JP2002182135A - Beam shutter for laser oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a beam shutter which transmits a part of feeble light beams of laser beams from a laser resonator for the position adjustment of the incidence end surface of an optical fiber or the observation of an outgoing light beam, without requiring an attenuator such as a beam attenuation plate. SOLUTION: The beam shutter for a laser oscillator has a reflecting mirror which can move inside and outside the optical path of a laser beam, and a light shielding plate which interrupts the feeble light beams passing through the reflecting mirror. The thickness of the parallel flat plate glass substrate of the reflecting mirror, its refractive index, and the angle of incidence of the laser beam to the reflecting mirror are determined so that the shift amount of the optical path after the light beams have passed through the reflecting mirror is 1 mm or less, preferably 0.5 mm or less, while enabling the easy attaching and detaching of the light shielding plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam shutter of a laser oscillator for blocking a laser beam emitted from a laser resonator outside the laser resonator, and more particularly to a position adjustment of an incident end face of an optical fiber. Also, the present invention relates to an improvement of a beam shutter that transmits a part of laser light when the shutter is shut off, for observation of laser light emitted from an optical fiber.

[0002]

2. Description of the Related Art A conventional beam shutter is disclosed, for example, in Japanese Patent Application Laid-Open No. 8-330658. This outline will be described with reference to FIGS. In addition,
5 and 6 are schematic structural views of this conventional beam shutter. FIG. 5 shows a state where the beam shutter is open, and FIG. 6 shows a state where the beam shutter is closed.

[0005] In FIGS. 5 and 6, reference numeral 1 denotes a laser resonator for generating a laser beam 2 such as a YAG laser, and 3 denotes a reflecting mirror which can be selectively moved into and out of the optical path of the laser beam 2. A glass substrate is coated with a total reflection film. 4 is disposed at the rear of the reflection mirror 3 and
Is a metal light-shielding plate that shields weak light passing through the laser light 2 and is configured to be selectively movable together with the reflection mirror 3 into or out of the optical path of the laser light 2. Reference numeral 5 denotes a metal water-cooled damper that absorbs the energy of the laser beam 2 reflected by the reflection mirror 3. The beam shutter 10 includes the reflection mirror 3, the light shielding plate 4, and the damper 5. Reference numeral 6 denotes a condenser lens for condensing the laser light 2. The laser light 2 condensed by the condenser lens 6 is incident on the incident end face 7 a of the optical fiber 7 and transmitted to the outside of the laser oscillator 8. Reference numeral 9 denotes an outgoing laser beam emitted after transmitting through the optical fiber 7.

Next, the function of the conventional beam shutter configured as described above will be described. As shown in FIG. 5, when the reflection mirror 3 and the light shielding plate 4 are located outside the optical path of the laser light 2, the laser light 2 goes straight and
Then, the light is converged by the condenser lens 6 to a spot diameter of several hundred μm, and is incident on the optical fiber 7. As shown in FIG. 6, when the reflection mirror 3 and the light shielding plate 4 are located in the optical path of the laser light 2, most of the laser light 2 is reflected by the total reflection film on the surface of the reflection mirror 3, and the optical path is 90 °. It is bent every time and reaches the water-cooled damper 5 to be absorbed as heat energy. In addition, since the weak light transmitted through the total reflection film is absorbed by the light shielding plate 4, the laser light reaching the condenser lens 6 is completely blocked. The means for moving the reflection mirror 3 and the light shielding plate 4 is a movable device capable of parallel movement and rotational movement, and is not shown and is omitted.

[0005]

As described above, the conventional beam shutter either transmits 100% of the laser beam 2 or completely blocks the laser beam 2. When the laser beam 2 is transmitted by being incident on the optical fiber 7, the laser beam 2 is incident on the core center position of the incident end face 7 a of the optical fiber 7 at an incident angle of 0 degree at the time of initial adjustment of the optical path incident on the optical fiber 7. In addition, the position of the incident end face 7a of the optical fiber 7 is adjusted.

