JPH09312430A - Zig-zag slab solid-state laser and amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state laser which can generate a strong laser beam by removing the restriction on cooling means about its mounting direction in a prior art zig-zag optical-path solid-state laser to increase the absorption efficiency of its stimulating laser beam. SOLUTION: A laser medium part provided by melting thin solid-state laser media 1 on both parallel planar sides of a solid-state laser base material 9 is disposed between reflecting mirrors 3 and 4, so that an exciting laser beam 5 is externally introduced through a beam splitter 11, advanced in a zig-zag manner, and then absorbed into the laser media 1 for photo excitation. At this time, heat generated in the laser media 1 is efficiently removed by a cooling means 8 provided contacted with the media 1 to avoid generation of thermal lens effect and thermal birefringence effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zigzag slab solid state laser which is excited by a semiconductor laser to generate laser light of a predetermined wavelength.

[0002]

2. Description of the Related Art As an example of a semiconductor laser (hereinafter abbreviated as LD) pumped zigzag optical path solid-state laser, for example, an academic journal "A.
"Physics Physics B", Volume 58, 19
Those described in 1994, pp. 365-372 (Germany) are known. This conventional example is shown in FIG. In the figure,
Quasi-three-level Y doped with Yb active ion of about 20 at%
b: YAG laser medium 1 having a diameter of 7 mm and a thickness of 0.35 m
m is processed as a thin disk-shaped parallel flat plate, and a plurality of the disk-shaped laser mediums 1 are slightly displaced from each other on the cooling plate 2 as shown in the drawing, and the upper and lower parts are 2, 3 and 5 in total. Sheets are arranged parallel to each other.

Each of the laser mediums 1 is provided with an antireflection (AR) coating on the incident surface for the pumping laser light having a wavelength of 940 nm and the Yb: YAG laser light having a wavelength of 1030 nm generated by the excitation, and is reflected. The surface is coated with a high reflectance (HR) at wavelengths of 940 nm and 1030 nm. Then, each laser medium 1 is irradiated with laser light for excitation in the directions 5 and 6 shown in FIG.
Excited light with intensity of 0 kw / cm ² and excited wavelength 1
A laser beam of 030 nm is reflected between the laser mediums in the zigzag direction and travels, and is amplified in an optical resonator formed by reflecting mirrors 3 and 4 using a concave mirror and a partially transmissive plane mirror provided at the optical path end. The laser output light 7 of about cw450w can be taken out from the one reflection mirror 4.

Generally, 5 is excited in the direction from the front side to the back side of the paper of FIG. 2, and 6 is excited in the reverse direction from the back side of the paper to the front side. 8
Is a cooling means for cooling with water w from the back surface of the cooling plate 2 made of copper, and is provided in contact with the back side of the cooling plate 2 which is arranged oppositely. Therefore, the heat generated when the laser light is excited in the laser medium 1 by the excitation laser light is
Is efficiently removed by the cooling water w through the cooling plate 2 having the reflective surface thereof closely attached.

[0005]

However, with the configuration of the above-mentioned conventional solid-state laser device, the heat generated when the laser beam is excited in the solid-state laser medium is only in one direction of the copper cooling plate. There is a problem in that the structure of the cooling unit becomes complicated if the solid laser medium is directly water-cooled without being removed.

Further, when the solid-state laser medium is excited by the exciting laser beams from the upper and lower two directions and the generated laser beam is reflected by the reflection mirror and travels again, the heat absorption efficiency by water cooling in each thin laser medium. To increase
It becomes extremely difficult to arrange the reflection mirror for the excitation laser light.

The present invention takes note of the problems in such a conventional zigzag optical path solid-state laser, makes it easy and highly efficient to excite with a laser beam, and makes it possible to obtain high efficiency from a solid-state laser medium excited with a laser beam for excitation. An object of the present invention is to provide a zigzag slab solid-state laser capable of removing heat.

A second aspect of the present invention is to provide a solid-state laser amplifier capable of utilizing as a laser amplifier the device obtained by highly efficiently LD-pumping similarly to the solid-state laser obtained by the first aspect. And the subject.

