JP2000349379A - Optic element and its forming method and/or solid laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optic element made of a single crystal with high efficiency by cutting the single crystal with a surface being inclined to the specific vertical surface by a specific value or more, and by polishing the surface as a light-transmission end face. SOLUTION: A laser crystal 10 is a YVO4 crystal where Nd is doped by 3 atom.%, a single crystal 10C of Nd: YVO4 is cut by a surface where a surface being vertical to one axis (a) is inclined at an angle θaround the other, the cut surface is polished for forming a light-transmission end faces 10a and 10b. Polishing is made by applying the cut Nd: YVO4 and packing glass (BK7) to the glass substrate of the BK7 by wax, and by finishing both surfaces one by one. Although an acquisition rate is greatly improved when an incline angle is set to 0.5 deg. or larger, the completion rate is gradually increased as the incline angle exceeds 0.5 deg.. Then, when the incline angle exceeds 20 deg., the acquisition rate reaches the maximum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-crystal optical element used as a solid-state laser medium or the like, and a method for producing the same.

The present invention also relates to a solid-state laser using a single crystal optical element as a laser medium.

[0003]

2. Description of the Related Art Conventionally, Ra: RVO ₄ or RVO
₄ (R is Y or Gd, Ra is Nd, Er, T
m, Eu, Pr, Ho, Ce, Yb, Dy, Cr, Tb
Solid-state lasers using a single crystal of one or more of the above) as a laser medium are known. Such a laser medium is generally produced by cutting the single crystal into a shape having a flat light-passing end face, and then polishing the cut face to a mirror surface.

[0004] Conventionally, the single crystal has been cut out on a plane perpendicular to its a-axis or c-axis (that is, a plane parallel to another c-axis or a-axis), and used as a laser medium. For example, in a so-called c-axis end-pumped solid-state laser in which the linear polarization direction of the excitation light is matched with the direction of the c-axis of the laser medium, the single crystal is cut out and polished at a plane perpendicular to the a-axis. Was used as a laser medium.

[0005]

However, in the conventional solid-state laser using the above-mentioned laser medium, the cost is high because the light-passing end face of the laser medium is easily scratched and its yield is low. The problem of having been recognized.

Accordingly, an object of the present invention is to provide a method capable of producing an optical element made of the above-mentioned single crystal used as a laser medium or the like at a high yield.

Another object of the present invention is to provide an optical element produced at a high yield and a solid-state laser that can be reduced in cost by using the optical element as a laser medium.

[0008]

According to the present invention, there is provided an optical element comprising:
The creation method is Ra: RVO described above.₄Or RVO
₄(R is Y or Gd, Ra is Nd, Er, T
m, Eu, Pr, Ho, Ce, Yb, Dy, Cr, Tb
One or more combinations of the above)
Creating an optical element by cutting it into a shape with a light passing end face
In the method, the single crystal is placed on its a-axis or c-axis.
0.5 ° or more to a vertical plane, preferably 0.5 to 2
Cut out at a surface inclined at 0 °, polished the cut surface and light
It is characterized by being a passing end face.

In the method of manufacturing an optical element according to the present invention, it is preferable that the single crystal is cut out from a plane perpendicular to the a-axis at an angle of 0.5 ° or more around the c-axis. New

[0010] The single crystal may be cut out from a plane perpendicular to one a-axis at an angle of 0.5 ° or more around another a-axis.

On the other hand, the optical element according to the present invention has Ra: RV
In an optical element formed by processing a single crystal of O ₄ or RVO ₄ (R and Ra are the same as described above, for example, R is Y and Ra is Nd) into a shape having a flat light-passing end face, It is characterized in that a plane inclined by 0.5 ° or more, preferably 0.5 to 20 ° with respect to a plane perpendicular to the a-axis or c-axis of the crystal is a light-passing end face.

