JPH0983042A - Pulse gas laser tube - Google Patents

Abstract

(57) Abstract: The present invention can uniformly irradiate ultraviolet light and dramatically improve the utilization efficiency of ultraviolet light. SOLUTION: A cathode 11 and an anode 13 are respectively provided at both ends of a discharge thin tube 10, and an end of the cathode 11 has a high reflectance at least in an ultraviolet region,
An ultraviolet light reflection mirror 14 that reflects the ultraviolet light emitted at the time of corona discharge in the discharge narrow tube 10 toward the discharge narrow tube 10 is provided, and the ultraviolet light emitted at the time of occurrence of corona discharge in the discharge thin tube 10 is arranged. , The ultraviolet light reflecting mirror 14 provided at the end of the cathode 11 reflects the light with high efficiency,
Return to the discharge region within 0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse gas laser tube used for fluorescence analysis, for a remote sensing device using absorption of gas, application of various photochemical reaction processes, and other light sources.

[0002]

2. Description of the Related Art Currently, in a laser tube with a high filling gas pressure, in order to ignite a discharge stably and uniformly to optimize laser excitation, ultraviolet light is irradiated to the discharge region immediately before the main discharge to make a preliminary operation. The method of ionization is widely used.

This preionization method is initially based on TEA (Tran
sversely Excited Atmospheric pressure) CO ₂ laser as described in (Appl. Phys. Lett., 22, 55-57, (1973)). S. Although it has been tried by Levine et al., It is now used as an effective method also in various pulse gas lasers such as excimer laser and N ₂ laser which require similar discharge excitation.

As another preionization method, a method using corona discharge or X-ray is being developed or put into practical use. On the other hand, a laser tube with a high filling gas pressure requires a high voltage to start and maintain discharge, so a long electrode along the optical axis of laser oscillation is used to excite discharge in the transverse direction orthogonal to the optical axis. Occupy most.

FIG. 5 is a block diagram of a laser tube of a lateral discharge excitation system by such ultraviolet light preionization, and FIG. 6 is a block diagram of a discharge part. This laser tube is (Appl.Phys.Lett.,
22,95-96, (1973)). P. Ju
The technology of irradiating ultraviolet light from the side of the main discharge by dd is the basic type.

That is, the anode 1 and the cathode 2 are arranged so as to face each other, and the discharge region 3 is formed between the anode 1 and the cathode 2. A plurality of pin electrodes 4 for preionization are arranged along the longitudinal direction of the anode 1 and the cathode 2.

A high reflection mirror 5 and an output mirror 6 which form a laser resonator are arranged on the optical axis of the laser oscillation. With such a configuration, when a high voltage is applied between the anode 1 and the cathode 2 and pre-ionization discharge occurs at the pin electrode 4, ultraviolet light is generated by this pre-ionization discharge, and this ultraviolet light is generated by the anode. 1 and the cathode 2 are irradiated from the lateral direction.

By this irradiation of ultraviolet light, the discharge region 3 is preionized, and a main discharge is generated between the anode 1 and the cathode 2. Subsequently, laser resonance occurs between the high-reflection mirror 5 and the output mirror 6, and a laser beam is output.

However, such a lateral discharge excitation type laser tube has the following problems. First,
Since the discharge region 3 is irradiated with the ultraviolet light emitted from the pin electrode 4, the regions other than the discharge region 3 are indiscriminately preionized.

Therefore, the anode 1 and the cathode 2 (both serve as main electrodes) are processed into a surface shape approximated by a complicated function, and the electric field intensity distribution is matched to make the discharge region 3 and the current distribution uniform. Although controlled, normally, the ultraviolet light is emitted from the discharge of the plurality of pin electrodes 4, so that the discharge region 3 cannot be uniformly irradiated.

Secondly, since the ultraviolet light emitted from the discharge of each pin electrode 4 is a point light source and is emitted in all directions, the ratio of the ultraviolet light emitted to the discharge region 3 is small. Therefore, the utilization factor of ultraviolet light is low, and the intensity decreases exponentially due to absorption and inversely proportional to the square of the distance with distance as the distance from the point light source increases, and the controllability of discharge is poor. .