[0009]

According to the present invention, as means for solving the above-mentioned first problem, a solid-state laser medium doped with active ions is fused on both sides of a parallel surface of a slab solid-state laser base material. A laser medium portion having a reflection surface opposite to the fusion surface of the laser medium portion is disposed in an optical resonator composed of a pair of reflection mirrors for amplifying laser light generated in the laser medium portion, and The cooling means is provided in contact with the surface opposite to the laser base material, and the laser light for excitation is introduced into the laser base material from the input / output end surface of the laser base material and the laser light excited by the laser medium and the excitation laser. The light is reflected by the reflecting surface of the laser medium and is zigzag-traveled to be excited /
The amplified laser light is further amplified in the optical resonator,
The zigzag slab solid state laser is configured to output from the output mirror.

In a second aspect of the present invention, as means for solving the above second problem, a solid laser medium doped with active ions is fused on both sides of a parallel plane of a slab-fixed laser base material to melt the laser medium. A cooling medium is provided in contact with the surface of the laser medium opposite to the surface of the laser that is the reflection surface of the surface opposite to the attachment surface, and laser excitation light is introduced into the laser material from the input / output end faces of the laser material. Then, a zigzag slab solid-state laser amplifier is configured so that the laser light pumped by the laser medium and the pumping light are reflected by the reflection surface of the laser medium and are zigzag-traveled to be pumped / amplified.

In the solid-state laser according to the first aspect of the invention, pumping laser light is introduced into the inside through the input / output end of the laser base material from between the reflection mirror of the optical resonator and the laser medium portion, and the pumping laser light is introduced. When the laser light travels in a zigzag manner and is absorbed by the solid-state laser medium, the laser light rises due to spontaneous emission. This laser light has a different wavelength from the excitation laser light and is obtained as a laser light having a predetermined wavelength determined by the material of the solid-state laser medium.

The laser light generated in the laser medium portion travels in the solid laser base material while being reflected in zigzag in the same direction as the excitation laser light, and the laser light is generated in the regions sequentially excited by the excitation laser light. It is amplified in the laser medium by being superposed. The amplified laser light is emitted from the solid-state laser base material, is reflected by the boundary surface on the opposite side to the incident side of the excitation laser light or is reflected by a reflection mirror, and enters the solid-state laser base material again in a zigzag manner. The light reaches the boundary surface or the reflection mirror on the same side as the incident side of the excitation laser light, and is reflected there, and the same operation is repeated thereafter.

When the laser light generated as described above reciprocates in the optical resonator and is gradually amplified and the light intensity reaches a steady state, it is taken out from one of the reflecting mirrors as a laser light output. In this way, when the laser light is extracted, the solid-state laser of the present invention is provided with the cooling means in direct contact with or in contact with the solid-state laser medium, so that heat generated in the solid-state laser medium can be removed with high efficiency.

The heat generated when the laser light for excitation is absorbed by the solid-state laser medium to generate the laser light moves both inside the solid-state laser base material which is in contact with the solid-state laser medium and in the cooling means. Accordingly, the heat that has moved into the base material is removed directly on the side in contact with the cooling means, and indirectly by the cooling means in contact with the solid-state laser medium on the opposite side. Therefore, the thermal birefringence effect and the thermal lens effect hardly occur.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a main sectional view of a zigzag slab solid state laser according to the embodiment. The solid-state laser of this embodiment is
It is suitable for obtaining a high-quality beam of laser light with a high cw (continuous) output that is excited by the laser light of a semiconductor laser (LD).

In the figure, 1 is a solid-state laser medium, 9 is a slab solid-state laser base material, 3 and 4 are reflection mirrors constituting an optical resonator, 5 is pumping laser light introduced from the outside, and 8 is cooling means. Reference numeral 10 is an input / output surface of the solid-state laser base material, and 11 is a beam splitter.