In the optical element according to the present invention, it is preferable that a plane perpendicular to the a-axis of one of the single crystals is inclined by 0.5 ° or more around the c-axis as a light passing end face. Further, a plane perpendicular to one a-axis of the single crystal may be inclined by 0.5 ° or more around another a-axis as a light passing end face.

On the other hand, a solid-state laser according to the present invention is characterized by using the above-described optical element according to the present invention as a laser medium.

In the solid-state laser according to the present invention, in particular, the optical element constituting the laser medium is such that a plane perpendicular to one a-axis of the single crystal is inclined at least 0.5 ° around the c-axis to a light-passing end face. In this case, it is desirable that the direction of linear polarization of the excitation light for exciting the laser medium is set in a direction parallel to the c-axis of the single crystal.

In the solid-state laser according to the present invention, the optical element constituting the laser medium is preferably a single crystal a.
When the plane perpendicular to the axis is inclined by 0.5 ° or more around another a-axis as the light-passing end face, the linear polarization direction of the excitation light for exciting the laser medium is determined by the light passing through the single crystal. It is desirable to set the direction perpendicular to the a-axis included in the end face.

[0016]

According to the study of the present inventor, the problem that the light passing end face of the laser medium is apt to be scratched in the conventional solid-state laser is mainly due to the fact that the single crystal after the cutting is polished. It was found that the corners were chipped, and the light-transmitting end face was rubbed by the chipped crystal pieces. And the defect that the corner of this single crystal is chipped,
This is due to the fact that the single crystal is cut along a plane that is easily cleaved, that is, a plane perpendicular to the a-axis or the c-axis.

Therefore, when a single crystal of an element material is cut out on a plane inclined with respect to a plane perpendicular to the a-axis or the c-axis, as in the method of manufacturing an optical element according to the present invention, the cut-out plane is shifted from the cleavage plane. Therefore, the corners of the single crystal are hardly chipped. In that case, when the single crystal is polished after cutting, the light passing end face is less likely to be rubbed by the missing crystal pieces, and the light passing end face is prevented from being scratched. Therefore, according to this method, an optical element made of the single crystal can be produced at a high yield.

As described above, an optical element which can be manufactured with a high yield is inexpensive as a result. Therefore, the solid-state laser of the present invention using this optical element as a laser medium has a lower cost than a conventional apparatus. It can be manufactured with.

The effect of increasing the yield of the optical element can be clearly obtained if the cut surface of the single crystal is inclined at least 0.5 ° with respect to the plane perpendicular to the a-axis or c-axis. The yield also increases as the angle of this inclination is made larger than 0.5 °, but the tendency of the increase in the yield decreases gradually when the inclination exceeds 5 °, and the yield increases when the inclination exceeds 20 °. The effect of the climb will level off.

In the case where this optical element is used as a laser medium of a solid-state laser or the like, it is preferable in terms of luminous efficiency and the like if the cut surface of the single crystal is inclined with respect to a plane perpendicular to the a-axis or c-axis. Considering that the effect of increasing the yield leveled off, the angle of the inclination is desirably suppressed to 20 ° or less, more preferably 5 ° or less.

In the solid-state laser according to the present invention, in particular, the single crystal constituting the laser medium has a plane perpendicular to the a-axis inclined at least 0.5 ° around the c-axis as a light passing end face. And the linear polarization direction of the excitation light for exciting the laser medium is set in a direction parallel to the c-axis of the single crystal. As in the case of the solid-state laser pumped at the c-axis end face, the effect of the c-axis having a large stimulated emission cross-sectional area and a large absorption coefficient can be used as it is, so that there is no problem such as a decrease in efficiency.

