JPH079408Y2 - High frequency pumped coaxial CO2 laser - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial type CO ₂ laser excited by high frequency.

[0002]

_2. Description of the Related Art High-frequency excitation in a CO ₂ laser is a) there is no chemical reaction because the metal electrode and carbon dioxide (CO ₂ ) are not in contact with each other b) It is a reactive ballast and therefore energy efficient c) Longitudinal discharge Since the voltage is low, it is possible to use a power source as an individual element. Therefore, a) small size b) high efficiency oscillator can be constructed.

However, in the case of general high-frequency excitation, longitudinal discharge occurs, and the gain distribution in the cross section of the laser tube lacks circular symmetry. Therefore, it is also used in combination with an orthogonal gas flow that lacks circular symmetry in the gain distribution. High quality beam mode cannot be expected. For this reason, a DC excitation coaxial type CO ₂ laser is used as a cutting CO ₂ laser that requires a high-quality beam mode. However, this laser is inferior to high-frequency excitation except in beam mode.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention solves the above-mentioned drawbacks of the prior art and combines the advantages of high-frequency excitation with the advantages of the coaxial type, and a high-frequency excited coaxial CO that can obtain a high-quality beam mode. ₂ to provide a laser.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a laser tube having a circular cross section made of a dielectric material, in which CO ₂ laser gas is flowed in the axial direction, and the outer circumference of the laser tube. Two spiral conductors having the same pitch are adhered to the surface, and a high frequency voltage is applied from a high frequency power source between the two spiral conductors. The permittivity of the dielectric of the laser tube is ε and the discharge sustaining voltage is Is V, the frequency of the high frequency power source is ω, and the current density is I, the thickness of the laser tube is approximately Vεω.
The above problem was solved by setting / (2I).

[0006]

The CO ₂ laser gas flows in the tube axis direction of the laser tube made of a dielectric material in the tube axis direction, and the flow is substantially circularly symmetrical in the cross section of the laser tube. On the other hand, when a high-frequency voltage is applied from the high-frequency power source between the two conductors spirally bonded to the outer peripheral surface of the laser tube, a discharge is generated between the two spiral conductors in the laser tube, and the discharge direction Is rotated around the tube axis, and when viewed along the tube axis, this discharge is circularly symmetric, so the laser gain is also highly circularly symmetric, which is characteristic of coaxial lasers.
You can get 00 mode.

Furthermore, since the thickness of the laser tube is determined according to the discharge sustaining voltage during use, the frequency of the high frequency power supply, the current density and the dielectric constant of the dielectric, stable discharge can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the essential portions of an embodiment of the present invention, and FIG. 2 is a sectional view taken along line X--X of FIG. Reference numeral 3 denotes a laser tube made of a dielectric material, which is a pipe having a circular cross section as shown in FIG. Then, CO ₂ laser gas flows in the laser tube 3 in the tube axis direction. Conductive paint such as aqua duck is spirally applied to the outer peripheral surface of the laser tube at two equal pitches to form conductors 1 and 2, and between the two spiral conductors 1 and 2. A high frequency voltage is applied from the high frequency power source 4. Reference numeral 5 is a total reflection mirror, and 6 is an output coupling mirror.

In the above structure, when a CO ₂ laser gas is caused to flow in the laser tube 3 in the direction indicated by an arrow a in FIG. 1 and a high frequency voltage is applied from the high frequency power source 4 between the two spiral conductors 1 and 2, the laser beam is emitted. In the tube 3, a discharge occurs between the conductors 1 and 2 facing each other through the dielectric layer of the laser tube 3,
This discharge rotates around the tube axis because the two conductors 1 and 2 are applied spirally on the outer peripheral surface of the laser tube 3. When this is viewed along the tube axis, the discharge is circularly symmetrical. On the other hand, the CO ₂ gas flow affects the mode formation through affecting the gain distribution, but since the gas flow flows along the tube axis in the laser tube 3 having a circular cross section, the cross section of the laser tube 3 is substantially circular. Since they flow symmetrically, the laser gain is highly circularly symmetric, and the laser light 6 output from the laser tube 3 via the output coupling mirror 6
Takes a circular mode. Thus, the TEM00 mode peculiar to the coaxial laser is obtained.

