JPH05190938A - Solid laser equipment - Google Patents

Abstract

PURPOSE:To obtain a solid laser equipment excellent in beam quality and output stability. CONSTITUTION:An optical element 5 for inputting and outputting a beam, which is transparent to a laser beam 10, is bonded to an end surface ..b of an inside total reflection type slab type laser medium 1 through which surface 1b the laser beam is inputted and outputted. The sealing and the retaining of solvent 3b are performed on a surface 5a which does not contribute to the beam propagation of the optical element 5 for inputting and outputting a beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser device, and more particularly to a beam input / output of a slab type solid-state laser device, and further to a structure for supporting a laser medium and sealing a coolant.

[0002]

2. Description of the Related Art FIG. 4 and FIG.
2A and 2B are a perspective view and a cross-sectional view showing the outline of a conventional solid-state laser device disclosed in Japanese Patent No. 2269, wherein FIG. 5A shows a horizontal cross section and FIG. 5B shows a vertical cross section. In the figure, 1 is a slab, which is a laser medium having a rectangular cross section orthogonal to the optical axis. 1a is a slab surface, which is an optically smooth surface. Reference numeral 2 denotes a sealing material for the cooling medium 3b, which also serves as a support for the laser medium 1. 4 is a lamp, 6 is a cooling medium for the lamp, 7 is a condenser, 9 is a holder,
11 is the excitation light.

Next, the operation will be described. Laser medium 1
Is the excitation light 11 from the lamp 4 collected by the condenser 7.
Is absorbed and excited. Part of the excited energy is extracted out of the medium as a laser beam that propagates in a zigzag manner while repeating total internal reflection. However, most of the excitation light energy becomes thermal energy in the laser medium 1 and finally flows into the cooling medium 3b. The cooling medium 3b is sealed on the slab surface 1a by the sealing material 2 so as not to leak out.

FIG. 6 shows the sealing material 2 on the slab surface 1a.
It shows the seal position of. In this conventional example, in order to prevent the laser beam from being absorbed by the sealing material 2 and the chipping of the beam pattern caused thereby, the sealing position on the opposing slab surface 1a is shifted so that the laser beam does not exist in the dead space 1c. , Seals. A dashed line A indicates the center of the beam, a dotted line B indicates one end of the beam, and a solid line C indicates the other end of the beam.

[0005]

Since the conventional solid-state laser device is constructed as described above, the sealing material 2 is directly exposed to the laser beam and does not absorb it.
However, the diffracted light of the laser beam and the reflected light from the entrance / exit end face also exist in the dead space 1c, and the sealing material 2 absorbs and heats these lights, and the temperature distribution in the laser medium 1 and the resulting thermal strain 1d occur. give. In addition to the diffracted light and the end surface reflected light, the excitation light 11 itself may heat the sealing material 2 and cause the same thermal strain 1d in the laser medium 1. Even when the sealing material is not heated by the diffracted light, the end surface reflected light, and the excitation light, the distortion 1d is generated at the sealing position of the laser medium 1 due to the pressure of the sealing material 2 itself. As described above, in the slab surface 1a, in the solid-state laser device that seals the refrigerant, distortion is always generated in the vicinity of the sealing position, which distorts the laser beam and further causes fluctuation of output, which is very serious. There was a problem.

The present invention has been made in order to solve the above-mentioned problems, and suppresses thermal distortion of a laser medium due to heating of a sealing material to obtain a solid-state laser device having excellent beam quality and stable output. With the goal. Furthermore, it is an object of the present invention to obtain a solid-state laser device which suppresses stress strain applied to a laser medium by a sealing material and has excellent beam quality and stable output.

[0007]

In the solid-state laser device according to the present invention, a beam entrance / exit optical element transparent to laser light is installed on a laser beam entrance / exit end face of a slab type laser medium. The laser beam is made to enter and exit the slab type laser medium through the emission optical element, and the laser medium is not supported and the coolant is not sealed on the optically smooth surface of the laser medium. This is done on a surface that does not contribute to propagation.

Further, as the beam entrance / exit optical element, it is preferable to use an element whose cross section is larger than that of the laser medium.

