JPH04158588A - Semiconductor laser exciting solid laser device - Google Patents

Abstract

PURPOSE:To take out a plurality of wavelength converted beams of the same wavelength from one laser module by arranging an optical material, which has an optical film of high transmittance and high reflectivity, obliquely to the optical axis of a laser beam, between a laser medium and a nonlinear optical material. CONSTITUTION:A substrate 25 is disposed at a proper angle to the optical axis of a laser beam, and an optical film 29, which prevents the reflection of a laser beam, is made on the side in the direction of a laser medium 15, and an optical film 27, which prevents the reflection of the laser beam and reflects the wavelength converted beam fully, is made on the side in the direction of a nonlinear optical material 17. When the laser beam passes the nonlinear optical material 17, the wavelength of the laser beam is partly halved. The wavelength-converted beam emitted in the direction of arrow A' passes the optical film 20 of an output mirror 19, and is output in the direction of arrow A. The wavelength-converted beam emitted in the direction of arrow B is reflected in the direction of arrow C by the optical film 27 of the substrate 25, and further it is reflected in the direction of arrow D by a mirror 31. As a result, the two wavelength-converted beams can be taken out in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present patent relates to a solid-state laser device in which a semiconductor laser is used as an excitation light source and a laser medium and a nonlinear optical material are arranged in a laser resonator.

“Conventional technology” In recent years, semiconductor lasers, especially laser diodes (LD
There is active research and development into solid-state laser devices that use lasers as excitation light sources. This LD-pumped solid-state laser has a longer excitation light source life than conventional lamp pumping,
Since there is almost no thermal effect on the laser medium and there is no need for water cooling, it is attracting attention as a compact, long-life all-solid-state laser.

LDs are currently well known as all-solid-state lasers, but LDs have problems such as an elliptical spatial output shape and instantaneous end face destruction. With LD-pumped solid-state lasers, these problems have been solved, and the lifetime at the pumped level is long, so energy can be stored, and as a result, high peak output can be obtained through Q-switch oscillation. There is.

Further, by providing a nonlinear optical material inside the laser resonator, visible light such as green or blue light, which is difficult to emit depending on the LD, can be easily generated by wavelength conversion.

Since the LD pumped solid-state laser has such characteristics,
Applications are expected in the field of optical information transmission devices, such as optical recording and reproducing devices.

FIG. 3 shows an example of a conventional LD-pumped solid-state laser device including a nonlinear optical material inside a laser resonator. That is, the LD 41 is arranged as an excitation light source, and the condenser lens 43 is arranged in the direction in which the excitation light 51 is emitted. For example, in the light output direction of the condensing lens 43,
A laser medium 45 such as G is arranged. The excitation light 51 is transmitted through the incidence surface of the excitation light 51 of the laser medium 45,
An optical film 53 that reflects the laser oscillation light 52 is provided. This optical film 53 functions as a mirror, and the optical film 53 functions as a mirror.
3 and the output mirror 49 constitute a laser resonator. A nonlinear optical material 47 is arranged between the laser medium 45 and the output mirror 49. An optical film 50 that reflects the laser oscillation light and transmits the wavelength-converted light converted by the nonlinear optical material 47 is formed on the incident surface of the output mirror 49 .

The excitation light 51 emitted from the LD 41 passes through the condensing lens 43
The laser beam passes through the optical film 53 and enters the laser medium 45 from one end surface thereof through the optical film 53 . Most of the excitation light 51 is absorbed when passing through the laser medium 45, and a laser beam of a specific wavelength is generated from the laser medium. This laser beam passes through the nonlinear optical material 47, is reflected by the optical film 50 of the output mirror 49, and is repeatedly reflected with the optical film 53 formed on the incident surface of the laser medium 45.
It becomes laser oscillation light. When this laser oscillation light 52 passes through a nonlinear optical material, a portion thereof is converted into a second harmonic having a wavelength of 1/2, and this wavelength-converted light is transmitted through an output mirror 49 and output.

``Problems that patents aim to solve'' LD-pumped solid-state YAG laser (DPY) devices such as those described above are used for various purposes such as optical pickup, optical recording, and laser printers. the same light (for example, in the case of YAG, 2ω532n
Only one piece of m) was taken out. For this reason, for example, LD
In the case of optical pickups used for reading CDs and CDs,
One DPY module can only read one disc.If you want to take out multiple beams from one DPY module and read multiple discs at the same time, the user can use an optical component such as a beam splitter to read out multiple beams. There is a problem in that it is necessary to form a beam, and the amount of light decreases as the beam is split.

