JP2000077753A - Side excitation solid-state laser provided with anisotropic crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state laser device that is provided with an anisotropic crystal such as a YLF as a laser crystal and capable of efficiently exciting a laser crystal by applying exciting rays to its side face from all directions and outputting a high power. SOLUTION: This laser 10 is equipped with a cylindrical laser rod 12 which is formed of an anisotropic crystal (for instance, YLF crystal) that is possessed of two axes a and c which cross its growth axis (a axis) at right angles, the axis c is different from the growth axis is characteristics and the axis a is equal to the growth axis in characteristics, and whose center axis is the axis c and an exciting light irradiation means 14 which irradiates the side face of the laser rod 12 with exciting light. At this point, the exciting light irradiation 15 that is excited by the exciting light irradiator means 14 is made to irradiate ortho-gonally to the C-axis of the laser rod, and its polarization direction 16 is set in parallel with C-axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a side-pumped solid-state laser using an anisotropic crystal.

[0002]

2. Description of the Related Art A YAG solid-state laser is a YAG (Yttrium A).
It excites a crystal of aluminum garnet (Nd) doped with Nd, and provides a CW output of several tens of watts with 1.06 μm infrared light. The second harmonic generator also converts green light of 0.53 μm with high efficiency and is used for the laser industry. Yd doped with Nd
Since (Nd: YAG) is an isotropic crystal, two means of edge excitation (A) and side excitation (B) schematically shown in FIG. 2 are conventionally used for its excitation. . The end surface excitation (A) is to excite by irradiating the excitation light 2 from the end surface of the cylindrical YAG laser rod 1, and the side excitation (B) is to irradiate the excitation light 2 from the end surface of the YAG laser rod 1. Exciting. In the end face excitation (A), since the excitation light 2 can be irradiated from the end face by increasing the energy density by the lens 3 or the like, high efficiency can be easily obtained, but on the other hand, the irradiation surface is limited, so that the output tends to be small. On the other hand, the side excitation (B) has a feature that although the efficiency is low, the irradiation surface can be widened so that the output can be increased. Therefore, conventionally, high power has been achieved mainly by a side-pumped solid-state laser using an isotropic crystal such as YAG.

On the other hand, in recent years, YLF (Lithium Yttrium Flu
oride) crystals have been developed and used in some YLF lasers. This YLF laser is composed of Nd-doped phosphate glass (Phosphate and fluorophosphate).
Since it oscillates a laser beam of 1.05 μm which matches the peak gain of glass, it is mainly used for a master resonator for exciting these glasses. This YLF
The crystal has a fluorescence lifetime (Fluorescent l
ifetime) is not nearly twice as long, so long-term excitation is possible,
It also has high heat resistance and is suitable for high output.

[0004]

However, the crystal of YLF is an anisotropic crystal. As shown in FIG. 3, two axes orthogonal to the crystal growth axis (a-axis) are different from the growth axis. There are an a-axis with the same characteristics and a c-axis with different characteristics. Therefore, FIG.
In the case of irradiating polarized light in the directions indicated by the arrows (A) and (B) (referred to as π-polarized light and σ-polarized light, respectively), there is a great difference in the excitation characteristics (absorbance, gain, etc.) of the laser light. For example, FIG. 4 shows a comparison of the absorptance, which has a characteristic that the absorptivity of σ polarized light is lower than that of π polarized light.

For this reason, in a laser device using a YLF crystal, as shown in FIG. 5, by irradiating the end face of a YLF laser rod 1 with excitation light 2 of π-polarized light, a high absorptance is ensured and efficient. Laser light was being excited. That is, by making the polarization direction 4 of the irradiation light 2 irradiating the end face coincide with the c-axis of the YLF crystal 1, the absorption rate of the excitation light is increased and efficient excitation is enabled. In this end-pumped solid-state laser, the output laser light 6 also has the same polarization direction 7 as the pump light 2.

However, such a conventional YLF laser is limited to the end face pumping, and thus has a problem that it is not possible to further increase the output unlike the side face pumping of the YAG laser. That is, even if the side surface (cylindrical surface) of the YLF laser rod 1 shown in FIG. 5 is irradiated with the excitation light 2 from multiple directions, the polarization direction of the excitation light 2 is not directed to the c-axis of the YLF crystal 1. As described above, there is a problem that the absorption rate of the excitation light 2 is low, so that the loss becomes large and efficient excitation cannot be performed. Accordingly, there has been no example of a side-pumped solid-state laser using an anisotropic crystal such as a YLF crystal, and all have been used for edge-pumped lasers.

The present invention has been made to solve such a problem. That is, the object of the present invention is YL
Provided is a side-pumped solid-state laser using an anisotropic crystal, such as an F crystal, which can efficiently pump from multiple directions on a side surface by using an anisotropic crystal as a laser crystal, thereby increasing the output. It is in.

[0008]

According to the present invention, two axes orthogonal to the crystal growth axis (a axis) are composed of an a axis having the same characteristics as the growth axis and a c axis having different characteristics. A cylindrical laser rod (12) formed of an isotropic crystal and having a c-axis as an axis; and an excitation light irradiating means (14) for irradiating excitation light to a side surface of the laser rod. An anisotropic crystal, characterized in that the excitation light (15) by the means is irradiated orthogonally to the c-axis of the laser rod and the polarization direction (16) is set parallel to the c-axis. A side-pumped solid state laser is provided. According to a preferred embodiment of the present invention, the anisotropic crystal is a YLF crystal.