However, the greatest problem in the laser tube of the lateral discharge excitation system is the nonuniform discharge current. In reality, the operating conditions that are suitable for uniform discharge and the conditions that are suitable for laser oscillation do not match.Therefore, it is unavoidable to establish matching conditions by setting constraint conditions that give priority to the operating conditions that are suitable for uniform discharge. There is.

Further, although the preionization makes a great contribution to the homogenization of the discharge, it is impossible in principle to irradiate the discharge region 3 with ultraviolet light uniformly and efficiently.
Further, since it is desirable to irradiate the ultraviolet light only to the discharge region 3, the anode 1 and the cathode 2 are formed of metal mesh, and the ultraviolet light source is arranged on the back surface of the anode 1 and the cathode 2. Although there is an example in which ultraviolet light is transmitted through the anode 1 and the cathode 2 for irradiation, the electric field uniformity on the electrode surfaces of the anode 1 and the cathode 2 is lost, which causes nonuniform discharge.

On the other hand, as a practical level laser tube for exciting discharge in the vertical direction (optical axis direction), for example, He-
There are a Ne laser tube, an argon laser tube, a CO ₂ laser tube and the like.

In these laser tubes, discharge is usually started by superimposing a high voltage pulse on an applied voltage. There are other examples of starting discharge by induction discharge, but no example of starting discharge or preionization by ultraviolet light as described above is found.

[0016]

As described above, the ultraviolet light emitted from the pin electrode 4 cannot be uniformly applied to the discharge area 3, and the ratio of the ultraviolet light applied to the discharge area 3 is small. Therefore, the uniformity of the main discharge is reduced, and the entire main discharge cannot be put into an optimum state for laser oscillation, so that highly efficient laser oscillation cannot be performed.

Therefore, an object of the present invention is to provide a pulse gas laser tube capable of uniformly and efficiently irradiating the discharge region with ultraviolet light and capable of stable and highly efficient laser oscillation.

[0018]

According to a first aspect of the present invention, a cylindrical cathode is coaxially provided at one end of a discharge capillary formed of an insulating material, and a cylindrical anode is also provided at the other end of the discharge capillary. In a pulse gas laser tube that is provided coaxially and ignites a discharge between the anode and the cathode to cause pre-ionization in the discharge thin tube to oscillate a pulse laser, either one of the end of the cathode and the end of the anode. And a mirror having a function of reflecting ultraviolet light emitted at the time of ignition of preionization discharge in the discharge capillary toward the discharge capillary, the mirror having at least a reflection surface for the ultraviolet region. It is a pulse gas laser tube to be achieved.

According to the first aspect, the cathode is provided at one end of the discharge capillary and the anode is provided at the other end thereof.
When a high pulse voltage is applied between the anode and the cathode, corona discharge occurs on the inner wall of the discharge capillary,
Along with this, ultraviolet light is emitted. This ultraviolet light is highly efficiently reflected by a mirror provided on either the end of the cathode or the end of the anode, and returns to the discharge region in the discharge capillary. As a result, the irradiation of ultraviolet light can be made uniform, and the utilization efficiency of ultraviolet light can be dramatically improved.

According to claim 2, the mirror is a pulse gas laser tube which is an aluminum mirror. According to the second aspect, the ultraviolet light for pre-ionization is highly efficiently reflected by the aluminum mirror and returned to the inside of the discharge capillary, the irradiation of the ultraviolet light is made uniform, and the utilization efficiency of the ultraviolet light is dramatically improved.

According to a third aspect of the present invention, the mirror is a pulse gas laser tube having an aluminum substrate having a polished reflecting surface or a substrate having aluminum vapor-deposited on the surface. According to this aspect, an aluminum substrate having a polished reflecting surface or a substrate having aluminum vapor-deposited on the surface is used to highly efficiently reflect the ultraviolet light for pre-ionization and return it into the discharge capillary to irradiate it with ultraviolet light. It makes uniform and dramatically improves the utilization efficiency of ultraviolet light.

According to a fourth aspect of the present invention, the reflecting surface of the mirror is formed of a dielectric multilayer film having a reflection characteristic for both laser oscillation light and ultraviolet light, or a composite film of a metal film and a dielectric multilayer film. Pulsed gas laser tube.

