JPH0529694A - Laser apparatus - Google Patents

Abstract

PURPOSE:To obtain a conversion wavelength laser beam having a high output and a high quality by providing a first mirror for reflecting a laser beam, a second mirror having a transmission unit, a wavelength converter, a third mirror having a wavelength selecting optical thin film, and a laser medium. CONSTITUTION:A laser beam 70 is generated in a resonator formed of first, second and third mirrors 1, 2, 3 by an operation of a laser medium 4. Only a part having high quality of its center is guided to a wavelength converter 5 through a laser beam transmission unit 20 provided on the mirror 2. It is converted to a laser beam wavelength-converted in high quality, and externally output as a laser beam 70 from the mirror 3. The laser beam which is not wavelength-converted is reflected by the mirror 3, returned into a resonator, again amplified by the medium 4 to contribute to an improvement in an intensity of the beam 70 in the resonator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device for generating a high-quality and high-output wavelength-converted laser beam.

[0002]

2. Description of the Related Art FIG. 12 shows a publication (Yariv,
"Basics of Optoelectronics", Maruzen, p. FIG. 27 is a cross-sectional view showing the conventional laser device shown in FIG. In the figure, 1 is a total reflection mirror, that is, a first mirror, 3 is a reflection mirror, that is, a third mirror, and 4 is a laser medium. For example, a solid-state element excited by a lamp is a Yg laser. Aluminum Garnet) solid-state element, 5 is a wavelength conversion element, for example, a solid-state element that exhibits a non-linear effect with respect to incident light. A laser beam 30 generated in a laser resonator constituted by three mirrors 1, 3 reflects most of the fundamental wavelength laser beam 7 generated by the laser medium 4, and the wavelength conversion element 5 converts the wavelength of the laser beam 7 into a wavelength. A wavelength-selective optical thin film configured to transmit most of the converted wavelength-converted laser beam, and 70 is a wavelength-converted laser beam extracted to the outside. , 100 is an outer frame.

The conventional laser device is constructed as described above, and the laser beam 7 generated by the laser medium 4 is confined in the resonator formed by the first mirror 1 and the third mirror 3 and has a high brightness. Is generated in the resonator, the high-brightness laser beam is wavelength-converted by the wavelength conversion element 5 in the resonator, and most of the wavelength-converted laser beam is taken out from the resonator mirror 3.

[0004]

When a conventional laser device as described above is used to take out a high-power wavelength-converted laser beam to the outside, it is necessary to increase the laser power confined in the resonator. Can be applied to the laser medium 4 by a large amount, but since there is a limit to the amount of energy that can be applied to the laser medium 4 having a certain size, eventually the laser medium 4 is made larger to increase the input energy. As a result, the laser beam power in the resonator is increased. However, the increase in the size of the laser medium 4 in the resonator means the deterioration of the beam quality of the laser beam generated in the resonator. As described above, when the conventional laser device enlarges the laser medium 4 in order to take out a high-output wavelength-converted laser beam to the outside, the quality of the beam generated in the resonator is deteriorated, resulting in high output and good quality. The laser beam could not be obtained.

The present invention has been made to solve the above problems, and an object thereof is to obtain a converted wavelength laser beam having high output and good quality.

[0006]

A laser device according to the present invention comprises a first mirror for reflecting a laser beam, a second mirror partially provided with a laser beam transmitting portion, and a laser beam transmitting portion of the second mirror. A wavelength conversion element for wavelength conversion of a fundamental wavelength laser beam disposed in a portion, a wavelength selection optical thin film that reflects most of the fundamental wavelength laser beam and passes most of the converted wavelength laser beam wavelength-converted by the wavelength conversion element. It comprises a third mirror provided and a laser medium arranged at any position between the first mirror and the third mirror to generate the fundamental wavelength laser beam.

At least one of the first, second and third mirrors is formed by forming an optical thin film on the end face of the wavelength conversion element.

Further, means for adjusting the distance between the second mirror and the third mirror is provided.

Further, a laser beam non-reflective coating is applied to a portion of the second mirror excluding the transmitting portion, and the wavelength converting element is arranged in the transmitting portion.

In the laser device configured as described above, the first mirror, the second mirror partially provided with the laser beam transmitting portion, and the third reflecting mirror provided on the outer surface of the second mirror are used. The fundamental wavelength laser beam generated from the laser medium arranged in the laser resonator is confined in the resonator to have high brightness, and the laser beam transmitting portion provided in a part of the second mirror Only a part of the high-intensity fundamental-wavelength laser beam of good quality is guided to the wavelength conversion element provided between the second mirror and the third mirror, wavelength-converted, and provided on the third mirror. Due to the action of the optical thin film, most of the wavelength-converted laser beam is extracted to the outside. On the other hand, most of the wavelength-unconverted laser beam is reflected by the action of the optical thin film also provided on the third mirror, returned to the inside of the resonator, and amplified again by the laser medium.