The dielectric material of the laser tube 3 is preferably barium titanate, quartz, alumina, mylar, Kapton or the like in terms of strength against dielectric breakdown, and these materials are used as a ceramic tube to form a conductive paint.
It may be applied in a spiral shape.

Regarding the thickness of the laser tube 3, the thickness of the laser tube 3 is D, the discharge sustaining voltage is V, the dielectric constant is ε, the frequency of the high frequency power source is ω, and the current density is I. The voltage drop across the dielectric layer is I · (2
Since D) / εω, it suffices that this value be equal to the discharge sustaining voltage V of the laser plasma for stable discharge, so that D = Vεω / (2I) is given.

Although the conductors 1 and 2 are obtained by applying a conductive coating material in the above embodiment, the conductors 1 and 2 may be formed by metal spraying copper or gold.

Further, since the conductors 1 and 2 may be in the form of thin films and have a spiral shape, the conductors 1 and 2 and the derivative of the laser tube 3 are electrically conductive even if there is a difference in thermal expansion. Body 1,
Since the 2 and the dielectric are not separated from each other, the optimum dielectric can be selected from the electric constant characteristics. Further, as described above, the thickness D of the dielectric can be made thicker by increasing the dielectric constant ε and the frequency of the high frequency power source, so that when the dielectric is made of ceramic, manufacturing pinholes and the like do not occur, and it is stable. A discharge can be obtained.

[0014]

As described above, according to the present invention, two spiral conductors are adhered to the outer peripheral surface of the laser tube made of a dielectric material, and the two spiral conductors are connected to each other by a high frequency power source. Since a high-frequency voltage is applied to cause discharge in the laser tube between both conductors, CO flowing in the laser tube
_{2 Since the} gas flow is circularly symmetric and the discharge is generated by rotating around the tube axis by the spiral conductor, the discharge is also circularly symmetric, and the TEM00 mode peculiar to the coaxial laser has the advantage of high frequency excitation, that is, , There is no chemical reaction with CO ₂ gas, energy efficiency is good, the power source can be solidified, and the like, and the advantages can be obtained, and the CO ₂ laser for cutting can be made compact and efficient.

Further, according to the present invention, since a thin conductor is adhered to a laser tube composed of a dielectric material to form a spiral shape, peeling does not occur even if the thermal characteristics of the dielectric material and the conductor do not match, and the dielectric The body can be freely chosen from those with sufficient electrical properties.

Further, according to the discharge sustaining voltage V, the frequency ω of the high frequency power source, the current density I and the dielectric constant ε of the dielectric when the laser tube is used, the thickness of the laser tube is approximately Vε.
Since ω / (2I) is set, stable discharge can be obtained. By using a dielectric having a high frequency ω and a large dielectric constant ε of the high frequency power source, the thickness of the laser tube can be increased, and even if the dielectric is made of ceramic, it is sufficient to prevent pinholes in manufacturing. Thickness can be
The laser tube can be designed and manufactured easily.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

[Explanation of symbols]

 1, 2 conductor 3 laser tube 4 high frequency power supply 5 total reflection mirror 6 output coupling mirror

Claims (2)

[Scope of utility model registration request] 1. A laser tube having a circular cross section composed of a dielectric material in which CO ₂ laser gas flows in the tube in the axial direction, and two spiral conductors of the same pitch adhered to the outer peripheral surface of the laser tube, And a high frequency power source for applying a high frequency voltage between the two spiral conductors, wherein the dielectric constant of the dielectric of the laser tube is ε, the discharge sustaining voltage is V, the frequency of the high frequency power source is ω, and the current density is I. And a thickness of the laser tube is about Vεω / (2I), a high-frequency excited coaxial CO ₂ laser. 2. The high frequency excitation coaxial type CO ₂ laser according to claim 1, wherein the conductor is formed by applying a conductive paint to the outer peripheral surface of the laser tube.