According to the fourth aspect, the reflecting surface of the mirror has a dielectric multilayer film having a high reflection characteristic for both laser oscillation light and ultraviolet light, or a composite film of a metal film and a dielectric multilayer film. By forming by, it is possible to highly reflect the ultraviolet light for pre-ionization, thereby returning the ultraviolet light to the discharge tube, uniform irradiation of ultraviolet light, and dramatically improve the utilization efficiency of ultraviolet light. .

According to claim 5, the inner wall of the cathode is
It is a pulse gas laser tube provided with a cylinder formed of aluminum. According to the fifth aspect, by providing the aluminum cylinder on the inner wall of the cathode, it is possible to prevent the reflection characteristic of the ultraviolet light from changing even if the sputtered material is deposited on the mirror surface.

According to a sixth aspect of the present invention, the mirror is a pulse gas laser tube whose central portion is used as a reflecting surface of the laser resonator and whose peripheral portion is used as a reflecting surface for ultraviolet light.

According to the sixth aspect, the laser light is reflected on the reflecting surface in the central portion of the mirror, and the ultraviolet light for preionization is reflected on the reflecting surface in the peripheral portion. By separating the reflection surface regions of the laser light and the ultraviolet light in this way, the mirror design and manufacture can be facilitated, and the effective reduction of the area of the ultraviolet light reflection portion can be reduced.

According to the seventh aspect, the peripheral reflection surface for the ultraviolet light is a pulse gas laser tube formed on the reflection surface of aluminum. According to the seventh aspect, the peripheral reflecting surface is formed of an aluminum reflecting surface to reflect the ultraviolet light for preionization.

According to claim 8, on the reflecting surface side of the mirror,
It is a pulse gas laser tube in which a circular ring having at least the surface formed of aluminum is arranged. According to the eighth aspect, the aluminum ring is arranged on the front surface of the mirror, the laser light is reflected on the reflecting surface at the center of the mirror, and the ultraviolet light for pre-ionization is reflected on the aluminum ring around it. By disposing the aluminum ring in this way, it is possible to prevent contamination of the laser reflection surface with a simple configuration.

According to claim 9, the aluminum ring is
It is a pulsed gas laser tube formed on a concave surface. According to the ninth aspect, by forming the aluminum ring in the concave surface, it is possible to collect as much ultraviolet light as possible and reflect it in the discharge capillary.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional configuration diagram of a pulse gas laser tube of a longitudinal direction excitation type corresponding to claims 1 to 4 of the present invention.

The cylindrical discharge thin tube 10 is made of an insulating material such as ceramics. A gas laser medium such as CO ₂ gas, excimer gas, or N ₂ gas is enclosed in the discharge thin tube 10.

A cylindrical metal cathode 11 is joined to one end of the discharge thin tube 10 with the shaft 12 in common.
The cathode 11 is joined to the outer wall of the discharge capillary 10.

The cathode 11 is hermetically sealed (hard seal) with the ceramic discharge thin tube 10 by brazing or the like.
It is desirable to improve the reliability of the product, and as the metal material for the brazing, Kovar, which is close to that of ceramics having a small coefficient of thermal expansion, is usually used.

A cylindrical metal anode 13 is joined to the other end of the discharge capillary 10 with the shaft 12 in common.
The anode 13 is fitted and joined to the inner wall of the discharge thin tube 10.

A cylindrical metal to be the anode 13 or the intermediate potential electrode (not shown) is joined to the other end of the discharge thin tube 10. Although the figure shows the one without such an intermediate potential electrode, when this intermediate potential electrode is added, the anode 13 becomes an intermediate potential electrode, and another discharge capillary is joined to the right end of this intermediate potential electrode in the drawing. Further, the anode 13 is attached to the right end thereof.

An ultraviolet light reflecting mirror 14 constituting a laser resonator is joined to the end of the cathode 11 by a mirror sealing portion 15. The mirror sealing portion 15 changes the bonding method depending on the mirror substrate material.

The ultraviolet light reflecting mirror 14 is bonded to the end of the cathode 11 so that its reflecting surface is orthogonal to the axis 12. As the ultraviolet light reflection mirror 14, an aluminum (Al) mirror having a high reflectance in a wide band up to a short wavelength region of ultraviolet light is used.

