JPH1098228A - Shutter for laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shutter of a laser device which can be used continuously without breakage of a constituent member, even if applied to a pulse laser device, etc., of peak output of about 10kW. SOLUTION: The shutter has a reflection plate 2 which is arranged to enable displacement outside a resonator in a laser 1, and reflects laser light output from a laser device in a shut-off position 2a and transmits it in an open position 2b, a water-cooled damper 4 which absorbs laser light, reflected from a reflection plate displaced to a shut-off position and a movement member 3 which displaces a reflection plate to a shut-off position or an open position. The reflecting plate 2 is constituted of a transparent substrate 21, wherein an incidence surface of laser light is projected or recessed and laser light is not absorbed, and a dielectric multilayer reflection film 22 is formed in a surface thereof. A water-cooled damper 4 is arranged at a position, wherein a beam diameter of laser light reflected from the reflection plate is larger than an original beam diameter of laser light output from the laser.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shutter of a laser device for controlling passage and cutoff of a laser beam output from a pulse laser device or the like, and more particularly, to a shutter disposed outside a resonator in the laser device. It relates to the improvement of the shutter.

[0002]

2. Description of the Related Art In a pulse laser device or the like, a shutter is provided inside or / and outside a resonator of the device in order to arbitrarily control the passage and cutoff of a laser beam output from the laser device. .

By the way, when the above-mentioned shutter is arranged in the resonator of the laser device, the laser oscillation itself stops when the shutter is closed. This has the advantage that it is not necessary to take measures against heat generated by the laser beam when the shutter is closed, but has the disadvantage that the intensity of the laser beam becomes unstable when the shutter is opened and laser oscillation is started. Was.

On the other hand, when a shutter is disposed outside the above-mentioned resonator, laser oscillation does not stop even when the shutter is closed, so that the laser light intensity stability immediately after opening the shutter is excellent. . For this reason, in a laser device applied to a processing application in which it is important to stably obtain a laser beam of a desired intensity for a desired time, a configuration in which a shutter is arranged outside a resonator is usually adopted. .

As shown in FIG. 4, this type of shutter is disposed so as to be displaceable outside a resonator (not shown) in a laser device a, and reflects a laser beam output from the laser device a at a closed position. A reflector b to be passed at the open position, a water-cooled damper c for absorbing the laser beam reflected from the reflector b displaced to the closed position, and the reflector b to the closed position or the open position by rotation or translation. The main part is constituted by the moving means d for displacement. Then, in a state where the shutter is opened (that is, a state where the reflection plate b is displaced to the open position), the laser light output from the laser device a can pass through the shutter without being obstructed by the reflection plate b. But,
In a state where the shutter is closed (that is, a state where the reflection plate b is displaced to the closed position), the laser beam output from the laser device a is bent by 90 degrees in the optical path by the reflection plate b as shown in FIG. Since it is absorbed by the water-cooled damper c, it cannot pass through the shutter. That is, in this type of shutter, the passage and cutoff of the laser light output from the laser device are controlled by the above-described operation of the reflection plate b.

In the shutter, the reflecting plate b is
As shown in FIG. 4, a mirror-polished metal substrate b1 and a dielectric multilayer film b2 deposited on the laser beam incident surface of the metal substrate b1
Is conventionally used. Further, a copper plate or an aluminum plate was generally used as the metal substrate. Further, a blackened aluminum is used for the water-cooled damper c, and a method of water-cooling the opposite side of the laser beam irradiation surface is adopted.

[0007]

By the way, the conventional shutter shown in FIG.
Nd-doped YAG with an average output of 800 W oscillating under the conditions of W, pulse width of 2 ms, and pulse repetition of 40 pps
When applied to a laser device (hereinafter simply referred to as “YAG”), the number of pulses applied to the water-cooled damper c is 10
Damper breaks in about ⁴ counts, that is, about 4 minutes,
There was a problem that the shutter could not be used.

Further, when the number of pulses applied to the reflector b is about 10 ⁶ counts, that is, about 7 hours, the dielectric multilayer film b2 is peeled off, and cannot be used as a shutter like the water-cooled damper c. Had a point.

The present invention has been made in view of such a problem, and the problem is that the peak output is 10%.
An object of the present invention is to provide a shutter of a laser device which can be continuously used without being damaged even when applied to a pulse laser device having a kW class or an average output of 1 kW class.

[0010]

Therefore, in order to solve the above-mentioned problems, the present inventor first examined the height of the laser peak output density which is considered to be the cause of breakage of the water-cooled damper.