Further, the beam entrance / exit optical element and the end surface of the laser medium are optically joined (optical contact).
It is good to join by.

[0010]

The optical element for beam entrance / exit according to the present invention comprises:
A slab that is a laser medium and a free space outside the housing, such as a light guide path of laser light that connects the atmosphere, seals the refrigerant,
This is performed on the surface that does not contribute to the beam propagation on the beam entrance / exit optical element. Therefore, the optically smooth surface of the slab does not include a sealing material for supporting the medium and sealing the refrigerant, and the lack of a beam due to the absorption of the laser beam by the sealing material does not occur. Further, neither thermal strain of the slab due to heating of the sealing material nor stress strain of the slab due to pressure bonding of the sealing material occurs.

The cross section of the beam entrance / exit optical element is
Since it is made larger than the cross section of the laser medium, the laser beam optical path in the beam entrance / exit optical element and the sealing position of the sealing material are sufficiently separated from each other, and the sealing material is not heated by the diffracted light of the laser beam, and The stress strain of the seal portion does not extend into the optical path of the laser beam, and the laser beam is not distorted in the beam entrance / exit optical element.

Further, if the laser beam entrance / exit optical element and the end surface of the laser medium are joined by optical joining (optical contact), absorption of the laser beam at the interface can be suppressed, and optical distortion of the optical path is small, and It is possible to obtain a solid-state laser device having excellent light resistance strength.

[0013]

EXAMPLES Example 1. 1A and 1B are sectional views showing an embodiment of the present invention. FIG. 1A is a front sectional view, FIG. 1B is a top sectional view, and FIG. 1C is a side sectional view.

In the figure, reference numeral 1 is a laser medium, that is, a slab having a substantially rectangular cross section and having opposite optical smooth surfaces (1a). Reference numeral 1b is a laser beam entrance / exit end surface of the slab 1, and numeral 5 is a laser beam entrance / exit optical element arranged in contact with the laser beam entrance / exit end surface 1b. 2 is a surface 5a of the beam entry / exit optical element for the seal of the slab coolant 3b
This is the sealing material used in. 8 is a side support.

Next, the operation and operation of the above embodiment will be described. The laser medium 1 absorbs the excitation light 11 from the lamp 4 collected by the condenser 7 and is excited. A part of the excited energy is extracted out of the medium through the laser beam entrance / exit optical element 5 as the laser beam 10 propagating in a zigzag manner while repeating the total internal reflection. Most of the excitation light energy becomes thermal energy in the laser medium 1 and finally flows into the cooling medium 3b. Cooling medium 3b
Is sealed on the surface 5a of the laser beam entrance / exit optical element 5 by the sealing material 2 so as not to leak out.

The laser beam 10 propagating in the laser beam entrance / exit optical element 5 propagates substantially parallel to the surface 5a thereof, and is not the internal total reflection type beam propagation in the slab 1. There is no laser beam at. That is, the surface 5a is a surface that does not contribute to beam propagation, and therefore, the sealing material 2 is not inside the optical path of the laser beam and does not absorb the laser beam 10. Therefore, there is no omission of the portion corresponding to the sealing position of the beam pattern. Does not happen. Further, since the sealing material 2 does not absorb the laser beam 10, it does not generate heat and heats the vicinity of the sealing position as seen in the conventional example.
There is no thermo-optical distortion associated with this, and a solid-state laser having no beam distortion and excellent output stability can be realized. As described above, according to the present invention, since the slab laser medium is not supported and the refrigerant is not sealed, the laser medium is not optically distorted and a solid-state laser having excellent beam quality can be realized.

The above is 0 of the main beam 10 propagating in the optical path.
Although the improvement effect on the ring absorption was described, as the light that is absorbed by the 0 ring and heats it to distort the optical path, diffracted light of the main beam other than the main beam 10, end face reflected light of the main beam, There is stray light of excitation light 11. The effectiveness of the present invention for the O-ring heating due to the main beam diffracted light, the end face reflected light of the main beam, and the stray light of the excitation light will be described below in order.

The diffracted light of the laser main beam 10 is almost parallel to the laser main beam 10 (half angle of diffraction: θd 0.0015 °).
Since 5a is almost parallel, as with the main beam 10, the sealing material 2
It is hardly absorbed by.