Furthermore, in the LD pumped solid-state laser shown in FIG. 3, the wavelength-converted light generated when the laser oscillation light passes through the nonlinear optical material 47 is not only emitted in the direction of arrow A' in the figure, but also emitted in the direction of arrow A' in the figure. It also emits in the direction of the middle arrow B. The wavelength-converted light emitted in the A° force direction passes through the output mirror 49 and is output in six directions, but the wavelength-converted light emitted in the B direction is
It will not be output. For this reason, it is also possible to provide an optical film that reflects the wavelength-converted light between the laser medium 45 and the nonlinear optical material 47 to reflect the wavelength-converted light emitted in the B direction and output it in the Ao and six directions. However, even in that case, there was a problem in that only one beam could be extracted from one module.

Therefore, an object of this patent is to provide a semiconductor laser-excited solid-state laser device that can extract a plurality of wavelength-converted lights of the same wavelength from one laser module.

"Means for Solving the Problem" In order to achieve the above object, this patent provides a semiconductor laser pumped solid-state laser device that uses a semiconductor laser as an excitation light source and includes a laser medium and a nonlinear optical material in a resonator. An optical material having an optical film that is highly transparent to the laser oscillation light and highly reflective to the wavelength converted light is placed between the laser medium and the nonlinear optical material on the optical axis of the laser oscillation light. A mirror is provided to make the wavelength-converted light reflected by the optical film of the patent material, which is disposed obliquely with respect to the wavelength-converted light outputted from the resonator, parallel to the wavelength-converted light output from the resonator.

"Effect j" When the laser oscillation light passes through the nonlinear optical material in the laser resonator, a part of it is wavelength-converted to the second harmonic and is transmitted through the output mirror and taken out to the outside.However,
The wavelength-converted light generated by the nonlinear optical material is emitted not only to the output mirror side but also to the laser medium side. In this patent, wavelength-converted light emitted to the laser medium side is reflected by the optical film made of an optical material disposed obliquely with respect to the optical axis, and is extracted in an oblique direction. Therefore, 1
Two wavelength-converted light beams can be extracted from one laser module. In addition, the wavelength-converted light taken out in an oblique direction is emitted to the laser medium side and was not originally output, so even if it is taken out as two beams as described above, the power will decrease. There's nothing to do.

In this way, a plurality of second harmonics of the same wavelength can be simultaneously extracted from one laser module, and, for example, it is possible to read and compare a plurality of disks at the same time with one laser module.

"Embodiment" FIG. 1 shows an embodiment of the semiconductor laser pumped solid-state laser device of this patent.

In the figure, 11 is a semiconductor laser (LD) that serves as an excitation light source.
) and emits excitation light 21. A condensing lens 13 is disposed in the direction in which the excitation light 21 is emitted.
Focus the light and narrow it down. In the aperture direction of the condensing lens 13,
A laser medium 15 is provided. As the laser medium 15, for example, a crystal such as YAG, YLF, YAP, YVO4, etc. is used, and in this embodiment, YAG is used. The excitation light 2 is placed on the excitation surface of the laser medium 15.
An optical film 23 is formed that transmits the laser oscillation light 22 and reflects the laser oscillation light 22. The optical film 23 plays the role of a resonant mirror in cooperation with the output mirror 19 arranged in the laser beam emission direction of the laser medium 15 .

On the output side of the laser oscillation light 22 of the laser medium 15, there is a parallel plane substrate 25 made of an optical material such as BK-7 or quartz glass, and a parallel plane substrate 25 made of an optical material such as KNbO, LfNbO, KTi.
Nonlinear optical materials 17 made of OPO4, KHz PO4, BBO, etc. are arranged in this order. The substrate 25 is
At an appropriate angle (e.g. 45°) with respect to the optical axis of the laser oscillation light
) is installed at an angle, and the laser medium 1 of this substrate 25
An optical film 29 that prevents reflection of laser oscillation light is formed on the surfaces in five directions, and an optical film 29 that prevents reflection of laser oscillation light and prevents reflection of wavelength-converted light is formed on the surface of the nonlinear optical material 17. An optical film 27 that causes total reflection is formed.

Note that an optical film similar to the optical film 27 described above may also be formed on the surface of the substrate 25 facing the laser medium 15 .

An output mirror 19 is arranged on the opposite side of the nonlinear optical material 17 from the laser medium 15 . Output mirror 1
An optical film 20 that reflects the laser oscillation light and transmits the wavelength-converted light converted by the nonlinear optical material 17 is formed on the laser light incident surface 9 . Then, the laser medium 15
The optical film 23 of the output mirror 19 and the optical film 20 of the output mirror 19 constitute a resonator.

Furthermore, in the traveling direction of the wavelength-converted light reflected by the substrate 25, a mirror 31 is arranged to completely reflect the wavelength-converted light. This mirror 31 is installed at an angle (for example, 45°) to reflect the wavelength-converted light reflected by the substrate 25 in a direction parallel to the wavelength-converted light output from the output mirror 19.

However, by changing the angle of the mirror 31, the wavelength-converted light reflected by the substrate 25 can be reflected again in an arbitrary direction and extracted.

