JP3540741B2 - Variable cavity length laser cavity and pulsed laser light source device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of this application relates to a variable cavity length laser resonator. More specifically, the invention of this application relates to a small-cavity-length-variable laser resonator capable of easily extending a laser resonator length, and a pulse laser light source device including the same.
[0002]
[Prior art and its problems]
Conventionally, in a laser resonator, the length of the resonator is extended without largely changing the transverse mode size inside the laser resonator (the diameter at which the Gaussian beam intensity of the TEM matched to the resonator becomes 1 / e ² of the peak intensity). As a method, an image relay system in which two convex lenses as shown in FIG. 7 are combined with a position A on the laser optical path of an external resonator designed with a constant resonator length as shown in FIG. 6 is used. A method of incorporating and taking a configuration as shown in FIG. 8 is widely known.
[0003]
In this method, there has been a problem that the size of the entire laser resonator becomes large, and accordingly, it becomes mechanically unstable. When a laser having a high peak intensity is used, a discharge is generated by the laser beam at the focal position of the convex lens system. To prevent this, the convex lens system needs to be sealed in a vacuum. Furthermore, it is pointed out that only one resonator length can be selected for one optical component of an image relay, and it takes time and effort to adjust when changing the resonator length. I have.
[0004]
Therefore, the invention of this application has been made in view of the circumstances described above, and realizes extension of the resonator length without largely changing the size of the entire resonator, and has high mechanical stability and high mechanical stability. Even when dealing with an intense laser, a vacuum for preventing discharge is not required, and it is possible to select a plurality of resonator lengths for one set of optical components used to extend the resonator length. Another object of the present invention is to provide a laser resonator in which the length of the resonator can be easily readjusted. Furthermore, a pulse laser light source device provided with such a laser resonator is provided.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present application provides, as a first invention, a resonator that resonates laser light emitted from a laser gain medium, and a part of a reflecting mirror provided in the resonator faces the resonator. This is a two-fold high-reflection mirror with curvature, and the number of times of folding of the laser light in the multi-fold high-reflection mirror with curvature is changed by adjusting the incident angle of the laser light to the multi-fold high reflectance mirror with curvature. And a variable resonator length laser resonator characterized in that the resonator length can be set arbitrarily.
[0006]
Further, the present invention relates to a second invention, as a second invention, a first reflecting mirror for reflecting a laser beam emitted from a laser gain medium, and a multi-fold high reflectance with a curvature by reflecting the laser beam reflected by the first reflecting mirror. A second reflecting mirror for entering the mirror, a third reflecting mirror for reflecting the laser light emitted from the multi-turn high reflectance mirror with curvature, and a first reflecting mirror for the laser light reflected by the third reflecting mirror. A fourth reflecting mirror for entering the reflecting mirror, and by changing the installation angle of the second reflecting mirror, the angle of incidence of the laser light on the multi-fold high-reflection mirror with curvature is adjusted, and the multi-fold height with curvature is adjusted. A variable cavity length laser cavity, wherein the number of times laser light is folded back in the reflectivity mirror is changed so that the cavity length can be arbitrarily set.
[0007]
Further, this application also provides, as a third invention, a pulsed laser light source including the above-described variable cavity length laser resonator.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an example of a configuration of a main part of a variable cavity length laser resonator according to the invention of the present application.
[0009]
For example, as illustrated in FIG. 1, in the variable cavity length laser resonator of the invention of this application, a part of the reflecting mirror is two opposed multi-turn high reflection mirrors with curvature (4) with a curvature. By adjusting the angle of incidence of the laser beam on the multi-fold high reflectance mirror with curvature (4), the number of times the laser beam is folded in the multi-fold high reflectance mirror with curvature (4) is changed, and the resonator length is reduced. It can be set arbitrarily.
