JPH04196374A - Resonator and pattern light generating device - Google Patents

Abstract

PURPOSE:To decrease the radiation energy density at the surface of a polarizing element and to enhance high power operation without deteriorating a resonator in service life by a method wherein a beam magnifier is provided to enlarges a beam which impinges on a polarizing element in diameter. CONSTITUTION:A polarizing plane rotational element 4 is provided between a laser rod and one of a pair of reflective mirrors 3A and 3B. A beam magnifier 5 is provided between the laser rod 2 and a polarizing element 6 so as to enable a laser beam emitted from the laser rod 2 to be enlarged in diameter and made to impinge on the polarizing element 6. At this point, as the beam magnifier 5 enables a laser beam emitted from the laser rod 2 to impinge on the polarizing element enlarging it in diameter, radiation energy density can be reduced to a loss threshold or below at the surface of the polarizing element 6, so that a polarizer can be prevented from deteriorating in service life even if the laser rays becomes high in intensity. By this setup, radiation energy can be lessened in density at the surface of a pattern forming means, and a laser can be enhanced in output power.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state laser resonator and a laser pattern light generation device using the resonator.

[Conventional technology]

BACKGROUND ART Conventionally, as a resonator for a solid-state laser, a type called a polarization coupling type is known in which a laser beam having a size approximately equal to the diameter of a laser rod is obtained from a polarizing element. Further, Japanese Patent Application Laid-Open No. 11088/1988 discloses a device in which a liquid crystal element for pattern formation is provided inside the polarization coupling type resonator.

[Invention tries to solve the problem lol! Title]

Among the above-mentioned conventional technologies, the polarization coupling type was developed for low-power machines for physical and chemical use, and had the following problems when used as a high-power machine for laser processing.

First, the laser proof strength of the polarizing element for extracting laser light is low, and the element is easily damaged. Second, as the output increases, the excitation energy irradiated to the laser rod increases, resulting in uneven temperature distribution within the rond. This non-uniform temperature distribution within the rond generates a refractive index distribution within the lot, disturbs the laser polarization characteristics, and causes the intensity of the output laser beam to become non-uniform within the beam cross section.

Furthermore, in a polarization-coupled resonator equipped with a liquid crystal element for pattern formation, the liquid crystal element is located at a position facing the laser rod, so the transmission binary energy density is high, and the liquid crystal element is Lifespan will be limited. Further, since the diameter of the pattern forming region was small and approximately equal to the laser rod diameter, the pattern definition was not sufficient.

An object of the present invention is to obtain a high-output, uniformly linearly polarized laser beam. Another object of the present invention is to stably output large-diameter pattern light directly from the resonator.

[Means for Solving Problem 1] The above problem is solved by a laser rod, a pair of reflecting mirrors disposed with the laser rod in between, and a gap between the laser rod and one of the pair of reflecting mirrors. a polarization plane rotating element disposed between the laser rod and the other of the pair of reflecting mirrors; This is achieved by including a beam expander disposed between the laser rod and the polarizing element to expand the beam diameter of the beam from the laser rod and making it incident on the polarizing element.

The above problem is also solved by arranging a first reflecting mirror, a polarization plane rotating element, a laser rod, a beam expander, a polarizing element, and a second reflecting mirror in this order at least on the optical axis, and the beam expander This can also be achieved by using a resonator that allows laser light with a beam diameter larger than the diameter of the laser rod to enter the polarizing element.

The other object described above is achieved by a pattern generating device configured by arranging a pattern forming means on the optical path of the beam expanded by the beam expander of the resonator according to claim 1 or 2.

The other object described above is also achieved by the pattern generating device according to claim 3, wherein the pattern forming means is made of liquid crystal.

The other object described above is also achieved by the pattern generating device according to claim 3 or 4, wherein the pattern forming means is arranged within the resonator.

Another problem described above is that a part of the optical path between the laser rod and the beam expander is an optical fiber, and a second polarizing element is arranged on the optical path between the pattern forming means and the beam expander. This can also be achieved by the pattern generator according to claim 5, further comprising a third reflecting mirror that causes the beam reflected by the second polarizing element to enter the second polarizing element again.

