JPH0388380A - Solid state laser device - Google Patents

Abstract

PURPOSE:To enable reduction in quantity of light caused by loss of a fundamental laser light within a resonator by placing a pair of optic means with optic characteristics which become the resonator for the fundamental laser light generated from a laser activation substance at the opposing end surface for a solid state laser medium. CONSTITUTION:The title item has a solid state laser medium with opposing end faces 1a and 1b and a semiconductor laser light source 1 which supplies an excited light L1 to this solid state laser medium 1 and this solid state laser medium 1 consists of a non-linear optic crystal with Nd which is a laser activation substance. In this case, a pair of optic means 2a and 2b with optic characteristics which becomes a resonator for a fundamental laser light L2 which is excited from an excitation light L1 and is generated from the laser activation substance are placed on the end faces 1a and 1b. Then, at least one of a pair of optic means 2a and 2b has an optic characteristic for enabling a high-harmonic laser light L3 whose wavelength is converted from the fundamental wave laser light L2 to be passed, thus enabling the reduction in the quantity of light of the high-harmonic laser light L3 obtained from the solid state laser medium 1 to be restricted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a solid-state laser device that wavelength-converts fundamental laser light into harmonic laser light and emits it, and in particular, it relates to a solid-state laser device that converts the wavelength of fundamental laser light into harmonic laser light and emits it. The present invention relates to a solid-state laser device including a solid-state laser medium that oscillates a fundamental laser beam, and then wavelength-converts a part of the oscillated fundamental laser beam into a harmonic laser beam and emits the harmonic laser beam.

[Prior Art] Conventionally, as this type of solid-state laser device, for example, “E
xcited Emission And Self-
Frequency-Doubling Effect
of N d x Yl-x (803) ac
rysta+ J Chinese Physics
Letters, Vol 3. NO, 9, PP413~
416. (1986) is known.

This solid-state laser device uses a composition formula N as a solid-state laser medium.
dx Yl-X (803) In 4, set the value of X to 0.
It has crystals smaller than 2. Since this solid-state laser medium is a nonlinear optical crystal containing Nd, which is a so-called laser active substance, it oscillates a fundamental wave laser beam of Nd by being excited, and then oscillates a part of this fundamental wave laser beam. It is possible to convert the wavelength into harmonic laser light internally and emit it to the outside. In particular, as mentioned above, this solid-state laser medium can convert the fundamental laser beam with a wavelength of 1.064 m into the second harmonic laser beam with a wavelength of 0.53 m by selecting the value of X in the composition formula to be smaller than 0.2. It can stably convert the wavelength of light.

The basic configuration of this solid-state laser device is to form an external resonator for the fundamental laser beam by using an output mirror and a reflecting mirror, which sandwich both end faces of the solid-state laser medium in the halo direction with a space between them. In addition, a dye laser serving as an excitation means is arranged to face 11 surfaces extending from opposite end surfaces of the solid-state laser medium.

Both the output mirror and the reflecting mirror have optical characteristics that substantially 100% of the fundamental laser beam emitted from the solid-state laser medium is reflected. In addition, for harmonic laser light, the reflecting mirror has the optical property of almost 100% reflection, and the output mirror has the optical property of reflecting almost 100%.
Each has the optical property of transmitting approximately 80% of the light.

The dye laser can emit excitation light of 587.9 ns, which is the wavelength at which the solid-state laser medium has the highest absorption spectrum.

In the above configuration, by supplying excitation light from the dye laser to the side surface of the solid-state laser medium, first, a resonant optical path of the fundamental laser beam oscillated from the solid-state laser medium is formed between the output mirror and the reflecting mirror. .

Next, a harmonic laser beam whose wavelength is converted from a part of the fundamental laser beam is generated from a region of the solid-state laser medium that corresponds to the resonant optical path of the fundamental laser beam, and is emitted from the output mirror.

