JPH05259540A - Light excitation solid-state laser - Google Patents

Abstract

PURPOSE:To generate a laser beam, which is stable, has a high output and is good in quality, at a high efficiency by a low-cost constitution. CONSTITUTION:A solid-state element 3 containing an active solid medium is arranged in a condenser 8, whose inner surface is constituted of a light diffusion reflective surface, an excitation light source 4 is installed outside of the condenser 8, excitation light 40 is introduced in the condenser 8 through an opening part 80 opened in the condenser 8, the element 3 is light-excited from the side surface of the condenser 8 and a laser beam 70 is taken out by a laser resonator constituted of mirrors 1 and 2. In such a way, a light excitation solid-state laser is constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically pumped solid-state laser device which is inexpensive and can stably generate a high-quality laser beam with high efficiency.

[0002]

2. Description of the Related Art FIG. 10 shows, for example, a document (Solid-State La).
Ser Engineering, Springer-Verlag, p.119-120), which is a side view showing a conventional optically pumped solid state laser device. In the figure, 1 is a reflection mirror, 2 is a partial reflection mirror, and 3 is a solid-state element including an active solid medium. In the case of a YAG laser, N is doped with Nd as the active solid medium.
d: YAG (Yttrium Aluminum Garnet), 4 is a light source, for example, a semiconductor laser whose main component is GaAlAs, 5 is a power source for driving the light source 4, 6 is a condenser lens, and 7 is a laser including mirrors 1 and 2. Laser beam generated in the resonator, 1
Reference numeral 0 is an optical thin film that makes the reflection mirror 1 totally reflect the laser beam 7 and totally transmit the light of the semiconductor laser, 40 is the light emitted from the semiconductor laser 4, and 70 is the partial reflection mirror 2. It is a laser beam extracted to the outside. 100 is a base.

The conventional photoexcitation solid-state laser device is constructed as described above, and the light of the semiconductor laser 4 turned on by the power supply 5 is introduced from the end face of the solid medium 3 by the condenser lens 6 to excite it. As a laser medium. The spontaneous emission light generated from the laser medium is amplified while traveling back and forth between the resonators formed by the mirror 1 and the mirror 2, and becomes a laser beam 7. When reaching a certain size or more, a laser with good directivity is obtained. It is emitted to the outside as a beam 70.

[0004]

In the conventional laser device as described above, since the light of the semiconductor laser is guided from the end surface to the solid-state element, the central portion of the end surface is strongly excited to generate a high output. When excited by a semiconductor laser with a large output, a light intensity distribution was generated in the cross section of the solid state element, and the beam shape was destroyed. Further, since the absorption rate of the solid-state element depends on the wavelength of the semiconductor laser, it is necessary to match the wavelength of the semiconductor laser with the absorption wavelength of the solid-state element for stable operation. Figure 11 is an example of Nd: YAG laser,
The relationship between the wavelength of the semiconductor laser and the pumping efficiency is shown. For stable operation with the pumping oscillation efficiency kept constant, the central wavelength is 810
It is necessary to select a semiconductor laser of nm and further control its temperature. This not only complicates the structure of the device, but also deteriorates the yield in the manufacture of semiconductor lasers, raises the price, and makes the device expensive.

The present invention has been made to solve the above problems, and uniformly guides light into a solid state element,
An object is to obtain a photo-excited solid-state laser device that can obtain a uniform laser medium and can stably generate a high-output and high-quality laser beam with high efficiency, with little fluctuation in output even if the wavelength of the light source changes. I am trying.

[0006]

In the photoexcited solid-state laser device according to the present invention, a solid-state element containing an active solid medium is arranged in a condenser whose inner surface is a light diffusive reflection surface to collect an excitation light source. It is arranged outside the optical device, and excitation light is introduced into the light collector through an opening formed in the light collector so that the solid-state element is optically excited from the side surface.