Here, the laser peak output density is represented by [laser peak output density] = [laser average output] / [pulse repetition number × pulse width × laser beam cross-sectional area].

The laser peak output density of the YAG laser device under the above conditions is about 51 kW from the above relational expression.
/ Cm ² . From this, it has been found that a conventional water-cooled damper substrate made of aluminum or the like cannot cope with a laser peak output density of about 51 kW / cm ² irrespective of being a highly reflective material for laser light. In this case, it is considered that the water-cooled damper is damaged not by water cooling from the back surface of the damper but by sputtering on the laser beam irradiation surface of the damper. Therefore, the laser peak output density of the laser beam irradiated to the water-cooled damper is 51%.
It has been found that the development of a reflector structure smaller than kW / cm ² can prevent breakage of the water-cooled damper.

Next, when the cause of the peeling of the dielectric multilayer film was examined, it was found that the heat generation phenomenon of the metal substrate constituting a part of the reflection plate was closely related to the peeling of the dielectric multilayer film. found. That is, the reflectance of a conventional reflector composed of a metal substrate and a dielectric multilayer film is about 99% according to the measurement by the present inventors, and about 1% of the irradiated laser beam is absorbed by the metal substrate. Has been converted to heat. Therefore, it is presumed that the temperature of the metal substrate rises due to this heat conversion, and the dielectric multilayer film has peeled off due to a difference in thermal expansion coefficient between the metal substrate and the dielectric multilayer film. Therefore, it has been found that the problem of peeling of the dielectric multilayer film can be solved by using a material that does not absorb laser light, such as quartz glass, as the substrate of the reflector.

The present invention has been completed through such technical studies.

That is, the invention according to claim 1 is a reflector plate that is displaceably disposed outside a resonator of a laser device, reflects a laser beam output from the laser device at a closed position and passes the laser beam at an open position, Assuming a shutter of a laser device including a water-cooled damper that absorbs a laser beam reflected from a reflecting plate displaced to a closed position and a moving unit that displaces the reflecting plate to a closed position or an open position, at least incidence of laser light The reflector is composed of a substrate having a convex or concave surface and not absorbing the laser light, and a dielectric multilayer reflective film formed on the laser light incident surface of the substrate, and is reflected from the reflector. The water-cooled damper is located at a position where the beam diameter of the laser beam is larger than the original beam diameter of the laser beam output from the laser device. The invention according to claim 2 is based on the premise that the shutter of the laser device according to the invention according to claim 1 is provided, and the laser leaks from the substrate on the side opposite to the laser light incidence surface of the substrate. A light-shielding plate for reflecting or absorbing light is provided.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

That is, the shutter of the laser device according to the present invention is disposed outside the resonator (not shown) in the laser device 1 as shown in FIGS. A transparent substrate 21 made of quartz glass or the like having a convex or concave shape (a convex shape is illustrated in the figure) and a dielectric multilayer formed on the surface of the transparent substrate 21 to reflect an incident laser beam. A reflecting plate 2 composed of a reflecting film 22 and a rotary solenoid 30 attached to the base end and the above-mentioned reflecting plate 2 fixed to the distal end side, and the reflecting plate 2 is closed at a closed position as shown in FIG. 2
a, a movable member 3 for displacing to the open position 2b, and a water-cooling damper 4 for absorbing the laser light reflected from the reflector 2 displaced to the closed position 2a.

When the reflecting plate 2 is displaced to the closed position 2a in this shutter, the laser beam 5 is first applied to the dielectric multilayer reflecting film 22 as shown in FIG. The light is reflected by the action of the multilayer reflective film 22 to bend the optical path, and at the same time is irradiated to the water-cooled damper 4. At this time, the transparent substrate 2 in the reflection plate 2 is used.
Since the laser light incident surface of the first laser beam has a convex shape, the beam diameter (that is, the cross-sectional area) of the laser beam applied to the water-cooled damper 4 is significantly increased as shown in FIG. Therefore, the laser peak output density can be significantly reduced from the above-mentioned relational expression, and thereby the breakage of the water-cooled damper 4 constituting a part of the shutter can be prevented. For example, even if the shutter according to the present invention is applied, the shutter can be used continuously for a long time.