The solid-state laser medium 1 is the same light-transmissive material as the solid-state laser base material 9 doped with a high concentration of active ions. In this embodiment, a YAG (yttrium aluminum garnet) crystal is used as a base material. To this and Y
For example, b (ytterbium) added with 20 at% is used. In addition to the above, the active ions to be added may be any of rare earth elements for quasi-three level laser such as Er, Ho and Tm, and other appropriate materials may be used as the base material. The solid laser base material 9 is not doped with active ions.

The solid-state laser base material 9 is formed as a parallel plate having a narrow light-transmissive width to form a parallel-plate slab, and thin (for example, 0.35 mm) solid-state laser medium 1 is fused on both parallel surfaces. ing. Further, the outer surface of the solid-state laser medium 1 is coated with a high reflection (HR) for the laser light, or the total reflection phenomenon at the boundary surface is used to totally reflect the laser light at this reflection surface.

On the outside of the laser medium portion composed of the solid laser base material 9 and the thin solid laser medium 1, cooling means 8 is directly joined or in contact with the entire surface of both sides thereof. The cooling means 8 is formed so that the cooling water w can flow directly between water or two cooling plates made of copper, for example.

The laser medium portion is arranged between the reflection mirrors 3 and 4 of the optical resonator. The reflection mirror 3 is a concave mirror, and the reflection mirror 4 is a partially transmissive plane mirror. And
The laser beam excited by the laser medium is reflected by one of the reflection mirrors 3, and is output from the reflection mirror 4 which is an output mirror, in the middle of each optical path.
Is provided, and the laser light generated outside is introduced as the excitation laser light 5 from the left and right beam splitters 11 and is introduced inside from the input / output surface 10 of the solid-state laser base material 9.

The input / output surface 10 is formed at an angle close to a Brewster's angle or a right angle with respect to the incident light, and the input / output surface itself is a flat surface. When the input / output surface 10 has a vertical or oblique incidence shape, an antireflection (AR) coating is applied to the excitation laser light 5 and the laser light 7. Further, the beam splitter 11 is provided on its inner surface side with an AR coating for the excitation laser light 5 and a high reflection (HR) coating for the laser light 7.

The zigzag slab solid-state laser of the embodiment configured as described above operates as follows to obtain high-quality laser light.

When the pumping laser light 5 from the outside is introduced into the optical path in the optical resonator via the left and right beam splitters 11, the pumping laser light is internally fed from the input / output surface 10 of the solid laser base material 9. The solid laser medium 1 is absorbed by the solid laser medium 1 as it enters the base material 9 and laser light is generated there.

A part of the pumping laser light is totally reflected by the reflecting surface 1a of the solid-state laser medium 1, passes through the base material 9 and reaches the solid-state laser medium 1 on the opposite side, where it is again absorbed by the solid-state laser medium 1. Laser light is generated as a result, a part of the laser light for excitation is reflected by the reflection surface 1a of the solid-state laser medium 1, and the laser light for excitation advances zigzag in the solid-state laser medium portion by repeating this.

The laser light pumped by the pumping laser light also travels in a zigzag direction in the same direction as the pumping laser light and is amplified while repeating total reflection, and then exits the solid-state laser base material 9 and is beam splitter 11. It is reflected (in the case of the laser light excited by the excitation laser light incident from the beam splitter 11 on the right side in FIG. 1), reflected by the reflection mirror 3 (in the case of the left side is reflected by the reflection mirror 4), and the forward path is obtained. After returning to the same path and repeating total reflection, the light travels to the reflection mirror 4 on the opposite side, where it is reflected and travels in the same path again in a zigzag manner, and positive feedback is performed.

The excitation of the laser medium by the above-mentioned laser light for excitation is performed from both left and right directions, and the solid-state laser medium 1 is uniformly excited along the length direction. In this way, the laser light is gradually amplified by going back and forth along the same optical path, the laser light intensity reaches a steady state, and is taken out as the laser light 7 from the reflecting mirror 4 which is a partially transmissive plane mirror. The laser light 7 acts as an ideal slab solid-state laser because the solid-state laser medium 1 is thin. The pumping laser light 5 from one side travels in the solid-state laser base material 9 in a zigzag manner and is returned to the original direction by the reflecting mirror on the opposite side to increase the absorption rate of the pumping laser light 5 in the solid-state laser medium 1. You can also

As described above, when laser light is generated in the solid-state laser medium 1 by the excitation laser light, the heat generated in the slab solid-state laser of the above embodiment is efficiently removed. As described above, the heat generated in the solid-state laser medium 1 moves from the solid-state laser medium 1 to the outer and inner solid-state laser base materials 9, so that water in the cooling means 8 directly joined to the outer side Be removed directly.