[0006] This adjustment work is performed particularly when the laser output of the laser resonator 1 is a high-power laser of several hundred W to several kW, by opening the beam shutter 10 and applying the laser light 2 to the laser beam 10.
It is very dangerous if it is carried out with 0% passing. Further, when the incident position on the incident end face 7a of the optical fiber 7 is shifted, there is a problem that the incident end face 7a is broken. Therefore, in the above adjustment work, usually, a beam attenuating plate for adjusting the laser beam 2 is inserted between the laser resonator 1 and the condenser lens 6, and most of the laser beam 2 is out of the optical path by the beam attenuating plate. The adjustment operation has been performed using weak light that is reflected, transmitted through the beam attenuation plate, and reaches the optical fiber 7.

In the above laser device, the divergence angle and the beam energy distribution of the outgoing laser light 9 emitted from the optical fiber 7 are observed at the time of regular maintenance of the laser oscillator 8 or at the time of occurrence of some trouble.
The work to confirm whether the beam quality of the sample did not deteriorate was performed. In addition, if the position and angle of the laser beam 2 incident on the incident end face 7a of the optical fiber 7 are found to be shifted as a result of this checking operation, readjustment has been performed. However, in any of these cases, that is, when observing the beam quality of the emitted laser light 9 and when adjusting the position of the incident end face 7a of the optical fiber 7, it is necessary to cause the weak light to enter the optical fiber 7. In some cases, it was necessary to newly insert the above-described beam attenuating plate to reconstruct the optical path system.

As described above, in the conventional beam shutter, when observing the beam quality of the outgoing laser beam 9 or adjusting the position of the incident end face 7a of the optical fiber 7, some beam of the laser beam 2 such as a beam attenuating plate is used. A separate attenuator for attenuating the light output was required. In addition, there is a problem that it takes time and labor to set up the damping device. In particular, when the above-described conventional laser device is used in a production line, the setting of the attenuator requires time and effort as described above, which has been a serious problem in maintaining productivity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a part of the laser light from the laser resonator can be reduced without requiring an additional attenuating device such as a beam attenuating plate. It is an object of the present invention to provide a beam shutter that can transmit light for adjusting the position of an incident end face of an optical fiber or observing emitted light.

[0010]

A beam shutter of a laser oscillator according to the present invention comprises a laser resonator for generating laser light, and a laser for condensing laser light emitted from the laser resonator and causing the laser light to enter an optical fiber. A beam shutter of a laser oscillator installed between the condenser lens and a parallel-reflective glass substrate, which is provided with a total reflection film, in an optical path between the laser resonator and the condenser lens or outside the optical path. A reflecting mirror configured to be selectively movable;
When the reflection mirror is in the optical path, a light-shielding plate removably mounted at a rear position of the reflection mirror, and a damper for absorbing laser light reflected by the reflection mirror, Optical path shift amount after transmission through the reflecting mirror = t × sin θ × (1−n ₀ / n ₁ × cos θ / √ (1−n ₀ ²
/ N ₁ ² × sin ² θ)) t = thickness of the parallel plate glass substrate θ = incident angle of laser light in the optical path of the reflection mirror n ₁ = refractive index of the parallel plate glass substrate n ₀ = of the reflection mirror Δ is 1 mm or less, preferably 0.01 m, where
m, the thickness t of the parallel flat glass substrate, the incident angle θ of the laser beam to the reflection mirror, and the refractive index n ₁ of the parallel flat glass substrate are set.

