JP2000164954A - Zigzag slab type solid state laser amplifier and oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain energy coupling efficiency of 10% even when an inner reflective angle is 45 deg. or below. SOLUTION: An amplifying flux beam 16 of light in parallel with a thickness of d is cast as an incident light, with an inner reflective angle of θ with respect to a lower totally reflecting face 22a of a solid state laser material 10. In this case, d is 2t (cos θ) for uniformly propagating the beam 16 in the solid state laser material 10. A triangle prism-shaped incident light part 12 is provided. The length of a light incident face 18 in the thickness direction is set at d or longer. The light incident face 18 passes a point (w), extending by a given length determined by θ and t from a rising position (p) of the light incident part 12, and at the same time the light incident face 18 is provided at an angle of 90 deg.-θ with respect to the lower total reflection face 22a. A light outgoing part 14 has the same shape as with the light incident part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zigzag slab type solid-state laser amplifier and an oscillator which are pumped at an end face or a side face by a pumping light source such as a semiconductor laser (LD) or a flash lamp.

[0002]

2. Description of the Related Art Conventionally, in a zigzag slab type solid-state laser amplifier and an oscillator, a cross-sectional area of an amplified beam of a parallel light beam is made smaller than an area of an input / output surface of a zigzag slab type solid-state laser material so that diffraction does not occur. The beam to be amplified has been amplified by vertically incident on the laser material. As a typical conventional example, FIG. 3 shows a configuration diagram of an amplifier and an oscillator of a zigzag slab type solid-state laser.

[0003] As shown in FIG. 3, a zigzag slab type solid-state laser is a zigzag slab type solid-state laser material.
00 and an excitation light source 102. Solid laser material 1
No. 00 has an incident surface 106 perpendicular to the amplified beam 104 of the incident parallel light beam, and an emission surface 108 perpendicular to the emitted amplified beam 104. The solid-state laser material 100 is made of, for example, Nd: YAG. The excitation light source 102 is composed of, for example, a semiconductor laser or a flash lamp. Reference numeral 110 denotes the excitation light source 102
3 shows an excitation region of the solid-state laser material 100 which is excited by. As shown in FIG. 3, the amplified beam 104 is
Incident on the solid-state laser material 100 from the entrance surface 106,
Opposing total reflection surfaces 112 in the solid state laser material 100
The laser light is totally reflected at the points a and 112b and propagates in a zigzag manner to the emission surface 108. During this time, energy is obtained from the excited solid-state laser material 100, amplified, and emitted from the emission surface 108.

Now, it is assumed that the cross section of the amplified beam 104 completely matches the incident surface 106 and the exit surface 108 of the solid-state laser material 100. Assuming that the internal reflection angle at which the amplified beam 104 is totally reflected by the total reflection surfaces 112a and 112b of the solid-state laser material 100 is θ, the solid-state laser material 100
The energy coupling efficiency C indicating the ratio of the amount of the amplified beam 104 propagating in the portion surrounded by the excitation region 110 is given by the following equation.

[0005]

[Number 1] ^{C = (1 / (2COS 2} θ)) · (2-1 / (2COS 2 θ)) (1) The energy coupling efficiency C is a laser mode volume of propagation of the amplified beam of parallel light beams The ratio of overlap with the excitation volume of the solid-state laser material excited by the excitation light source,
This corresponds to the ratio occupied by hatched portions in the solid-state laser material 100 shown in FIG.

FIG. 4 shows a calculation result of the energy coupling efficiency C with respect to the internal reflection angle θ. According to FIG. 4, the internal reflection angle is 45.
At 0 °, the energy coupling efficiency is 100%, indicating that extremely efficient amplification can be performed. When the internal reflection angle is 45 °, the incidence surface 106 and the emission surface 108 in FIG. 3 have an inclination of 45 ° with respect to the total reflection surfaces 112a and 112b of the solid-state laser material 100, and The white part disappears and the hatched shape.