On the other hand, among the solid-state lasers according to the present invention, in particular, the single crystal constituting the laser medium has a surface perpendicular to one a-axis inclined by 0.5 ° or more around another a-axis. What is set as a passing end face, wherein the linear polarization direction of the excitation light for exciting the laser medium is set in a direction orthogonal to the a-axis included in the light passing end face of the single crystal,
The component that coincides with the linear polarization direction of the excitation light is a composite component of the one a-axis and the c-axis. In other words, in this case, in order to secure a greater effect of the c-axis having a large stimulated emission cross section or absorption coefficient, the c-axis component in the composite component should be made larger, that is, the inclination angle should be made smaller. Is required.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a laser crystal 10 which is an optical element according to one embodiment of the present invention, and FIG. 2 shows how the laser crystal 10 is cut from a single crystal 10C.

The laser crystal 10 of the present embodiment is, for example, Nd
Is a 3 at% doped YVO ₄ crystal (Nd: YVO _4
As shown in FIG. 2, a single crystal 10C of Nd: YVO ₄ is obtained by tilting a plane perpendicular to one a-axis (a plane shaded in the figure) by an angle θ around another a-axis. And the cut surfaces are polished and the light-passing end surfaces 10a and 10b
Is created. The conventional uniaxial laser crystal was prepared by cutting out a single crystal from a plane perpendicular to the a-axis or c-axis, such as a hatched surface in FIG.

In this embodiment, the inclination angle θ is set variously,
The yield of the laser crystal 10 in each case was measured. Here, the shape of the laser crystal 10 is 2.5 mm × 2.5 m
m, the flatness of the light passing end faces 10a and 10b is λ / 1
0, the parallelism was 30 ″, and the surface roughness was 0.5 nm (nanometers) rms. The laser crystal 10 of 10 samples was prepared for each tilt angle θ, and both end faces of each sample were prepared. The occurrence of flaws was examined for 10a and 10b (that is, a total of 20 surfaces) in a dark field with a magnification of 100 times within a circular area of 1 mm in diameter at the center of both light passing end faces 10a and 10b of each sample. The product was observed with a head microscope and no scratch was found.

The polishing a glass substrate of BK7, excised Nd: YVO ₄ and Yatoigarasu the (BK7) affixed with wax was carried out by finishing the double-sided one surface at a time. Sanding was performed with free abrasive grains (green carbon), and when the surface came out, pitch polishing was performed using cerium oxide. This polishing is performed on the light passing end face 10a.
The process was terminated when the flatness, parallelism, and surface roughness of Samples 10b and 10b satisfied the above specified values.

The results of measuring the yield are shown in the following (Table 1) and FIG. As shown in these figures, the inclination angle θ
Is set to 0.5 ° or more, the yield is remarkably improved. As the inclination angle θ becomes larger than 0.5 °, the yield also increases. However, when the inclination angle θ exceeds 5 °, the tendency of the increase in the yield decreases, and when it exceeds 20 °, the effect of the increase in the yield increases. Will peak off.

[0028]

[Table 1] Next, a solid-state laser using the laser crystal 10 will be described with reference to FIG. This solid-state laser includes, in addition to a laser crystal 10, a semiconductor laser 12 that emits a laser beam 11 that excites the laser crystal 10, condensing lenses 13 a and 13 b that converge the laser beam 11 that is divergent light, A resonator mirror 14 disposed on the front side (right side in the figure) of the laser crystal 10.

The semiconductor laser 12 has a wavelength of 810 n.
One that emits m laser beams 11 is used.
The laser crystal 10 excites neodymium ions by the incident laser beam 11 and emits light having a wavelength of 1064 nm.

On the mirror surface 14a of the resonator mirror 14,
A coat for reflecting light having a wavelength of 1064 nm at a reflectance of 99% is provided. On the other hand, an excitation laser beam 11 having a wavelength of 810 nm is transmitted well with a reflectance of less than 3% to a light passing end face (rear end face) 10a of the laser crystal 10, and a light having a wavelength of 1064 nm has a reflectance exceeding 99.99%. Coating that reflects well. Laser crystal 1
The light passing end face (front end face) 10b of the light emitting element 10 has a wavelength 1064.
A coat for transmitting light of nm with a reflectance of less than 0.5% and transmitting well is provided.