Also, a beam shutter of a laser oscillator according to the present invention, instead of the above configuration, has a laser resonator for generating laser light, and condenses laser light emitted from the laser resonator and makes the laser light incident on an optical fiber. A beam shutter of a laser oscillator installed between the condensing lens for, a total reflection film is applied to a parallel plate glass substrate,
A reflecting mirror configured to be selectively movable in or out of an optical path between the laser resonator and the condenser lens; and a rear portion of the reflecting mirror when the reflecting mirror is in the optical path. A light-shielding plate detachably mounted at a position, and a damper for absorbing the laser light reflected by the reflection mirror, δ = optical path shift amount after transmission through the reflection mirror = t × sin θ × (1-n ₀ / n ₁ × cos θ / √ (1-n ₀ ²
/ N ₁ ² × sin ² θ)) t = thickness of the parallel plate glass substrate θ = incident angle of laser light in the optical path of the reflection mirror n ₁ = refractive index of the parallel plate glass substrate n ₀ = of the reflection mirror When the refractive index of the surrounding space f = focal length of the condenser lens, the thickness t of the parallel flat glass substrate and the incident angle θ of the laser beam with respect to the reflection mirror so that δ / f ≦ 0.01. , The refractive index n of the parallel plate glass substrate
You may set ₁ .

Further, in the beam shutter of the laser oscillator according to the present invention, the laser beam incident angle θ is preferably set to 45
°.

[0013] In the beam shutter of the laser oscillator according to the present invention, preferably, the material of the glass substrate forming the reflection mirror is made of synthetic quartz glass, and the total reflection film formed on the glass substrate is made of a dielectric material. Body multilayer film.

[0014]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is an explanatory diagram of a configuration of a beam shutter according to the present invention, FIG. 2 is an explanatory diagram of an optical path shift by a reflection mirror in the beam shutter of the present invention, and FIG. 3 is an optical path when the beam shutter of the present invention is opened. FIG. 4 is a diagram illustrating the correlation between the incident angle of the optical fiber and the beam quality in the beam shutter according to the present invention. In these drawings, the same and corresponding elements as those in the related art are denoted by the same reference numerals.

In FIG. 1, 1 is an oscillation wavelength λ = 1.06.
A high-power YAG laser resonator having a laser output of 4 μm and a kW class is provided. A reflecting mirror 3 is a parallel flat synthetic quartz glass substrate having a thickness t = 3.2 mm. This reflection mirror 3
Are arranged so that the laser beam 2 is incident at an incident angle of 45 °, and a dielectric multilayer film that reflects 99.5% or more of 45 ° incident light of λ = 1.64 μm on the incident surface is provided. Coated.

Reference numeral 4 denotes a metal light-shielding plate which can be easily attached and detached, and completely blocks weak light transmitted through the dielectric multilayer film on the incident surface of the reflection mirror 3. Also, this light shielding plate 4
When the reflecting mirror 3 closes the optical path, it can be positioned in the optical path at the same time, and is easily and detachably attached to the rear position of the reflecting mirror 3 according to the selection of the operator. Reference numeral 5 denotes a metal water-cooled damper for absorbing the energy of the laser beam 2 reflected by the reflection mirror 3, and 6
Denotes a condensing lens having a focal length f = 100 mm, and 7 denotes a graded index optical fiber in which a quartz core is doped with Ge and has a square refractive index distribution.

Next, the function of the beam shutter 10 in the embodiment configured as described above will be described. As shown in FIG. 1, the light shielding plate 4 is removed with the beam shutter 10 closed, that is, with the reflection mirror 3 positioned in the optical path. Then, 99.5% of the laser beam 2 emitted from the laser resonator 1 is reflected by the dielectric multilayer film on the surface of the reflection mirror 3, reaches the water-cooled damper 5, and is absorbed as heat energy. The remaining 0.5% is transmitted through the reflection mirror 3. Laser output of laser resonator 1 is 1
In the case of kW, the transmitted laser light is 5 W. Further, it is also possible to easily make the reflectance of the dielectric multilayer film 99.9% or more, in which case the transmitted laser beam can be made 1 W or less.

