JPH0638530B2 - Q switch laser device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a Q-switch laser device that performs giant pulse oscillation by laser light.

[Technical background of the invention]

Recently, in practical Q-switch laser devices, for example, Q-switch elements having electro-optical properties such as the Pockels effect have been widely used because the high-speed switching elements can perform high-speed switching and the extinction ratio is good.

Moreover, as an optical resonator of such a Q-switch laser,
It has been devised to use a roof prism to make the laser light output change minute with respect to the angle change of the roof prism.

FIG. 3 shows such a conventional Q-switch laser device. In FIG. 3, the laser medium 5 is, for example,
It is YAG. The laser light output from the laser medium 5 is
The light having a plane of polarization parallel to the X axis is reflected as the output laser beam 6, and the light having a plane of polarization parallel to the Y axis is transmitted. And is supplied to the electro-optical element 3 such as a Pockels cell.

When the output laser beam 6 is not obtained, no voltage is applied to the electro-optical element 3. In this case, the beam splitting polarizer 4
Linearly polarized light from is transmitted through the electro-optical element 3 as it is,
It is supplied to the prism 1.

The prism 1 totally reflects light having a polarization plane parallel to the Y axis, and at that time, the polarization plane is converted into a polarization plane parallel to the X axis. Therefore, the light that has passed through the electro-optical element 3 again and is supplied to the beam splitter 4 has a polarization plane parallel to the X axis, and therefore this light is reflected as reflected light 61 and is not output to the laser medium 5. Therefore, the laser medium 5 does not cause stimulated emission and the output laser beam 6 cannot be obtained from the beam splitting polarizer 4.

On the other hand, when obtaining the output laser beam 6, the electro-optical element 3
Is applied with a voltage of about 3000 V at room temperature. In this case, the linearly polarized light from the beam splitter 4 is converted into circularly polarized light by the electro-optical element 3.

The circularly polarized light is totally reflected by the prism 1, supplied again to the electro-optical element 3, and converted into linearly polarized light. This linearly polarized light is supplied to the beam splitting polarizer 4, but since its polarization plane is parallel to the Y axis, almost all is transmitted and supplied to the laser medium 5. Therefore, this light passes through the laser medium 5 and is supplied to the prism 2 where it is totally reflected again, but the reflected light also includes light having a plane of polarization parallel to the X axis.

As a result, of the light that passes through the laser medium 5 from the prism 2 and is supplied to the beam splitter / polarizer 4, light having a polarization plane parallel to the X axis is output as the output laser light 6 and is parallel to the Y axis. Light having a different plane of polarization is transmitted and supplied to the electro-optical element 3, and the above operation is repeated.

As a result, the output laser light 6 is obtained as the output of the Q switch laser device. In this case, the switching of the Q-switch laser device is performed by switching the voltage supplied to the electro-optical element 3.

[Problems of background technology]

In such a Q-switch laser device, as shown in FIG. 5, the laser light extraction ratio from the beam-splitting polarizer 4 is defined by the angle α between the polarization plane 2A of the prism 2 and the polarization plane 4A of the beam-splitting polarizer 4. It is determined by the refractive index of the prism 2.

Therefore, in order to maximize the laser efficiency, it is necessary to adjust the angle α (mechanical adjustment of the position).

4 is a sketch of the prism 1 of FIG.
The prism 1 has a characteristic of a corner reflector in terms of geometrical optics, and has the same effect on polarized light at the time of reflection as a corner reflector of metal reflection.

This is because the P component (vertical component) and the S component (parallel component) of the polarized light alternate between the right-angle prism portion and the roof prism portion while utilizing the total reflection, so that the P component and the S component of the polarized light due to the total reflection. This is because the phase difference shifts of the components cancel each other out.

In such a Q-switch laser device, it is necessary to apply a voltage that causes an optical phase difference of 1/4 wavelength to the electro-optical element 3 at the time of pulse oscillation of the laser, and this voltage is considerably high (about 3000 V).

[Object of the Invention]

This invention has been made to eliminate the above-mentioned conventional drawbacks, and makes it possible to reduce the output change accompanying a minute angle change of the prism to be small and to reduce the voltage applied to the electro-optical element to about half. An object of the present invention is to provide a Q-switch laser device that can easily obtain the maximum efficiency by changing the extraction ratio of laser light by adjusting this voltage.