Next, the oscillation operation of this semiconductor laser pumped solid-state laser device will be explained.

The semiconductor laser 11 emits excitation light 2 with a wavelength g08 nm, for example.
The excitation light 21 is focused into a narrow beam by the condenser lens 13, passes through the optical film 23, and enters the laser medium 15. The laser medium 15 is excited by this excitation light 21 and generates a laser beam with a wavelength of 11064n. This laser light is emitted from the other end surface of the laser medium, passes through the substrate 25 and the nonlinear optical material 17, is reflected by the optical film 20 of the output mirror 19, and is connected to the optical film 23 of the laser medium 15 constituting the resonator. It is repeatedly reflected between the two and becomes laser oscillation light.

When the laser oscillation light passes through the nonlinear optical material 17, a portion of the laser oscillation light has a wavelength of 172 nm, in this example, a wavelength of 532 nm.
The wavelength of the converted light is converted into the second harmonic of , and this wavelength-converted light is emitted eight times with the same efficiency in the directions of arrows A' and B in the figure. The wavelength-converted light emitted in the direction of the arrow A' force passes through the optical film 2 of the output mirror 19.
0 and is output in the six directions of the arrows. Further, the wavelength-converted light emitted in the direction of arrow B is reflected by the optical film 27 of the substrate 25 in the direction of arrow C, and further reflected by the mirror 31 in the direction of arrow C. As a result, two beams of wavelength-converted light can be extracted in parallel.

FIG. 2 shows another embodiment of the semiconductor laser pumped solid-state laser device of this patent. Components that are substantially the same as those of the apparatus of the embodiment shown in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted.

This embodiment is a so-called fiber-coupled type, and a condenser lens 33 is disposed in the direction in which the excitation light 21 emitted from the semiconductor laser 11 is emitted.
The excitation light 21 focused by 3 is irradiated onto the condenser lens 13 through the optical fiber 35. Then, the excitation light 21 is focused again by the condenser lens 13 and enters the laser medium 15. Also in this embodiment, the laser medium 15 and the nonlinear optical material 17
A parallel plane substrate 25 having an optical film 27, 29 similar to that described above is placed between the two at an appropriate angle (for example, 60°). However, the mirror 31 in the previous embodiment is not installed.

In this device, wavelength-converted light emitted from the nonlinear optical material 17 in the direction of arrow B is reflected by the optical film 27 of the parallel plane substrate 25 and extracted in the direction of arrow C. Therefore, although it is not possible to make the wavelength-converted light output in the six directions of arrows and the wavelength-converted light extracted in the direction of arrow C parallel, the number of parts is reduced and the device can be expected to be made more compact.

"Effects of the Patent" As explained above, according to this patent, there is a structure between the laser medium and the nonlinear optical material placed in the resonator that is highly transparent to the laser oscillation light and that allows the wavelength-converted light to be transmitted between the laser medium and the nonlinear optical material. By arranging an optical material having a highly reflective optical film at an angle with respect to the optical axis of the laser oscillation light, the wavelength-converted light emitted from the nonlinear optical material toward the laser medium is transferred to the optical material. It can be reflected by a membrane and taken out in a different direction. therefore,
Two wavelength-converted lights can be extracted from one module at the same time, and when applied to an optical pickup device, for example, it becomes possible to read a plurality of discs at the same time.

Furthermore, by providing the above-mentioned optical material with the function of an etalon, a single longitudinal mode of laser light can be achieved, and even more efficient wavelength conversion can be realized.

[Brief explanation of drawings]

1 and 2 are block diagrams showing different embodiments of a semiconductor laser pumped solid-state laser device according to the present patent, and FIG. 3 is a block diagram showing an example of a conventional semiconductor laser pumped solid-state laser device. In the figure, 11 is a semiconductor laser for excitation, 13 is a condensing lens,
15 is a laser medium, 17 is a nonlinear optical material, 19 is an output mirror, 21 is an excitation light, 25 is a parallel plane substrate, 27.2
9 is an optical film, 31 is a mirror, arrows A, A'', B, C,
D is the optical path of the wavelength-converted light.

Claims (2)

[Claims] (1) In a semiconductor laser-pumped solid-state laser device that uses a semiconductor laser as an excitation light source and includes a laser medium and a nonlinear optical material in a resonator, there is a space between the laser medium and the nonlinear optical material that is connected to the laser oscillation light. A semiconductor laser-pumped solid-state laser device characterized in that an optical material having an optical film that is highly transparent for wavelength-converted light and highly reflective for wavelength-converted light is arranged obliquely to the optical axis of laser oscillation light. . (2) The semiconductor laser pumped solid-state laser device according to claim 1, further comprising a mirror for making the wavelength-converted light reflected by the optical material parallel to the wavelength-converted light output from the resonator. .