Further, by using a synthetic quartz having excellent transmission characteristics, containing few impurities and bubbles, and having a very small thermal expansion coefficient for the glass substrate, the laser beam 2 caused by the transmission through the glass substrate can be used.
Wavefront disturbances and changes can be eliminated.

Therefore, when observing the beam quality of the outgoing laser light 9 or when adjusting the position of the incident end face 7a of the optical fiber 7 at the time of initial adjustment or at the time of occurrence of trouble, this weak transmitted laser light is incident on the incident end face. 7a. Also, in this case, the degree of danger of the work can be greatly reduced as compared with the case where the laser light 2 is not attenuated, and even when the incident position on the incident end face 7a of the optical fiber 7 is shifted, the incident end face 7a is broken. Never.

However, in the above configuration, when the reflection mirror 3 is in the optical path, simply removing the light-shielding plate 4 shifts the optical path in parallel, and the position of the incident end face 7a of the optical fiber 7 cannot be adjusted accurately. In addition, there is a problem that the emitted light 9 from the optical fiber 7 cannot be accurately observed. That is, as shown in FIG. 2, when the laser beam 2 is incident from a space having a refractive index n ₀ to a parallel flat glass substrate having a thickness t and a refractive index n _{1 at} an incident angle θ, the laser beam 2 after passing through the glass substrate becomes , Δ = t × si
_{nθ × (1-n 0 /} n 1 × cosθ / √ (1- n 0 2 / n 1 2 × s
in ² θ)), the optical path shifts in parallel by the amount represented by:
Therefore, the laser beam 2 incident on the condenser lens 6 having the focal length f is shifted by δ, and is incident on the incident end face 7a of the optical fiber 7 at an angle represented by α = δ / f.

On the other hand, as shown in FIG.
When the beam oscillator 10 is opened and the laser oscillator 8 is used, the incident angle α = 0 ° is set at the center position of the incident end face 7a of the optical fiber 7 when the laser oscillator 8 is used.
It must be adjusted so that it is incident at However,
As described above, the weak laser light 2 transmitted through the reflecting mirror 3 is deviated from the predetermined optical path, or the incident end face 7a of the optical fiber 7 is
When the light is not incident on the center position at right angles, the position of the incident end face 7a of the optical fiber 7 is shifted, and the beam quality of the output laser light 9 of the optical fiber 7 is changed depending on the use state of the laser oscillator 8 with the beam shutter 10 opened. Will be different.

Therefore, in the present invention, the thickness t of the parallel flat glass substrate of the reflection mirror 3, the incident angle θ of the laser beam 2 with respect to the reflection mirror 3, the refractive index n of the parallel flat glass substrate
By setting ₁ appropriately, this problem did not occur.

First, FIG. 4 shows an experimental result of the beam quality deterioration characteristics of the outgoing laser light 9 after transmitting the optical fiber 7 with respect to the incident angle α of the laser light 2 incident on the incident end face 7a of the graded index optical fiber 7. Shown in In FIG. 4, an M ² value obtained by dividing the product of the beam waist diameter and the divergence angle by (4 × λ / π) is used as the beam quality. The M ² value represents the best beam quality theoretical limit when it is 1, the beam quality M ² value is deteriorated doubled in case of a lens focusing an identical incident conditions, the deterioration in the focused spot area 4 times I do. As shown by the characteristic curve in FIG. 4, it was found that the M ² value did not deteriorate until the incident angle was about 10 mrad.

Accordingly, when the incident angle α of the laser beam 2 incident on the incident end face 7a of the optical fiber 7 is large, the laser beam transmitted inside the optical fiber 7 meanders as shown in FIG. It has been found that the beam quality of the emitted laser light 9 after transmission deteriorates and the emission divergence angle β increases.