Further, the first, second or third mirror formed by forming an optical thin film on the end face of the wavelength conversion element reduces the loss of the laser beam confined in the resonator and reduces the number of parts. Therefore, inexpensive and stable operation of the laser device can be expected.

Also, the means for adjusting the distance between the second mirror and the third mirror can adjust the beam shape in the resonator, and can realize efficient wavelength conversion.

Further, if the laser beam non-reflective coating is applied to the portion other than the transmitting portion of the second mirror and the wavelength converting element is arranged in the transmitting portion, the number of adjustment points of the mirror is reduced and the operation is simplified. Stabilize.

EXAMPLES Example 1. FIG. 1 is a sectional view showing an embodiment of the present invention, in which 1, 3, 4, 7, 30, 70 and 100 are exactly the same as those of the conventional device. Reference numeral 2 is a total reflection mirror, that is, a second mirror having a laser beam transmitting portion 20 in the central portion.

In the laser device constructed as described above, of the laser beam 70 generated by the action of the laser medium 4 in the resonator composed of the first, second and third mirrors 1, 2, 3 Only the high-quality portion of the central portion is converted into a high-quality wavelength-converted laser beam by being guided to the wavelength conversion element 5 through the laser beam transmission section 20 provided on the second mirror 2. It is taken out as a laser beam 70 from the third mirror 3. The laser beam whose wavelength has not been converted is reflected by the third mirror 3, returned to the resonator, amplified by the laser medium 4 again, and the laser beam 70 in the resonator is transmitted.
Contributes to the improvement of strength.

FIG. 2 shows the relationship between the size d of the transmitting portion 20 on the second mirror 2, the size φout of the laser medium 4 and the quality of the laser beam extracted from the third mirror 3. Here, the beam quality is expressed by the product of the divergence angle θ and the beam size d. The smaller this value is, the better the beam quality is. Therefore, when the beam is focused by a lens or the like, the beam quality can be narrowed down. It can be seen from FIG. 2 that the beam quality can be proportionally improved by reducing the size d of the transmitting portion 20 on the reflecting mirror, that is, the second mirror 2.

Example 2. Although the laser beam transmitting portion 20 has a hole-like shape provided in the central portion of the second mirror 2 in the above-described embodiment, as shown in FIG.
The non-reflective film 21 which is a kind of optical thin film may be applied only to the central portion of the above.

Embodiment 3. In another embodiment of the present invention shown in FIGS. 4, 5 and 6, at least one of the second mirror 3 and the third mirror 3 is constructed by forming optical thin films 21 and 30 on the end face of the wavelength conversion element 5. ing. That is, FIG.
In the second embodiment, the optical thin film 30 is formed on the end face of the wavelength conversion element 5 to form a third mirror, and in the embodiment of FIG. 5, the optical thin film 21 is formed on the end face of the wavelength conversion element 5 to form the second mirror. In the embodiment of FIG. 6, the optical thin films 21 and 30 are formed on both end faces of the wavelength conversion element 5, respectively, to form second and third mirrors. By doing so, it is possible to reduce the loss due to the laser beam that reciprocates in the resonator passing through the end face of the wavelength conversion element 5, and it is possible to expect an inexpensive and stable operation of the laser device by further reducing the number of parts. .

Embodiment 4. FIG. 7 adds a means for adjusting the distance between the second mirror 2 and the third mirror 3, for example a piezo element 8 whose length can be changed by applying a voltage. According to this adjusting means, it is possible to adjust the interference state between the laser beam resonating between the mirrors 1 and 2 and the laser beam resonating between the mirrors 1 and 3, whereby the intensity of the beam generated in the resonator is adjusted. By changing the distribution, for example, the transmission part 2 in the central part of the second mirror 2
The intensity of the laser beam passing through 0 can be increased,
Therefore, efficient wavelength conversion can be realized.

FIG. 8 shows an example of beam shape calculation. In the example of (a) in the figure, since the phase difference between the laser beam resonating between the mirrors 1 and 2 and the laser beam resonating between the mirrors 1 and 3 is set to zero, a beam having a high intensity distribution in the central portion. The pattern is obtained. On the other hand, in the example of (b) in the figure, the laser beam resonating between the mirrors 1 and 2 and the mirror 1,
Although the phase difference between the laser beams resonating among the three laser beams is set to a half wavelength, it can be seen that in this case, the central intensity is lowered.