However, when the solid-state laser material 100 has a small refractive index or when the solid-state laser material 100 is cooled by a coolant (for example, pure water), the internal reflection angle is 45 ° to satisfy the total reflection condition. Must be smaller. In this way, when the internal reflection angle is smaller than 45 °, as shown in FIG. 3, the entrance surface 106 and the exit surface 108 are 45 degrees away from the total reflection surfaces 112a and 112b.
Has a slope greater than 0 °, so that the amplified beam 10
4 propagating laser mode volume and solid laser material 1
The excitation volume surrounded by the excitation region 110 in 00 does not completely match, resulting in a white portion in FIG. For this reason, the energy coupling efficiency is lower than 100%, and the energy stored in the solid-state laser material 100 cannot be completely contributed to the amplification of the amplified beam 104, and the laser output and the overall efficiency are reduced. Or amplified beam 1
The stored energy in the region where the light does not propagate becomes heat, and the solid-state laser material 100 itself is deformed or a refractive index distribution is generated, so that the quality of the output laser beam is deteriorated.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a zigzag slab type solid-state laser amplifier and an oscillator capable of obtaining 100% energy coupling efficiency even when the internal reflection angle is smaller than 45 °. Is to do.

[0009]

In order to solve the above problems, a zigzag slab type solid-state laser amplifier of the present invention comprises:
A solid-state laser material portion, wherein the solid-state laser material portion is a laser mode volume in which a beam to be amplified of a parallel light beam incident on the solid-state laser material portion propagates and the solid-state laser material portion which is excited by an external excitation light source. The solid-state laser material portion is characterized by having an incident surface structure that allows the amplified beam to enter the solid-state laser material portion so that the excitation volume substantially overlaps the excitation volume.

In order to solve the above-mentioned problems, a zigzag slab type solid-state laser oscillator has a solid-state laser material part, and the solid-state laser material part is an amplified beam of a parallel light beam incident on the solid-state laser material part. Having an incident surface structure capable of injecting the amplified beam into the solid-state laser material portion such that the laser mode volume to be propagated and the excitation volume of the solid-state laser material portion excited by the external excitation light source substantially overlap. Features.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The concept of the present invention will be described first.
In the present invention, the plane of incidence of the solid-state laser material, and preferably the plane of emission, is adapted to or larger than the cross-section of the incident beam to be amplified of the parallel beam, and the incident beam can be propagated evenly through the solid-state laser material. That is, even when the internal reflection angle is smaller than 45 °, the laser mode volume in which the amplified beam of the parallel light beam propagates and the excitation volume of the solid laser material excited by the excitation means are completely overlapped. % Energy coupling efficiency.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a zigzag slab type solid-state laser amplifier or oscillator according to a preferred embodiment of the present invention. 1, elements denoted by the same reference numerals as those shown in FIG. 3 indicate the same elements as those in FIG. 3, and the description thereof will not be repeated. In FIG. 1, a solid laser material 10 of a zigzag slab type solid state laser amplifier or oscillator according to a preferred embodiment of the present invention is shown in FIG.
The same material as the solid-state laser material 100, for example, Nd: Y
A triangular prism-shaped input portion 12 and output portion 14 made of AG and made of the same material are newly provided at each of the input and output ends. Amplified beam 16 of parallel light beam
Are incident from the incident surface 18 of the incident portion 12, are amplified while being totally reflected in the solid-state laser material 10, and are output from the output portion 1.
4 is emitted from the emission surface 20.

FIG. 2 shows the same configuration as FIG. 1 except that hatching of the amplified beam 16 shown in FIG. Amplified beam 1 of parallel light beam
6 is assumed to be incident on the lower total reflection surface 22a of the solid-state laser material 10 at an internal reflection angle θ. The meanings of the symbols of the dimensions and positions shown in FIG. 2 are as follows.