[Outline of Invention]

The Q-switch laser device of the present invention has a shape in which a roof prism and a right-angle prism having an optical path bending plane orthogonal to the ridgeline thereof are integrally combined, and the polarization planes of incident light and reflected light are the same. And a roof prism and a second prism having a shape in which a right-angled prism having an optical path bending plane parallel to the ridge line thereof are integrally combined are arranged to face each other to form an optical resonator. A laser medium is disposed in the beam splitting polarizer, the laser light emitted from the laser medium is reflected by a beam splitter and the light having a polarization plane parallel to the X axis is reflected, and the light having a plane of polarization parallel to the Y axis is transmitted. An electro-optical element is linearly arranged between the first prism and the first prism, and the electro-optical element converts the linearly polarized laser light into an elliptical polarized light to generate an optical resonator for pulse oscillation of the laser light. Was carried out in, by adjusting the voltage applied to the electro-optical device, in which so as to vary the extraction ratio of the laser beam by changing the elliptical ratio of the elliptical polarization.

Example of Invention

Hereinafter, embodiments of the Q-switch laser device of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of the embodiment. In FIG. 1, a prism 11 and a prism 12 are arranged so as to face each other, and both prisms 11 and 12 constitute an optical resonator.

The prism 11 is similar to the prism 1 shown in FIG. 3, and has a shape in which a roof prism and a right-angle prism having an optical path bending plane parallel to the ridge of the roof prism are integrally combined as shown in FIG. Have.

On the other hand, the prism 12 has a roof prism and an optical path bending plane orthogonal to the ridgeline of the roof prism as shown in FIG. 2, and has a refractive index selected so that the polarization planes of the incident light and the reflected light coincide with each other. Have. The prism 12 has a characteristic of a corner reflector in terms of geometrical optics, and has the same effect as that of a plane mirror on the polarized light at the time of reflection. Therefore, the polarization component of the laser light that coincides with the polarization plane of the beam splitter 14 is 100% electro-optical element 13.
Will reach the side.

The laser light output from the laser medium 15 is supplied to the beam splitter / polarizer 14, and the beam splitter / polarizer 14 transmits light having a plane of polarization parallel to the Y-axis to allow electro-optics such as a Pockels cell. It is designed to be delivered to the element 13.

The light of the plane of polarization parallel to the Y plane is directly the electro-optical element 1
The light is transmitted through the prism 3 and is totally reflected by the prism 11. The prism 11 is arranged so that the polarization planes of the incident light and the reflected light are orthogonal to each other.

In the beam splitting polarizer 14, the polarization component parallel to the X-ray reflected from the prism 11 is output laser light 16
The polarization component parallel to the Y axis passes through the laser medium 15 and is incident on the prism 12, is further reflected, passes through the laser medium 15, and is supplied to the beam splitting polarizer 14. It has become so.

Next, the operation of the Q-switch laser device of the present invention configured as above will be described. The laser light output from the laser medium 15 is supplied to the beam splitting polarizer 14, the light having a polarization plane parallel to the X axis is reflected, and the light having a polarization plane parallel to the Y axis is transmitted as it is to a Pockels cell or the like. It is supplied to the electro-optical element 13.

When the output as the Q-switch laser device is not obtained, no voltage is applied to the electro-optical element 13. That is, the light of the plane of polarization parallel to the Y axis supplied to the electro-optical element 13 is transmitted as it is and is totally reflected by the prism 11. Since the prism 11 is arranged so that the polarization planes of the incident light and the reflected light are orthogonal to each other, the output light from the prism 11 is X
It has a plane of polarization parallel to the axis.

This light passes through the electro-optical element 13 as it is and is reflected by the beam splitting polarizer 14. Therefore, the laser medium 1
Since light does not return to 5, the system does not close. Therefore, in this case, the output laser beam 16 cannot be obtained.

On the other hand, when obtaining output as a Q-switch laser device,
A voltage of, for example, about 1500 V that causes a phase shift of 1/8 wavelength is applied to the electro-optical element 13. Therefore, the light of the plane of polarization parallel to the Y axis from the beam splitting polarizer 14 is
When transmitted through this electro-optical element 13, it is converted into elliptical polarized light.