Specifically, for the ultraviolet light reflecting mirror 14, for example, an aluminum substrate having a reflecting surface polished or a substrate having aluminum vapor-deposited on the surface is used. Further, the ultraviolet light reflection mirror 14 has, for example, a mirror reflection surface of a dielectric multilayer film having high reflection characteristics for both laser oscillation light and ultraviolet light, or a composite of a metal film and a dielectric multilayer film. It is formed of a film.

An output mirror 16 forming a laser resonator is joined to an end of the anode 13 by a mirror sealing portion 17. Next, the operation of the pulse gas laser tube configured as described above will be described.

When a high pulse voltage is applied between both electrodes of the cathode 11 and the anode 13, a silent corona discharge 18 is generated between the cathode 11 and the anode 13 in the discharge capillary 10, and charged particles are generated. , Together with this, ultraviolet light is emitted.

This corona discharge is efficient as a silent discharge through the discharge capillary 10 even at a relatively low voltage, if the end of the anode 13 extends to a position where it enters the cathode 11 side inside the discharge capillary 10. It can be easily generated.

The ultraviolet light emitted when the corona discharge 18 is generated is highly efficiently reflected by the ultraviolet light reflection mirror 14 provided at the end of the cathode 11 and returned to the discharge region in the discharge capillary 10.

As described above, the ultraviolet light is emitted and highly reflected by the ultraviolet light reflecting mirror 14, so that the discharge thin tube 10 can be obtained.
Ultraviolet light is homogenized and irradiated inside. Due to this ultraviolet light irradiation, the inside of the discharge thin tube 10 is preionized, and the anode 13
A main discharge is generated between the cathode 11 and the cathode 11. Subsequently, laser resonance occurs between the ultraviolet light reflection mirror 14 and the output mirror 16, and a laser beam is output.

As described above, in the first embodiment, the ultraviolet light emitted when the corona discharge occurs in the discharge capillary 10 is enhanced by the ultraviolet light reflecting mirror 14 provided at the end of the cathode 11. Since the light is efficiently reflected and returned to the discharge area in the discharge thin tube 10, the discharge area in the discharge thin tube 10 can be uniformly irradiated with ultraviolet light without using an electrode having a complicated shape, and the ultraviolet light can be stably emitted. The utilization efficiency of can be dramatically improved.

In this case, the ultraviolet light reflection mirror 14 has an aluminum substrate whose reflection surface is polished, a substrate on which aluminum is vapor-deposited, or a reflection surface having a high reflection characteristic for both laser oscillation light and ultraviolet light. It is possible to reflect the ultraviolet light for preionization with high efficiency by forming the dielectric multi-layered film having the above or a composite film of the metal film and the dielectric multi-layered film.

In this way, the ultraviolet light reflecting mirror 14 is adapted to reflect ultraviolet light.
By this, the efficiency of pre-ionization can be dramatically increased by reflecting in the discharge thin tube 10. For example, in N ₂ laser and ultraviolet excimer laser, aluminum having a high reflectance in a wide band up to a short wavelength region of ultraviolet is used. Using a mirror is effective and optimal from a practical point of view.

Considering the dependence of the reflection of the ultraviolet light on the curvature of the reflecting surface of the ultraviolet light reflecting mirror 14, the reflection characteristic of the ultraviolet light into the discharge thin tube 10 is improved and the utilization efficiency of the ultraviolet light is dramatically improved. Can be improved.

Therefore, in the longitudinally-excited pulse gas laser tube of the present invention, the ultraviolet light for preionization is emitted in the discharge region of the discharge capillary 10, so that it is absorbed or unnecessary in the middle of the conventional laser tube. There is no loss due to ultraviolet light irradiation to the area, and the utilization efficiency can be greatly improved.

Further, the ultraviolet light dissipated outside the discharge region in the discharge capillary 10 is further reflected by the ultraviolet light reflecting mirror 14 to the axis 12.
Since it is reflected in the direction and returned to the discharge region, not only the utilization efficiency of ultraviolet light but also the uniformity of irradiation of ultraviolet light can be dramatically improved.