Therefore, the light having the wavelength of 1064 nm resonates between the crystal end face 10a and the mirror face 14a to cause laser oscillation, and the thus generated wavelength 1064n
The m solid laser beam 15 is emitted from the resonator mirror 14 to the outside of the resonator. As described above, in this example, the laser crystal 1
The Fabry-Perot resonator is constituted by 0 and the resonator mirror 14.

Here, since the laser crystal 10 has been cut out as described above, as shown in detail in FIG. 1, a plane perpendicular to one a-axis is angled around another a-axis by an angle θ (0.5 ° or more). ) The inclined surfaces are the light passing end surfaces 10a and 10b. With respect to such a laser crystal 10, the semiconductor laser 12 adjusts the linear polarization direction (the direction of the arrow P in FIG. 4) of the laser beam 11 as the excitation light to the light passing end face 10
They are arranged in a direction orthogonal to the a-axis included in a and 10b.

In such a state, the component that coincides with the linear polarization direction P of the laser beam 11 is a composite component of the one a-axis and the c-axis. That is, the vector in the direction coinciding with the linear polarization direction P is a vector synthesized by the vector in the direction coincident with the one a-axis and the vector in the direction coincident with the c-axis. Therefore, in this case, in order to secure a greater effect of the c-axis having a large stimulated emission cross section or absorption coefficient, it is necessary to make the c-axis component in the composite component larger, that is, make the inclination angle θ smaller. Required. In consideration of the above points and the characteristic of the improvement of the yield shown in FIG. 3, the inclination angle θ is equal to or less than 20 °, more preferably 5 °.
° or less is desirable.

FIG. 5 shows a laser crystal 20 which is an optical element according to another embodiment of the present invention.
Shows a state in which the laser crystal 20 is cut out from the single crystal 20C.

The laser crystal 20 of the present embodiment also has Nd
Is a 3 at% doped YVO ₄ crystal (Nd: YVO _4
As shown in FIG. 6, an Nd: YVO ₄ single crystal 20C is cut out from a plane perpendicular to the a-axis (the plane shaded in the figure) at an angle θ around the c-axis. Is formed by polishing the cut surface to form the light passing end surfaces 20a and 20b.

With respect to the laser crystal 20, the inclination angle θ was set variously, and the yield of the laser crystal 20 was measured in each case. The results were the same as those shown in Table 1 and FIG. Met.

Next, a solid-state laser using the laser crystal 20 will be described with reference to FIG. This solid-state laser is basically different from the one shown in FIG. 4 in that the laser crystal 20 is used instead of the laser crystal 10. Further, since the laser crystal 20 is used, the relationship between the linear polarization direction P of the laser beam 11 and the direction of the crystal axis of the laser crystal is different from that in the solid-state laser shown in FIG.

That is, since the laser crystal 20 was cut out as described above, as shown in detail in FIG.
The planes perpendicular to the two a-axes are inclined about the c-axis by an angle θ (0.5 ° or more), and are defined as the light passing end faces 20a and 20b. With respect to such a laser crystal 20, the semiconductor laser 12 is arranged such that the linear polarization direction (the direction of the arrow P in FIG. 7) of the laser beam 11 as the excitation light is parallel to the c-axis.

As described above, if the linear polarization direction P of the laser beam 11 and the direction of the c-axis coincide with each other, the solid-state laser excited by the normal c-axis end face is not affected by the inclination angle θ. In addition, since the effect of the c-axis having a large stimulated emission cross-sectional area and a large absorption coefficient can be used as it is, there is no problem such as a decrease in efficiency.

The effect of the present invention described above is as follows.
A single crystal can be similarly obtained by inclining the cut plane of the single crystal by 0.5 ° or more with respect to a plane perpendicular to the a-axis or the c-axis in a direction different from that in the above embodiment.

