JPH07106669A - Laser oscillator - Google Patents

Abstract

PURPOSE:To provide a laser resonator in which a laser light having uniform power distribution can be taken out from a pumping space having a gain distribution. CONSTITUTION:A conical mirror 10 having inner reflective plane of 90 deg. vertical angle is employed as a rear mirror. The apex 10a and the optical axis 10b of the conical mirror 10 are aligned with the optical axis 11 of laser resonator. Furthermore, the conical mirror 10 and an output mirror 2 are disposed oppositely on the opposite sides of laser pumping space 4 and a mode selector 3 is interposed between the pumping space 4 and the output mirror 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser resonator having an improved mirror structure.

[0002]

_2. Description of the Related Art FIG. 5 shows an example of a conventional stable laser resonator in a CO ₂ laser oscillator. That is, on both sides of the laser excitation space 4, there are a rear mirror 5 and an output mirror 2 for oscillating and amplifying laser light.
Are arranged so as to face each other, and the rear mirror 5 and the output mirror 2 are provided between the laser excitation space 4 and the output mirror 2.
A mode selector 3 for defining the transverse mode of the laser light oscillated and amplified by is provided.

In such a laser resonator, the oscillation transverse mode (spatial intensity distribution) of the laser is generally
It is determined by the cavity length of the laser, the curvature of the mirror used and the mode selector that limits the oscillation volume. Further, the alignment of the resonator is performed by adjusting the installation angles of the output mirror 2 and the rear mirror 5.

In the transverse flow type CO ₂ laser oscillator, the gain coefficient of laser oscillation (hereinafter referred to as gain) is not uniform in the excitation space of the laser light, but is distributed in the laser gas flow direction. That is, FIG. 6 shows a typical gain distribution in the excitation space cross section of the laser light when the laser oscillation is not performed. When the laser light is extracted from the pumping space where such a gain distribution exists, it is expected that the gain distribution will be as shown in FIG. This means that when the resonator mirrors 2 and 5 are directly opposed to the excitation space of the laser light, the emitted light becomes asymmetric with respect to the laser oscillation optical axis 6, and the power density on the upstream side of the laser gas increases. It is shown that.

[0005]

However, the conventional laser resonator as described above has the following drawbacks. That is, FIG. 8 shows an example of the mode cross section of the laser light extracted from the lateral flow type stable laser resonator. As is clear from the figure, since the power density on the upstream side of the laser gas (the side where the gain distribution is high) becomes high, to make this a symmetrical mode, the resonator mirror 2,
It is necessary to shift the alignment of No. 5 from the position directly facing, so that the oscillation efficiency is deteriorated and the shape (outer shape) of the entire mode becomes asymmetric. Moreover, since the resonator mirror is displaced from the position directly facing, the margin of stability against misalignment is reduced, and the resonator becomes more sensitive to changes in the external environment.

If oscillation is performed in a mode as shown in FIG. 8 with priority given to efficiency, there will be a portion where the load is locally high with respect to the optical components, which is not preferable especially for a transmissive mirror and the Since there is a possibility that the asymmetry will be amplified in the case of transmitting, the power distribution has been desired to be as uniform as possible.

The present invention has been proposed to solve the above-mentioned problems of the prior art, and its object is to extract a laser beam having a uniform power distribution from an excitation space in which a gain distribution exists. It is to provide a laser resonator capable of

[0008]

According to a first aspect of the present invention, there is provided a laser resonator including an output side mirror and another mirror arranged opposite to the output side mirror with a laser excitation space interposed therebetween, and the other mirror. However, the reflective surface has an apex angle of 90.
It is a conical mirror having an inner cone shape of 0 °, and is arranged such that the apex of the apex angle thereof substantially coincides with the central optical axis of the output side mirror.

The invention described in claim 2 is the same as claim 1.
In the laser resonator described, the output side mirror,
It is characterized in that the reflecting surface is composed of a spherical surface, a cylindrical surface, or a flat surface, and is a semitransparent mirror for laser light.

Further, according to a third aspect of the present invention, in a laser resonator composed of three or more mirrors including an output side mirror, the mirror located at the reflection-side final end of the laser oscillation light has its reflection surface. Is a conical mirror having a conical inner surface shape with an apex angle of 90 °, and the apex of the apex angle is arranged so as to substantially coincide with the central axis of the laser oscillation light.

[0011]

In the laser resonator of the present invention, the other mirror, which is arranged to face the output side mirror with the laser pumping space in between, is composed of a conical mirror having a conical inner surface whose reflection surface is 90 ° in vertical angle, By arranging so that the apex of the apex coincides with the laser oscillation optical axis, each time the laser light reciprocates in the excitation space, it is possible to form a luminous flux that is symmetrical with respect to the laser oscillation optical axis on the outward path and the return path. it can. As a result, even if there is a gain distribution in the pumping space, it is possible to extract high-quality laser light whose intensity distribution is symmetrical with respect to the laser oscillation optical axis.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the laser resonator according to the present invention will be specifically described below with reference to FIGS. The laser resonator of this embodiment is a stable resonator in which the reflecting surface of the output mirror is concave. Further, the same members as those of the conventional type shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, as shown in FIG.
As the rear mirror, a conical mirror 10 whose mirror reflection surface has an inner cone shape with an apex angle of 90 ° is used. The apex 10a of the apex angle and the optical axis 10b of the conical mirror 10 are arranged to be on the same straight line as the laser oscillation optical axis 11 of the laser resonator. Further, the conical mirror 10 and the output mirror 2 are arranged so as to face each other with the laser excitation space 4 interposed therebetween, and further, a mode selector 3 is arranged between the laser excitation space 4 and the output mirror 2. 2 shows the mirror reflection surface of the conical mirror 10 used in this embodiment.