According to a more recent discharge simulation, as a factor that makes the discharge non-uniform, an electron disappearance layer is generated near the cathode 11 at the initial stage of discharge, and the current density up to that required for laser oscillation is compensated for. It has been clarified that the photoelectron emission from the cathode 11 acts extremely effectively to increase the emission (J.Phys.D: Appl.Phys.27, 10).
97-1106, (1974)).

On the ultraviolet light reflecting surface of the ultraviolet light reflecting mirror 14, the scattered component physically increases due to the shorter wavelength, but this scattered light irradiates the surface of the cathode 11 and contributes to photoelectron emission. It is lean and effective.

On the other hand, when the ultraviolet light reflecting mirror 14 is made of inexpensive and durable aluminum, the wavelength dependence of the reflectance is shown (American Inst.Phys.Handbook), and the wavelength (μm) reflectance is 0.120. It is 0.902 0.200 0.928 0.300 0.921 0.400 0.926.

The mechanism of ultraviolet light preionization is generally T
For EACO ₂ laser and excimer laser, the discharge tube 10
It has been confirmed that the impurities in the enclosed gas of (1) absorb and ionize a specific spectral component in approximately the above wavelength range.

Therefore, in the laser tube applied to the present invention, preionization can be effectively performed by the same mechanism. Next, a second embodiment of the present invention will be described. In addition,
The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 2 is a sectional view showing the structure of a pulse gas laser tube of the vertical direction pumping type according to the fifth aspect of the present invention. The cathode 11 is shown in FIG.
Only the ends of are shown.

A cylinder 20 made of aluminum, which is the same material as that of the ultraviolet light reflection mirror 14, is fitted in the cathode 11 having a metal cylindrical shape. That is, the material of the cathode 11 adheres to the surface of the ultraviolet light reflecting mirror 14 by sputtering due to corona discharge in the discharge capillary 10. When the cumulative time of the laser oscillation operation of the pulse gas laser tube reaches a long time, the characteristics of the ultraviolet light reflecting mirror 14 may change.

For this reason, moving the surface of the ultraviolet light reflecting mirror 14 away is one of the countermeasures, but since the compactness is lost, the cylinder 20 is fitted in the cathode 11. If the cylinder 20 is thus fitted to form a substantial cathode, the ultraviolet light reflecting mirror 14 formed by sputtering will be described.
It is possible to prevent deterioration of reflection.

As described above, in the second embodiment, since the aluminum cylinder 20 is provided on the inner wall of the cathode 11, it is possible to uniformly irradiate the discharge region in the discharge capillary 10 with ultraviolet light, and use the ultraviolet light. It is possible to dramatically improve the efficiency, and further, it is possible to prevent the reflection characteristic of the ultraviolet light from changing even if the sputtered material is deposited on the surface of the ultraviolet light reflection mirror 14.

It is easy to integrate the cathode 11 and the cylinder 20 with the same aluminum, but this is not suitable for practical use because it cannot be brazed and bonded to the discharge capillary 10.
By the way, in N ₂ lasers and excimer lasers, high-speed rising excitation is effective, and in particular, N ₂ lasers are preferable to perform short pulse excitation from the oscillation mechanism. Therefore, the mirror spacing of the laser resonator is set to the mirror of stimulated emission light. It is effective to narrow the round trip time as much as possible in order to shorten the round trip time and increase the gain and coherence.

However, when the mirror of the laser resonator is brought close to the discharge region, the mirror surface is contaminated by electrode sputtering. However, as in the present invention, the inner wall of the cathode 11 is formed of aluminum, which is the same as the vapor deposition material on the surface of the ultraviolet light reflecting mirror 14. Then
It suffices that the reflection characteristics do not change even if a sputtered material is deposited on the surface of the ultraviolet light reflection mirror 14.

In this case, if the inner wall of the cathode 11 is made a mirror surface, the reflection of ultraviolet light is increased, and the utilization efficiency of ultraviolet light and the uniformity of irradiation of ultraviolet light can be dramatically improved. Next, a third embodiment of the present invention will be described. FIG.
The same parts as those in FIG.

FIG. 3 is a sectional view showing the structure of a longitudinally-excited pulse gas laser tube according to claims 6 and 7 of the present invention. It should be noted that the figure shows only the cathode portion in order to show the portion different from FIG.