[Problem I to Solve by the Invention] However, since the above-mentioned conventional solid-state laser device uses a dye laser as an excitation means, it increases the size of the device, requires maintenance such as dye replacement, and shortens its lifespan. It had the disadvantage of inevitably shortening its lifespan. One possible way to overcome these drawbacks is to replace the excitation means with a semiconductor laser, but since conventional solid-state laser devices employ external resonators, it is simply a matter of replacing the dye laser with a semiconductor laser. If only replaced, the loss within the resonator may be large, and in some cases, there may be no electric flux even for oscillation of the fundamental laser beam. Even if it is possible to oscillate a fundamental laser beam, a decrease in the amount of fundamental laser beam due to resonator loss is unavoidable, and harmonics that are wavelength-converted from this fundamental laser beam There was a problem in that it also caused a decrease in the amount of laser light. Furthermore, another disadvantage of using an external resonator is that the solid-state laser medium has both the functions of oscillating the fundamental laser beam and converting the wavelength of the fundamental laser beam into harmonic laser beam. There are also inherent problems due to this. In other words, although wavelength conversion is performed only during the process in which the fundamental laser beam passes through the solid-state laser medium, the fundamental laser beam and the solid-state laser beam are arranged outside the solid-state laser medium and its both end faces. In other words, it is necessary to propagate spatially between a reflective mirror or an output mirror, that is, an optical path that does not contribute to wavelength conversion, which prevents high wavelength conversion efficiency from being obtained.

The present invention has been made in view of the above-mentioned problems, and aims to miniaturize the device in a solid-state laser IUT equipped with a solid-state laser medium made of a nonlinear optical crystal containing a laser active substance. Furthermore, the present invention
Another object of the present invention is to provide a solid-state laser i device that suppresses a decrease in the amount of harmonic laser light obtained from the solid-state laser 1f1 body and improves the efficiency of wavelength conversion from fundamental laser light to harmonic laser light. It is said that

[Means for Solving 111i] The solid-state laser device of the present invention includes a solid-state laser medium made of a nonlinear optical crystal containing a laser active substance and having opposing end surfaces, and supplying excitation light to the solid-state laser medium. a semiconductor laser light source, the solid-state laser medium comprising:
A pair of optical means having optical characteristics that act as a resonator for a fundamental laser beam excited by the excitation light and generated from the laser active substance is disposed on the end face, and the pair of optical means At least one of the means has an optical characteristic of transmitting harmonic laser light whose wavelength is converted from the fundamental laser light.

[Function] The solid-state laser device of the present invention comprises a pair of nonlinear optical crystals containing a laser active substance and having optical characteristics to act as a resonator for the fundamental laser beam generated from the laser active substance. A solid state laser medium is provided with optical means disposed on opposite end faces thereof. Thereby, when forming the resonant optical path of the fundamental laser beam generated from the laser active material, it is possible to suppress a decrease in the light amount due to the loss within the resonator of the fundamental laser beam. Further, when converting the wavelength from a fundamental laser beam to a harmonic laser beam, the fundamental laser beam to be wavelength converted is connected to the optical path contributing to the wavelength conversion, that is, the solid laser medium sandwiched between the pair of optical means. Only the inner optical path will proceed.

[Example] Hereinafter, an example of the solid-state laser @ snow of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a solid-state laser device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II in FIG. 1.

This solid-state laser device has a semiconductor laser light source 12 as an excitation means disposed in an opening 8a at one end of a substantially cylindrical container 8, and a collimator lens 3 at an opening 8b at the other end.
Further, the excitation light focusing means 4 and the solid-state laser medium 1 are sequentially housed inside the container M8 along the traveling direction of the excitation light L1 emitted from the semiconductor laser light 1!12. It is placed.