Next, an example in which the thickness t of the parallel flat glass substrate of the reflecting mirror 3, the incident angle θ of the laser beam 2 to the reflecting mirror 3, and the refractive index n ₁ of the parallel flat glass substrate are appropriately set will be described. In the first example, a 3.2 mm thick synthetic quartz glass substrate is used for the reflection mirror 3 and the incident angle of the laser beam is 45 °. Also, λ = 1.
Refractive index n ₁ = 1.449 for 064 μm, thickness t =
3.2 mm, the incident angle is θ = 45 °. Therefore, if the refractive index of the surrounding space is n ₀ = 1, δ = 1 mm.
When the focal length f of the condenser lens is 100 mm,
α = δ / f = 10 mrad, the emitted laser light 9 after transmission through the optical fiber 7 hardly deteriorates, and the actual use state with the beam shutter 10 opened and the optical fiber transmission state of the weak laser light 2 after passing through the glass substrate It has been found that the difference can be eliminated.

Therefore, as a second example, for example, in the above example, the thickness of the synthetic quartz glass substrate was set to 1.6 mm. In this case, δ = 0.5 mm, α = 5 mra
d, and the difference from the optical fiber transmission state in the actual use state can be further reduced. In addition,
It is sufficiently possible to mirror-polish the synthetic quartz glass substrate to a thickness of about 1 mm.

If the thickness of the synthetic quartz glass substrate is set to 1.6 mm in this way, for example, even if the focal length of the condenser lens is 50 mm, δ = 1 mm and α = 1
It turned out that it could be 0 mrad.

Therefore, as can be seen from the above example, the thickness t of the parallel flat glass substrate and the optical path of the reflection mirror are adjusted so that the optical path shift δ after transmission through the reflection mirror 3 is 1 mm or less, preferably 0.5 mm or less. By setting the incident angle θ of the laser light in the inside and the refractive index n ₁ of the parallel flat glass substrate, the weak operation of the laser light 2 can be performed by a simple operation of removing the light shielding plate 4 when the reflection mirror 3 is in the optical path. Incident end face 7a of optical fiber 7 with little shift of light
Can be incident. Therefore, it is not necessary to use an attenuating device such as a beam attenuating plate, and the time and labor required for the setting can be omitted.

Further, the thickness t of the parallel plate glass substrate and the laser beam incident angle θ in the optical path of the reflecting mirror are set so that the incident angle α of the laser beam 2 on the incident end face 7a of the optical fiber 7 is 0.01 rad or less. , setting the refractive index n ₁ of the parallel flat glass substrate, it is possible to obtain the same effect.

As described above, according to the present embodiment, the internal configuration of the laser oscillator 8 is simplified by using no attenuating device, and the light shielding plate 4 is simply removed when the reflection mirror 3 is in the optical path. With the simple operation described above, the beam quality of the emitted laser light 9 can be observed and the incident optical path of the optical fiber 7 can be accurately adjusted.

Further, since the incident angle θ of the laser beam with respect to the reflecting mirror 3 is set to 45 °, the optical path system can be further simplified, and the arrangement space of the water-cooled damper 5 for receiving the reflected laser beam 2 can be easily made. Can be secured. Further, since the glass substrate material of the reflection mirror 3 is made of synthetic quartz glass and the total reflection film is made of a dielectric multilayer film, it is possible to eliminate the disturbance or change of the wavefront of the laser light caused by the transmission of the glass substrate,
Weak light of 0.5 to 0.1% or less of the laser output can be easily extracted.

[0032]

