JPH04123479A - Laser diode(ld) excited solid state laser oscillator - Google Patents

Abstract

PURPOSE:To excite a laser medium by providing two laser diodes to become exciting sources, and a reflecting mirror having an opening at its center to coaxially combine excited lights. CONSTITUTION:Two LDs 20, 21 to become exciting sources are disposed at a predetermined interval in parallel, and the lights are respectively introduced to optical fibers 22, 23. Since the excited light output from one fiber 22 is enlarged at an angle to be determined according to the number of openings of the fiber from the outlet of the fiber, a lens 25 is disposed at a beam diameter position of the same degree of the beam diameter as the diameter of an opening 24a formed at the center of a 45 deg. reflecting mirror 24, and collimated to obtain a substantially parallel light. The excited light of a small diameter passing through the lens 25 is passed through the opening 24a at the center of the mirror 24, the excited light of a large diameter passed through a lens 26 is mostly reflected by a the mirror 24, and passed through a condensing lens 27 coaxially to a laser medium 28 to be excited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an LD-pumped solid-state laser oscillator that uses light from a laser diode (hereinafter referred to as LD) as an excitation light source.

[Conventional technology]

Conventionally, in LD-pumped solid-state lasers, there are roughly two methods for focusing LD light. One is the end-face excitation method, which pumps from the end face of the cylindrical laser medium 1, as shown in FIG. 3(A), and the other, which pumps from the side surface of the laser medium 1, as shown in FIG. 3(B). It is a side excitation method. These differences are mainly due to the structure of the LD that serves as the excitation source, and when using a multi-striped LD2 with a large emission area, the side excitation method shown in Figure 3 (B) is used. . Note that in FIG. 3(B), a cylindrical lens 3 is disposed between the laser medium 1 and the LD 2, and a partial reflection mirror 4 is disposed on the right side of the laser medium 1.

On the other hand, in the end face excitation method shown in FIG. 3(A), a single drive LD5 is used. This LD 5 has a relatively small light emitting area of several μm x several hundred μm, and can efficiently condense light onto the laser medium 1 via the condenser lens 6 . Therefore, although it has the feature of being able to obtain single mode oscillation with high efficiency, it is difficult to obtain a large LD optical output.
The laser output is also mainly low output. In addition, in FIG. 3(A), a partial reflection mirror 4 is disposed on the right end surface side of the laser medium 1.

For this reason, a configuration using a polarizing plate 7 shown in FIG. 4 has been proposed as a method for condensing a plurality of LD lights on the same axis. This configuration utilizes the property that the oscillated light of the LD 8.9 is polarized, and the LD 8.9 is tilted by 90 degrees to make the polarization directions of the light orthogonal. For example, if the polarization direction of the light from LD9 is perpendicular to the paper surface,
The light from the LD8 is arranged parallel to the plane of the paper.

Further, since the light from the LD 8 is transmitted through the polarizing plate 7 and the light from the LD 9 is reflected by the polarizing plate 7, the lights can be combined coaxially. Further, collimating lenses 10.11 are disposed between the LD 8.9 and the polarizing plate 7, and a condensing lens 13 is disposed between the polarizing plate 7 and the laser medium 12. . Furthermore, a partial reflection mirror 14 is arranged on the right end surface side of the laser medium 12.

[Problem to be solved by the invention]

However, in this conventional light focusing method using the polarizing plate 7,
Before combining on the same axis, each light must be polarized orthogonally to each other, and when passed through an optical fiber,
Since this polarization is canceled, the respective lights cannot be combined on the same axis, resulting in a disadvantage that the laser medium I2 cannot be excited.

An object of the present invention was made in view of the above-mentioned drawbacks, and is to provide an LD-pumped solid-state laser oscillator capable of exciting a laser medium.

[Indispensable means to solve problems]

The present invention provides an LD-pumped solid-state laser oscillator that uses a laser diode as a pumping light source for a solid-state laser. The configuration includes a reflecting mirror having a reflection mirror.

[Effect]

As described above, according to the present invention, by using a reflecting mirror having an opening in the center, it is possible to efficiently combine two unpolarized lights on the same axis and excite the laser medium.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of an LD pumped solid-state laser oscillator according to the present invention. In this embodiment, two LDs D20.21 serving as excitation sources are arranged in parallel at a predetermined interval, and the light from these LDs 20.21 is configured to be introduced into each optical fiber 22.23. has been done. In addition, the excitation light (
When using Nd:YAG as the laser medium, the wavelength is 809
rm) is the numerical aperture (NA) of the fiber from the fiber exit.
Since the beam spreads at an angle determined by It is collimated.

In addition, in the other optical fiber 23, 3 of the diameter of the aperture 24H
It is collimated by a lens 26 so that the beam becomes ~4 times as large.

However, the small diameter excitation light that has passed through the lens 25 is
The large diameter excitation light that passes through the opening 24a at the center of the 5° reflecting mirror 24 and the lens 26 is mostly reflected by the 45° reflecting mirror 24, and passes through the condensing lens 27 on the same axis. , is focused on the laser medium 28, and excites this laser medium 28. Moreover, this laser medium 28 (
7) The first surface 28a is coated with a non-reflection coating for the wavelength of the excitation light, and is coated with a guichroic coating that has almost 100% reflection for the laser oscillation wavelength, making it partially reflective. Together with the mirror 29, it becomes an optical resonator and laser oscillation can be obtained.

FIG. 2 shows a second embodiment of the invention. This embodiment differs from the above-mentioned first embodiment in that there is a 30a
By changing the 45° reflecting mirror 30 from a plane mirror to a concave mirror, the condenser lens 27 in FIG. 1 can be made unnecessary.

Therefore, in this embodiment, the 45° reflection mirror 30
A laser medium 28 is directly placed on the right side of the laser medium 28 at a predetermined distance. In addition, LD20.21, optical fiber 2
2.23, lenses 25, 26, and partial reflection mirror 29 are the same as in the embodiment described above, so their explanations will be omitted.

〔Effect of the invention〕

As explained above, according to the LD-pumped solid-state laser oscillator according to the present invention, by using a configuration using a reflecting mirror having an opening in the center, two undeflected beams can be efficiently synthesized coaxially. This has the excellent effect of making it possible to excite the laser medium.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the LD-pumped solid-state laser oscillator according to the present invention, FIG. 2 is a schematic diagram showing another embodiment of the LD-pumped solid-state laser oscillator according to the present invention, and FIG.
Figures (A), (B) and Figure 4 are schematic configuration diagrams showing conventional examples, respectively. 20.21...LD. 24.30...45° reflection mirrors 24a, 30
a...Aperture, 28...Laser medium.

Claims (1)

[Claims] L using a laser diode as an excitation light source for a solid-state laser
A D-pumped solid-state laser oscillator, which has two laser diodes serving as excitation sources, and is equipped with a reflecting mirror having an aperture in the center in order to coaxially combine the respective pumping lights. laser oscillator.