According to the configuration of the present invention, since the cylindrical laser rod (12) is formed so as to have the c-axis of the anisotropic crystal (for example, YLF crystal) as the axis, the axis of the laser rod is formed. Both axes orthogonal to the heart are a-axis. Therefore,
The excitation light irradiating means (14) irradiates excitation light (15) from the side surface of the laser rod in a direction orthogonal to the axis (c-axis) of the laser rod, and the polarization direction of the excitation light (16).
Is set parallel to the c-axis (that is, in the axial direction), the polarization plane of each excitation light can be directed to the c-axis of the YLF crystal, and the excitation light is efficiently maintained while maintaining a high absorption rate of the excitation light. be able to. Furthermore, compared to the end face excitation, the side face excitation can make the irradiation surface of the excitation light wider, so that the output can be increased.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common portions are denoted by the same reference numerals, and redundant description is omitted.
FIG. 1 is a configuration diagram of a side-pumped solid-state laser according to the present invention using an anisotropic crystal. As shown in FIG. 1, a side-pumped solid-state laser 10 according to the present invention includes a cylindrical laser rod 12 and excitation light irradiating means 14 for irradiating a side surface of the laser rod 12 with excitation light 15.

The cylindrical laser rod 12 is formed from an anisotropic crystal such as a YLF crystal. That is, YL
In an anisotropic crystal such as an F crystal, as shown in FIG. 3, two axes orthogonal to the crystal growth axis (a-axis) are a-axis having the same characteristics as the growth axis and c-axis having different characteristics. Consists of YL
In the case of F crystal, the c-axis is the axis having the highest absorptance.
The cylindrical laser rod 12 of the present invention forms a laser rod from such an anisotropic crystal such that the c-axis having unique characteristics becomes the axis. The laser rod 12 of the present invention formed in this way is significantly different from the conventional end-pumped solid-state laser shown in FIG. 5 in that its axis is the c-axis.

The side-pumped solid-state laser 10 of the present invention
In the above, the excitation light 15 by the excitation light irradiation means 14 is irradiated orthogonally to the c-axis (that is, the axis) of the laser rod 12, and the polarization direction 16 is set parallel to the c-axis (the axis). .

As described above, in the present invention, the cylindrical laser rod 12 is formed of an anisotropic crystal (for example, a YLF crystal).
The two axes perpendicular to the axis of the laser rod 12 are both a-axis because they are formed to have the axis as the axis. Therefore, the excitation light irradiating means 14 irradiates the excitation light 15 from the side surface of the laser rod 12 in a direction orthogonal to the axis (c-axis) of the laser rod, and changes the polarization direction 16 of the excitation light parallel to the c-axis (that is, the c-axis). It can be easily and easily set as shown in FIG. Further, the irradiation direction of the excitation light 15 is not limited to a two-axis direction orthogonal to the axis of the laser rod 12, as shown in this figure, but can be performed from multiple directions orthogonal to the axis.

With this configuration, the polarization plane 1 of each excitation light 15
6 can be directed to the c-axis of the anisotropic crystal (YLF crystal), and the absorption of the excitation light 15 can be kept high to perform efficient excitation. Furthermore, compared to the end face excitation, the side face excitation can make the irradiation surface of the excitation light wider, so that the output can be increased. In the side-pumped solid-state laser 10 of the present invention,
The oscillating laser light is, in principle, circularly polarized light, which is different from the conventional end-pumped type.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the spirit of the present invention.

[0016]

As described above, the side-pumped solid-state laser of the present invention uses an anisotropic crystal such as a YLF crystal as a laser crystal, and can efficiently pump from multiple directions on the side.
This has an excellent effect that a large output can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a side-pumped solid-state laser according to the present invention using an anisotropic crystal.

FIG. 2 is a schematic view of a conventional end face excitation (A) and a side face excitation (B) using an isotropic crystal.

FIG. 3 is an explanatory diagram of an anisotropic crystal.

FIG. 4 is a comparison diagram of absorptivity of π-polarized light and σ-polarized light.

FIG. 5 is a configuration diagram of an edge-pumped solid-state laser using an anisotropic crystal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser rod 2 Excitation light 3 Lens 4 Polarization direction 6 Output laser light 7 Polarization direction 10 Side-excitation solid laser 12 Cylindrical laser rod 14 Excitation light irradiation means 15 Excitation light 16 Polarization direction

Claims (2)

[Claims] 1. An anisotropic crystal having two axes perpendicular to a crystal growth axis (a-axis), comprising an a-axis having the same characteristics as the growth axis and a c-axis having different characteristics, and a c-axis. A cylindrical laser rod (12) having an axis as an axis, and excitation light irradiating means (14) for irradiating the side surface of the laser rod with excitation light, wherein the excitation light (15) by the excitation light irradiating means is a laser. Irradiated perpendicular to the c-axis of the rod and its polarization direction (16)
Is set parallel to the c-axis, wherein a side-pumped solid-state laser using an anisotropic crystal. 2. The side-pumped solid-state laser according to claim 1, wherein the anisotropic crystal is a YLF crystal.