JPH02122581A - Laser oscillator - Google Patents

Abstract

PURPOSE:To perform efficient excitation and obtain a laser oscillator having a capacity of high output of power by causing a plurality of excitation light sources to emit a light having absorption peak wave lengths which differ in absorption spectra of laser media and combining excitation rays with different wave lengths which are emitted from the above light sources on the same optical axis by means of dichroic mirrors. CONSTITUTION:Laser beams oscillated by the first semiconductor device 19 penetrate efficiently through the first-third dichroic mirrors 15-17 one after another to come into a condensing optical system 7. The second-the fourth semiconductor laser devices 21, 23, and 25 face to reflecting surfaces of the first - the third dichroic mirrors 15-17 at each angle of almost 45 deg. through the second-the fourth collimating systems 20, 22, and 24. The dichroic mirrors 15-17 allow the semiconductor laser beams emitted by a plurality of semiconductor laser devices 19, 21, 23, and 25 to be combined on the same optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a laser oscillation device that excites, for example, a YAG laser medium with a semiconductor laser.

(Prior Art) General YAG laser oscillation devices are shown in FIGS. 4 to 6. Laser oscillation device 1 shown in FIG.
has a cylindrical laser rod 2 formed of a YAG laser medium and a resonator 3 facing each other across the laser rod 2, and this resonator 3 is opposed to one end of the laser rod 2. It consists of a high reflection mirror 4 and an output mirror 5 facing the other end of the laser rod 2. The output mirror 5 has a concave reflective surface facing the laser rod 2, and has a concave surface that outputs the laser beam in the direction indicated by the arrow when the light intensity exceeds a predetermined level.
It has a reflective coating. In addition, the high reflection mirror 4 has a concave reflection surface similar to the output mirror 5, and this reflection surface is configured to transmit excitation light, which will be described later, with high efficiency and to highly efficiently transmit the light emitted from the laser rod 2. It has a reflective coating.

For example, a semiconductor laser device 6 as an excitation light source is arranged on an extension of the axis of the laser rod 2, and a condensing optical system 7 is disposed between the semiconductor laser device f6 and the high reflection mirror 4. It is arranged.

In the laser oscillation device 1 formed in this way, the semiconductor laser oscillated from the semiconductor laser device 6 passes through the focusing optical needle 7 and is focused, and also passes through the high reflection mirror 4 to form the laser rod 2. Irradiates inside from the end face. The laser rod 2 is excited by the incidence of this semiconductor laser and emits YAG laser light. This YAG laser resonates within the resonator 3 and is output from the output mirror 5 when it reaches a predetermined output.

However, since the excitation light source for exciting the laser rod 2 is only one semiconductor laser device 6, effective excitation to obtain a large output cannot be achieved.

For this reason, a laser oscillation device 8 as shown in FIG. 5 has been considered. A resonator 10 is formed by disposing a high reflection mirror 9 having a concave reflection surface and an output mirror 5 facing each other at both ends of a cylindrical laser rod 2. A semiconductor laser array 11 is provided facing the side surface of the laser rod 2 along the axial direction.

Such a laser oscillation device 8 includes the semiconductor laser array 1
The semiconductor laser from 1 is irradiated across the side surface of the laser rod 2 along the axial direction, and the excited laser rod 2 emits YAG laser, which oscillates between the resonators 10 and from the output mirror 5 as a YAG laser L. It is now output.

However, even if the semiconductor laser array 11 is provided along the axial direction of the laser rod 2 in this way, the laser pattern P emitted by the resonator 10 does not pass through the entire volume of the laser rod 2. Even if the middle hatched area H is excited, the output light is not oscillated and the output cannot be improved, so there is a drawback that highly efficient pumping cannot be performed.

For this reason, as shown in FIG. 6, there is a laser oscillation device 12 that can perform stronger excitation while emitting excitation laser light along a laser pattern P that resonates in the resonator 3. In this laser oscillation device 12, a high reflection mirror 4 formed into a concave surface is opposed to one end of a laser rod 2, and this high reflection mirror 4 reflects the wavelength of the laser emitted from the laser rod 2, and A coating is applied to transmit excitation light from an excitation light source, which will be described later.