A metal cylindrical cathode 30 is joined to one end of the discharge capillary 10. This cathode 30 is
The diameter is formed larger than the diameter of the discharge thin tube 10. A mirror 31 is joined to the open end of the cathode 30 by brazing 32 or the like.

The mirror surface of the mirror 31 is formed on the laser light reflecting surface 33 of the laser resonator and the outer peripheral annular reflecting surface 34 formed on the periphery of the laser light reflecting surface 33.

Of these, the laser light reflecting surface 3 of the laser resonator
3 is formed in the central portion of the mirror 31 and has a reflection characteristic of reflecting laser light. The diameter of the laser light reflecting surface 33 is formed to be approximately the same as the diameter of the discharge thin tube 10.

The outer peripheral annular reflecting surface 34 is formed of an aluminum reflecting surface and has a reflecting characteristic of reflecting ultraviolet light for preionization. Also, on the inner wall of the cathode 30,
A cylinder 35 made of aluminum, which is the same as the material of the outer peripheral annular reflecting surface 34, is fitted.

With such a structure, when a high pulse voltage is applied between the cathode 30 and the anode 13, corona discharge occurs between the cathode 30 and the anode 13 in the discharge capillary 10. , UV light is emitted into the narrow tube and charged particles are generated.

The ultraviolet light emitted at the time of occurrence of this corona discharge is highly reflected by the outer peripheral annular reflecting surface 34 provided at the end of the cathode 30 and returned to the discharge region in the discharge capillary 10.

As described above, the ultraviolet light is emitted and highly reflected by the outer peripheral annular reflecting surface 34, so that the ultraviolet light is evenly radiated into the discharge capillary 10. This irradiation of ultraviolet light preliminarily ionizes the inside of the discharge capillary 10 and a main discharge is generated between the anode 13 and the cathode 30. Subsequently, laser resonance occurs between the laser light reflecting surface 33 and the output mirror 16, and a laser beam is output.

As described above, in the third embodiment, the laser light reflecting surface 33 is formed in the central portion of the mirror 31, and the outer circumferential annular reflecting surface 34 for the ultraviolet light for preionization is formed in the peripheral portion thereof. Therefore, it is possible to uniformly irradiate the discharge region in the discharge narrow tube 10 with the ultraviolet light, and it is possible to dramatically improve the utilization efficiency of the ultraviolet light. Moreover, by separating the reflection surface region of the laser light and the ultraviolet light, the mirror design is made. Manufacturing becomes easier, and the effective reduction of the ultraviolet light reflection area can be reduced.

That is, in N ₂ lasers or excimer lasers that oscillate in the ultraviolet region, the high-reflecting mirror that constitutes the laser resonator can be commonly used for reflecting the ultraviolet light for preionization, but the laser in the visible and infrared regions is used. In the case of an oscillator, the dielectric multilayer film is usually used as a reflection film, and therefore the reflectance in the ultraviolet region is low and cannot be shared.

However, by devising the structure of the multilayer film, it is possible to provide the function of sharing the laser light and the ultraviolet light for preionization with each other. With respect to this, a technique devised is the third embodiment. In general, if the electron emission from the cathode 30 is insufficient, the sputtering of the laser resonator on the mirror will increase, and the contamination of the mirror and gas cleanup will have a serious adverse effect on the life of the laser tube. As in the example, it is necessary to increase the diameter of the cathode 30 to increase the electron emission area.

Therefore, the mirror 3 which constitutes the laser resonator
If the diameter of 1 is increased, the laser light reflecting surface 33 is formed to have a diameter substantially the same as the diameter of the discharge thin tube 10 for reflecting the laser light, and the outer circumferential annular reflecting surface 34 is an aluminum reflecting surface. It is possible to separate the reflection surface regions of the laser light and the ultraviolet light, and the mirror design and manufacture becomes much easier. The effective reduction in the area of the ultraviolet light reflecting portion can be reduced, and in this case, it is not limited to the ultraviolet laser, and the application to the visible and infrared lasers is easy.