Regarding the reflected light of the main beam at the laser medium end surface 1b, when the beam entering and exiting at the slab end surface 1b is obliquely incident, the end surface reflected light and the optical path of the main beam 10 are largely displaced, and the end surface reflected light is The sealing material 2 rarely irradiates to the coolant channel near the end face of the slab of the beam entrance / exit optical element 5 and is irradiated. When the beam entering / exiting the slab end face 1b is vertical incidence, the end face reflected light becomes substantially parallel to the main beam 10, and in the conventional case, the sealing material 2 may be irradiated,
In the case of the present invention, the incident angle of the end face reflected light on the beam entrance / exit optical element surface 5a is extremely large, and the sealing material 2 absorbs the end face reflected light very little.

As for the absorption of the stray light of the excitation light 11, the distance from the lamp is increased by the length of the laser beam entrance / exit optical element 5 as compared with the case of sealing in the vicinity of the slab end of the conventional example. The ratio is greatly reduced.

As described above, in the present embodiment, for any of the laser main beam 10, the main beam diffracted light, the end face reflected light, and the stray light of the excitation light 11 which caused the heating of the sealing material 2. However, since the absorption can be greatly reduced, and the sealing material 2 does not exist inside the optical path of the laser beam 10,
It is possible to greatly reduce the lack of the laser beam 10, the distortion of the beam, and the instability of the output due to these.

Further, in the conventional example, the sealing position of the 0 ring is limited to the dead space, but in the present invention, the sealing position of the 0 ring is on the surface 5a of the laser beam entrance / exit optical element 5. Optionally, the degree of freedom in designing the laser housing can be greatly improved.

The joining method of the laser beam entrance / exit optical element 5 and the slab end face 1b is as follows. It is bonded to the laser beam 10 using a transparent optical adhesive material or a silicon pod material. 2. Both end faces that have been optically polished are pressed and then heated to perform optical contact (optical contact). 3. A mechanism for pressing the beam entering / exiting optical element 5 in the direction of the laser medium 1 with a constant force is provided, and the laser medium end surface 1b is provided.
Then, the end surface of the beam entrance / exit optical element 5 is surface-pressed. Etc. In addition, the above 1. In the joining method of No. 3, the refrigerant does not enter the optical interface, but in the joining method of No. 3, a thin layer of the refrigerant is formed on the joining surface, and therefore the refrigerant is also required to be transparent to the laser beam.

The laser beam entrance / exit optical element 5 is required to be transparent to the laser light. Laser medium 1 is Nd: YAG, Nd: GGG, Nd: Neodymium such as glass: Nd ³⁺
In the case of a solid medium in which is the active element, the wavelength of the laser light is
1.06 μm, and optical glass such as BK7 quartz, sapphire, YAG, GGG containing no impurities, etc. can be applied to the material of the transparent laser beam entrance / exit optical element.
Further, it is desirable that the laser beam entrance / exit optical element 5 is transparent to the excitation light 11 (wavelength 200 to 1000 μm) from the lamp 4. This is an optical element 5 for entering and exiting a laser beam.
Absorbs the excitation light 11 and prevents thermo-optical distortion in the optical path of the laser beam.
The YAG and GGG materials almost satisfy this condition.

Example 2. In Example 1 shown in FIG. 1, the optical axis is perpendicular to the end surface 5b of the beam entrance / exit optical element 5,
The end face 5b is non-reflection coated to realize low loss coupling with the external space (atmosphere). However, as shown in FIG. 2, when the propagating laser beam 10 is linearly polarized, the end face 5b is It is also possible to achieve Brewster-cut and realize low loss coupling with the external space (atmosphere).