The solid-state laser medium 1 has a compositional formula of Ndo, zYa8(8
03) Consists of 4. In other words, the solid-state laser medium 1 is a nonlinear optical crystal (nonlinear constant d-4, 0×1 G'esu) containing Nd as a laser active substance.
Its shape is approximately cylindrical with a diameter of 3MX and a length of 5m.
An outwardly convex spherical lens (radius of curvature: 5 m) is formed on each of the two dovetail surfaces 1a11b in the optical axis direction. At the ends WJ1a and 1b, there are optical thin films 2a, which are a pair of optical means having optical characteristics to act as a resonator for the fundamental laser beam L2 (wavelength: 1.064#I) generated from Nd; 2b is attached. In other words, the optical thin films 2a and 2b both have a wavelength of 1.5 nm of the fundamental laser beam.
It has an optical property that reflects almost 100% of the wavelength of 0.064 m. Further, the optical thin film 2a emits harmonic laser light L3 (wavelength: 0.
The optical thin film 2b has an optical property of reflecting almost 100% of the excitation light L1 (531#l) and transmitting almost 100% of the excitation light L1, while the optical thin film 2b has an optical property of transmitting almost 80% of the harmonic laser beam L3. Each has unique characteristics. In this embodiment, the optical thin film 2a.

2b, respectively, T i so as to have the optical properties described above.
It is composed of a dielectric multi-layer film consisting of O*/S i 02.

The solid-state laser medium 1 includes a movable holder 5 made of a substantially cylindrical body with a flange disposed at the center of the outer peripheral surface in the annular direction.
8 through an adhesive (not shown). The movable holder 5a is further accommodated and held by the inner peripheral surface of a fixed holder 5b having a substantially cylindrical shape. The inner circumferential surface of the fixed holder 5b and the outer circumferential surface of the movable holder 5a are fitted with a clearance fit, and the groove provided on the inner circumferential surface of the fixed holder 5b and the flange of the movable holder 5a are fitted. By matching them together, the movable holder 5a can rotatably slide relative to the fixed holder 5b while being prevented from moving in the axial direction. In this way, by making the movable holder 5a that securely houses the solid-state laser medium 1 rotatable with respect to the fixed holder 5b, the polarization of the excitation light beam emitted from the semiconductor laser light source 12 is adjusted so as to satisfy the phase matching condition. The angle can be set in advance so that the crystalline surface of the solid-state laser medium 1 forms a predetermined angle with respect to the wavefront. Furthermore, the fixed holder 5b is a holding l! formed on the inner circumferential surface of the container 8 via an annular heat insulating material 7 having a notch at the bottom in the figure. It is held in the container 118 by l58e. In addition, a movable holder 5a is provided in the notch of the heat insulating material 7.
l! A Vertier element 6 that maintains the solid-state laser medium 1 at a constant temperature is inserted through a constant holder 5b. This Beltier element 6 is connected to a drive device 1 provided outside the container 8.
10, and is controlled by this driving device 10 to keep the temperature of the solid-state laser medium 1 constant.

The semiconductor laser light source 12 is composed of a GaAlAs semiconductor laser (maximum output 500 mW) that can emit a laser beam with a wavelength of 805n- as excitation light L1. Since the wavelength 805nl has relatively high absorption characteristics in the solid-state laser medium 1 and also has a high quantum efficiency, by supplying the excitation light L1 of this wavelength to the solid-state laser medium 1, high excitation efficiency can be achieved. can excite the solid-state laser medium 1. Furthermore, since a heat dissipation plate 9 having a comb-shaped longitudinal section is disposed on the back side of the semiconductor laser light source 12, the heat accumulated in the semiconductor laser light source 12 can be released. In addition, this semiconductor laser light source is very good! By the drive device 11 provided outside of 18,
Driven.

The excitation light focusing means 4 is composed of convex lenses 4a, 4b in order to improve the focusing characteristics.
The excitation light L1 supplied to is given focusing property.

In other words, the excitation light emitted from the semiconductor laser light source 12 is first converted into parallel light by the convex lens 4a, and then
The convex lens 4b focuses the light onto the optical axis near the end face 1a in the solid-state laser medium 1. Further, each of the convex lenses 4a and 4b is held in the container 8 by holding portions 8c and 8d protruding from the inner peripheral surface of the container 8.

Next, the operation of the solid-state laser device having the above-described configuration will be explained.

First, the excitation light L1 emitted from the semiconductor laser light source 12 is first converted into parallel light by the convex lens 4a, and then converted into parallel light by the convex lens 4b.
It is focused on the nearby optical axis.