An output mirror 5 formed into a concave surface is opposed to the other end of the laser rod 2, and is coated with a coating so as to output a laser beam with a predetermined output or more. The above-mentioned resonator 3 is formed by the above-mentioned high reflection mirror 4 and output mirror 5.
is configured. Further, a condensing optical system 7 is arranged outside the high reflection mirror 4, and one end of a plurality of optical fibers 13 are bundled together and opposed to the condensing optical system 7. There is. These optical fibers 13...
Semiconductor laser devices 6 are opposed to the respective ends of the laser beams 6 with condenser lenses 14 interposed therebetween.

In the laser oscillation device 12 configured as described above, the lasers oscillated by the plurality of semiconductor laser devices w16... pass through the condenser lenses 14..., thereby forming the optical fibers 13...
incident on . The semiconductor laser emitted from the bundled ends of the optical fibers 13 is condensed by passing through the condensing optical system 7, and is condensed by the high reflection mirror 4.
The laser rod 2 is excited by transmitting the laser beam. Due to this excitation, the laser rod 2 oscillates the YAG laser in a pattern shape P shown in the figure, and when the output exceeds a predetermined output, the laser rod 2 outputs an output from the output mirror 5.

Such a laser oscillation device 12 can intensively irradiate the laser rod 2 with excitation light from a plurality of semiconductor laser devices 6 through the optical fibers 13.
Compared to the other structures mentioned above, stronger excitation is possible. However, the optical fiber 13 . There was a situation in which the laser rod 2 was not efficiently irradiated with the laser.

(Problem to be solved by the invention) A general solid-state laser oscillation device efficiently oscillates a laser by exciting only the effective oscillation part of the laser rod that corresponds to the laser oscillation pattern formed between resonators. There is a structure to do this. However, such a structure irradiates excitation light along the oscillation direction of the laser rod, and it is necessary to provide an excitation light source within a very limited range. For this reason, there are methods that use optical fibers or the like to condense excitation light, but these have not been able to achieve highly efficient excitation.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser oscillation device that can perform highly efficient excitation and obtain high output.

[Structure of the invention]

(Means for Solving the Problem) A resonant means is provided in a laser medium, a plurality of excitation light sources are provided that emit light having different absorption peak wavelengths in the absorption spectrum of the laser medium, and the resonant means is provided in correspondence with these excitation light sources. A dichroic mirror is disposed on the optical axis that enters the laser medium along the oscillation direction, and the dichroic mirror reflects the wavelength of the corresponding excitation light source in the direction of incidence along the optical axis that enters the laser medium. The laser oscillation device is configured to transmit the wavelength of another excitation light source located outside and combine it with the reflected light along the optical axis.

(Function) A dichroic mirror can combine excitation light with different wavelengths emitted from multiple excitation light sources that emit light with different absorption peak wavelengths in the absorption spectra of the laser medium onto the same optical axis. The oscillation region of the laser medium can be irradiated with excitation light that is selectively combined with light having the absorption peak wavelength of the absorption spectrum of the medium.

(Example) An example of the present invention will be described with reference to the drawings. The laser oscillation device of this embodiment is constructed as shown in FIG. A laser rod 2 as a laser medium shown in the figure is, for example, a Nd:YAG crystal processed into a cylindrical shape, and the absorption spectrum of this laser rod 2 is as shown in FIG. The graph shown in the figure shows the absorbance on the vertical axis and the wavelength on the horizontal axis, and in particular, λ1. λ2. λ3. Four wavelengths of λ4 show absorbance peaks.

The laser rod 2 is provided with a resonator 3 arranged to sandwich the laser rod 2 therebetween. This resonator 3 is formed of a high reflection mirror 4 having a concave reflection surface and an output mirror 5. The reflection surface of the high reflection mirror 4 transmits the wavelength of excitation light, which will be described later, with high efficiency. A coating is applied to reflect the YAG laser emitted from the laser rod 2 with high efficiency. Further, the output mirror 5 is coated to reflect a portion of the YAG laser so that it reaches a predetermined output. With this configuration, the YAG laser emitted by the laser rod 2 is reflected and oscillated between the resonators 3 with a high reflectance, and a predetermined output is transmitted to the output mirror 5.
The data is output in the direction of the arrow.