Example 3. In the above-mentioned embodiment, the case where the cross section of the laser beam entrance / exit optical element 5 is substantially equal to the cross section of the slab type laser medium 1 has been described, but as shown in FIG. The cross section of 5 may be larger than the cross section of the slab type laser medium 1. In addition,
3A is a front sectional view, and FIG. 3B is a top sectional view. In this case, as shown in FIG. 3A, the passage position of the laser beam 10 inside the laser beam entrance / exit optical element 5 is separated from the pressure-bonding position of the sealing material 2, so that the sealing material 2
Laser main beam ・ End-face reflected light at normal incidence ・ Main beam
The absorption of the diffracted light of 10 is further reduced, and the optical distortion of the optical path of the laser beam is further reduced. Further, the mechanical distortion due to the pressure bonding of the sealing material 2 is greatly reduced because the sealing position is away from the optical path of the laser beam.
As described above, by making the cross section of the laser beam entrance / exit optical element 5 larger than the cross section of the slab type laser medium 1, the optical distortion in the optical path is further reduced, and the beam quality and the output stability are more excellent. Solid-state laser can be realized. Note that FIG.
As shown in (a) and (b), the actual laser beam has a slight spread, but the outer edge of the beam and the surface 5a of the beam entrance / exit optical element 5 need not be parallel to each other.

In the embodiment of FIG. 3 (a), the thickness of the laser beam entrance / exit optical element 5 is gradually increased from the joint with the end face of the slab in a taper shape to smooth the flow of the refrigerant. The slab end is also cooled sufficiently.

In the third embodiment, the case where the cross section of the laser beam entrance / exit optical element 5 is larger than the cross section of the laser medium in both the width direction and the thickness direction has been described. Either the width direction or the thickness direction of the cross section may be larger than the cross section of the laser medium.

[0029]

As described above, according to the present invention, the beam entrance / exit optical element transparent to the laser beam is bonded to the end face of the slab type laser medium, and the beam entrance / exit optical element is interposed therebetween. Since the laser beam is made to enter and exit the laser medium, and the surface of the optical element for beam entrance and exit that does not contribute to the beam propagation is sealed and supported by the cooling medium, no distortion occurs in the optical path of the laser beam, There is an effect that a solid-state laser excellent in beam quality and output stability can be obtained.

Further, since the cross section of the beam entrance / exit optical element is made larger than the slab cross section, the influence of distortion on the optical path at the seal / support position of the refrigerant can be further reduced, and the beam quality and output stability of the laser can be further improved. There is an effect that can be improved.

Furthermore, since the beam entrance / exit optical element and the end face of the slab medium are joined by optical joining (optical contact), there is no absorption of the laser beam at the interface, which is excellent in light resistance strength, and is large. There is an effect that a solid-state laser having excellent beam quality and output stability can be obtained even with respect to peak output.

[Brief description of drawings]

FIG. 1 is a sectional view showing a solid-state laser device according to a first embodiment of the present invention.

FIG. 2 is a partial sectional view showing a solid-state laser device according to a second embodiment of the present invention.

FIG. 3 is a partial sectional view showing a solid-state laser device according to a third embodiment of the present invention.

FIG. 4 is an exploded perspective view of a medium support portion of a conventional solid-state laser device.

FIG. 5 is a sectional view showing a conventional solid-state laser device.

FIG. 6 is a side sectional view showing a conventional O-ring seal / support state of a solid-state laser device.

[Explanation of symbols]

1 Slab type laser medium 1a Optically smooth surface of laser medium 1b Beam entrance / exit end face of laser medium 2 Sealant 3b Refrigerant 5 Beam entrance / exit optical element 5a Surface not contributing to beam propagation of beam entrance / exit optical element 10 Laser beam

Claims (3)

[Claims] 1. A fixed laser in which a laser beam propagates in a slab-type laser medium having a pair of opposing optically smooth surfaces and having a substantially rectangular cross section while performing total internal reflection between the optically smooth surfaces. In the apparatus, a laser beam entrance / exit end face of the laser medium is provided with a beam entrance / exit optical element transparent to the laser beam, and the laser beam is passed through the laser entrance / exit optical element via the beam entrance / exit optical element. It is characterized in that the laser medium is made to enter and exit the medium, and the cooling medium for cooling the laser medium is sealed on the surface of the beam entrance and exit optical element that does not contribute to beam propagation. Solid-state laser device. 2. The solid-state laser device according to claim 1, wherein the cross section of the beam entrance / exit optical element orthogonal to the laser beam propagation direction is larger than the cross section of the laser medium. 3. The fixed laser device according to claim 1, wherein the beam entrance / exit optical element is joined to the end face of the slab type laser medium by optical joining.