The present invention is configured as described above.
Therefore, the following effects are obtained. According to the invention of claim 1
For example, a laser resonator that generates laser light and this laser
Focuses the laser light emitted from the resonator to an optical fiber
Laser installed between condensing lens for incidence
Oscillator beam shutter, parallel plate glass
The plate is provided with a total reflection film, and the laser resonator and the condenser
Can be selectively moved into or out of the optical path between the lens
And a reflecting mirror configured as described above.
Detachable to the rear position of this mirror when in the optical path
A light-shielding plate that is mounted so that it can be reflected by the reflection mirror
Δ = optical path shift amount after passing through the reflecting mirror = t × sin θ × (1-n₀/ N₁× cos θ / √ (1-n₀ ^Two
/ N₁ ^Two× sin^Twoθ)) t = thickness of the parallel plate glass substrate θ = incident angle of laser light in the optical path of the reflection mirror n₁= Refractive index n of the parallel flat glass substrate₀= The refractive index of the surrounding space of the reflection mirror, and the parallel flat plate is set so that δ ≦ 1 mm.
The thickness t of the glass substrate and the laser beam to the reflecting mirror
The incident angle θ, the refractive index n of the parallel plate glass substrate ₁Set
As the beam shutter is closed,
Simply remove the laser from the beam path after the beam shutter.
A very small part of the light can be transmitted. Ma
Also, newly provide optical components that correct optical path deviation
Due to optical path shift with simple configuration
The incident angle of the laser light incident on the incident end face of the optical fiber
Can be smaller. And the beam shutter
Very little difference from optical fiber transmission when opened
A weak light transmission state can be obtained.

According to the second aspect of the present invention, δ ≦ 0.
The thickness t of the parallel plate glass substrate, the incident angle θ of the laser beam with respect to the reflection mirror, and the refractive index n ₁ of the parallel plate glass substrate are set so as to be 5 mm. In addition, the incident angle of the laser beam incident on the optical fiber incident end face due to the optical path shift can be further reduced. And, the difference from the optical fiber transmission when the beam shutter is opened can be further eliminated.

Further, according to the third aspect of the present invention, the incident angle α (α = δ) of the laser light incident on the incident end face of the optical fiber.
/ F, where f = focal length of the condenser lens) is 0.01
The thickness t of the parallel flat glass substrate, the incident angle θ of the laser beam to the reflection mirror, and the refractive index n ₁ of the parallel flat glass substrate are set so as to be equal to or less than rad. The effect can be achieved.

According to the invention of claim 4, according to claim 1,
In the inventions of (1) to (3), the incident angle θ of the laser beam with respect to the reflection mirror is set to 45 °, so that the optical path system can be simplified, and the arrangement space for the water-cooled damper that receives the reflected laser beam can be easily secured. .

According to the invention of claim 5, according to claim 1,
In the inventions of (1) to (3), since the material of the glass substrate forming the reflection mirror is made of synthetic quartz glass and the total reflection film applied to this glass substrate is made of a dielectric multilayer film, the laser light caused by the transmission of the glass substrate is obtained. Wavefront disturbances and changes can be eliminated. In addition, the laser output can be easily adjusted to 0.5 to
Weak light of 0.1% or less can be extracted.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of a beam shutter according to the present invention.

FIG. 2 is an explanatory diagram of an optical path shift by a reflection mirror in the beam shutter of the present invention.

FIG. 3 is an explanatory diagram of an optical path when a beam shutter of the present invention is opened.

FIG. 4 is a correlation diagram between an optical fiber incident angle and beam quality in a beam shutter according to the present invention.

FIG. 5 is a schematic configuration diagram of a conventional beam shutter, showing a state where the beam shutter is opened.

FIG. 6 is a schematic configuration diagram of a conventional beam shutter, showing a state in which the beam shutter is closed.

[Explanation of symbols]

1 laser resonator, 2 laser beam, 3 reflection mirror, 4
Shield plate, 5 damper, 6 condenser lens, 7 optical fiber, 7a entrance end face, 8 laser oscillator, 9 emission laser light, 10 beam shutter

Continued on the front page (72) Inventor Akira Kukuni 2-3-2 Marunouchi, Chiyoda-ku, Tokyo, Japan Mitsui Electric Co., Ltd. (72) Inventor Jin 2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo, Mitsubishi F term (reference) in Denki Co., Ltd. 2H041 AA04 AA13 AB02 AB13 AC01 AZ01 5F072 AB01 KK05 MM03 MM05 MM17