The focusing of the excitation light L1 onto the solid-state laser medium 1 is achieved by focusing the fundamental laser light L1 formed within the solid-state laser medium 1, which will be described later.
The resonant optical path of No. 2 includes the optical path of the excitation light L1 formed in the solid-state laser medium 1. The solid-state laser medium 1 is excited with high pumping efficiency by the pumping light L1 supplied as described above, so that the resonant optical path of the fundamental laser beam L2 generated from Nd forms a resonator between the pair of optical R112a, 2bflll is formed. At this time, since both the optical thin films 2a and 2b have optical properties that substantially 100% reflect the fundamental wave laser beam L2, the optical thin films 2a and 2b substantially reflect the fundamental wave laser beam L2.
Contained inside 1. Furthermore, the resonant optical path of the fundamental wave laser beam 2 is formed by forming an outwardly convex spherical lens on the end face 1a11b to which the pair of optical inner thin films 112a and 2b are applied, so that the solid laser medium A beam waist is formed at the center of the beam in the optical axis direction. A second harmonic laser beam L3, in which a part of the fundamental laser beam L2 is wavelength-converted, is generated from a region of the solid-state laser medium 1 corresponding to the resonant optical path of the fundamental laser beam L2 formed in this manner. This generated second harmonic laser beam L3 travels along the traveling direction of the fundamental laser beam L2, but this second harmonic laser beam L3 travels along the traveling direction of the fundamental wave laser beam L2.
The pair of optical inner thin layers 112a correspond to the wavelength of the harmonic light L3.

Among the optical thin films 2b, only the optical thin film 2b has transparency, so that the light is emitted from the end face 1b to which the optical thin film 2b is attached. The second harmonic laser beam L3 emitted from the solid-state laser medium 1 is a divergent beam along the resonant optical path of the fundamental laser beam L2, so it is converted into parallel light by the collimator lens 3 and the solid-state laser beam L3 is expanded. emitted from the device.

In this embodiment, from the semiconductor laser light source 12 to 450-
When the excitation light L1 was supplied to the solid-state laser medium 1 with an output of , the output of the second harmonic laser light L3 obtained was 10-.

The solid-state laser device of this embodiment includes a pair of optical thin films 2a12b on both end surfaces 1a and 1b of the solid-state laser medium 1, which have optical characteristics that form a resonant optical path for the fundamental laser beam L2.
is covered with. Thereby, during oscillation of the fundamental laser beam L2, it is possible to suppress a decrease in the optical image due to intra-cavity loss of the fundamental laser beam L2. Therefore, it is possible to use the semiconductor laser light source 12 with a relatively small output as the excitation light source, so the device can be downsized. In addition, when converting the wavelength from the fundamental laser beam L2 to the GA laser beam, as described above, since the decrease in the light amount of the fundamental laser beam is suppressed, the GA wave laser whose wavelength is converted from the fundamental laser beam L2 is suppressed. It is also possible to suppress a decrease in the amount of light. Furthermore, the fundamental laser beam L to be wavelength converted
2 is an optical path that contributes to wavelength conversion, that is, the optical thin film 2a.

High wavelength conversion efficiency can be obtained because the light travels only along the optical path within the solid-state laser medium 1 held between the two substrates 2b.

In particular, in the solid-state laser device of this embodiment, since the end surfaces 1a and lb covered with the pair of optical thin films 2a12b are both formed into outwardly convex spherical lenses, the fundamental wave laser beam L2 The resonant optical path of the solid-state laser medium 1 forms a beam waist at the center in the optical axis direction, and the power density of the fundamental laser beam 1.2 is improved. We were able to obtain a wavelength conversion efficiency of 2%, which is an extremely high value compared to the above.

Further, the solid-state laser device of this embodiment has a semiconductor laser light source 1.
2 is cooled by the heat dissipation plate 9 and the solid-state laser medium 1 is maintained at a constant temperature by the Peltier element 6, so that the resonator length can be kept constant when the fundamental laser beam L2 is oscillated. , it is possible to stably oscillate the fundamental laser beam L2. Furthermore, when converting the wavelength from the fundamental laser beam L2 to the second harmonic laser beam L3, the temperature phase matching condition can be kept constant, so that the fundamental wave laser beam L2 can be converted stably to the second harmonic laser beam L3. The wavelength can be converted into light L3.