Further, since the aluminum cylinder 35 is provided on the inner wall of the cathode 30, it is possible to uniformly irradiate the discharge region in the discharge capillary 10 with ultraviolet light, and it is possible to dramatically improve the utilization efficiency of ultraviolet light. Surface, especially the outer ring reflecting surface 3
It is possible to prevent the reflection characteristics of the ultraviolet light from changing even when the sputtered material is deposited on the surface of No.

Next, a fourth embodiment of the present invention will be described. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 4 shows claims 8 and 9 of the present invention.
FIG. 3 is a cross-sectional configuration diagram of a vertical excitation type pulse gas laser tube corresponding to FIG. It should be noted that the figure shows only the cathode portion in order to show the portion different from FIG.

A metal cylindrical cathode 40 is joined to one end of the discharge capillary 10. This cathode 40 is
The diameter is formed larger than the diameter of the discharge thin tube 10. A mirror 41 is joined to the open end of the cathode 40 by brazing 42 or the like.

This mirror 41 has a laser beam reflecting surface 43 formed only at the center thereof. The diameter of the laser light reflecting surface 43 is formed to be substantially the same as the diameter of the discharge thin tube 10.

On the entire surface of this mirror 41, an aluminum circular ring 44 is arranged so as to overlap. The aluminum ring 44 is formed of aluminum in the shape of a perforated coin. And this aluminum ring 44
, The front surface 44a of the ring is finished by polishing as much as possible to increase the reflectance with respect to the preionized ultraviolet light.

A cylinder 45 made of the same aluminum as the material of the aluminum ring 44 is fitted on the inner wall of the cathode 40. The material of the substrate of the mirror 41 and the aluminum ring 44 is not limited.

With this structure, when a high pulse voltage is applied between the cathode 40 and the anode 13, corona discharge occurs between the cathode 40 and the anode 13 in the discharge capillary 10. Ultraviolet light is emitted into the capillaries, and charged particles are generated with it.

The ultraviolet light emitted when the corona discharge occurs is highly reflected by the aluminum ring 44 provided at the end of the cathode 40 and returned to the discharge region in the discharge capillary 10.

As described above, the ultraviolet light is emitted and highly efficiently reflected by the aluminum ring 44, so that the ultraviolet light is uniformly radiated into the discharge capillary 10. By this ultraviolet light irradiation, the inside of the discharge capillary 10 is preionized, and a main discharge is generated between the anode 40 and the cathode 30. Subsequently, laser resonance occurs between the laser light reflecting surface 43 and the output mirror 16, and a laser beam is output.

As described above, in the fourth embodiment, the aluminum ring 44 is arranged on the front surface of the mirror 41, the laser light is reflected by the laser light reflecting surface 43 at the center of the mirror 41, and the surrounding area of the laser light is reflected. Since the aluminum ring 44 is configured to reflect the ultraviolet light for pre-ionization, the discharge region in the discharge capillary 10 can be uniformly irradiated with the ultraviolet light, and the utilization efficiency of the ultraviolet light can be dramatically improved. By disposing the ring 44, contamination of the laser reflection surface 43 can be prevented with a simple configuration.

That is, if the hole diameter of the aluminum ring 44 is made as small as possible and the thickness is appropriately selected to be approximately the same as that of the discharge capillary 10, contamination of the laser reflection surface 43 due to electrode sputtering can be prevented with a simple structure. .

The reflecting surface 44a of the aluminum ring 44 can be formed as a concave surface. If the aluminum ring 44 is formed as a concave surface in this manner, as much ultraviolet light as possible is reflected in the discharge thin tube 10 and the discharge thin tube 10 is reflected.
The ultraviolet light can be uniformly irradiated to the discharge area inside, and the utilization efficiency of the ultraviolet light can be dramatically improved.

In particular, since the aluminum ring 44 is disposed separately from the laser light reflecting surface 43, the aluminum ring 4 is
There is an advantage that the concave curvature of 4 can be selected independently of the laser light reflecting surface 43.

The present invention is not limited to the above embodiments, but may be modified as follows. For example, a preionization ultraviolet light reflection mirror is preferably arranged at the end of the cathode where sputtering is stronger than ions, but the preionization UV reflection mirror is not limited to this cathode end. May be provided.

As the pulsed gas laser tube, the discharge thin tube 10 is divided into two parts, the middle metal part is the anode or the cathode, and the metal parts at both ends are the cathodes or the anodes, respectively. It may be modified in various ways such as the arrangement of.