The heat flowing into the solid-state laser base material 9 is indirectly removed by the cooling means 8 outside the solid-state laser medium 1 on the opposite side. Therefore, the heat generated in the thin solid-state laser medium 1 flows in the vertical direction of FIG. 1 to prevent the generation of the thermal birefringence effect, and the thermal lens effect is compensated by the zigzag total reflection.

In the above embodiment, the case of the zigzag slab solid state laser has been described, but the reflection mirrors 3 and 4 are also described.
By removing the weak incident laser light of the same wavelength as the generated laser light is zigzag and amplified by the laser medium that is optically pumped, it can also be used as a zigzag slab solid state laser amplifier. Needless to say it will be obvious.

[0031]

As described in detail above, in the zigzag slab solid state laser of the first invention, the heat generated when the pumping laser light is sent from the inside of the solid state laser base material and absorbed in the solid state laser medium to be optically excited is parallel plane. Since the cooling means in contact with each other can directly and indirectly remove the heat, the generated heat can be removed with high efficiency, and high-output and high-quality laser light can be achieved. Further, since the pumping laser light and the generated laser light are propagated in the same direction, there is an effect that the structure is simplified.

Furthermore, if a laser amplifier of the first invention having no optical resonator is used as the second invention, a strong laser amplification effect can be obtained.

[Brief description of drawings]

FIG. 1 is a main longitudinal sectional view of a zigzag slab solid-state laser according to an embodiment.

FIG. 2 is a main sectional view of a conventional zigzag optical path solid-state laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid-state laser medium 1a Reflection surface 3 and 4 Reflection mirror 5 Laser light for excitation 7 Laser light 8 Cooling means 9 Solid-state laser base material 10 Input-output surface 11 Beam splitter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masahiro Nakatsuka 2-6 Yamadaoka, Suita City, Laser Fusion Research Center, Osaka University (72) Masanobu Yamanaka 2-6 Yamadaoka, Suita City Laser Fusion, Osaka University Inside the Research Center (72) Inventor Chiyoe Yamanaka 1-8-4 Tsubuhoncho, Nishi-ku, Osaka City

Claims (2)

[Claims] 1. A laser medium portion in which a solid-state laser medium doped with active ions is fused on both sides of a parallel surface of a slab solid-state laser base material and a surface opposite to the fused surface of the laser medium serves as a reflecting surface. The laser medium is arranged in an optical resonator composed of a pair of reflection mirrors for amplifying the laser light generated in the laser medium portion, and a cooling means is provided on the surface of the laser medium portion opposite to the laser base material. The pumping laser light is introduced into the laser base material from the input / output end face, and the laser light pumped by the laser medium and the pumping laser light are reflected by the reflecting surface of the laser medium and are zigzag-traveled to be pumped / amplified. A zigzag slab solid-state laser configured to further amplify the laser light in an optical resonator and output the amplified laser light from an output mirror. 2. A solid-state laser medium doped with active ions is fusion-bonded to both sides of a parallel plane of a slab-fixed laser base material, and a laser medium portion having a surface opposite to the fusion-bonding surface of the laser medium as a reflection surface is provided on the laser medium portion. The cooling means is provided in contact with the surface opposite to the laser base material, laser excitation light is introduced into the laser base material from the input / output end surface of the laser base material, and the laser light and the excitation light excited by the laser medium are supplied to the laser. A zigzag slab solid-state laser amplifier configured so as to be reflected by a reflecting surface of a medium, to be zigzag-progressed, and to be pumped / amplified.