T: thickness of the solid-state laser material 10 θ: internal reflection angle φ: angle between the incident surface 18 orthogonal to the incident direction of the amplified beam 16 and the total reflection surfaces 22a and 22b, and the internal reflection angle θ D: the thickness of the amplified beam 16 of the parallel light flux, p: the light 24 passing through the uppermost outermost side in the thickness direction d of the amplified beam 16 of the parallel light flux, and the entire upper side. The position where the reflecting surface 22b first intersects q: The position where the light 24 passing through the uppermost outermost surface in the thickness direction d of the amplified beam 16 of the parallel light beam first intersects the lower total reflection surface 22a r: The position of the parallel light beam The position where the light 26 passing through the lowermost outermost side in the thickness direction d of the amplified beam 16 and the lower total reflection surface 22a first intersect u: the upper end position of the incident surface 18 on the upper total reflection surface 22b side v: the incident surface 18 Lower total reflection surface 2 Lower end position on a side w: Point at which upper total reflection surface 22b extends from point p to incidence surface 18 and intersects with incidence surface 18 g: Distance between p-w e: Length between w-u f: w Length between -v

As can be seen from FIG. 2, the amplified beam 16
Propagates evenly in the solid-state laser material 10, that is, the laser mode volume in which the amplified beam 16 of the parallel light beam propagates and the excitation volume of the solid-state laser material 10 excited by the excitation light source 102 (excitation of the solid-state laser material 10). The thickness d of the amplified beam 16 for completely overlapping the portion surrounded by the region 110) is

## EQU2 ## d = 2t · cos θ (2) Irrespective of the value of the internal reflection angle θ, 100% energy coupling efficiency can be achieved by using a beam satisfying the expression (2). As described above, since θ is smaller than 45 °, the beam thickness d is larger than √2t. On the other hand, θ
Is smaller than 45 °, φ is larger than 45 °,
Therefore, the length in the beam thickness d direction of the incident surface of the solid-state laser material 10 obtained by obliquely cutting the incident end surface is shorter than √2t. Therefore, the incident surface on which the beam having the above-mentioned thickness d is incident cannot be realized by simply cutting the incident end surface of the solid-state laser material 10 obliquely. Therefore, in the present invention, a structure protruding above the upper total reflection surface 22b of the solid-state laser material 10 is used as an incident portion.

The size of the triangular prism-shaped incident portion 12, which is the incident portion, is such that all the amplified beams 16 satisfying the expression (2) can be incident on the solid-state laser material 10 and propagate therethrough. Therefore, the following equation must be satisfied.

The first condition is a condition for making the incident surface 18 of the beam in the solid-state laser material 10 flat, that is, for causing the amplified beam 16 to be perpendicularly incident on the incident surface 18. Is done.

[0019]

＝= 90 ° -θ (3) The second condition is a condition for securing the incident surface 18 of the solid-state laser material 10 that receives the amplified beam 16 having the beam thickness d. The dimension e + f in the direction of the beam thickness d only needs to be the beam thickness d in principle.
However, in practice, it is preferable to have a larger dimension because the incident position of the amplified beam 16 is slightly shifted or diffraction occurs. Therefore, the second condition is expressed by the following equation.

[0020]

E + f ≧ d (4) The third condition is a condition for the incident beam turned back in the solid-state laser material to be turned back to the total reflection surface of the solid-state laser material 10, in other words, the condition of the parallel light beam. Light 26 passing through the lowermost outermost side in the thickness direction d of the amplified beam 16 is totally reflected at point r of the lower total reflection surface 22a, and the totally reflected light is then totally reflected at point p of the upper total reflection surface 22b. The light that has been reflected, and the light that has been totally reflected is the thickness direction d of the amplified beam 16 of the parallel light flux
Are conditions for receiving the amplified beam 16 from the incident surface 18 and propagating in the solid-state laser material 10 so as to overlap with the light 24 passing through the uppermost outermost surface and to reach the point q of the lower total reflection surface 22a. . Therefore, this condition is equal to or greater than the length of g when the point v on the incident surface 18 coincides with the point r in terms of the length of g.

