JP2903817B2 - Solid-state laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the stabilization of the quality of a two-dimensional axially symmetric laser beam generated from a solid-state laser device, particularly a solid-state laser device having a rod-shaped solid element.

[0002]

2. Description of the Related Art FIG. 8 is a sectional view showing a conventional solid-state laser device described in, for example, a laser handbook (Ohm Co., Ltd., 1982). In the figure, 1 is a rod-shaped solid element, for example, Y _{3-X in the} case of a YAG laser.
A crystal made of Nd _x Al ₅ O ₁₂ , a light source 2 for uniformly irradiating the cylindrical surface of the solid-state device 1 and exciting the solid-state device 1, a power source for turning on the light source 2, a total reflection mirror 4, a total reflection mirror 5, An output mirror 6 opposed to the reflection mirror 4 is exposed,
Reference numeral 7 denotes a laser beam generated inside the laser resonator constituted by the mirrors 4 and 5, and reference numeral 8 denotes a laser beam extracted outside the laser resonator by the output mirror 5.

Next, the operation will be described. The solid state device 1 is excited by direct light from a light source 2 turned on by a power supply 3 and forms a laser medium. On the other hand, the laser beam 7 confined in the laser resonator composed of the total reflection mirror 4 and the output mirror 5 is amplified by the solid-state element 1 every time the laser beam 7 reciprocates through the mirrors 4 and 5, and becomes larger than a certain value. A part thereof is taken out as a laser beam 8 outside the laser resonator through the output mirror 5.

[0004]

Since the conventional solid-state laser device is constructed as described above, it is provided with a single solid-state device, and the power supplied to the light source for exciting this solid-state device is changed to change the laser. Since the output was changed, the
As shown in FIG. 9, there is a problem that the divergence angle of the beam changes depending on the power supplied to the light source, that is, the laser output. This is because the degree of thermal lensing of the solid state element due to the temperature gradient generated in the solid state element changes with the change in the power supplied to the solid state element, and changes the state of the laser resonator.

The divergence angle of the laser beam can be said to be the light-collecting performance of the laser beam itself. This is because the condensing beam diameter φs of the converging lens having the focal length f is roughly expressed by φs = f · θ with respect to the divergence angle θ. Therefore, the focusing beam is proportional to the divergence angle.
The size of the memory diameter is determined. The fact that the divergence angle changes with the laser output means that the light collection characteristics change,
There is a problem that stable laser processing cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a solid-state laser device capable of generating a high-power laser beam with a constant divergence angle. I do.

[0007]

The solid-state laser device according to the present invention is provided with two sets of rod-shaped solid elements in series on the optical path of a laser resonator. A sound wave generating element is mounted around one solid element, the sound wave element is driven, and the frequency of the sound wave emitted from the sound wave generating element according to the value of the power supplied to the light source.
And means for adjusting the output, around the sound wave generating element.
Refractive index distribution that converts the solid-state element attached to the lens into a lens
A standing wave of a sound wave is formed so as to be generated in the element .

In another solid-state laser device according to the present invention, a part of a rod-shaped solid element placed on an optical path of a laser resonator is excited by a light source, and another part of the solid-state element is excited. A sound wave generating element is attached to the periphery, the sound wave generating element is driven, and the frequency and output of the sound wave emitted from the sound wave generating element are adjusted according to the value of the power supplied to the light source.
A solid body having
Generates a refractive index distribution in the solid state element that converts the element part into a lens
In this case, a standing wave of a sound wave is formed .

[0009]

In the solid-state laser device constructed as described above, two sets of rod-shaped solid elements provided in series on the optical path of the laser resonator or one rod-shaped solid element is divided into two parts. A thermal lens in the thickness direction generated when one rod-shaped solid element is excited by a light source, and a frequency and an output of a sound wave generated by a sound-wave generating element mounted around the other rod-shaped solid element. It is compensated by adjusting. As a result, an extremely stable laser beam having a constant divergence angle can be taken out even when the input power to the light source, that is, the laser output is changed.

[0010]

[Embodiment 1] FIG. 1 is a block diagram of a solid-state laser device according to an embodiment of the present invention, and reference numerals 1 to 8 are exactly the same as those of the conventional device. 9 is a cylindrical sound wave generating element provided in the solid-state laser device of the present invention, 10 is a driving device for driving the sound wave generating element 9, and 11 is a rod-shaped solid state element. The sound wave generating element 9 is a solid state element 11
Is adjusted so that a sound wave of a standing wave that is axially symmetric in the radial direction can be generated within the crystal of the crystal, and the driving device 10 arbitrarily sets the frequency and output of the sound wave generated from the sound wave generation element 9. can do. In this embodiment, it is assumed that the driving device 10 is adjusted so that the relationship of D / Λ = 1 is established between the diameter D of the rod-shaped solid element 11 and the wavelength 音波 of the sound wave.