In the shutter of the laser device according to the present invention, the water-cooled damper 4 has a beam diameter of the laser beam reflected from the reflection plate 2 larger than the original beam diameter of the laser beam output from the laser device 1. It needs to be arranged at such a position. When the laser light incident surface of the transparent substrate 21 has a convex shape, the focal length has a negative value. Larger than the diameter (see FIG. 2A). On the other hand, when the laser light incident surface of the transparent substrate 21 is concave, the focal length is at least twice as long as the focal length (in fact, the laser light incident on the reflector 2 is not parallel light but spread light, so It is required to arrange the water-cooling damper 4 at a remote position (which needs to be larger than twice) (see FIG. 2B).

In this shutter, the reflection plate 2
About 99% of the laser light incident on the substrate is reflected by the dielectric multilayer reflective film 22 and absorbed by the water-cooled damper 4,
The remaining 1% of the laser light is incident on the transparent substrate 21.
However, since the transparent substrate 21 is made of a material that does not absorb laser light, it does not generate heat. Therefore, thermal deformation of the transparent substrate 21 hardly occurs, and peeling of the dielectric multilayer reflective film 22 from the transparent substrate 21 hardly occurs. Accordingly, since the reflection plate 2 constituting the main part of the shutter can be prevented from being damaged, there is an advantage that the shutter can be continuously used for a longer period.

Here, as described above, about 1% of the laser light incident on the reflector 2 is incident on the transparent substrate 21 and is transmitted out of the transparent substrate 21 as leakage light. For this reason, there is a possibility that the leaked light may cause partial heat generation on the outer wall of the shutter or the like and threaten the safety of the person handling the apparatus. However, the transmitted light of this laser is expanded and radiated over a wide area by the convex or concave surface of the transparent substrate 21, thereby decreasing the intensity of laser light per unit area of the transmitted laser irradiation area, which may hinder the apparatus. And there is almost no danger of compromising the safety of the operator of the equipment.

In order to completely block the leaked light, as shown in FIG. 3, a light shield for reflecting or absorbing the laser light leaking from the transparent substrate 21 is provided on the side opposite to the laser light incident surface of the transparent substrate 21. A plate 60 may be provided. As a material constituting such a light shielding plate, a metal plate such as a copper plate,
Examples thereof include graphite and a blackened aluminum plate.

When the wavelength of the laser beam is in the infrared region of 1.06 μm as in a YAG laser device, a visible laser beam such as He—Ne that emits light in the visible region (infrared region) is used as guide light. By indicating the irradiation position of the laser light with the guide light, safety of the user of the apparatus is achieved. That is, since the user of the laser device recognizes that the irradiation position of the guide light is irradiated with the YAG laser light, there is no possibility that the user is carelessly exposed to the laser light. And
When the light-shielding plate is arranged on the side of the transparent substrate opposite to the laser light incident surface, the guide light is also formed of the transparent plate 21 and the dielectric multilayer reflective film 22 similarly to the YAG laser light. In addition, since the light is reflected by the light-shielding plate 60, the function as the guide light can be still maintained despite the use of a reflector having a structure different from that of the conventional reflector.

Next, the substrate constituting the reflection plate in the present invention is appropriately selected depending on the type of laser oscillation wavelength in the laser device incorporating the shutter. For example, when the laser device is a YAG laser device,
Optical glass such as quartz glass or BK7 is applied. Since these optical glasses do not absorb light having a wavelength of 1.06 μm, there is no possibility that heat is generated on the substrate. For this reason, even if the shutter is continuously used, there is no possibility that the substrate having a convex or concave shape causes thermal deformation accompanying laser beam absorption.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail.

As shown in FIGS. 1A and 1B, this shutter is disposed outside a resonator (not shown) in the laser device 1 and has a focal length of 30 mm on the laser light incident surface side.
A transparent substrate (quartz glass) 21 having a convex surface and a dielectric multilayer reflective film 22 (having a wavelength of 1.0) formed on the surface of the transparent substrate 21 to reflect incident laser light.
64 .mu.m light is reflected at an angle of 45.degree. With respect to the perpendicular to the transparent substrate 21), and a rotary solenoid 30 is provided on the base end side.
Is mounted and the reflecting plate 2 is fixed to the distal end side. A moving member 3 for displacing the reflecting plate 2 to a closed position 2a and an open position 2b as shown in FIG. 1A, and displaced to the closed position 2a. And a water-cooling damper 4 for absorbing the laser beam reflected from the reflection plate 2.