[0021]

G ≧ t (1 / tan θ−1 / tan (90 ° −θ)) (5) If the above three conditions are satisfied, the point v on the incident surface 18 is the thickness of the amplified beam 16 of the parallel light flux. Located on or below the lowermost outermost light 26 in direction d;
Since the point u is located on or above the light 24 passing through the uppermost outermost side in the thickness direction d of the amplified beam 16 of the parallel light flux, all of the amplified beam 16 always enters the solid-state laser material 10. Then, the light propagates evenly in the solid-state laser material 10 after the incidence. In the embodiment shown in FIG. 2, the upper side surface represented by the line segment up is a plane (a straight line in the line segment up), but the upper side surface of the amplified beam 16 of the parallel light beam after the incidence. Any shape may be used as long as the light 24 passing the outermost can propagate through the solid-state laser material 10. Further, in the embodiment shown in FIG. 2, the lower side surface represented by the line segment vr is a plane (a straight line in the line segment vr) obtained by extending the lower total reflection surface 22a. As long as the light 26 passing through the lowermost outermost side of the amplified beam 16 of the parallel light beam can propagate through the solid-state laser material 10, any shape may be used, including that the point v coincides with the point r. FIG. 2 of the triangular prism-shaped entrance part 12
The cross-sectional shape of pu satisfying the above three conditions is
What is necessary is just to take the form represented by -w.

The beam to be amplified 16 is the solid-state laser material 10
In order to propagate the light evenly in the inside, it is only necessary to have the above-described triangular prism-shaped incident portion 12 and the lower side surface (the line segment v-r of the cross-sectional shape in FIG. 2) as described above. Beam 1 thus amplified in solid-state laser material 10
In order to emit all of the light, the outgoing portion 14 and the upper side surface opposite to the outgoing portion (portion of the line segment v′-r ′ in the cross-sectional shape of FIG. 2) are formed by the incident portion 12 and the lower side surface (the cross-sectional portion in FIG. 2). It will be apparent to those skilled in the art that a structure similar to the shape line segment vr) may be employed. The triangular prism-shaped emission portion 14 may also have a structure that satisfies the above three conditions of the incidence portion 12. In FIG. 2, u 'is the lower end position of the lower total reflection surface 22a on the exit surface 20, v' is the upper end position of the upper total reflection surface 22b of the exit surface 20, and p 'is the amplified beam of the parallel light flux. The position where light 30 passing through the lowermost outermost part in the thickness direction and the lower total reflection surface 22a intersect last when the light 16 is emitted, and r 'is the thickness direction when the amplified beam 16 of the parallel light flux is emitted Assuming that the light 32 passing through the uppermost outermost surface and the upper total reflection surface 22b intersect at the end, the lower side surface represented by the line segment u'-p 'is a flat surface (a straight line in the line segment u'-p'). However, any shape may be used as long as the light 30 passing through the uppermost outer side of the amplified beam 16 of the parallel light beam when emitted can propagate through the solid-state laser material 10, and may be represented by a line segment v'-r '. The upper side surface is formed by extending the upper total reflection surface 22b. Plane (line segment v'-r '
However, if the light 32 passing through the uppermost outermost side of the amplified beam 16 of the parallel light beam when emitted can propagate through the solid-state laser material 10, the point v 'coincides with the point r'. Any shape may be used.

In the structure shown in FIG.
0 is directed toward the lower total reflection surface 22a, but may be directed toward the upper total reflection surface 22b.

In the present invention, the material of the solid-state laser material 10 is not limited to the above-mentioned materials, but may be any material that can be used as a solid-state laser material for a zigzag slab-type solid-state laser amplifier or an oscillator.

Further, a direction orthogonal to the thickness d direction in the cross section of the amplified beam 16 of the parallel light flux, that is, the width,
The corresponding relationship with the width of the incident surface of the solid-state laser material 10 is the same as in the case of the conventional zigzag slab type solid-state laser amplifier and oscillator, and it is sufficient that the width of the solid-state laser material 10 is not less than the width of the amplified beam 16. it is obvious.