[0089]

As described in detail above, claims 1 to 5 of the present invention.
According to 4, it is possible to provide a pulse gas laser tube capable of uniformly irradiating ultraviolet light and dramatically improving the utilization efficiency of ultraviolet light.

Further, according to claim 5 of the present invention, the irradiation efficiency of ultraviolet light can be dramatically improved by uniformizing the irradiation of ultraviolet light.
Moreover, it is possible to provide a pulse gas laser tube capable of preventing the reflection characteristics of ultraviolet light from changing even if a sputtered material is deposited on the mirror surface.

Further, according to the sixth and seventh aspects of the present invention, the ultraviolet light irradiation can be made uniform, and the utilization efficiency of the ultraviolet light can be remarkably improved. Moreover, the mirror design and manufacture can be facilitated, and the effective ultraviolet light reflection can be achieved. It is possible to provide a pulse gas laser tube capable of reducing the area reduction of a part.

According to the eighth aspect of the present invention, the irradiation efficiency of ultraviolet light can be dramatically improved by uniformizing the irradiation of ultraviolet light.
Moreover, it is possible to provide a pulse gas laser tube capable of preventing contamination of the laser reflection surface with a simple configuration.

According to claim 9 of the present invention, it is possible to reflect as much ultraviolet light as possible into the discharge capillary.
It is possible to provide a pulsed gas laser tube by uniformly irradiating ultraviolet light and dramatically improving the utilization efficiency of ultraviolet light.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a pulse gas laser tube according to the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of a pulse gas laser tube according to the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of a pulse gas laser tube according to the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of a pulse gas laser tube according to the present invention.

FIG. 5 is a configuration diagram of a conventional lateral discharge excitation type laser tube.

FIG. 6 is a configuration diagram of a discharge part of the laser tube.

[Explanation of symbols]

10 ... discharge tube, 11, 30, 40 ... cathode, 13 ...
Anode, 14 ... Ultraviolet light reflecting mirror, 16 ... Output mirror, 20, 35, 45 ... Cylinder, 31 ... Mirror, 33, 4
3 ... Laser light reflecting surface, 34 ... Peripheral annular reflecting surface, 44 ... Aluminum annular ring.

Claims (9)

[Claims] 1. A cylindrical cathode is coaxially provided on one end side of a discharge thin tube made of an insulating material, and a cylindrical anode is coaxially provided on the other end side of the discharge thin tube. In a pulse gas laser tube that ignites a discharge between the cathode and the cathode to cause pre-ionization in the discharge thin tube to oscillate a pulse laser, at least one of the end portion of the cathode and the end portion of the anode is provided, and at least A pulse having a reflection surface for an ultraviolet region, the mirror having a function of reflecting ultraviolet light emitted at the time of ignition of preionization discharge in the discharge capillary toward the discharge capillary. Gas laser tube. 2. The pulse gas laser tube according to claim 1, wherein the mirror is an aluminum mirror. 3. The pulse gas laser tube according to claim 2, wherein the mirror is an aluminum substrate having a polished reflecting surface or a substrate having aluminum vapor-deposited on the surface. 4. The reflecting surface of the mirror is formed of a dielectric multilayer film having a reflection characteristic for both laser oscillation light and ultraviolet light, or a composite film of a metal film and a dielectric multilayer film. The pulse gas laser tube according to claim 1, which is characterized in that. 5. The pulse gas laser tube according to claim 1, wherein a cylinder made of aluminum is provided on an inner wall of the cathode. 6. The pulse gas laser according to claim 1, wherein a central portion of the mirror is used as a reflecting surface of the laser resonator, and a peripheral portion of the reflecting surface is used as a reflecting surface for ultraviolet light. tube. 7. The pulse gas laser tube according to claim 6, wherein the reflection surface for the ultraviolet light in the peripheral portion is formed of an aluminum reflection surface. 8. The pulse gas laser tube according to claim 1, wherein an annular ring, at least the surface of which is made of aluminum, is arranged on the reflecting surface side of the mirror. 9. The pulse gas laser tube according to claim 8, wherein the aluminum ring is formed in a concave surface.