[0010]
To explain this further, in the example of FIG. 1, the laser light emitted from the laser gain medium (1) has its optical path changed by the first reflecting mirror (2) to the second reflecting mirror (3). Incident. The second reflecting mirror (3) is for making a laser beam incident on two opposed multi-turn high-reflecting mirrors with curvature (4), and is reflected by the second reflecting mirror (3). The reflected laser light is incident on one of the multiple-fold high-reflectivity mirrors with curvature (4). Then, the laser light is repeatedly reflected a plurality of times between the multiple-fold high-reflectance mirrors with curvature (4). After a plurality of reflections, the laser light emitted from the multi-turn high-reflection mirror with curvature (4) is reflected by the third reflection mirror (5) and is incident on the fourth reflection mirror (6). . The fourth reflecting mirror (6) makes the incident laser light re-enter the first reflecting mirror (2).
[0011]
Thus, in the variable resonator length laser resonator of the invention of this application, the laser light is repeatedly reflected between two opposed multi-fold high reflection mirrors with curvature (4), so that the resonator length can be reduced. The extension has been realized. That is, the length of the resonator can be freely changed by changing the number of times of reflection of the laser light between the multiple reflection mirrors with curvature (4) with curvature.
[0012]
More specifically, in FIG. 1, a broken line connecting the second reflecting mirror (3) and the third reflecting mirror (5) indicates a laser light path in the case where the multi-turn high reflectance mirror with curvature is not used. On the other hand, a solid line connecting the second reflecting mirror (3) and the third reflecting mirror (5) indicates a case in which reciprocating reflection is repeated seven times between two curved multi-reflection high reflectance mirrors (4). 3 shows the laser light path of FIG. It is clear that the length of the resonator is much longer than that of the broken line. The interval (7) between adjacent reflection points of the multi-turn high reflectance mirror with curvature (4) is substantially equal regardless of the number of reciprocating reflections, as shown in FIG.
[0013]
In the laser resonator shown in FIG. 1, by changing the installation angle of the second reflecting mirror (3), the angle of incidence of the laser light on the multi-turn high reflectance mirror with curvature (4) is adjusted, and the laser light is adjusted. Can be controlled. Of course, by changing the angle of incidence of the laser beam on the multi-fold high reflectance mirror with curvature (4), the emission angle of the laser beam from the multi-fold high reflectance mirror with curvature also changes. It goes without saying that the installation angles of the third reflecting mirror (5) and the fourth reflecting mirror (6) also need to be adjusted accordingly.
[0014]
In the variable cavity length laser resonator of the invention of this application, since there is no optical system for narrowing the laser beam system, even when applied to a laser having a high peak intensity, air discharge is not caused. Absent.
[0015]
Then, by providing the pulse laser light source with the variable resonator length laser resonator of the invention of this application, easy change of the pulse length is technically realized. As described above, the variable resonator length laser resonator according to the invention of this application realizes the extension of the resonator length without substantially changing the transverse mode size. The pulse laser light source including the laser resonator is also small in size and has high mechanical stability.
[0016]
Of course, the configuration of the small resonator length variable laser resonator of the invention of this application is not limited to the ring resonator type configuration illustrated in FIG. Needless to say, the length of the resonator can be easily changed by incorporating the multi-fold high reflectance mirror.
[0017]
The invention of this application has the features as described above. Hereinafter, embodiments will be described with reference to the accompanying drawings, and embodiments of the invention of this application will be described in more detail.
[0018]
【Example】
Here, the effectiveness of the variable cavity length laser resonator according to the invention of the present application illustrated in FIG. 1 was examined by simulation, and will be described.
[0019]
In the simulation, as illustrated in FIGS. 2A, 2B, and 2C, the Z-type ring resonator including the reflecting mirrors (2), (3), (5), and (6) has a resonator length of 78 cm. In this ring resonator, two multiply folded high reflectivity mirrors (4) having a curvature of 20 m were placed so as to completely face each other at an interval (mn) of 18 cm. The intervals between the reflecting mirrors (2), (3), (5), (6) and the multi-folded high-reflectance mirror with curvature (4) are as follows: a-b = 20 cm, b-c = 18 cm, cd-d = 22 cm , D-a = 18 cm, b-m = 18 cm, nc = 18 cm. The curvature of the reflecting mirrors (2) and (6) is 8 m, and the curvature of the reflecting mirrors (3) and (5) is ∞m.