The laser resonator of this embodiment having such a structure operates as described below. Conical mirror 10
The incident light on is reflected by an optical path as shown in FIG. That is, the light is emitted from the point A and the conical mirror 1
Light incident on the inner surface of the cone of 0 (point P) at an incident angle of 45 ° is
The light is reflected at a reflection angle of 45 ° and is incident on the inner surface of the cone (point Q) of the conical mirror 10 at a position symmetrical with respect to the incident point (point P) with respect to the laser oscillation optical axis 11 at an incident angle of 45 °. Here, it is reflected again at a reflection angle of 45 ° and is reflected at a point B spatially symmetric with respect to the laser oscillation optical axis 11. Therefore,
Each time the laser light reciprocates in the excitation space 4, the light flux becomes a light flux symmetrical with respect to the laser oscillation optical axis in the forward path and the backward path.

On the other hand, the gain distribution in the pumping space of the cross flow type CO ₂ laser oscillator decreases almost uniformly in the gas flow direction as shown in FIG. 7, so that the laser taken out by the laser resonator of this embodiment is used. The light has a mode in which the intensity distribution is symmetric with respect to the laser oscillation optical axis.

As described above, according to the laser resonator of the present embodiment, by using the conical mirror 10 as the rear mirror of the laser resonator, even when the gain distribution exists in the excitation space, the laser oscillation optical axis can be obtained. In this mode, the intensity distribution is symmetrical, and good quality laser light can be extracted.

The present invention is not limited to the above-described embodiment, but the apex angle apex 10a of the conical mirror 10 is not limited thereto.
However, if it is arranged so as to be on the laser oscillation optical axis of the laser resonator, the optical axis 10b is not necessarily the laser oscillation optical axis 1.
It does not have to be on the same straight line as 1. That is, the conical mirror 10
Since the apex angle of the conical mirror 10 is 90 °, if the apex 10a of the apex angle of the conical mirror 10 is located on the laser oscillation optical axis, the light incident parallel to the laser oscillation optical axis will be conical. This is because the laser beam is reflected by and is always emitted parallel to the laser oscillation optical axis.

The present invention can also be applied to a laser resonator composed of three or more mirrors, as shown in FIG. That is, in FIG. 4, one or more folding mirrors 20 are arranged on the laser oscillation optical axis, and the incident light reflected by these folding mirrors 20 is a conical mirror arranged at the final end on the reflection side of the laser oscillation light. 10 is configured to be reflected symmetrically with respect to the laser oscillation optical axis. Also in this case, the same effect as that of the above-described embodiment can be obtained.

Further, the same effect can be obtained not only in the stable resonator but also in the unstable resonator. Further, it goes without saying that the laser can be applied to laser oscillators other than the cross current CO ₂ laser oscillator.

[0020]

As described above, according to the present invention, the other mirror, which is arranged to face the output side mirror across the laser excitation space, has a conical inner surface whose reflection surface is 90 °. It is composed of a mirror, and is arranged so that the apex of the apex of the mirror substantially coincides with the central optical axis of the output side mirror. Therefore, even if there is a gain distribution in the excitation space, excellent symmetry and good quality A laser resonator capable of extracting laser light can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a laser resonator of the present invention.

FIG. 2 is a perspective view showing a mirror reflecting surface of a conical mirror used in the present invention.

FIG. 3 is a diagram showing an optical path of incident light on a conical mirror.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

FIG. 5 is a configuration diagram showing an example of a conventional stable laser resonator.

FIG. 6 is a diagram showing a gain distribution in a laser gas flow direction when laser oscillation is not performed.

FIG. 7 is a diagram showing a gain distribution in a laser gas flow direction when laser oscillation is performed.

FIG. 8 is a mode cross-sectional view of laser light extracted from a cross-flow type stable laser resonator.

[Explanation of symbols]

 2 ... Output mirror 3 ... Mode selector 4 ... Excitation space 5 ... Rear mirror 6 ... Laser oscillation optical axis 10 ... Conical mirror 10a ... Apex 10b ... Optical axis 11 ... Laser oscillation optical axis 20 ... Folding mirror

Claims (3)

[Claims] 1. A laser resonator comprising an output-side mirror and another mirror arranged opposite to the output-side mirror with a laser pumping space interposed therebetween, wherein the other mirror has a reflection inner surface of a conical inner surface having an apex angle of 90 °. A laser resonator, which is a conical mirror having a shape, and is arranged such that the apex of the apex angle thereof substantially coincides with the central optical axis of the output side mirror. 2. The output-side mirror is characterized in that its reflecting surface is formed of a spherical surface, a cylindrical surface, or a flat surface, and is a semi-transmissive mirror for laser light. Laser cavity. 3. A laser resonator composed of three or more mirrors including an output-side mirror, wherein the mirror located at the final end on the reflection side of the laser oscillation light has a conical inner surface whose apex angle is 90 °. Is a conical mirror, and the apex of the apex angle is arranged so as to substantially coincide with the central axis of laser oscillation light.