[0041] The present invention is explained above the Nd is not limited to doped YVO ₄ crystal, other single crystal or undoped, if the non-Nd creates an optical element cut out single crystal doped Are similarly applicable, and in those cases, a similar effect can be obtained.

Although the embodiment in which a laser crystal is formed has been described above, the method of forming an optical element of the present invention is not limited to the case of forming a laser crystal, but is applicable to the case of forming other optical elements. And have a similar effect.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an optical element of the present invention.

FIG. 2 is a schematic diagram illustrating a state in which the optical element is cut out of a single crystal.

FIG. 3 is a graph showing the yield obtained by the method for producing an optical element of the present invention.

FIG. 4 is a perspective view showing a solid-state laser using the optical element as a laser crystal.

FIG. 5 is a perspective view showing another embodiment of the optical element of the present invention.

FIG. 6 is a schematic diagram illustrating a state in which the optical element of FIG. 5 is cut out of a single crystal.

FIG. 7 is a perspective view showing a solid-state laser using the optical element of FIG. 5 as a laser crystal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Laser crystal 10a, 10b Light transmission end face of laser crystal 11 Laser beam (excitation light) 12 Semiconductor laser 13a, 13b Condensing lens 14 Resonator mirror 20 Laser crystal 20a, 20b Light transmission end face of laser crystal

Claims (12)

[Claims] 1. Ra: RVO ₄ or RVO ₄ (R
Is Y or Gd, and Ra is Nd, Er, Tm, E
a single crystal of u, Pr, Ho, Ce, Yb, Dy, Cr, or Tb), and cutting out the single crystal into a shape having a flat light-passing end face to form an optical element. A method for producing an optical element, comprising: cutting a single crystal at a plane inclined by 0.5 ° or more with respect to a plane perpendicular to the a-axis or the c-axis, and polishing the cut surface to a light-passing end face. . 2. The method for producing an optical element according to claim 1, wherein the single crystal is cut out from a plane perpendicular to the a-axis at an angle of 0.5 ° or more around the c-axis. 3. The optical element according to claim 1, wherein a plane perpendicular to one a-axis is cut out from the single crystal by a plane inclined at least 0.5 ° around another a-axis. Method. 4. The single crystal according to claim 1, wherein the single crystal is cut at a plane inclined by 0.5 to 20 ° with respect to a plane perpendicular to the a-axis or the c-axis. How to make an optical element. 5. Ra: RVO ₄ or RVO ₄ (R
Is Y or Gd, and Ra is Nd, Er, Tm, E
u, Pr, Ho, Ce, Yb, Dy, Cr, or Tb) or a single crystal thereof is processed into a shape having a flat light-passing end face. 0 with respect to a plane perpendicular to the a-axis or c-axis of
An optical element characterized in that a surface inclined by 5 ° or more is used as a light passing end surface. 6. A plane perpendicular to one a-axis of the single crystal,
6. The optical element according to claim 5, wherein a surface inclined by 0.5 ° or more around the c axis is a light passing end surface. 7. A plane perpendicular to one a-axis of the single crystal,
6. The optical element according to claim 5, wherein a surface inclined by 0.5 [deg.] Or more around another a axis is a light passing end surface. 8. A light passing end face which is inclined by 0.5 to 20 ° with respect to a plane perpendicular to the a-axis or c-axis of the single crystal. Or 1
Item 6. The optical element according to item 1. 9. The optical element according to claim 5, wherein said Ra is Y and said Ra is Nd. 10. A solid-state laser using the optical element according to claim 5 as a laser medium. 11. The optical element according to claim 6, wherein a linear polarization direction of excitation light for exciting the laser medium is set in a direction parallel to a c-axis of the single crystal. Solid-state laser. 12. The optical element according to claim 7, which is used as a laser medium, wherein the direction of linear polarization of the excitation light for exciting the laser medium is set to a direction orthogonal to the a-axis included in the light passing end face of the single crystal. A solid-state laser.