[0020]
As shown in FIGS. 2A, 2B, and 2C, the number of round-trip reflections of laser light between the curved multi-fold high-reflectance mirrors (4) in the cavity length variable laser resonator set in this manner. Was calculated 0 times, 3 times, and 7 times, that is, when the cavity length was 78 cm, 222 cm, and 330 cm, the transverse mode size on the laser light path in the cavity was simulated and calculated. Here, the transverse mode size refers to a diameter of a portion where the intensity of the Gaussian beam of the TEM ₀₀ matched to the laser resonator is 1 / e ^{2 of the} peak intensity.
[0021]
3 to 5 show the calculation results of the transverse mode size in the cases of FIGS. 2A, 2B, and 2C, respectively. In addition, the starting point (point of 0 mm) of the laser beam path was the surface of the reflecting mirror (6).
[0022]
As is apparent from FIGS. 3 to 5, even if the resonator length is greatly changed from 78 cm to 330 cm, the transverse mode size becomes almost constant (1.2 mm ± 0.07 mm), which impairs the characteristics of laser light. It can be seen that laser resonance can be performed without any problem.
[0023]
【The invention's effect】
As described in detail above, the invention of this application realizes the extension of the resonator length without largely changing the size of the entire resonator, has high mechanical stability, and prevents discharge even when handling a high-intensity laser. It is possible to select a plurality of resonator lengths for one set of optical components used for extending the resonator length without requiring a vacuum, and further, it is easy to readjust the resonator length. A new variable cavity length laser resonator is provided.
[0024]
Further, a pulse laser light source device whose pulse length can be easily varied is also provided by this resonator length variable laser resonator. For example, when applied to a nanosecond pulse laser at the Fourier limit, it is possible to easily change the pulse length while maintaining the quality of the Fourier limit, and greatly contribute to the development of nanosecond optical pulse shaping technology. .
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of a main configuration of a variable resonator length laser resonator according to the invention of the present application.
FIGS. 2A, 2B, and 2C respectively show the arrangement of a multi-turn high-reflectance mirror with a curvature and a reflection mirror in an embodiment of a variable resonator length laser resonator according to the present invention; FIG.
FIG. 3 is a diagram illustrating a relationship between an optical path length and a transverse mode size in the case of FIG.
FIG. 4 is a diagram showing a relationship between an optical path length and a transverse mode size in the case of FIG. 2 (B).
FIG. 5 is a diagram showing the relationship between the optical path length and the transverse mode size in the case of FIG. 2 (C).
FIG. 6 is a schematic diagram illustrating a configuration of a laser resonator according to the related art.
FIG. 7 is a schematic diagram showing a configuration of an image relay system for extending a resonator length of a laser resonator according to the related art.
FIG. 8 is a schematic diagram showing a configuration in which an image relay system is incorporated in a laser resonator according to the related art.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 laser gain medium 2 first reflecting mirror 3 second reflecting mirror 4 multi-turn high-reflecting mirror with curvature 5 third reflecting mirror 6 fourth reflecting mirror 7

Claims (3)

A resonator for resonating the laser light emitted from the laser gain medium, wherein a part of a reflecting mirror provided in the resonator is two opposed multi-fold high reflection mirrors with a curvature, and a multi-fold height with a curvature; By adjusting the angle of incidence of the laser beam on the reflectivity mirror, the number of turns of the laser beam in the multi-fold high-reflectance mirror with curvature is changed, and the resonator length can be set arbitrarily. Variable length laser resonator. A first reflecting mirror for reflecting a laser beam emitted from a laser gain medium, a second reflecting mirror for causing the laser beam reflected by the first reflecting mirror to be incident on a multi-turn high reflectance mirror with a curvature, and a curvature A third reflecting mirror for reflecting the laser light emitted from the multi-folded high-reflectance mirror, and a fourth reflecting mirror for making the laser light reflected by the third reflecting mirror incident on the first reflecting mirror. By changing the installation angle of the second reflecting mirror, the angle of incidence of the laser beam on the curved multi-fold high reflection mirror with curvature is adjusted, and the number of times the laser beam is folded in the multi-fold high reflection mirror with curvature is changed. A variable cavity length laser resonator characterized in that the cavity length can be set arbitrarily. A pulse laser light source device comprising the variable resonator length laser resonator according to claim 1.

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