In the above embodiment, the amplification of the amplified beam 16 in the solid-state laser material 10 has been described. However, it will be apparent to those skilled in the art that this configuration is also used for a zigzag slab type solid-state laser oscillator.

Since the present invention is constructed as described above, the cross section of the beam to be amplified can be adjusted so that the cross section of the beam to be amplified enters and exits the zigzag slab type solid-state laser material. Even if not perfectly coincident with the plane, all of the amplified beam will be incident on the solid state laser material and propagate evenly through it,
An energy coupling efficiency of 00% can be achieved.
Therefore, the energy stored in the solid-state laser material can be completely contributed to the amplification of the amplified beam, and the laser output and the overall efficiency can be improved. At the same time, since there is no portion that does not contribute to the amplification of the amplified beam, a decrease in the quality of the output laser beam due to a heat problem due to energy in a region where the amplified beam does not propagate can be reduced. In addition, since the internal reflection angle θ can be reduced, the edge portion (the portion near the points v and v ′ in FIG. 2) of the solid-state laser material can be made very gentle (that is, φ is increased), so that parasitic oscillation can be greatly suppressed. . Furthermore, in a preferred aspect of the present invention, the length in the thickness direction of the amplified beam on the incident surface of the solid-state laser material can be longer than the thickness of the amplified beam, so that the edge portion can be chamfered. The material itself can have high mechanical strength.

That is, according to the present invention, the energy coupling efficiency, which is a main parameter characterizing the efficiency of the laser operating characteristics, can be made 100% with a simple configuration. Therefore, since it is possible to obtain a high output efficiently and compactly more easily than in the past, and to improve the mechanical strength of the solid-state laser material itself in the preferred embodiment,
Suitable for high repetition, high power, high efficiency, high beam quality solid state laser.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a zigzag slab type solid-state laser amplifier or oscillator according to a preferred embodiment of the present invention.

FIG. 2 is the same configuration diagram as FIG. 1 except that hatching of an amplified beam 16 shown in FIG.

FIG. 3 is a configuration diagram of a zigzag slab type solid-state laser amplifier or oscillator as a typical conventional example.

FIG. 4 is a diagram showing a calculation result of an energy coupling efficiency C with respect to an internal reflection angle θ.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Solid-state laser material 12 Incident part 14 Outgoing part 16 Amplified beam 18 Incident surface 20 Exit surface 22a, 22b Total reflection surface 102 Excitation light source 110 Excitation area

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Takashi Arisawa Inventor Takashi Arisawa 2-4 Shirane, Shirakata, Tokai-mura, Naka-gun, Ibaraki Prefecture F-term in the Tokai Research Institute of Japan Atomic Energy Research Institute (reference) 5F072 AB02 AK03 JJ02 KK18 PP01 PP07

Claims (6)