A condensing optical system 7 is disposed at a position facing the back side of the high reflection mirror 4, and this condensing optical system 7
is located on an extension of the optical axis of the YAG laser oscillated by the resonator 3. Furthermore, first to third dichroic mirrors 15, 16, and 17 are arranged outside the converging optical system 7 along the optical axis of the YAG laser. The first dichroic mirror 15 located farthest from the resonator 3 is tilted at an angle of approximately 45@ with respect to the optical axis of the YAG laser, and is provided with its reflecting surface facing the resonator 3 side. There is.

This reflective surface is coated with a film that has the property of highly efficiently reflecting light with a wavelength of λ2 and transmitting light with a wavelength of λ1 with high efficiency.

Further, a second dichroic mirror 1 is located between the first dichroic mirror 15 and the condensing optical system 7.
6, the reflective surface is approximately 45 degrees with respect to the optical axis of the YAG laser.
It is tilted at an angle of `` and is directed toward the resonator 3 side,
This reflective surface reflects light with a wavelength of λ3 with high efficiency,
It is coated with a film that transmits light at wavelengths λ1 and λ2 with high efficiency.

Furthermore, between this second dichroic mirror 16 and the above-mentioned condensing optical system 7, there is provided a third mirror which is inclined at an angle of approximately 45° to the optical axis of the YAG laser and has a reflecting surface facing the above-mentioned resonator 3 side. A dichroic mirror 17 is provided. This third dichroic mirror 17 reflects light with a wavelength of λ4 on its reflecting surface with high efficiency, and reflects light with a wavelength of λ1. λ2. It is coated with a film that transmits light with a wavelength of λ3 with high efficiency.

A first semiconductor laser device 19 is opposed to the back surface of the first dichroic mirror provided as described above via a first collimating optical system 18. This first semiconductor laser device 19 is located on an extension of the optical axis of the YAG laser oscillated by the resonator 3, and is configured to oscillate the semiconductor laser concentrically with this optical axis. Further, the first semiconductor laser device 19 is set to oscillate a laser beam having a wavelength of λ1. In other words, the laser beam oscillated from the first semiconductor laser device 19 passes through the first to third dichroic mirrors 15.16° 17 in sequence with high efficiency and enters the condensing optical system 7. ing.

Further, the reflective surface of the first dichroic mirror 15 is provided with a second collimating optical system 2 at an angle of approximately 45''.
A second semiconductor laser device 21 is opposed to the semiconductor laser device 21 via the laser beam. This second semiconductor laser device 21 is set to oscillate a laser beam with a wavelength of λ2, and the laser beam oscillated from this second semiconductor laser device 21 is
The light is reflected with high efficiency by the reflecting surface of the dichroic mirror 15, is combined with the light of λl, and is sequentially transmitted through the second and third dichroic mirrors 16 and 17, and is sent to the condensing optical system 7.
It is designed to be incident on .

Further, a third collimating optical system 22 is provided on the reflecting surface of the second dichroic mirror 16 at an angle of approximately 45°.
A third semiconductor laser device 23 is opposed to the third semiconductor laser device 23 via. This third semiconductor laser device 23 is set to oscillate a laser beam with a wavelength of λ3, and the laser beam oscillated from this semiconductor laser device 23 is reflected by the second dichroic mirror 16. The light is combined with the other two wavelengths λ1 and λ2 that have passed through the mirror 16, and is then transmitted through the third dichroic mirror 17 and enters the condensing optical system 7.

Further, the reflective surface of the third dichroic mirror 17 has a fourth collimating optical system 2 at an angle of approximately 45''.
A fourth semiconductor laser device 25 is opposed to the fourth semiconductor laser device 25 via 4. This third semiconductor laser device 25 is set to oscillate a laser beam with a wavelength of λ4, which is reflected with high efficiency by the third dichroic mirror 17 and transmitted through the third dichroic mirror 17. Other wavelength λ1. λ2. The light is combined with λ3 and enters the condensing optical system 7.

The semiconductor laser beams having their respective wavelengths combined are collected by a focusing optical system 7 and irradiated onto the laser rod 2. At this time, the semiconductor laser as excitation light is transmitted to the resonator 3.
The excitation laser beam is irradiated within a pattern P of the laser beam oscillated between the laser rods 2 and 2, so that only the necessary portions of the laser rod 2 can be irradiated with the excitation laser beam. In addition, the optical loss due to dichroic mirrors is usually at least 20 to 30
%, the efficiency can be increased compared to structures using optical fibers or the like.