In this example, the output stability of the second harmonic laser L3 was within 1%.

Next, other aspects of the components constituting the solid-state laser device of this example will be described.

First, the composition formula NdY (803) is used as a solid-state laser medium.
In addition to 4, a nonlinear optical crystal made of Nd:MCJO:Li0NbO3 may be used. Further, in addition to Nd, a rare earth element such as Er may be contained as a laser active substance. A pair of optical means disposed on both end surfaces of the solid-state laser medium and having optical characteristics to act as a resonator for the fundamental laser beam include a pair of optical means having reflective surfaces in contact with both end surfaces. You may also use a mirror. In addition, in order to form a beam waste of the resonant light of the fundamental laser light in the solid-state laser medium, it is not necessary to form both end faces outward into a spherical lens of white ginseng. good.

Next, as the semiconductor laser light source, a semiconductor laser that emits a wavelength matching the absorption wavelength band of various laser active substances contained in the solid-state laser medium may be appropriately selected. If an optical crystal is to be excited, a semiconductor laser that emits a laser beam containing a wavelength component of 797ni+ may be used.Also, the output of the semiconductor laser is 30m, which is the lowest output among those currently commercially available. %#, it has been confirmed that it is possible to stably oscillate a fundamental laser beam and then convert the wavelength of the fundamental laser beam into a harmonic laser beam. The direction of excitation is not limited to end-face excitation, and excitation may be performed from the copper surface.

Furthermore, as the excitation light focusing means, a known beam cross section shaper composed of an aspherical lens, a prism, a gradient index lens, etc. may be used, or a combination of these excitation light focusing means and a semiconductor laser light source may be used. may be optically coupled by fibers, fiber bundles, etc.

[Effects of the Invention] The solid-state laser device of the present invention is made of a nonlinear optical crystal containing a laser active substance, and has optical characteristics that serve as a resonator for the fundamental laser beam generated from the laser active substance. The solid-state laser medium has a pair of optical means disposed on opposite end faces thereof. As a result, when the fundamental laser beam generated from the laser active substance is oscillated, it is possible to suppress a decrease in the light amount due to the loss within the resonator of the fundamental laser beam, so that a semiconductor laser light source with relatively low output can be used. Even if it is present, it can be used as an excitation light source, so the device can be made smaller. In addition, when converting the wavelength from the fundamental laser beam to the harmonic laser beam,
As mentioned above, since it is possible to suppress the decrease in the light intensity due to the intra-cavity loss of the fundamental laser beam, it is also possible to suppress the decrease in the light intensity of the harmonic laser beam whose wavelength is converted from the fundamental laser beam to the harmonic laser beam. Can be suppressed.

Furthermore, since the fundamental laser beam to be wavelength converted travels only on the optical path that contributes to wavelength conversion, that is, the optical path within the solid-state laser medium sandwiched between the pair of optical means, it can be harmonized with high wavelength conversion efficiency. Wave laser light can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the solid-state laser lil of the present invention, and FIG. 2 is a sectional view taken along the line II in FIG. 1. 1... Solid laser medium, 1a, 1b... End surface 2a,
2b...Optical 1111.4...Excitation light focusing means 1
2... Semiconductor laser light source.

Claims (1)

[Scope of Claims] The solid-state laser comprises a solid-state laser medium made of a nonlinear optical crystal containing a laser active substance and having opposing end faces, and a semiconductor laser light source that supplies excitation light to the solid-state laser medium. The medium is provided with a pair of optical means on the end face, each having an optical characteristic to serve as a resonator for the fundamental laser beam excited by the excitation light and generated from the laser active substance, and A solid-state laser device, wherein at least one of the pair of optical means has an optical property of transmitting harmonic laser light that is wavelength-converted from the fundamental laser light.