 3... Positive electrode 4... Cathode electrodes 5, 6... Electrode support flange 7... Discharge space 8... Copper piece 9...・Insulating layer 10...Protection tube'' 1...Vacuum container 12...Vacuum insulation chamber 13...Exhaust device 14...Break tube 15...Buffer gas supply source 16...High voltage power supply 17...Pulse circuit 18...Pulse drive power supply 19.20...Brewster window 21...Laser beam oscillator 22...Output mirror 23...Total reflection mirror 24...Discharge 25... - Infrared rays 26... Laser light 27... Brewster window of the present invention 28... Cylindrical mounting body 9... Pedestal 0... Optical filter... Holding plate 2... Quartz glass 3. ...Zn5b film 4...5in2 film (8733) Agent: Patent attorney Yoshiaki Inomata (and others)
1 person) Figure Figure Figure Figure 900 1000 1100 1200 Skin length nm 300 Figure Figure Figure Figure

Claims (1)

[Claims] A furnace core tube that houses a metal vapor source, and a furnace core tube that is provided opposite to each other at both ends of the furnace core tube and that applies discharge energy for excitation to the metal vapor source by performing a pulse discharge in the furnace core tube, and also provides a laser medium. a pair of discharge electrodes that generate plasma, and a heat insulating layer formed on the outer periphery of the furnace core tube;
A metal vapor laser device comprising Brewster windows for guiding laser light provided on the outside of both ends of the furnace core tube, wherein the Brewster windows are comprised of an optical filter that reflects infrared rays and transmits laser light. metal vapor laser equipment.