[Effect]

A beam expander disposed between the laser rod and the polarizing element expands the beam diameter of the beam coming out of the laser rod, and the beam is incident on the polarizing element. Since the beam diameter is expanded,
It becomes possible to reduce the irradiation energy density on the surface of the polarizing element to below the damage threshold, and even if the output of the laser beam becomes high, the life of the polarizing element is prevented from becoming short. The polarization plane rotation element placed between the laser rod and the reflector is
The shift in the polarization plane caused by passing through the laser rod is corrected by passing through the polarization plane rotating element twice to reverse the phase and directing it toward the laser rod again. By this correction, the irradiation energy density in the beam cross section of the output linearly polarized beam is made uniform.

In addition, since the pattern forming means is placed on the optical path of the beam expanded by the beam expander, pattern light is formed with low irradiation energy density, and the pattern light passes through the laser rod again to be optically amplified. be done. Therefore, the irradiation energy density on the surface of the pattern forming means is reduced, making it possible to prevent the pattern forming means from being damaged by the irradiated laser beam, and to stably obtain a laser beam with a large diameter and the necessary output. be able to.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. 1st
- The resonator 1 shown in the figure has a laser rod 2 with a diameter of 10+n.
, a reflector 93A disposed on the optical axis at the rear of the laser rod 2 (with the final laser emission direction being the front) with the polarization plane rotation element 4 sandwiched between the laser rod 2 and the laser rod 2; 2, and the beam diameter D2 is 4.
A beam expander 5 that expands to 0 m, a polarizing element 6 placed on the front optical axis of the beam expander 5, and a polarizing element 6 placed on the optical axis (reflected optical axis) of the light reflected by the polarizing element 6. A reflex!
3B, and a laser output cuff is obtained from the polarizing element 6 in the output optical axis direction.

The resonator 1 having the above configuration operates as follows. Among the laser beams 8 that go from the laser rod 2 through the beam expander 5 to the polarizing element 6, the P-polarized light 9 passes through the polarizing element 6 and is output in the direction of the output optical axis, and the S-polarized light 10 is outputted by the polarizing element 6. It is reflected in the direction perpendicular to the optical axis (direction of the reflected optical axis) and is reflected by the reflecting mirror 3.
At B, the light is reflected toward the polarizing element 6 along the reflected optical axis. The S-polarized light reflected by the reflection 13B and incident on the polarizing element 6 is again reflected by the polarizing element 6 in a direction parallel to the output optical axis, and returns to the laser rod 2 via the beam expander 5. The light returning to the laser rod 2 passes through the laser rod 2, passes through the polarization plane rotation element 4, and then turns around the reflecting mirror 3A and returns to P.
The light becomes polarized light 9, passes through the polarizing element 6, and becomes a laser output cuff from the resonator 1.

If the diameter of the laser rod 2 is Dl, and the beam diameter when passing through five beam expanders is D2, the diameter of the laser rod 2 is about 10 mm at most, and the energy required for laser processing of laser markers, etc. is about IOJ, so the beam If no magnifying device is used, the irradiation energy density on the surface of the polarizing element reaches 9 J/cdL2. This value exceeds 2 to 5 J/d, which is said to be the standard laser proof strength of a polarizing element, and the polarizing element 6 is damaged. For this reason, such a polarization-coupled high-output device could not be realized. In this example,
The beam diameter D2 is expanded to 40 cm by the beam expander 5, and the irradiation energy density on the polarizing element surface is approximately 0.6 J/c.
xj. Further, in this embodiment, the beam cross-sectional shape is enlarged while remaining circular, but depending on the method of utilizing the laser output, the beam cross-sectional shape may be shaped and enlarged to a rectangular shape.

According to this example, a high-output, large-diameter linearly polarized laser could be obtained without limiting the life of the polarizing element of the polarization-coupled resonator.