[Claims] 1. A zigzag slab-type solid-state laser amplifier having a solid-state laser material part, wherein the solid-state laser material part comprises a laser mode volume through which an amplified beam of a parallel beam incident on the solid-state laser material part propagates and an external pump. A zigzag slab type solid-state laser amplifier having an incident surface structure that allows an amplified beam to be incident on the solid-state laser material part so that an excitation volume of the solid-state laser material part excited by a light source substantially overlaps with the solid-state laser material part. . 2. The solid-state laser material section has a predetermined thickness, and first and second perpendicular to the thickness direction and opposed to each other.
A total reflection surface, an internal reflection angle for totally reflecting the amplified beam at the first and second total reflection surfaces at an internal reflection angle, and the internal reflection angle substantially relative to the first total reflection surface. An incident surface substantially orthogonal to the incident direction of the amplified beam of the parallel light beam incident at a reflection angle, and having a dimension substantially equal to or greater than the thickness of the amplified beam of the parallel light beam; A position where the outermost light in the thickness direction of the amplified beam of the parallel light beam intersects with the second total reflection surface and extends the second total reflection surface to the incident surface. The distance from the position intersecting with the incident surface has a predetermined length or more determined by the internal reflection angle and the predetermined thickness, and the incident surface substantially covers the entire thickness of the amplified beam of the parallel light flux. The solid laser material portion is arranged so as to include The shape between the surface and the first and second total reflection surfaces has a shape in which the amplified beam of the parallel light beam after being incident from the incident surface propagates through the solid-state laser material portion. The zigzag slab type solid-state laser amplifier according to claim 1, wherein 3. The solid-state laser material portion is an emission surface substantially orthogonal to an emission direction of an amplified beam of the parallel light beam emitted from the solid-state laser material portion, and is provided with the parallel light beam. An output surface having a dimension substantially equal to or larger than the thickness of the amplified beam, wherein the outermost light in the thickness direction of the amplified beam of the parallel light flux is the first and second total reflections; A distance between a position intersecting one of the surfaces and the one total reflection surface and a position intersecting the one total reflection surface to the emission surface and intersecting the emission surface is determined by the internal reflection angle and the predetermined thickness. The emission surface is disposed so as to substantially include the entire thickness of the amplified beam of the parallel light beam, and the emission surface of the solid-state laser material portion and the first and second total surfaces are arranged. The shape between the reflective surface and 3. The zigzag slab type solid-state laser amplifier according to claim 2, wherein the zigzag slab type solid-state laser amplifier has a shape in which the amplified beam of the row light beam propagates in the solid-state laser material portion until the beam is emitted from the emission surface. 4. A zigzag slab type solid-state laser oscillator having a solid-state laser material portion, wherein the solid-state laser material portion includes a laser mode volume through which an amplified beam of a parallel light beam incident on the solid-state laser material portion propagates and an external excitation. A zigzag slab type solid-state laser oscillator having an incident surface structure capable of causing an amplified beam to enter the solid-state laser material portion so that an excitation volume of the solid-state laser material portion excited by a light source substantially overlaps with the solid-state laser material portion. . 5. The solid-state laser material section has a predetermined thickness, and first and second sections orthogonal to each other in the thickness direction and opposed to each other.
A total reflection surface, an internal reflection angle for totally reflecting the amplified beam at the first and second total reflection surfaces at an internal reflection angle, and the internal reflection angle substantially relative to the first total reflection surface. An incident surface substantially orthogonal to the incident direction of the amplified beam of the parallel light beam incident at a reflection angle, and having a dimension substantially equal to or greater than the thickness of the amplified beam of the parallel light beam; A position where the outermost light in the thickness direction of the amplified beam of the parallel light beam intersects with the second total reflection surface and extends the second total reflection surface to the incident surface. The distance from the position intersecting with the incident surface has a predetermined length or more determined by the internal reflection angle and the predetermined thickness, and the incident surface substantially covers the entire thickness of the amplified beam of the parallel light flux. The solid laser material portion is arranged so as to include The shape between the surface and the first and second total reflection surfaces has a shape in which the amplified beam of the parallel light beam after being incident from the incident surface propagates through the solid-state laser material portion. The zigzag slab type solid-state laser oscillator according to claim 3, wherein 6. The solid-state laser material portion is an emission surface substantially orthogonal to an emission direction of an amplified beam of the parallel light beam emitted from the solid-state laser material portion, and is provided with the parallel light beam. An output surface having a dimension substantially equal to or larger than the thickness of the amplified beam, wherein the outermost light in the thickness direction of the amplified beam of the parallel light flux is the first and second total reflections; A distance between a position intersecting one of the surfaces and the one total reflection surface and a position intersecting the one total reflection surface to the emission surface and intersecting the emission surface is determined by the internal reflection angle and the predetermined thickness. The emission surface is disposed so as to substantially include the entire thickness of the amplified beam of the parallel light beam, and the emission surface of the solid-state laser material portion and the first and second total surfaces are arranged. The shape between the reflective surface and 6. The zigzag slab type solid-state laser oscillator according to claim 5, wherein the zigzag slab type solid-state laser oscillator has a shape in which the amplified beam of the row light beam propagates in the solid-state laser material portion until the amplified beam is emitted from the emission surface.