By providing the dichroic mirrors 15.16°17 as described above, a plurality of semiconductor laser devices 19.21
．． Semiconductor laser beams from 23.25 can be combined on the same optical axis. Further, each of the plurality of semiconductor laser devices 19, 21, 23° 25 has an absorption peak wavelength of λ1. λ2. λ3. Since they each emit light of λ4, more efficient excitation can be performed. Note that the number of semiconductor laser devices may be two or more, and is not limited to the four mentioned above.

Here, the first to fourth semiconductor laser devices 19.2
1, 23, and 25, the emission wavelength is selected by adjusting the semiconductor device configuration. However, the wavelength may be controlled by controlling the temperature of semiconductor laser devices that emit light of similar wavelengths.

In addition, as one application example of the present invention to obtain even stronger excitation light, a laser device having a polarizing beam splitter 26 as shown in FIG. It is also possible to change it to 27.

This laser device 27 is provided with two semiconductor laser devices 19.19 that emit laser beams of the same wavelength, for example, λ1.One of the semiconductor laser devices 19 emits a laser beam polarized in the direction of arrow A, and the other semiconductor The laser device 19 emits a laser beam polarized in the direction of arrow B (direction perpendicular to the direction A), each of which is provided with a collimating optical system 29, and is further provided with a polarized beam that combines the laser beams from the two semiconductor laser devices 19 and 19. It is configured by providing a splitter 26.

In other words, by providing the polarizing beam splitter 26,
It is possible to combine two lights of the same wavelength with different polarization directions. And the laser device 27 formed in this way
Each semiconductor laser device 19 shown in FIG.
, 21, 23.25 and collimating optics 18.20
, 22.24°, the excitation energy can be further doubled.

Further, the laser rod 2 is a YAG laser medium, but is not limited to this, and may be YLF (YL i F4) or N
d"GGG (G d3 Ga5 CH2) or the like, a dye laser medium, etc. may be used. Furthermore, the excitation light source is not limited to a semiconductor laser device, and may be, for example, a wavelength tunable dye laser, an alexandrite laser, or the like.

Furthermore, although the resonator 3 is the resonator, it may be formed by, for example, applying a finishing coating to the end face of the laser rod 2.

〔Effect of the invention〕

By providing multiple excitation light sources that emit light with different absorption peak wavelengths in the absorption spectra of the laser medium, and combining the excitation light with different wavelengths from these excitation light sources using a dichroic mirror, it is possible to create a laser beam that is strong in the oscillation region of the laser medium. Since excitation light can be concentrated, excitation efficiency can be increased, and a high-output laser oscillation device can be provided.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, in which FIG. 1 is a plan view of a laser oscillation device, and FIG. 2 is an absorption spectrum diagram showing the relationship between the wavelength and absorbance of excitation light that excites a laser medium.
Figure 3 is a plan view showing a laser device that combines the same wavelength using a polarizing beam splitter, Figures 4 to 6 are conventional examples, and Figure 4 shows an excitation light source composed of one semiconductor laser device. Figure 5 is a plan view of a side-pump type laser oscillation device using a semiconductor laser array, and Figure 6 is a plan view showing a side-pump type laser oscillation device using a semiconductor laser array. FIG. 2 is a plan view of a laser oscillation device that uses the pump as an excitation light source. 2... Laser rod (laser medium) 3... Resonator (resonant means) 15... First dichroic mirror 16... Second dichroic mirror 17... Third dichroic mirror 19...・First semiconductor laser device (pumping light i!1X), 21... Second semiconductor laser device (pumping light source) 23... Third semiconductor laser device (pumping light 1g,) 25... th No. 4 semiconductor laser device (excitation light source).

Claims (1)

[Claims] A solid-state laser medium, a resonator mirror provided at both ends of the solid-state laser medium, and a resonator mirror provided outside the laser oscillation section between the resonator mirrors to excite different absorption peak wavelengths of the absorption spectra of the solid-state laser medium. A plurality of semiconductor laser oscillators that output laser beams, and a plurality of semiconductor laser oscillators arranged on the resonant axis of the resonator mirror to correspond to each of the excitation laser beams, respectively, reflect each of the laser beams to the optical axis of incidence on the solid-state laser medium. A laser oscillation device comprising: a plurality of dichroic mirrors that transmit excitation laser light of a wavelength other than the reflected excitation laser light.