Claims (5)

[Claims] 1. A laser resonator for generating a laser beam.
Laser light emitted from the
Installed between the lens and the condenser lens
A total-reflection film formed on a parallel plate glass substrate,
Selectable in the optical path between the shaker and the condenser lens or outside the optical path
A reflecting mirror configured to be able to move freely; and a reflecting mirror when the reflecting mirror is in the optical path.
A light-shielding plate detachably mounted at a rear position of the mirror, and a damper for absorbing laser light reflected by the reflection mirror
Δ = optical path shift amount after transmission through the reflecting mirror = t × sin θ × (1-n₀/ N₁× cos θ / √ (1-n₀ ^Two
/ N₁ ^Two× sin^Twoθ)) t = thickness of the parallel flat glass substrate θ = incident angle n of laser light to the reflection mirror n₁= Refractive index n of the parallel flat glass substrate₀= The refractive index of the surrounding space of the reflection mirror, and the parallel flat plate is set so that δ ≦ 1 mm.
The thickness t of the glass substrate and the laser beam to the reflecting mirror
The incident angle θ, the refractive index n of the parallel plate glass substrate ₁Set
Beam shutter for laser oscillator
- 2. A beam shutter of a laser oscillator installed between a laser resonator for generating laser light and a condensing lens for condensing laser light emitted from the laser resonator and making the laser light incident on an optical fiber. A reflecting mirror, which is provided with a total reflection film on a parallel plate glass substrate and is configured to be selectively movable in or out of an optical path between the laser resonator and the condenser lens; When the mirror is in the optical path, a light-shielding plate is detachably mounted at a rear position of the reflection mirror, and a damper that absorbs laser light reflected by the reflection mirror, δ = the reflection mirror Optical path shift amount after transmission = t × sin θ × (1−n ₀ / n ₁ × cos θ / √ (1−n ₀ ²
/ N ₁ ² × sin ² θ)) t = thickness of the parallel plate glass substrate θ = incident angle of laser light to the reflection mirror n ₁ = refractive index of the parallel plate glass substrate n ₀ = space around the reflection mirror The thickness t of the parallel plate glass substrate, the incident angle θ of the laser beam with respect to the reflection mirror, and the refractive index n _{1 of the} parallel plate glass substrate so that δ ≦ 0.5 mm.
A beam shutter of a laser oscillator characterized by setting: 3. A beam shutter of a laser oscillator installed between a laser resonator for generating laser light and a condensing lens for condensing laser light emitted from the laser resonator and making the laser light incident on an optical fiber. A reflecting mirror, which is provided with a total reflection film on a parallel plate glass substrate and is configured to be selectively movable in or out of an optical path between the laser resonator and the condenser lens; When the mirror is in the optical path, a light-shielding plate removably mounted at a rear position of the reflection mirror and a damper for absorbing laser light reflected by the reflection mirror; δ = the reflection mirror Optical path shift amount after transmission = t × sin θ × (1−n ₀ / n ₁ × cos θ / √ (1−n ₀ ²
/ N ₁ ² × sin ² θ)) t = thickness of the parallel plate glass substrate θ = incident angle of laser light to the reflection mirror n ₁ = refractive index of the parallel plate glass substrate n ₀ = space around the reflection mirror When the refractive index f = focal length of the condenser lens, the thickness t of the parallel flat glass substrate, the incident angle θ of the laser beam with respect to the reflection mirror, Refractive index n of parallel flat glass substrate
A beam shutter of a laser oscillator, wherein ₁ is set. 4. The beam shutter of a laser oscillator according to claim 1, wherein an incident angle θ of the laser beam with respect to the reflection mirror is 45 °. 5. The method according to claim 1, wherein a material of said glass substrate forming said reflection mirror is synthetic quartz glass, and said total reflection film applied to said glass substrate is a dielectric multilayer film. 4. The beam shutter of the laser oscillator according to any one of 3.