When the reflecting plate 2 is displaced to the closing position 2a in this shutter, the laser beam 5 is applied to the dielectric multilayer reflecting film 22 of the reflecting plate 2 as shown in FIG.
As a result, the laser beam is reflected by 99% or more, the optical path is bent, and the laser beam is incident on the surface of the water-cooled damper 4 while expanding the beam diameter (cross-sectional area) of the laser beam. In this shutter, from the reflector 2 to the water-cooled damper 4, the laser peak output density on the surface of the damper 4 at this time is 1/16 of the laser peak output density when a conventional planar reflector is used. Distance is set.

As a driving means for displacing the reflection plate 2 to the closed position 2a and the open position 2b, the rotary solenoid 30 is applied as described above. And
When the shutter switch is turned ON / OFF, the rectangular moving member 3 rotates around the mounting portion of the rotary solenoid 30 to move the reflecting plate 2 fixed to the distal end side of the moving member 3 to the closed position 2a and the open position 2b. To be displaced. The water-cooled damper 4 is made of an aluminum plate whose surface is blackened so as to be able to absorb laser light well, and has a structure in which heat generated by the absorbed laser light is water-cooled from the back side.

Then, for this shutter, a peak output of 12.5 kW, a pulse width of 2 ms, and a pulse repetition of 4
Y with an average output of 1000 W oscillating under the condition of 0 pps
When installed outside the resonator of the AG laser device and subjected to a durability test, no damage occurred to the water-cooled damper 4 and the reflection plate 2, which are the components of the shutter, even after 10 hours of laser light irradiation.

In this embodiment, the reflection plate 2 is used.
A rotary solenoid is applied as a driving means for displacing the reflecting plate 2 to the closed position 2a and the opening position 2b. Instead of this rotary solenoid, a driving means for displacing the reflecting plate 2 to the closing position 2a and the opening position 2b by parallel movement. It goes without saying that it is possible to apply.

[0031]

According to the shutter according to the first aspect of the present invention, at least the laser light incident surface has a convex or concave shape and the substrate does not absorb the laser light, and the film is formed on the laser light incident surface of the substrate. The above-mentioned reflector is constituted by the dielectric multilayer reflective film, and the water-cooled portion is located at a position where the beam diameter of the laser beam reflected from the reflector is larger than the original beam diameter of the laser beam output from the laser device. Since the damper is provided, breakage of the water-cooled damper during use of the shutter can be prevented, and peeling of the dielectric multilayer reflective film from the substrate hardly occurs.

Accordingly, even when applied to a pulse laser device or the like having a peak output of a 10 kW class or an average output of a 1 kW class, it has an effect of enabling continuous use.

According to the shutter according to the second aspect of the present invention, since the light shielding plate for reflecting or absorbing the laser light leaking from the substrate is disposed on the side of the substrate opposite to the laser light incident surface, This has the effect of completely preventing the partial heat generation of the shutter outer wall and the like due to the light and the danger to the operator of the apparatus.

[Brief description of the drawings]

FIG. 1A is a schematic front view of a shutter according to the present invention and a laser device incorporating the shutter, and FIG. 1B is an explanatory view showing the operation of a reflector of the shutter.

FIG. 2A is an explanatory view showing a positional relationship between a reflector and a water-cooled damper when a convex substrate is used, and FIG. 2B is a diagram when a concave substrate is used. Explanatory drawing which shows the positional relationship between a reflector and a water-cooled damper.

FIG. 3 is an explanatory diagram of a shutter according to a modification in which a light shielding plate is arranged.

FIG. 4 is an explanatory view showing a configuration and an operation of a reflector constituting a main part of a shutter according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser device 2 Reflector 3 Moving member 4 Water-cooled damper 21 Transparent substrate 22 Dielectric multilayer reflective film 30 Rotary solenoid 2a Closed position 2b Open position

Claims (2)

[Claims] 1. A reflector that is displaceable outside a resonator of a laser device and reflects a laser beam output from the laser device at a closed position and passes at an open position, and a reflector that is displaced to a closed position. A shutter of a laser device comprising a water-cooled damper for absorbing reflected laser light and a moving means for displacing the reflection plate to a closed position or an open position, wherein at least a laser light incident surface has a convex or concave shape and the laser The reflector is composed of a substrate that does not absorb light and a dielectric multilayer reflective film formed on the laser light incident surface of the substrate, and the beam diameter of the laser light reflected from the reflector is controlled by the laser device. A laser device wherein the water-cooled damper is arranged at a position larger than the original beam diameter of the output laser beam. Shutter. 2. A shutter according to claim 1, wherein a light-shielding plate for reflecting or absorbing laser light leaking from the substrate is disposed on a side of the substrate opposite to the laser light incident surface.