The converted circularly polarized light is supplied to the electro-optical element 13 again as the circularly polarized light reflected by the prism 11.
In this case, the output light of the electro-optical element 13 becomes almost circularly polarized light and is supplied to the beam splitting polarizer 14, and the polarization component parallel to the X axis is reflected as the output laser light 16 and Y
The polarization component parallel to the axis is transmitted as it is.

The transmitted light of the plane of polarization parallel to the Y-axis is the laser medium 1.
After passing through 5, the light is reflected by the prism 12 while maintaining its polarization plane. Then, this reflected light is again reflected by the laser medium 15.
Light having a plane of polarization parallel to the Y-axis is supplied to the beam splitting polarizer 14 after passing through (the system is closed), and the output laser beam 16 is obtained by repeating the above operation.

In such a Q switch laser device, the adjustment of the laser efficiency is performed by adjusting the voltage applied to the electro-optical element 13. That is, since the magnitudes of the X-axis and Y-axis components of the elliptical polarization can be changed by changing the applied voltage, the output laser light can be easily adjusted to the maximum. Utilizing this, the extraction ratio of laser light can be optimized and maximum efficiency can be obtained.

Further, the prism 12 is a roof prism and a right-angled prism having an optical path bending plane orthogonal to the ridgeline of the roof prism is a total reflection surface of the right-angled prism and a bisecting surface of an angle forming a right angle of the roof prism depending on the refractive index. The same effect can be obtained for the same reason even if the prism is selected so that the polarization planes of the incident light and the reflected light coincide with each other and is replaced by a prism having a combined shape.

〔The invention's effect〕

As described above, according to the Q-switch laser device of the present invention, the optical resonator is configured by arranging the two predetermined prisms so as to face each other. Therefore, the output change caused by the minute angle change of the prism is made minute. In addition, the voltage applied to the electro-optical element can be halved, and by adjusting this voltage, the extraction ratio of the laser light can be changed and the maximum efficiency can be easily obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the Q-switch laser device of the present invention, FIG. 2 is a schematic diagram of a prism 12 in the Q-switch laser device of FIG. 1, and FIG. 3 is a block diagram of a conventional Q-switch laser device. FIG. 4 is a schematic view of the prism 1 of the Q-switch laser device of FIG. 3, and FIG. 5 is a diagram for explaining a laser light extraction ratio from the beam splitter / polarizer of the Q-switch laser device of FIG. . 11, 12 ... Prism, 13 ... Electro-optical element, 14 ... Beam splitting polarizer, 15 ... Laser medium, 16 ... Output laser light.

Claims (3)

[Claims] 1. A first prism having a shape in which a roof prism and a right-angle prism having a plane for bending an optical path orthogonal to a ridge of the roof prism are integrally combined and the polarization planes of incident light and reflected light are matched, and a roof. It has a shape in which a prism and a right-angle prism having an optical path bending plane parallel to its ridge are integrally combined,
A second prism that forms an optical resonator in combination with the first prism, a laser medium that is arranged in the optical resonator and outputs laser light, and a laser medium that is arranged linearly with the laser medium and has a linear polarization. Laser light is converted into elliptical polarized light, pulsed laser light is generated in the optical resonator, and the applied voltage is adjusted to change the elliptic ratio of the elliptical polarized light to extract the laser light. A Q-switch laser device comprising an electro-optical element capable of changing a ratio. 2. The first prism has a shape in which a roof prism and a right-angled prism having an optical path bending plane orthogonal to the ridgeline thereof are integrally combined, and the total reflection surface of the right-angled prism is perpendicular to the roof prism. 2. The Q-switch laser device according to claim 1, wherein the angle formed by the bisector of the angle is set so that the polarization planes of the incident light and the reflected light coincide with each other. 3. The first prism has a shape in which a roof prism and a right-angled prism having an optical path bending plane orthogonal to the ridgeline thereof are integrally combined, and incident light and reflected light are selected by selecting a refractive index. 2. The Q switch laser device according to claim 1, wherein the polarization planes of and are the same.