Further, a second solid-state element covering the solid-state element containing the active solid medium is provided.

Further, the cross section of the solid element containing the active solid medium is circular, the second solid element is annular, and the outer diameter of the second solid element is q = the outer diameter of the solid element containing the active solid medium. The refractive index of the material of the second solid element / the refractive index of the medium packed in the condenser is larger than the ratio.

Further, a thin film medium which is sufficiently smaller than the thickness of the second solid element is inserted between the solid element containing the active solid medium and the second solid element.

[0010]

In the photo-excited solid-state laser device configured as described above, the light of the semiconductor laser is guided from the opening of the condenser into the condenser, and the solid-state element is moved from the side surface in the process of spreading in the condenser. To excite. The light not absorbed by the solid-state element is diffused and reflected on the inner surface of the light collector, and again excites the solid-state element uniformly from the side surface. Further, in the photoexcited solid-state laser device configured as described above, even if the wavelength of the semiconductor laser changes and the absorptance of the solid-state element decreases, the change in excitation efficiency is gradual, so that a wider range of wavelengths is used. A light source with can be used.

Further, the annular second solid-state element which covers the solid-state element refracts the light of the semiconductor laser on its surface to collect the light and efficiently guide it to the solid-state element.

The outer diameter of the solid element containing the active solid medium is greater than or equal to q = (refractive index of the material of the second solid element / refractive index of the medium packed in the condenser). The second solid-state element, which is configured to be large, spreads the light incident on its periphery into a fan shape in the cross section,
This is uniformly excited by including a solid-state element containing an active solid medium in the fan.

Further, the thin film medium inserted between the solid element containing the active solid medium and the second solid element is designed so that the heat radiation from the surroundings of the solid element is evenly distributed around the second solid element. It leads to the element and thus homogenizes the heat distribution of the solid element in its circumferential direction.

[0014]

EXAMPLES Example 1. FIG. 1 is a configuration diagram showing an embodiment of the present invention, and (a) and (b) are a side configuration diagram and a sectional configuration diagram, respectively. Also 1, 2, 3, 4, 5, 7, 40, 7
0 and 100 are exactly the same as those of the conventional device. 8
Is a condenser whose inner surface is a diffuse reflection surface, and 80 is an opening of the condenser 8.

In the laser device configured as described above, the solid medium 3 including the active solid medium is arranged in the condenser 8 whose inner surface is a diffuse reflection surface, and is introduced from the opening 80 to the power source. A laser medium is excited by the light 40 emitted from the semiconductor laser 4 which is turned on by the laser diode 5. The spontaneous emission light generated from the laser medium is amplified while traveling back and forth between the resonators formed by the mirror 1 and the mirror 2, and becomes a laser beam 7. When reaching a certain size or more, the laser beam having a good directivity is obtained. It is released to the outside as 70.

In the above structure, the light of the semiconductor laser which is not absorbed by the solid-state element 3 passes through the solid-state element,
Diffuse reflection is performed on the inner surface of the light collector, and the solid-state element is uniformly excited again. The excitation efficiency in this case can be calculated in consideration of the probability of the number of times the light is reflected on the inner surface of the diffuse reflection until it is finally absorbed by the solid-state element. FIG. 2 shows the result of calculating the excitation efficiency of the solid state element as a function of the reflectance of the inner surface of the light collector and the excitation efficiency (absorption rate) when the excitation light passes through the solid state element only once. It can be seen that even if the wavelength of the excitation light, for example, the semiconductor laser changes, and the absorptance of the solid-state element changes from 20 to 100%, the change in the excitation efficiency is gradual. This indicates that a light source having a wider wavelength range can be used as compared with the conventional example.

Further, in the above-mentioned structure, since the light source 4 which emits the excitation light is installed outside the condenser 8, the housing of the light source is not exposed to the light from the diffuse reflection surface, so that it is guided into the condenser. The excited light thus emitted is guided to the solid-state element 3 without loss after being reflected by the diffuse reflection surface a plurality of times.