Next, a patterned light generating device 17, which is a second embodiment of the present invention, will be explained with reference to FIG. This example and the first
This embodiment differs from the first embodiment in that a liquid crystal element 11 as a pattern forming means is disposed between the polarizing element 6 and the reflection 1 (3B) of the first embodiment, and the polarizing element 6 An absorbing plate 14 is disposed at a position opposite to the reflecting mirror 3B with the absorbing plate 14 interposed therebetween.The absorbing plate 14 is disposed outside the resonator 1.

As in the case of the large embodiment, among the laser beams 8 which go from the laser rod 2 through the beam expander 5 to the polarizing element 6, the P-polarized light 9 passes through the polarizing element 6 and is output in the direction of the output optical axis. The S-polarized light 10 is reflected by the polarizing element 6 in a direction perpendicular to the output optical axis (reflected optical axis direction). In this embodiment, the S-polarized light 10 reflected by the polarizing element 6 passes through the liquid crystal element 11, is reflected by the reflecting mirror 3B, and while passing through the liquid crystal element 11 again, the processing S polarized light 12 that reflects the pattern information of and P polarized light 13 that is unnecessary.
is converted into The unnecessary P-polarized light 13 passes straight through the polarizing element 6 and is absorbed by the absorption plate 4 outside the resonator 1.

The S-polarized light 12 reflecting the pattern information is reflected by the polarizing element 6 in the direction of the beam expander 5 . Laser rod 2. The light passes through the polarization plane rotation element 4 and enters the reflecting mirror 3A. The light incident on the reflection 1ft3A is reflected again in the direction of the laser rod 2 and passes through the polarization plane rotation element 4. Laser rod 2. The light enters the polarizing element 6 through the beam expander 5, but is amplified while traveling back and forth through the laser rod 2, and the polarization plane is rotated 90 degrees by traveling back and forth through the polarization plane rotation element 4, reflecting pattern information. Since it becomes P-polarized light, it passes straight through the polarizing element 6 and is extracted as a laser output 15 reflecting the pattern information.

According to this embodiment, the patterned light reflecting the pattern information is generated at a location with low energy density, and then the patterned light is amplified, so that the energy for irradiating the liquid crystal element is reduced, and the life of the liquid crystal element is extended. Large-diameter pattern light can be obtained.

A patterned light generating bag [17] which is a third embodiment of the present invention will be described with reference to FIG. The difference between this embodiment and the first embodiment is that in this embodiment, the laser rod 2 and the beam expander 5 are connected by an optical fiber 16, and the beam expander 5 and the polarizing element are connected. A liquid crystal element 11 on which pattern information is set as a pattern forming means is arranged between 6 and 6, and a second polarizing element 19 is arranged between the liquid crystal element 11 and the beam expander 5, The reflecting mirrors 3C are arranged on the reflection optical axis of the element unit 9, respectively.

The beam 20 entering the optical fiber 16 is depolarized due to the depolarization property of the optical fiber, and enters the polarizing element 19 as a beam 21 via the beam expander 5 . The beam 21 incident on the polarizing element 19 is divided into P polarized light 22 and S polarized light 23.
The S-polarized light 23 is reflected and enters the reflecting mirror 3C. The S-polarized light 23 is reflected again by the reflecting mirror 3C, enters the polarizing element 19, passes through the beam expander 5, and enters the optical fiber 16 again. S-polarized light 2 incident on the optical fiber 16
3 is made non-polarized by the optical fiber 16, and the laser rod 2
is amplified by going back and forth. The amplified beam is beam 2
1 and repeat the above operation.

On the other hand, the P-polarized light 22 separated by the polarizing element 19 passes through the liquid crystal element 11 and enters the polarizing element 6 as pattern light reflecting pattern information.

Next, the P polarized light 25 reflecting the pattern information with the polarizing element 6
and S-polarized light 24 that does not reflect pattern information, and P-polarized light 25 is extracted as laser output 15.

The S-polarized light 24 is reflected by the reflecting mirror 3B and passes through the polarizing element 6. Liquid crystal element 11. The light enters the optical fiber 16 through the polarizing element 19 and the beam expander 5, is made non-polarized by the optical fiber 16, similar to the S-polarized light 23, and is amplified by traveling back and forth through the laser rod 2. The amplified beam repeats the above operation as beam 21.