Example 5. FIG. 9 shows a lens 9 in the resonator.
Is inserted to increase the intensity of the laser beam in the wavelength conversion element 5. By doing so, efficient wavelength conversion can be realized.

Example 6. The mirror 2 is shown in FIGS.
The laser beam non-reflective coating 31 is applied to the portion excluding the transmissive portion 20, and the wavelength conversion element 5 is embedded in or attached to the transmissive portion 20. In this way, the laser beam that passes through the transmission part 20 and the laser beam that does not pass around it resonate between the same resonator mirrors 1 and 3, so that the number of adjustment points of the mirrors is reduced, and the operation is simplified and the operation is improved. Is stable.

Although not particularly described in any of the above-mentioned embodiments, the non-reflective thin film 21 is provided at a portion of the optical element where there is no particular instruction, at a portion through which the laser beam passes, like an ordinary optical element. By applying the above, the loss in the resonator is reduced, and efficient wavelength conversion can be realized.

In any of the above embodiments, any one of the mirrors 1, 2, and 3 may be produced by applying an optical thin film to the end face of the laser medium 4. In this case, the loss at the end surface of the laser medium 4 is reduced, the laser beam intensity in the resonator is increased, and efficient wavelength conversion can be realized.

[0023]

As described above, according to the present invention, the first mirror for reflecting the laser beam, the second mirror partially including the laser beam transmitting portion, and the laser beam transmitting portion of the second mirror are provided. A wavelength conversion element for converting the wavelength of the fundamental wavelength laser beam, and a wavelength selective optical thin film for reflecting most of the fundamental wavelength laser beam and transmitting most of the converted wavelength laser beam wavelength-converted by the wavelength conversion element. Since the third mirror and the laser medium for generating the fundamental wavelength laser beam disposed at any position between the first mirror and the third mirror are provided, a high output and high quality conversion wavelength laser is provided. Beam is obtained.

Further, at least one of the first, second and third mirrors is formed by forming an optical thin film on the end face of the wavelength conversion element to reduce the loss of the laser beam confined in the resonator. By reducing the number of parts and the number of parts, an inexpensive and stable operation of the laser device can be expected.

By adjusting the distance between the second mirror and the third mirror, the beam shape inside the resonator can be adjusted, and efficient wavelength conversion can be realized.

Further, if the laser beam non-reflective coating is applied to the portion other than the transmitting portion of the second mirror and the wavelength converting element is arranged in the transmitting portion, the number of adjustment points of the mirror is reduced and the operation is stable and the operation is stable. To do.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a characteristic diagram illustrating the operation of the laser device according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a sectional view showing an example of a third embodiment of the present invention.

FIG. 5 is a sectional view showing an example of a third embodiment of the present invention.

FIG. 6 is a sectional view showing an example of a third embodiment of the present invention.

FIG. 7 is a sectional view showing Embodiment 4 of the present invention.

FIG. 8 is a waveform diagram for explaining the operation of the laser device according to the fourth embodiment of the present invention.

FIG. 9 is a sectional view showing an example of a fifth embodiment of the present invention.

FIG. 10 is a sectional view showing an example of Embodiment 6 of the present invention.

FIG. 11 is a sectional view showing an example of Embodiment 6 of the present invention.

FIG. 12 is a cross-sectional view showing a conventional laser device.

[Explanation of symbols]

1 first mirror 2 second mirror 3 third mirror 4 Laser medium 5 Wavelength conversion element 7 laser beam 70 laser beam 20 Laser beam transmission part 30 wavelength selective optical thin film

Claims (4)

[Claims] 1. A first mirror for reflecting a laser beam, a second mirror partially provided with a laser beam transmitting portion,
A wavelength conversion element disposed in the laser beam transmission part of the second mirror for converting the wavelength of the fundamental wavelength laser beam, of the converted wavelength laser beam wavelength-converted by the wavelength conversion element while reflecting most of the fundamental wavelength laser beam. A laser device including a third mirror having a wavelength-selective optical thin film that allows most of light to pass therethrough, and a laser medium disposed anywhere between the first mirror and the third mirror to generate the fundamental wavelength laser beam. . 2. The laser device according to claim 1, wherein at least one of the first, second and third mirrors is formed by forming an optical thin film on the end face of the wavelength conversion element. 3. The laser device according to claim 1, further comprising means for adjusting a distance between the second mirror and the third mirror. 4. The laser device according to claim 1, wherein a laser beam non-reflection coating is applied to a portion of the second mirror excluding the transmitting portion, and the wavelength converting element is arranged in the transmitting portion.