In the solid-state laser device configured as described above, the rod-shaped solid-state element 1 is excited by direct light from the light source 2 turned on by the power supply 3 and forms a laser medium. On the other hand, the laser beam 7 confined in the laser resonator composed of the total reflection mirror 4 and the output mirror 5 is amplified by the solid-state element 1 each time the laser beam 7 reciprocates through the mirrors 4 and 5, and becomes larger than a certain value. Part of it is an output mirror 5
Is extracted as a laser beam 8 to the outside of the laser resonator.

A method for compensating the thermal lensing of the solid-state element by the sound wave will be described in detail. FIGS. 2A and 2B show the states of the laser resonator before and after laser oscillation of the solid-state laser device according to the embodiment of the present invention, respectively.
As shown in FIG. 2A, before the laser oscillation, no thermal lens is generated in the solid-state device 1, and the laser resonator is a total reflection mirror 4
And the output mirror 5. When the light source 2 is turned on to excite the solid-state device 1 and start laser oscillation, the solid-state device 1 becomes a thermal lens having a focal length f _t related to the laser output as shown in FIG. By the conventional thermal lens of the solid-state element 1, and changes the state of the laser resonator, although the divergence angle has changed, in the present invention the focal length f _t of the thermal lens of the solid-state element 1, by using sound waves since compensated by generating a lens with a focal length -f _t the solid element 11, it can always be maintained the state of a stable laser resonator.

When a standing sound wave as shown in FIG. 3A is applied in the radial direction of the solid state element 11 using the sound wave generating element 9 and the driving device 10, as shown in FIG. 11
In the radial direction, a refractive index distribution caused by the density of the sound wave is generated. The phase distribution of the laser beam that has passed through the solid-state element 11 having this refractive index distribution changes as shown in FIG. 4, and this distribution is equivalent to that just after the laser beam has just passed through the concave lens. Since this phase distribution changes when the output of the sound wave is changed, by adjusting the driving device 10, that is, by adjusting the output of the sound wave, the focal length f _{t of the} thermal lens generated in the solid-state element 1 can be changed. just a lens having a focal length -f _t of opposite sign it is possible to generate a solid element 11. Thus, the solid state device 11
A standing wave of a sound wave is formed on the solid-state device 11 to form a lens.
To generate a refractive index distribution in the solid-state element 11,
The raw element 9 generates a sound wave, and the frequency of the sound wave
Thermal lens generated in solid-state device 1 by adjusting output
Can be compensated for.

Although the focal length f _t of the thermal lens generated in the solid state element 1 changes depending on the laser output, the output of the sound wave is adjusted according to the change in the laser output.
Can be compensated for, and the state of the laser resonator does not change before and after laser oscillation.

FIG. 5 shows the measurement results of the dependence of the divergence angle on the applied power when an experiment was conducted using the solid-state laser device of the above embodiment. The experimental conditions are the same as the result of the same experiment as the conventional example, that is, the same as that of FIG. 9, but the result of FIG. It shows that it shows a constant value with respect to the change of.

An advantage of the present invention is that since the thermal lens of the solid-state element is compensated by using sound waves, the time required for compensation is extremely short, and the time response is excellent. Therefore, for example, even in laser processing performed while changing the laser output, the diameter of the focused beam can always be kept constant, so that it can be performed extremely stably.

In this example, an example in which two sets of solid state elements are used has been described. However, it is needless to say that the same effect can be obtained by using two or more sets of solid state elements.

Embodiment 2 FIG. In the first embodiment, the solid state element 11
Although the sound wave generating element 9 is adjusted so that a concave lens is generated, the sound wave generating element 9 may be adjusted so that the solid-state element 11 becomes a convex lens.

FIGS. 6A and 6B show the state of the resonator before and after laser oscillation in the above embodiment. In FIG. 6A, before the laser oscillation, the solid element 1 has no thermal lens, but the solid element 11 is given a standing sound wave in advance so that the solid element 11 becomes a convex lens having a focal length f. Keep it. Therefore, the state of the resonator before laser oscillation is such that a convex lens having a focal length f exists in the laser resonator. When laser oscillation starts, FIG.
The solid element 1 as shown in (b) but caused thermal lens with a focal length f _t, this time, the convex lens caused in the solid-state element 11 by adjusting the driving device 10 the focal length f _a of 1 / f _{= 1 / f t + 1 /} f a by is adjusted so satisfied, it is possible to keep the resonator condition before and after the laser oscillation does not change.

Using the solid-state laser device of the above embodiment,
The divergence angle shows a constant value that does not depend on the applied power, and the focused beam diameter can be kept constant, so that extremely stable laser processing can be realized.