According to this embodiment, even in a laser rod in which the uniformity of the polarization plane is lost during the beam propagation process within the laser rod, the beam is made non-polarized when it passes through the optical fiber 16. Since the linearly polarized light is incident on the polarizing element] 9, the liquid crystal element 11 can be irradiated with linearly polarized light with a stable output, and the output level in the beam cross section of the resulting patterned light is made uniform. Furthermore, since the laser rod 2 and the polarizing element are coupled through the optical fiber 16, there is a large degree of freedom in selecting the position of the polarizing element, which is the laser output section.

In addition, a liquid crystal element for pattern formation is provided inside the resonator,
Since the resulting patterned light is amplified and output, the irradiation energy density of the beam irradiated onto the liquid crystal element can be reduced, which has the effect of extending the life of the liquid crystal element.

Furthermore, since the laser pattern light can be stably output directly from the resonator, it is possible to miniaturize the device and improve the efficiency of laser light utilization. In addition, since a large-diameter pattern light can be obtained, a high-definition pattern can be drawn by forming a reduced image.

In addition, in the second and third embodiments described above, an example was explained in which a liquid crystal element was used as the pattern forming means, but the pattern forming means does not necessarily have to be a liquid crystal. For example, as shown in FIG. 4A, the surface of a glass plate 41 may be coated with a reflective coating 42 in a necessary pattern, or as shown in FIG. 4B, a glass plate 43 may have a necessary pattern of unevenness. , and a reflective coating 44 is provided on the concave or convex portions.
It may also be applied. Further, instead of the reflective coating 44, fine irregularities may be provided on the surface of the glass plate 43.

〔Effect of the invention〕

As explained above, according to the present invention, since a beam expander is provided to expand the diameter of the beam incident on the polarizing element of the polarization-coupled resonator, it is possible to reduce the irradiation energy density on the surface of the polarizing element. This has the effect of increasing the output without shortening the life of the resonator.

Furthermore, since the liquid crystal element for pattern formation is provided inside the resonator, it becomes possible to output laser pattern light directly from the resonator, which has the effect of downsizing the device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of main parts of a first embodiment of the present invention, FIG. 2 is a block diagram showing the structure of main parts of a second embodiment of the invention, and FIG. FIG. 4A and FIG. 4B are sectional views showing examples of pattern forming means. 1...Resonator, 2...Laser rod, 3A, 3B. 3C... Reflector, 4... Polarization plane rotation element, 5... Beam expander, 6, 19... Polarizing element, 7, 15. Laser output, 11... Pattern forming means (liquid crystal element) ,1
6... Optical fiber, 17... Pattern light generator.

Claims (1)

[Claims] 1. A laser rod, a pair of reflecting mirrors disposed with the laser rod in between, and a polarizing element disposed between the laser rod and one of the pair of reflecting mirrors. a resonator which obtains a laser beam output from the polarizing element, a polarization plane rotating element disposed between the laser rod and the other of the pair of reflecting mirrors, and the laser rod and the polarizing element. and a beam expander disposed between the laser rod and the beam expander to expand the beam diameter of the beam from the laser rod and make the beam incident on the polarizing element. A reflecting mirror, a polarization plane rotation element, a laser rod, a beam expander, a polarizing element, and a second reflecting mirror are arranged in this order, and the beam expander directs the laser beam with a beam diameter larger than the diameter of the laser rod. A resonator 3 that is incident on a polarizing element, comprising the resonator according to claim 1 or 2, and pattern forming means disposed on the optical path of the beam expanded by a beam expander of the resonator. 4. A pattern generating device 5 according to claim 3, wherein the pattern generating device 4 is made of liquid crystal, and the pattern forming device is disposed within a resonator. In the pattern generator 6 according to item 3 or 4, a part of the optical path between the laser rod and the beam expander is an optical fiber, and the second polarized light is arranged on the optical path between the pattern forming means and the beam expander. Claim 5, further comprising a third reflecting mirror that makes the beam reflected by the second polarizing element enter the second polarizing element again.
The pattern generator described in