Example 2. In the example shown in FIG. 3, the solid-state element (first solid-state element) 3 containing the active solid medium is covered with the second solid-state element 30. Firstly, since the refractive index of the first solid-state element 3 is higher than that of the surrounding medium, for example, air, the excitation light is refracted on the surface of the solid-state element 3, and the central portion of the solid-state element is selectively. This is to prevent the shape of the laser beam generated due to the strong excitation of the laser beam from collapsing. Secondly, the light incident on the periphery of the solid-state element 30 is condensed by refraction on the surface of the second solid-state element 30 and efficiently guided to the first solid-state element 3. As shown in FIG. 4, the first solid-state element 3 including an active solid medium in the central portion of the excitation light fanned out on the surface of the second solid-state element 30.
Can be arranged to keep the intensity distribution therein uniform. In this case, the outer diameter of the first solid-state element 3 is larger than that of the second solid-state element 30 by q ₀ = (refractive index of material of second solid-state element / refractive index of medium packed in concentrator) ) When it is made twice smaller, a light emission distribution with almost no dark part can be generated in the first solid-state device.

Example 3. In the example shown in FIG. 5, a thin film medium 9 that is sufficiently smaller than the thickness of the second solid element is inserted between the first solid element 3 and the second solid element 30. In the state without the thin film, the distribution of the clearance between the solid elements may occur, but the clearance is made constant by the thin film having a constant thickness. Further, it goes without saying that if the thin film is made into a liquid such as gel or water, the uniformity is increased.

Example 4. Further, although FIG. 1 shows an example in which one opening 80 has a hole shape, a plurality of openings may be provided as shown in FIG. 6, and a slit-shaped opening is provided in the longitudinal direction of the solid-state element 3 to form an array. It may be excited by a light source having a circular shape. In this way, higher power photoexcitation can be performed, and as a result, a higher power laser beam can be obtained.

Embodiment 5. Further, as shown in FIG. 7, when the light 40 of the light source is guided to the inside of the condenser by the condensing optical system such as the SELFOC lens 45, the loss of light on the wall surface of the opening 80 is reduced and the excitation efficiency is reduced. Is improved.

Embodiment 6. Alternatively, as shown in FIGS. 8 and 9, the excitation light 40 may be diffused and reflected on the inner surface of the light collector and then excite the solid-state element 3, so that the solid-state element is more uniformly excited from the surroundings. As a result, the uniformity of the generated laser beam is improved.

In each of the above-mentioned embodiments, the solid-state element has a circular cross section, but it is not limited to a circular shape and may be a rectangular shape or an elliptical shape.

Although not particularly described in any of the above-mentioned embodiments, a non-reflective thin film is provided in a portion of the optical element where there is no particular instruction, in a portion through which the laser beam passes, like an ordinary optical element. By applying the above, the loss in the resonator can be reduced, and efficient laser oscillation can be realized.

[0025]

As described above, according to the present invention, the solid-state element including the active solid medium is arranged in the light collector in which the inner surface arranged so as to surround the solid-state element is composed of the light diffuse reflection surface, The excitation light source was installed outside the condenser, and the excitation light was introduced from the opening opened in the condenser to excite the above-mentioned solid-state element, so that the light not absorbed by the solid-state element is again inside the condenser. It is possible to irradiate the solid-state device uniformly by diffuse reflection, and as a result, it is possible to secure the irradiation and reduce the influence of the fluctuation of the excitation light wavelength on the excitation efficiency of the solid-state device. It is possible to realize a stable laser device that is hardly affected by. For this reason, when a semiconductor laser is used as the excitation light, for example, a temperature control for controlling the oscillation wavelength is not required, the device is simplified, and the range of the permitted oscillation wavelength is expanded. The production yield is increased, and as a result, an inexpensive laser device can be realized. Further, since the inner surface of the condenser is composed of the diffuse reflection surface, the light from the light source can be evenly distributed and guided around the solid-state element, and a laser medium that emits more uniformly in the cross section can be obtained. An extremely high quality laser beam can be stably obtained by using the laser resonator. Further, since the light source that emits the excitation light is installed outside the condenser, the housing of the light source is not exposed to the light from the diffuse reflection surface, and therefore the excitation light guided into the condenser is diffuse reflection surface. After being reflected multiple times, it is guided to the solid state element without loss,
An efficient laser device can be obtained.