In this example, an example in which two sets of solid state elements are used has been described, but it is needless to say that the same effect can be obtained even if two or more sets of solid state elements are used.

Embodiment 3 FIG. In the first embodiment, two sets of solid-state elements are used, one for excitation and the other for thermal lens compensation. However, as shown in FIG. The lens may be compensated. Solid state device 1
The thermal lens generated in the lamp excitation part 2 is the solid state element 1
Since the compensation can be made by generating a sound wave at the portion where the second sound wave generating element 9 is attached, the state of the laser resonator does not change before and after laser oscillation.

Also in this case, since the thermal lens compensation is performed by dividing the function of one solid-state element 12, the same operation as in the first and second embodiments can be performed, and therefore, extremely stable operation can be achieved. Laser processing can be performed.

As described above, according to the present invention, two sets of rod-shaped solid elements are provided in series on the optical path of the laser resonator,
While exciting one rod-shaped solid element with a light source,
A sound wave generating element is attached around the other rod-shaped solid element, the sound wave element is driven, and the frequency of the sound wave emitted from the sound wave generating element according to the value of the power supplied to the light source.
And adjust the output so that the other solid state device
To generate a refractive index distribution in a solid-state device
Since a standing wave of a sound wave is formed at a time, a thermal lens generated when one solid element is excited by a light source is converted into a frequency and an output of a sound wave generated by a sound element mounted on the other solid element. Can be compensated for by adjusting the power, so that even if the input power to the light source, that is, the laser output is changed, a very stable laser beam having a constant divergence angle can be obtained. In addition, since the thermal lens is compensated by using a sound wave, there is an advantage that the time required for compensation is extremely short and the time response is excellent. Therefore, for example, even in laser processing performed while changing the laser output, the diameter of the focused beam can always be kept constant, so that it can be performed extremely stably.

Further, a part of the rod-shaped solid element placed on the optical path of the laser resonator is excited by a light source, and a sound wave generating element is mounted around another part of the rod-shaped solid element. The sound wave generator drives the sound wave generator, and the sound wave emitted from the sound wave generator according to the value of the power supplied to the light source.
Means for adjusting the frequency and output of the sound wave generator.
Of the solid-state element with the element around it
The standing wave of the sound wave is generated so that the
Even if it is formed, the same effect as that of the solid-state laser device can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a solid-state laser device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an operation of the solid-state laser device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating the principle of lens generation by sound waves in Embodiment 1 of the present invention.

FIG. 4 is a distribution diagram showing a phase distribution immediately after a laser beam passes through a lens generated by sound waves in Embodiment 1 of the present invention.

FIG. 5 is a characteristic diagram showing a divergence angle of a laser beam generated according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating an operation of the solid-state laser device according to the second embodiment of the present invention.

FIG. 7 is a configuration diagram of a solid-state laser device according to a third embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional solid-state laser device.

FIG. 9 is a characteristic diagram showing a divergence angle of a laser beam generated by a conventional solid-state laser device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid element 2 Light source 4 Total reflection mirror 5 Output mirror 7 Laser beam 8 Laser beam 9 Sound wave generation element 10 Driving device 11 Solid element 12 Solid element

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Taku Yamamoto 8-1-1 Tsukaguchi Honmachi, Amagasaki City Mitsubishi Electric Corporation Central Research Laboratory (56) References JP-A 1-260874 (JP, A) JP JP-A-3-85779 (JP, A) JP-A-2-158182 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01S 3/136 H01S 3/106 H01S 3/06 H01S 3 / 10 H01S 3/117

Claims (2)

(57) [Claims] 1. A laser resonator comprising an output mirror and a total reflection mirror, first and second rod-shaped solid elements placed in series on the optical path of the laser resonator, and exciting the first solid element. A light source, a sound wave generator mounted cylindrically around the solid surface of the second solid state element along the optical path,
Driving the sound wave generating element, and the frequency of the sound wave emitted from the sound wave generating element according to the value of the power supplied to the light source.
Means for adjusting the number and the output, and
Forming a standing wave of sound waves, lensing the second solid-state element
In the second solid state element.
Wherein the sound wave generating element generates a sound wave.
Solid-state laser apparatus that. 2. A laser resonator comprising an output mirror and a total reflection mirror, a rod-shaped solid element placed in series on an optical path of the laser resonator, a light source for exciting a part of the solid element, and the solid element In another part of the solid-state element, a sound wave generating element attached by surrounding the solid surface along the optical path in a cylindrical shape, and driving the sound wave generating element, the value of the power input to the light source Means for adjusting the frequency and output of the sound wave emitted from the sound wave generating element accordingly , forming a standing wave of the sound wave on a part of the solid-state element,
The refractive index distribution for converting a part of the solid
The above-mentioned sound wave generating element
A solid-state laser device characterized by generating .