Further, if a second solid-state element covering the solid-state element containing the active solid-state medium is further provided in addition to the above-mentioned structure, a laser medium that emits light almost uniformly in the cross section can be obtained. A high-quality laser beam can be stably obtained by using the device.

Further, the outer diameter of the second solid-state element is calculated from the outer diameter of the solid-state element containing the active solid medium by q = (refractive index of material of second solid-state element / refraction of medium packed in concentrator). If it is configured to be larger than the ratio, the light incident on the periphery can be fan-shaped in the cross section, and a solid-state element containing an active solid medium can be included in the fan. Is reliably excited to obtain a laser medium that emits light almost uniformly in the cross section. From this, a high-quality laser beam can be stably obtained using a laser resonator.

If a thin film medium is inserted between the solid element containing the active solid medium and the second solid element, the heat distribution of the solid element is made uniform in the circumferential direction, and it is stable and substantially uniform in the cross section. A laser medium that emits light is obtained, and a high-quality laser beam can be stably obtained from this by using a laser resonator.

[Brief description of drawings]

FIG. 1 is a side view and a sectional view showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an operation of the photoexcitation solid-state laser device according to the first embodiment of the present invention.

3A and 3B are a side view and a sectional view showing a second embodiment of the present invention.

FIG. 4 is an explanatory view explaining the operation of the optically pumped solid state laser device according to the second embodiment of the present invention.

5A and 5B are a side view and a cross-sectional view showing a third embodiment of the present invention.

6A and 6B are a side view and a cross-sectional view showing a fourth embodiment of the present invention.

7A and 7B are a side view and a sectional view showing a fifth embodiment of the present invention.

FIG. 8 is a side view and a sectional view showing a sixth embodiment of the present invention.

9A and 9B are a side view and a sectional view showing a sixth embodiment of the present invention.

FIG. 10 is a side view showing a configuration of a conventional optically pumped solid state laser device.

FIG. 11 is an explanatory diagram for explaining the operation of the conventional optically pumped solid-state laser device.

[Explanation of symbols]

 1 Reflection Mirror 2 Partial Reflection Mirror 3 Solid State Element 4 Light Source 7 Laser Beam 8 Condenser 9 Medium 30 Second Solid State Element 40 Excitation Light 70 Laser Beam 80 Opening

Claims (4)

[Claims] 1. A solid-state element containing an active solid medium, a condenser arranged so as to surround the solid-state element and having an inner surface made of a light diffusive / reflecting surface, an opening formed in the condenser, and the above-mentioned collector. An optically pumped solid-state laser device comprising a light source that is disposed outside the optical device, emits light that is introduced from the opening to excite the solid-state element, and an optical resonator that extracts light from the solid-state element. 2. The optically pumped solid-state laser device according to claim 1, wherein the periphery of the solid-state element is covered with a second solid-state element. 3. The cross section of the solid element containing the active solid medium is circular, the second solid element is cylindrical, and the outer diameter of the second solid element is larger than the outer diameter of the solid element containing the active solid medium. 3. The photoexcited solid-state laser device according to claim 2, wherein q = (refractive index of material of second solid-state element / refractive index of medium packed in light collector). 4. A thin film medium sufficiently smaller than the thickness of the second solid element is inserted between the solid element containing the active solid medium and the second solid element. The optically pumped solid-state laser device according to any one of claims.